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Introduction to Composite Materials
... Another useful concept for the analysis of composite structures are lamination parameters, first proposed by Tsai [241]. These allow the stiffness of any (non-hybrid) composite layup to be represented using at most twelve continuous parameters (ξ 1 to ξ 12 ) and a thickness, h. ...
... (2.12) of material invariants U 1 to U 5 , which are linear combinations of the reduced stiffness matrix terms, Q ij , as follows [241]: where θ represents the fibre angle of a unidirectional ply, and u = 2z/t, with z referring to the distance away from the laminate reference plane, and t the individual ply thickness. Lamination parameters are another way to sum the contributions of the fibre angles to the laminate stiffness through the thickness of the laminate, and can act as elegant laminate design parameters. ...
... The ξ i terms refer to lamination parameters [241] (see Chapter 2 for a full definition), which allow the stiffness of any (non-hybrid) composite layup to be represented using at most 12 continuous parameters. Using this approach it is possible to gain physical insight into the underlying behaviour of the system without having to consider specific layups. ...
... In the above equations, the quantities ξ i , i = 1, ..., 12, are the so-called lamination parameters [13,25], quantities accounting for the geometry of the stacking sequence (i.e. for orientations and position of the layers on the stack): ...
... We consider here the first sequence among the six in Tab. 1. The plies are carbon-epoxy T300-5208 layers, [25], whose characteristics are shown in Tab. 4. The characteristics of the laminate, with a thickness h = 2 mm, are presented in Tab. 5. The Table 4: Characteristics of carbon-epoxy T300-5208 plies. ...
We consider in this paper the general properties of laminates designed to be isotropic in extension and in bending and with a coupling between the in- and out-of plane responses. In particular, we analyze the mathematical properties of the tensors describing the elastic and thermal behavior and the mechanical consequences of these properties. The differences, from the mathematical and mechanical point of view, between the hybrid laminates, i.e. composed by layers of different materials, and those made of identical plies, are pointed out and analyzed. The polar formalism for planar tensors is used in this study.
MSC Classification: 74A40 , 74B05 , 74E10 , 74E30 , 74K20.
... In the above equations, the quantities ξ i , i = 1, ..., 12, are the so-called lamination parameters [12,20], quantities accounting for the geometry of the stacking sequence (i.e. for orientations and position of the layers on the stack): ...
... Moreover, A = D, U = W, u = w and R A 1 = R D 1 = R B 0 = 0 for all the cases. The material for the plies is carbon-epoxy T300/5208, [12], whose characteristics are: ...
The analysis of the mathematical and mechanical properties of thermoelastic coupling tensors in anisotropic laminates is the topic of this paper. Some theoretical results concerning the compliance tensors are shown and their mechanical consequences analyzed. Moreover, the case of thermally stable laminates, important for practical applications, is also considered. The study is carried out in the framework of the polar method, a mathematical formalism particularly well suited for the analysis of planar anisotropic problems, introduced by Prof. G. Verchery in 1979.
... It has been widely proven that the matrix microstructure and its consequent mechanical properties have a considerable influence on the overall performance of the composites [28,29]. The matrix structure strongly depends on the semisolid forming temperature. ...
... The liquid fraction of a composite depends not only on the forming temperature but also on the amount of reinforcement. As prescribed by the rule of mixtures, the theoretical density of the samples rises linearly with the increase of Al 2 O 3 content [28]. As seen in Fig. 10, the measured relative density for high loading composites decreased by increasing Al 2 O 3 volume fraction. ...
The mechanical properties and physical characteristics of aluminum alloy composites can be significantly improved by adding reinforcing phases. However, the high loading of the reinforcement phase in Al7075-Al 2 O 3 composites has not been thoroughly studied. In this work, a combination of semisolid metal powder processing and powder metallurgy is used to process and manufacture Al7075-Al 2 O 3 composites with a high reinforcement fraction of > 40 vol.%. The effects of processing parameters on the microstructures and mechanical properties of the composite material are discussed in detail. The loading limits of the high volume Al 2 O 3 reinforcement in Al7075 composites are identified and linked to the processing parameters. A methodology is introduced to estimate the consolidation temperature of Al7075 alloy using compaction testing. Al 2 O 3 particles (the average particle size of 120 µm) were mechanically milled with Al7075 powder (the average particle size of 20 µm) for 10 min and 5 h using a high-energy planetary ball mill. The mixture was then compacted in the semisolid state at 615 °C under the compaction pressures of 50 MPa and 100 MPa. By increasing the milling time from 10 min to 5 h, the deformation of aluminum powders and the fracture of Al 2 O 3 reinforcement particles occur, restricting the loading limit of reinforcement. The milling time also shows a dominant effect on the powder morphology, microstructure, and mechanical properties of Al7075-Al 2 O 3 composites. Increasing compaction pressure from 50 to 100 MPa significantly improved the compressive strength of the composite from 218 to 652 MPa. Al7075-Al 2 O 3 composite with 40 vol.% of reinforcing phase exhibits the highest hardness of 198.2 HV and 96.9% relative density when it is milled for 5 h and compacted at 100 MPa. However, this composite shows the highest strength of 652 MPa when it is milled for 10 min. By increasing the reinforcing phase to 50 vol.% and 60 vol.%, the hardness, density, and compressive strength of composites decreased. The composites with 60 vol.% of reinforcing phase appeared overloaded. Results show that semisolid metal powder processing has huge potential for the fabrication of high loading Al 2 O 3 in Al7075 matrix with near theoretical density.
... Nevertheless, this approach can be costly due to the large number of structural evaluations needed to converge to an optimised design. A solution to this issue is given by homogenisation techniques applied to the composite behaviour that allows to represent the mechanical properties of a composite plate with a reduced set of continuous parameters at the expense of loosing the detailed information on the stacking sequence of the plies [6,7]. This reduced design space allows for more computationally efficient approaches to aeroelastic tailoring [8,9], where the complete stack information is reconstructed a-posteriori by the solution of an inverse problem [10,11]. ...
... The order in which the different plies are stacked is called stacking-sequence, that drives the mechanical behaviour of the laminate-plate. The latter can be locally expressed in the form of the constitutive law, where and are the local in-plane and bending loads applied to the composite stack and and the local strains and curvatures of the plate [6,29]. The relation between load and deformation is given by the stiffness matrix. ...
Composite materials allow to tailor the elastic properties of a structure. In aeroelasticity, this opens up the possibility to passively enhance the coupled aerostructural characteristics. In this work, the design of a composite wing is addressed with the aim to alleviate static and dynamic aeroelastic loads; these two objectives are quantified by the root-bending-moment in a high load-factor condition and the deformation amplitude of the wing under gust. A two-step approach of the optimal design of the structure is adopted. A Pareto front is computed via an aeroelastic model of the wing; the aerodynamic loads are modelled, depending on the load-case, either via the DLM or the RANS equations. The best-compromise design is chosen via a criterion based on the jig-shape and, finally, the stacking-sequences are computed via a specialised evolutionary algorithm.
... Several experimental studies and practical applications have been carried out which have shown that strengthening effects can be reflected in a wide range of aspects, such as improving structural stiffness, load-bearing capacity, ductility and corrosion resistance [3].For the repair and reconstruction of various reinforced concrete structures, FRP is a widely used technology [4]. The mechanical properties of FRP are determined by the mechanical behavior of both the fibers and the matrix, as well as their interaction [5]. EBR and NSM are the two main techniques developed for strengthening concrete structures using FRP. ...
... The results show that the deflections of strengthened beams showed acceptable decrease in the deflection as compared with reference beam at same load level expect the beams which strengthened by 60 and 90 cm of CFRP bar showed marginal decrease in the deflection compared with reference beam. Table (5) shown the results for all beams experiments. ...
This study investigated the flexural behavior of reinforcement concrete beam strengthened with different techniques. The purpose of this research to study the various techniques of strengthening and knowing the effect of each technique on the beam behavior .Ten simply supported beams tested in this study. The total length of the beams and clear span were 1800mm and 1650mm, respectively. The cross section was (180×250) mm. Tested beams were divided into two categories’ the first category consist of one beams and considered as reference, while the second category consist of nine beams divided into Two groups according to the Strengthening techniques such as near surface mounted (NSM) and external bonded reinforcement (EBR).The experimental results showed improvement in ultimate load capacity for strengthened beams ranging from (6 to 89%) for NSM and (31 to 96%) for EBR and reduction in deflection for strengthened beams ranging from (6 to 43%) as compared with reference beam. When the number and length of CFRP bars are increased, the number of cracks increase while the width of the cracks and the spacing decrease, and the same observation is made when the width of the CFRP sheet is increased. The experimental load capacities of strengthened beams were compared with the design provisions given by ACI440.2R-17 guideline for NSM and EBR technique and EC2 guideline for EBR technique, the average ratio (1.2 and 0.97) respectively ,which showed that reasonable and a good agreement for all strengthened beams.
... where, , and are the in-plane stiffness, bending-stretching coupling and bending stiffness matrices, respectively. The calculation of these matrices is provided in Ref. [29]. Also, is the array (1, 1) of the matrix and is the total thickness of the fibermetal laminates. ...
... The mechanical properties of aluminum alloy and thermoplastic composites are provided in Table 4. [D] are the in-plane stiffness, bending-stretching coupling and bending stiffness matrices, respectively. The calculation of these matrices is provided in Ref. [29]. Also, d 11 is the array (1, 1) of the [d] matrix and h is the total thickness of the fiber-metal laminates. ...
Fiber metal laminates (FMLs) are a type of hybrid materials interlacing composites and metals. In the present work, FMLs with aluminum alloy 6061 as the skin and E-glass fiber-reinforced polypropylene (PP) as the core material are fabricated and formed by the creep age forming (CAF) process. The effects of time and temperature as the process parameters and thickness and stacking sequences of composites layers as the FML parameters are evaluated on the springback of glass-reinforced aluminum laminates (GLARE) FMLs. After the CAF process, the springback of creep age-formed FMLs is calculated. The results show that the FMLs can be successfully formed with the CAF process by considering appropriate time and temperature. In addition, the stacking sequence of composite layers can affect the springback behavior of FMLs significantly.
... As a result, some intermediate variables for the description of the anisotropy are practically used to define univocally the laminate elastic properties. The most common optimisation approaches available in the literature make use of the well-known Lamination parameters (LPs) coupled with the parameters of Tsai and Pagano, see (Tsai & Pagano, 1968;Tsai & Hahn, 1980;Jones, 2018). These parameters unquestionably provide a compact representation of the stiffness tensors of the laminate. ...
... These parameters unquestionably provide a compact representation of the stiffness tensors of the laminate. Nevertheless, they are not all tensor invariants, as discussed in (Tsai & Hahn, 1980). Both LPs and Tsai and Pagano parameters are easier to understand than PPs, in the sense that the formers are moment-weighted average of trigonometric functions of ply orientations. ...
L’objectif de cette Thèse est de développer une méthodologie de conception multi-échelle innovante utilisant un algorithme déterministe pour la conception de structures composites multicouches.L'innovation par rapport aux travaux existants est représentée par la formalisation de deux aspects qui influent grandement sur la fiabilité et la qualité de la solution finale.Le premier aspect porte sur la prise en compte de l'intégration dans la formulation du problème de conception des réponses structurelles critiques intervenants aux différentes échelles du problème. En effet, puisque certaines réponses se manifestent à différentes échelles d'observation, la transition d’échelle se révèle nécessaire afin de bien saisir ces phénomènes. Dans ce travail, une attention particulière sera portée sur l'évaluation de la charge critique de flambage de panneaux raidis constituant l'élément fondamental de la structure des aéronefs. Cependant, la transition d’échelle doit être prise en compte dans la dérivation du gradient des réponses physiques, nécessaire au bon fonctionnement de l'algorithme déterministe pour la recherche de l'optimum.Le deuxième aspect porte sur la contrainte technologique dite de textit{blending}, un problème intrinsèquement lié à la variation du nombre de plis (et des orientations associées) entre stratifiés adjacents de différentes épaisseurs. En effet, les plis des stratifiés plus minces doivent être contenus dans l'empilement des stratifiés les plus épais, sans intersection entre plis. De plus, le blending permet une modulation de l’épaisseur de la structure. De par son importance, il est nécessaire de prendre en compte la contrainte de blending dès les premières phases de conception. De plus, une stratégie générale dont l’objectif est d’identifier le séquence d’empilement des couches du composite en satisfant la contrainte de blending a été développée : permettant ainsi de proposer une solution faisable. Deux approches possibles sont présentées : la première est une approche numérique et la seconde une approche combinatoire, basée sur la recherche des solutions dans une classe particulière de stratifiés (les séquences quasi-triviales).Une fois formalisée, cette approche a été appliquée au problème de la conception d’une architecture aéronautique complexe et innovante : le caisson alaire du PrandtlPlane développé au sein du projet PARSIFAL. Les résultats obtenus sont prometteurs.A coté de ces aspects, les travaux de Thèse abordent aussi deux sujets purement théoriques : la non-convexité du domaine de faisabilité des laminés, ainsi que une justification variationnelle de la modélisation des panneaux raidis. Des résultats inattendus et originals ont été déterminés pour chacun de ces deux thèmes.
... where Xf is the tensile strength of fiber. In-plane shear strength LT can be predicted by Eq. 15 (Tsai et al, 2018). 337 ...
... t can be predicted by Eq. 14(Tsai et al, 2018). ...
Pultruded profiles are usually assumed to being a transverse-isotropic material, which means that fiber and resin are regarded as the uniformly distributed across the profile sections by default. However, this is not the case due to the limitations of the pultrusion technology. The non-uniform fiber-resin distribution as a type of initial imperfection for pultruded glass fiber reinforced polymer (GFRP) profiles was investigated. The resin contents of 49 different pultruded GFRP sections were tested and analyzed. The standard calcination method was used to measure the resin content. The sections were provided by three different manufactures and included the I-sections, box-sections, angle-sections, circular tubes, channel-sections and flat plates. Multiple sampling locations were specified for each type of section. The test results showed that the degree of non-uniformity of fiber-resin distribution of each type of section is different. In particular, the I-sections showed the most significant material non-uniformity. The largest COVs (Coefficients of variation) of the measured resin contents is 0.16. Additionally, the influence of non-uniform fiber-resin distribution on mechanical properties of GFRP members was addressed. The material non-uniformity would increase the initial section eccentricity. Finite element models were built to simulate the compressive GFRP members. It was found that with fiber-resin non-uniformity considered the critical buckling loads of GFRP compressive members will be reduced.
... Here, the first optimization stage consists in optimizing the so-called lamination parameters (LPs) and the second identifies the stacking sequence which fulfils the optimal values of the lamination parameters. The 12 lamination parameters where introduced by Tsai et al. [26,27] and represent together with material invariants the stiffness tensors of laminated composites based on a set of uni-directional laminae; they are trigonometric functions of the ply orientations. Because the LPs are interrelated, additional inequality constraints have to be introduced to describe the feasible regions for the LPs. ...
A new method for numerical optimization of fiber-steered composites is presented, which allows to control efficiently and effectively the curvature of the fibers of single- or multi-layer composite structures. It is based on the introduction of an artificial surface defined and controlled by a relatively small number of control points, which is optimized to identify optimal fiber orientations varying smoothly over the panels. Curvature
constraints like the maximum fiber curvature constraint, MFCC, or the average fiber curvature constraint, AFCC, are respected explicitly by the method to ensure manufacturability of the composite component. Three validation cases are regarded where results of the unconstrained case are compared to those of established methods to illustrate the validity of the new approach. They are complemented by results considering curvature constraints showing that optimal structures depend strongly on the chosen curvature thresholds. Finally, a rib
optimization of a wingbox structure is realized as a more complex case.
... Capitalizing on the Tsai-Hill failure criterion (Tsai and Hahn 1980), a more sophisticated model was established by deriving the complex stress state of FRP reinforcement at bent corners by Imjai et al. (2017). Calibrated against over 100 tested specimens, the model has shown the best validity compared to the previous ones. ...
... Since 1940, spearheaded by the aerospace and military industries, composite materials have been widely exploited in many facets of the national economy, bringing immense convenience to human life while supporting modern science and social economics [1]. Fiber-reinforced composites are the most popular and flexible composite materials because of their high specific strength and modulus, fatigue resistance, and versatility [2,3]. During the molding process of short fiber reinforced composites, the short fibers present different orientations under the action of external force fields [4]. ...
The orientation of fibers in composites reinforced with short fibers can provide insight into the microstructure of the material and considerably affect its macroscopic characteristics. However, the present standard techniques for detecting fiber orientation and length based on microscopic image processing have faults in practical applications, including high effort, low efficiency, and unreliable measurement results. In this study, a method for measuring fiber orientation based on 3D reconstructions of scanning electron microscope (SEM) images is provided. The geodesic active contour (GAC) model is applied to segment the fibers in the SEM images. Matching the fiber contours with the scale-invariant feature transformation (SIFT) algorithm successfully extracts 3D orientation information from the fiber contours. The unit vector of the fiber axis is fitted from the extracted point cloud using the ordinary least squares (OLS) method. With a maximum deviation of 3.83° and an average deviation of 1.50°, the measurement findings of this method are substantially comparable to those of the image-measuring instrument. This paper offers a quantitative approach to studying the microstructure of short fiber-reinforced composites, thereby furnishing objective evidence to support the development and research of such materials.
... Elements of the stiffness matrices are related to lamination parameters and laminate invariants, originally conceived by Tsai and Hahn [13], through the following equations: These ply orientation dependent lamination parameters of are related to the non-dimensional parameters n , and for the A, B and D matrices, respectively, through the following expressions: ...
This article presents details of the development of a special class of laminate, possessing Extension-Shearing Bending-Twisting coupling, necessary for optimised passive-adaptive flexible wing-box structures. The possibility of achieving a measurable drag reduction in cruise flight, without the cost or reliability issues associated with active control mechanisms, is of significant interest for achieving increased fuel burn efficiency, and meeting associated emissions targets. The introduction of passive Bending-Twisting coupling at the wing-box level has been previously demonstrated through laminate level tailoring with Extension-Shearing coupling only, but the limited design space and the possibility for ply terminations (to produce tapered thickness) effectively rule out this special class of laminate for practical construction. The study is now broadened to consider laminates with Extension-Shearing Bending-Twisting coupling, beyond the less well-known un-balanced and symmetric design rule or indeed balanced and symmetric designs with off-axis alignment. Results reveal a vast laminate design space with Extension-Shearing coupling that can be maximised without the unfavourable strength characteristics associated with off-axis alignment. Results also reveal that shear buckling strength can be maximised through Bending-Twisting coupling when load reversal is not a design constraint.
... The stress components responsible for the adhesion/delamination damage propagation in the adhesively bonded T-joint structure are obtained from the stress analysis. By using these stress components and their corresponding strength values in the Tsai-Wu quadratic failure criterion [43], the failure location in the joint structure can be identi ed. ...
... Carbon fibers exhibit a higher stiffness over weight along the fiber direction than most metal alloys. With the help of an appropriate matrix resin and weaving techniques, the long fibers can be woven into various patterns and shapes for practical use, while maintaining most of their stiffness in the loading direction [1,2]. To increase the resistance of long fibers composites to delamination, twodimensional and three-dimensional reinforced architecture patterns have been developed such as plain weave, satin, interlock, or orthogonal weave [3]. ...
Decohesion processes involved in debonding between yarns and matrix or sliding between contacting yarns constitute important failure mechanisms in woven composites. The geometry of the yarn architecture however makes it difficult to avoid interpenetrations between neighboring yarns in their geometrical description. This motivated recent works using a level set-based methodology to generate smooth geometries without interpenetration for generated Representative Volume Elements (RVEs) and experimental image-based samples. Such tools require introducing gaps between contacting yarns, which may be debatable when taken too large or may be computationally costly for thin gap, locally dictating the mesh size. To avoid this, the yarns contacting surfaces can be discretized using interface elements. Yet, identifying such contacting surfaces is complex. An implicit geometry description based on distance fields is used here to extract a geometry that supports cohesive zones, identifying the interface of yarn-yarn contacts and eliminating the gaps using manipulations on distance fields of the individual yarns. This allows generating conforming tetrahedral meshes with inserted cohesive elements in the contact areas. The methodology is shown to reduce the size of finite element models of woven composite RVEs by over two orders of magnitude, thereby paving the way towards affordable damage simulations on such RVEs.
... In the aerospace industry, known for its stringent standards, composite systems are used as the main building block, even in primary aerostructures. By the proper mix of composite system phases, almost any material characteristic (Conductivity, Corrosion Resistance, Density, Ductility, Elasticity/Stiffness, Fracture Toughness, Hardness, Plasticity, Fatigue Strength, Shear Strength, Tensile Strength, Yield Strength, Toughness, etc.) can be designed to meet specific requirements [1][2]. ...
In the present work, the aeroelastic stability of tapered composite plates is investigated. Existing flutter models, based on the typical section approach, are reviewed for quasi-steady and unsteady low Mach number axial flows and modified for the thin composite tapered plates. The numerical approach, based on panel vortex methods for flutter analysis, is presented, and results are compared to typical section flutter methods for the tapered composite fins. Experimental work is performed in the subsonic wind tunnel at flow speeds of 20 - 30 m/s range. Good agreement between experimental, analytical, and numerical results is obtained, and it was concluded that the presented methodology could be used for estimating the flutter boundary velocities for the composite thin flat plates.
... Sharma and Gatoo [21] investigated the effect of the processing methods on the mechanical properties of bamboo and later attributed the difference in the results to the fraction of vascular bundles [22] in the LBL laminates, as bamboo is a functionally graded material. Since bamboo is highly anisotropic, Qiu et al. [23] investigated the mechanical properties of bamboo scrimber with varying fibre orientations and concluded that the classical strength failure criteria, such as the Norris criterion [24] and the Hill-Tsai theory [25], may be used to predict the failure strengths. Moreover, studies were conducted on bamboo scrimber under quasi-static loading [26] and drop-weight penetration impact [27]; the obtained results concluded that the compressive response of bamboo scrimber is strain-rate sensitive and the failure mechanism under drop-weight penetration is highly affected by the fibre orientation. ...
The mechanical properties of the structural components (i.e., columns and beams produced from engineered bamboo products), such as, bamboo scrimber (also known as parallel bamboo strand lumber, PBSL) and Laminated Bamboo Lumber (LBL), have attracted considerable attention from researchers in recent years. In previous studies, researchers reported on the stress-strain behaviour of bamboo scrimber, LBL and glue laminated bamboo under compression and proposed some empirical and semi-empirical models, based on their individual studies. However, a generic constitutive model for engineered bamboo products is still not available. The compressive stress-strain curves of bamboo scrimber and LBL are reported to show a similar behaviour with three distinct stages i.e., a linear elastic stage followed by a nonlinear plastic stage and a plateau. As part of the current study, the previously proposed models for bamboo scrimber were carefully studied and all available material test results on engineered bamboo were used to develop a generic constitutive model, based on the Ramberg-Osgood (RO) formulation considering its suitability to capture its material nonlinearity. Based on the test results, it was observed that 1% proof stress can be used in a compound RO model to predict an accurate material response for bamboo scrimber. The proposed modelling technique has also been applied to predict the compressive behaviour of LBL. This paper proposes the RO coefficients for both bamboo scrimber and LBL that can be used to develop accurate nonlinear models for engineered bamboo products.
... Except for most spacecrafts, moisture swelling effects are not as severe as those pertaining to temperature and, therefore, are usually neglected at the design stage. Table 3 outlines the effect of different environmental, operational, and damage mechanisms on the mechanical properties of composite structures based on reviewing References [33,34,[49][50][51]. For instance, the composite material stiffness is highly sensitive to the temperature and moisture variations as well as the presence of fiber cracks. ...
This study presents a comprehensive review of the history of research and development of different damage-detection methods in the realm of composite structures. Different fields of engineering, such as mechanical, architectural, civil, and aerospace engineering, benefit excellent mechanical properties of composite materials. Due to their heterogeneous nature, composite materials can suffer from several complex nonlinear damage modes, including impact damage, delamination, matrix crack, fiber breakage, and voids. Therefore, early damage detection of composite structures can help avoid catastrophic events and tragic consequences, such as airplane crashes, further demanding the development of robust structural health monitoring (SHM) algorithms. This study first reviews different non-destructive damage testing techniques, then investigates vibration-based damage-detection methods along with their respective pros and cons, and concludes with a thorough discussion of a nonlinear hybrid method termed the Vibro-Acoustic Modulation technique. Advanced signal processing, machine learning, and deep learning have been widely employed for solving damage-detection problems of composite structures. Therefore, all of these methods have been fully studied. Considering the wide use of a new generation of smart composites in different applications, a section is dedicated to these materials. At the end of this paper, some final remarks and suggestions for future work are presented.
... Il est généralement considéré que la déformation à la rupture du matériau composite diminue avec l'augmentation de la teneur de la fraction en fibres. Le modèle des propriétés mécaniques de la plaque FRP décrit un matériau composite qui suit la théorie de Tsai and Hahn's (1980), conduisant aux équations (4.1) -(4.4) Pour l'étude de la contrainte interfaciale, on prendra les hypothèses de base suivante : ...
Cette présente thèse est réalisée dans le but d’étudier et d’analyser les contraintes interfaciales des structures dégradées par leur milieu agressif ou par des surcharges, et qui sont renforcées et réhabilitées par les matériaux composites FRP précontraints. La solution de réparation par les nouveaux matériaux composites appliqués par collage sur les faces extérieures des structures endommagées a pris une place prépondérante dans le domaine de la réparation et du renforcement par rapport aux méthodes classiques (soudure, rivetage, greffage, etc.…). Ces dernières techniques ont prouvé leurs complexités et leurs limites dans le sens de résistance aux efforts et à la corrosion.
Cependant, le phénomène de délaminage des plaques FRP de renforcement à leurs extrémités du à une forte concentration des contraintes qui peuvent dépasser la valeur ultime de résistance, et ainsi la structure peut se dégrader et se ruiner de façon partielle ou totale.
La connaissance ou la prédiction de ces contraintes d’interface joue un rôle prépondérant dans la compréhension du phénomène de décollement pour éviter tout endommagement.
Dans cette optique, on s’est intéressé à étudier le phénomène de délaminage pour une structure renforcée par composites FRP, en développant de nouvelles approches tels que le couplage des charges mécaniques et thermiques, la fraction volumique de fibres et le modèle des précontraintes, visant à améliorer les modèles déjà existants, tout en essayant de réduire les contraintes d’interface. Une approche théorique et une modélisation par éléments finis ont été réalisées dans le but de valider le modèle analytique.
Les résultats numériques développés dans cette thèse semblent corréler avec ceux de la littérature, ainsi que des études comparatives ont été faites avec celles déjà existantes comme les travaux de Smith et al (2001)., Deng et al.(2004), ainsi que Denton et al.2004) . Des études paramétriques ont été réalisées afin de montrer leurs effets sur la concentration des contraintes.
... Il est généralement considéré que la déformation à la rupture du matériau composite diminue avec l'augmentation de la teneur de la fraction en fibres. Le modèle des propriétés mécaniques de la plaque FRP décrit un matériau composite qui suit la théorie de Tsai and Hahn's (1980), conduisant aux équations (4.1) -(4.4) Pour l'étude de la contrainte interfaciale, on prendra les hypothèses de base suivante : ...
... Layers of anisotropic material are stacked through the thickness of the plate. This new type of structural component prompted the development of new plate theories [5][6][7], often based on classical lamination theory [8,9]. The comprehensive review of the many shell theories that have been developed is beyond the scope of this paper but can be found in several publications [10,11]. ...
This paper presents a finite element implementation of plates and shells for the analysis of flexible multibody systems. The developments are set within the framework of the motion formalism that (1) uses configuration and motion to describe the kinematics of flexible multibody systems, (2) couples their displacement and rotation components by recognizing that configuration and motion are members of the Special Euclidean group, and (3) resolves all tensors components in local frames. The formulation based on the motion formalism (1) provides a theoretical framework that streamlines the formulation of shell elements, (2) leads to governing equations of motion that are objective, intrinsic, and present a reduced order of nonlinearity, (3) improves the efficiency of the solution process, (4) circumvents the shear locking phenomenon that plagues shell formulations based on classical kinematic descriptions, and (5) prevents the occurrence of singularities in the treatment of finite rotation. Numerical examples are presented to illustrate the advantageous features of the proposed formulation.
... The thickness of the plate is 0.762 mm with each ply's thickness equal to 0.254 mm. Material constants and other details can be found in [38][39][40]. The RP-503 charge is located 50.8 mm from the center of the outer surface of the plate. ...
Solution of near-field underwater explosion (UNDEX) problems frequently require the modeling of two-way coupled fluid-structure interaction (FSI). This paper describes the addition of an embedded boundary method to an UNDEX modeling framework for multiphase, compressible and inviscid fluid using the combined algorithms of Runge–Kutta, discontinuous-Galerkin, level-set and direct ghost-fluid methods. A computational fluid dynamics (CFD) solver based on these algorithms has been developed as described in previous work. A fluid-structure coupling approach was required to perform FSI simulation interfacing with an external structural mechanics solver. Large structural deformation and possible rupture and cracking characterize the FSI phenomenon in an UNDEX, so the embedded boundary method (EBM) is more appealing for this application in comparison to dynamic mesh methods such as the arbitrary Lagrangian-Eulerian (ALE) method to enable the fluid-structure coupling algorithm in the fluid. Its limitation requiring a closed interface that is fully submerged in the fluid domain is relaxed by an adjustment described in this paper so that its applicability is extended. Two methods of implementing the fluid-structure wall boundary condition are also compared. The first solves a local 1D fluid-structure Riemann problem at each intersecting point between the wetted elements and fluid mesh. In this method, iterations are required when the Tait equation of state is utilized. A second method that does not require the Riemann solution and iterations is also implemented and the results are compared.
... As mentioned above, the continuous optimization step implements lamination parameter as design variables, which were first introduced by Tsai et al. [20], [21]. They allow for a representation of laminate stiffness matrices in a continuous form, enabling the use of gradient based optimizers independent of the number of plies. ...
Within the scope of the "DLR - ONERA Partnership in Transport Aircraft Research", a common research program (CRP) called FIGURE - Flexible Wind Gust Response - was launched to investigate means of passive load control in the transonic regime. To this end, two aeroelastic tailoring methodologies, independently developed at ONERA and DLR, were applied to a common model geometry. A choice was made in favor of the publicly available NASA Common Research Model (CRM) wing, featuring a comprehensive database with respect to geometry, as well as analytical and experimental research results. The span of the wing half to be investigated was set to 0.55 m, limited by the test section dimensions. While wind tunnel testing was part of ONERA's workshare, the model building was performed by DLR. This report at hand focusses on the structural, aeroelastic optimization of the DLR wing. It is based on an optimization framework developed and constantly being enhanced and extended at the DLR - Institute of Aeroelasticity (DLR-AE). The report describes the consideration of different structural objective functions, structural and aeroelastic constraint combinations, design field considerations, as well as the application of an aero load correction applied in the course of the optimization. The final results consist of the selection of an appropriate fiber type, optimized fiber layers represented as stacking sequence tables for the upper and lower wing skins, and the corresponding optimized jig twist distribution, required for manufacturing the lamination molds; in summary, all data required to start the construction of the wind tunnel model.
... Composite materials are produced by combining two or more distinct constituents or phases with different physical or chemical properties [25]. Although the different materials do not blend into each other, they yield unique properties (mechanical, physical, thermal, and electrical) in a supplementary manner upon being composited and engineered into a complex architecture at the micro-or macro-scale levels [26]. ...
Polymeric nanocomposites have received significant attention in both scientific and industrial research in recent years. The demand for new methods of food preservation to ensure high-quality, healthy foods with an extended shelf life has increased. Packaging, a crucial feature of the food industry, plays a vital role in satisfying this demand. Polymeric nanocomposites exhibit remarkably improved packaging properties, including barrier properties, oxygen impermeability, solvent resistance, moisture permeability, thermal stability, and antimicrobial characteristics. Bio-based polymers have drawn considerable interest to mitigate the influence and application of petroleum-derived polymeric materials and related environmental concerns. The integration of nanotechnology in food packaging systems has shown promise for enhancing the quality and shelf life of food. This article provides a general overview of bio-based polymeric nanocomposites comprising polymer matrices and inorganic nanoparticles, and describes their classification, fabrication, properties, and applications for active food packaging systems with future perspectives.
3D printing technologies have helped researchers fabricate cellular structures and have lightweight and desirable mechanical properties. One such structure is called “auxetic” structures. “Auxetics” is the term used for structures that exhibit a negative Poisson’s ratio (NPR) and offer a wide range of wide range of potential applications in automotive, aerospace and military industries due to their great load-bearing capabilities in association with excellent energy dissipating performance. PLA (Poly Lactic Acid) material is used to 3D print eight different unit cell design. For each unit cell design with three different core thickness of 1.00 mm, 1.50 mm and 2.00 subjected to projectile impact with 10J of kinetic energy were studied by means of explicit nonlinear finite element simulations using LS-DYNA. Studies were carried out. The energy absorbed by the sample, contact force and projectile kinetic energy time history are compared and the damage on each sample is also compared. It was found that the Chiral unit cell absorbs the max energy and have less damage compared to other unit cell design.
The analysis of the mathematical and mechanical properties of thermoelastic coupling tensors in anisotropic laminates is the topic of this paper. Some theoretical results concerning the compliance tensors are shown and their mechanical consequences analyzed. Moreover, the case of thermally stable laminates, important for practical applications, is also considered. The study is carried out in the framework of the polar method, a mathematical formalism particularly well-suited for the analysis of planar anisotropic problems, introduced by Prof. G. Verchery in 1979.
Description
Documents theoretical and experimental techniques used for practicing, analyzing or measuring elastic modulus in solid materials. 15 papers offer guidance in the selection of appropriate methods of modulus where temperature, frequency and strain amplitude are of concern.
In this paper, the failure of polymeric composite laminates made of unsaturated polyester reinforced with glass fibers was studied when loading on tensile to failure, for different types of glass fibers in order to extrapolate the values of tensile loads to failure and to study the deformation and failure patterns that occur. To achieve this goal, a group of samples was prepared from unsaturated polyester material as a polymeric basis and glass fiber as a reinforcement material, where three types of fibers were used (Mat, Mesh, Unidirectional Fiberglass), and these samples were subjected to a tensile test. Experimental results showed that samples reinforced with oriented glass fibers are more bearing for tensile forces than plates with random fibers, also thickness of samples effect on values and form of failure. Samples upon collapse recorded different and complex patterns of damage and deformation, which increase with the number of layers and vary according to the type of fiberglass used. The experimental results were verified programmatically using Matlab.
Sandwich composites are a special class of material because of distinctive properties such as lightweight, high damping and high energy absorbing capacity, which in turn make this material highly suitable for the shipbuilding industry. The traditionally used materials for hull construction in the shipbuilding industry are steel, Glass Reinforced Plastic (GRP) and wood which is prone to problems such as weight and strength reduction due to water absorption over a period of time. This manuscript presents a comparative study of specific energy absorption (SEA) of GRP sheets and two different aluminium honeycomb sandwich composites one of which has aluminium honeycomb core and aluminium face sheet/skin and the other has aluminium honeycomb core and GRP face sheet. Experiments are carried out on the GRP sheet and sandwich composite with aluminium honeycomb core and aluminium as face sheet using Charpy ASTM E-23 machine. The experimental results are compared with the numerical results obtained from Abaqus and are found to be in good agreement. Further, the numerical simulation has been carried out on sandwich composites and GRP sheets varying several parameters such as foil thickness of honeycomb in sandwich composites, and skin of sandwich composites (aluminium sheet and GRP). Failures have been discussed based on stress theories and the deformation patterns of sandwich composites and GRP sheets (obtained from the numerical and experimental investigation) have been compared. The maximum impulse force has also been presented by using the impulse-momentum equation. It has been found in the study that the aluminium honeycomb sandwich composites with aluminium as face sheet possess high energy absorption to mass ratio than the pure GRP sheets and the aluminium honeycomb sandwich composites with GRP sheet as skin. Further parametric study reveals that the energy absorption to mass ratio increases with increase in foil thickness in both type of honeycomb sandwich composites.
An accurate nonlinear buckling analysis of functional graded multilayer GPL‐Fiber reinforced hybrid composites (FG multilayer GPL‐Fiber RHCs) cylindrical shells under hygro‐thermo‐mechanical loadings is performed. The axisymmetric pre‐buckling effect, which is usually neglected in the classical eigen‐buckling analysis, is considered to improve the accuracy of critical buckling loads. Nonlinear governing equations are derived by adopting the high‐order shear deformation theory and Novozhilov's nonlinear shell theory. Accurate critical buckling loads and explicit buckling mode shapes are obtained by the Galerkin method. Comparisons with results of existing literature are presented to validate the accuracy of present solutions. A comprehensive parametric study of key influencing parameters on the structural stability of the FG multilayer GPL‐Fiber RHCs cylindrical shell is investigated in detail. The numerical results indicate that the stability of such shell highly depends on the temperature rise and moisture absorption, and contents and distribution profiles of GPLs and fibers could be optimized to enhance the anti‐buckling performance of the shell.
To improve the mechanical response of filament-wound composite structures, it is necessary to identify the damage mechanisms and assess the effect each mechanism has on the energy absorption capacity. To investigate this, crashworthiness characteristics of glass fiber composite tubes were experimentally studied. Due to the limitations of eye inspection and scanning electron microscopy methods, it seemed necessary to use a precise technique to gain more detailed insight into the damage mechanisms. For this purpose, the acoustic emission technique was adopted. From the macroscale view, experimental results revealed that the failure mechanisms of tubes are generated by longitudinal cracks along the winding direction due to the plastic deformation in the buckling region. On the micro-scale, the acoustic emission-based procedure based on wavelet packet transform (WPT) was adopted, where the released energy affiliated to each damage mechanism was quantified and three damage mechanisms, including matrix cracking, debonding, and fiber breakage were identified. Among them, matrix cracking was determined as the main contributor to the damage in the structure, while fiber breakage and debonding were the next main damages. Comparing the results obtained from micro and macro scales of the composite tube, the local buckling failure mode was attributed to the low content of debonding in the structure. Further, a finite element analysis (FEA) was carried out to predict the failure behavior. Key results revealed that the FEA can effectively predict the linear behavior and maximum load value of the specimen. However, some differences were found between the predicted force–displacement curves and experimental tests after the force drop.
In the present study, the main objective is to find the three-dimensional bending stresses and displacement of the two cylindrical shells made up of laminated composite laminates (of different materials) which is subjected to the following pressure loading and boundary conditions: a) Thick Shell (S=4) of axial length (L=4S) and circumferential span ( 𝛼=45°) made up of cross ply laminate [90°/0°/90°] with simply supported boundary conditions and subjected to the normal sinusoidal load 𝑝=𝑝_0 𝑐𝑜𝑠(𝜋 𝑧/𝐿)𝑐𝑜𝑠(𝜋 𝜃/𝛼) on its inner surface and b) the fiber direction is denoted by the angle measured from the z-axis to the fiber direction. In the present work, material 1 is carbon epoxy and material 2 is Polyphenylene sulfide (PPS) composites. The other objective is to find the lowest natural frequency of the composite shell of both Carbon Epoxy and Carbon PPS by using free vibrational dynamic analysis and visualize and further compare the results obtained by their mode shapes.
A finite element model that incorporates a 3D progressive fatigue damage model (3D PFDM) is developed to simulate the fatigue behavior of Flax-epoxy (FE) composites. Input parameters of the model are determined from testing the material properties in all directions. A double-notched shear test is used to characterize the out-of-plane shear properties of the laminate under both static and fatigue loading conditions. The 3D PFDM, which employs a stochastic distribution of the material properties, is implemented thorough a user-defined subroutine in ABAQUS finite element software. Results of the finite element analysis of voids-containing laminates are in good agreement with experimental results. The predicted fatigue life of all layups is more influenced by voids at higher loading levels compared to laminates without voids. A further verification of the 3D PFDM model was performed using the cross ply and quasi-isotropic configurations and comparing the predicted free-edge delamination at the interface of the 90° ply and adjacent layers to the SEM micrographs of free edges of specimens. From a practical perspective, the proposed 3D PFDM could be applied to a wide range of composite materials to predict edge delamination in laminates with different fiber orientations.
The bend corner of Fiber‐reinforced polymer (FRP) reinforcement has been shown significantly lower tensile strength than the straight portion. To date, various prediction models were developed for the bend corner strength. In this study, three types of six prediction models are reviewed and evaluated based on a most extensive database to date, including tests from 15 investigations from 1999 to 2020. The validities of the models for cross‐section types and test methods are analyzed. The logarithmic and linear regression models are further modified. The macro‐mechanical model provides the best predictions for the whole database with similar validity for test specimens with different cross‐section types. The linear regression and logarithmic models show lower accuracy and inconsistency in cross‐section types. The different test methods adopted in the literature show limited influence on the bend corner strength and the performance of the prediction models. The proposed cross‐section geometry factor can effectively consider the cross‐section types and the modified linear regression and logarithmic models could provide more accurate predictions. The model evaluations and modifications in this study could provide a more comprehensive understanding of the calculation philosophy of the bend corner strength of FRP reinforcement, which could be used for the future updates of shear design provisions for FRP reinforced concrete structures.
A new easy-to-implement approach based on the energy of recorded signals is proposed to estimate the acoustic source location in orthotropic plates. The proposed approach (a) requires no time-of-arrival or time-difference-of-arrival estimates, (b) is free from the implicit assumption of the propagation of elastic wave energy along a linear path from an acoustic source to a sensor despite the material anisotropy and (c) can be applied without requiring any direct information on the mechanical properties of the plate material. It is demonstrated that a function of the signal energy at a sensor installed on an orthotropic plate can be modeled as a three-parameter function of the distance of the sensor from the source and its angular position with respect to the source. Considering the source coordinates and the three parameters as unknowns, this model leads to a nonlinear equation involving five unknowns. Considering several sensors, this results in a system of simultaneous nonlinear equations to be solved in the least squares sense by minimizing an objective function of five design variables to obtain an optimum source location estimate. Numerical validations of the proposed approach are performed via four numerical examples with varying plate boundary conditions and excitation pulses, as well as via another numerical example with a Gaussian noise (with a high enough signal-to-noise ratio) added artificially to the signals of one of the above examples. These illustrations reveal that in general the methodology yields sufficiently accurate estimates of the source location.
The study of the mechanical behavior of composite materials has acquired great importance due to the innumerable number of applications in new technological developments. As a result, many theories and analytical models have been developed with which its mechanical behavior is predicted; these models require knowledge of elastic properties. This work describes a basic theoretical framework, based on linear elasticity theory and classical lamination theory, to generate constitutive models of laminated materials made up of orthotropic layers. Thus, the models of three orthotropic laminated composite materials made up of layers of epoxy resin reinforced with fiberglass were also obtained. Finally, by means of experimental axial load tests, the constants of the orthotropic layers were determined.
The development of a density-based 3D minimum compliance topology optimization approach for sandwich structures with anisotropic shells is presented. A constant thickness shell is enforced at the interface of a base structure through a two-step filtering approach. Homogenous effective properties of a cellular material are assigned to the base structure while the shell is treated as a constant stiffness laminate with anisotropic properties. Local shell normal vectors are obtained from the density gradient introduced in the second filtering step and local material orientations in the shell’s tangent plane are approximated based on the fabrication process of the structure. Simple approximating strategies using the Gauss map are presented for a fabric draping process and the fused filament fabrication additive manufacturing process. The effect of material anisotropy on the optimal topology is studied on the Messerschmitt Bölkow Blohm beam benchmark problem. An application to composite structures is then presented where a square, simply supported laminate is reinforced on one face by a topology optimized sandwich structure. Though manufacturability cannot be ensured in the current implementation, careful consideration of the optimization parameters allow to constrain the problem towards manufacturable solutions using additively manufactured cores.
In tape placement process, the laying angle and laying sequence of laminates have proven their significant effects on the mechanical properties of carbon fibre reinforced composite material, specifically, laminates. In order to optimise these process parameters, an optimisation algorithm is developed based on the principles of genetic algorithms for improving the precision of traditional genetic algorithms and resolving the premature phenomenon in the optimisation process. Taking multi-layer symmetrically laid carbon fibre laminates as the research object, this algorithm adopts binary coding to conduct the optimisation of process parameters and mechanical analysis with the laying angle as the design variable and the strength ratio R as the response variable. A case study was conducted and its results were validated by the finite element analyses. The results show that the stresses before and after optimisation are 116.0 MPa and 100.9 MPa, respectively, with a decrease of strength ratio by 13.02%. The results comparison indicates that, in the iterative process, the search range is reduced by determining the code and location of important genes, thereby reducing the computational workload by 21.03% in terms of time consumed. Through multiple calculations, it validates that "gene mutation" is an indispensable part of the genetic algorithm in the iterative process .
A significant increase in the rate of composite manufacture is needed to meet demand for short-range commercial aircraft. The enabling automated manufacturing processes can, however, induce undesirable process features such as wrinkles. Additionally, the potential for Barely Visible Impact Damage has resulted in widespread use of overly-conservative strain allowables which has led to overweight aircraft structures.
Two new constraints are presented which enable formability and damage tolerance to be incorporated into a two-stage minimum-mass optimisation framework for performance and manufacturability. An efficient, approximate method is presented for determining a conservative lower bound on the strain required to propagate a single, circular delamination, given a general through-thickness position and an upper bound on delamination size. A Compatibility Index is used to predict the propensity for wrinkles to occur during a forming manufacturing process.
Optimised stacking sequences for two benchmark design problems; a flat plate and blade-stiffened panel, are obtained subject to minimum formability, damage tolerance and buckling constraints alongside common industry design rules. The damage tolerance and formability constraints are met for a diverse set of design requirements, without increasing mass or reducing buckling load, thereby demonstrating that components may be optimised for manufacture using high-rate processes without detriment to performance.
The material properties of composite materials are affected by changes in temperature and moisture. This study used the glass/carbon fiber reinforced plastic hybrid composite (G/CFRPHC) laminate as the research object. The stiffness and strength of the composite lamina were expressed as a function of hydrothermal parameters. Based on classical lamination theory(CLT) and macro-mechanical analysis, using MATLAB programming, the tensile strength of G/CFRPHC laminates under a hydrothermal environment was studied. In addition, the influence of temperature, ply thickness, ply stacking sequence, and ply angle on the tensile strength of G/CFRPHC laminates under a hydrothermal environment was discussed. The results show that the tensile strength of G/CFRPHC laminates decreases with the increase of temperature and laying angle in the temperature range of 20℃~110℃ in the hydrothermal environment (moisture absorption rate C 1 =0.5%). Furthermore, for the G/CFRPHC laminates with laying modes of (0 2G /90 mC ) S , (0 4G /90 mC ) S , (0 6G /90 mC ) S , as m increases, their tensile strength gradually decreases. The tensile strength of G/CFRPHC laminates with the same ply angle but different ply stacking sequence is also not the same.
Since ancient times, the concept of reinforcing brittle building materials such as mud with grass straws, animal hair, etc. is common. In the past century, the use of metallic and synthetic fibers made of iron, steel, carbon, glass, and many more materials explored new possibilities for thin and flexible concrete designs with efficient strength. However, multi-axial textiles with open meshed/grid structures are the most recent reinforcing materials for fine-graded cement-based structures. The combination of textiles (as reinforcement) with finely graded concrete (as a matrix) is known as Textile Reinforced Concrete (TRC), or Fabric-Reinforced Cementitious Matrix (FRCM), or Textile Reinforced Mortars (TRM). These sustainable building components have numerous advantages (lightweight, thin-structure, design flexibility, high durability, and chemical non-reactiveness) that cannot be fulfilled by conventional load-bearing steel-reinforced concrete (RC). Due to the availability of various reinforcing materials, a wide range of cement-based designs can be fabricated depending upon the area of application. The advancement phase of reinforced cementitious materials has a history of more than 150 years, and it is still going on. This chapter attempts to analyze the evolution of reinforced cementitious materials and their future possibilities as advanced building materials.
In recent years, demand for environment friendly materials with low energy consumption increases the considerable interest of researcher to develop polymer composite reinforced with natural fibers. Polymer composites reinforced with natural fibers (NFRCs) are extensively employed for various application in commercial sector owing to their low density, easy availability, biodegradability, biocompatibility, nonabrasive, and satisfactory mechanical properties. However, their inherent characteristics such as variable fibers distribution, water susceptibility, low thermal stability, lack of good interfacial adhesion, and tendency to agglomerate largely influences process of NFRCs development and their applications in the commercial sector. Considerable research efforts have been directed to overcome the disadvantages of natural fibers in order to manage their performance up to the requirement of commercial applications. This chapter focuses on recent advancement in natural fibers reinforced polymer composites with their applications. Besides, this chapter cover the current research efforts carried out in the area of NFRCs development, major approaches, and revolutions in enhancing their performance. Different fibers pre‐treatment and modification techniques are also discussed along with their effect on characteristics of natural fibers reinforced polymer composites with natural fibers and their recent development, challenges, and opportunities in the area of NFRCs.
Le contrôle des structures déformables dans les applications navales, telles que les hélices et les safrans offre des perspectives de développements et de rupture technologique. Cette thèse traite du contrôle des performances hydrodynamiques d’un hydrofoil déformable afin d’élargir son domaine de fonctionnement et de retarder l’apparition de la cavitation. Une étude paramétrique est menée afin d’évaluer les effets de la position de l’épaisseur maximale et des volets de bord d’attaque et de bord de fuite sur les performances hydrodynamiques d’un profil NACA 0012. L’analyse numérique est effectuée avec le code potentiel-couche limite Xfoil et montre que les volets ont un effet significatif sur le domaine de fonctionnement de l’hydrofoil ainsi que sur l’étendue de son domaine sub-cavitant. Des essais sont réalisés dans le tunnel hydrodynamique de l’IRENav sur des profils non déformables avec des volets de bord d’attaque et de bord de fuite imposés. Les mesures de portance et des cartes de cavitation montrent que les résultats numériques sont cohérents avec les observations expérimentales. A la suite de ces résultats, un hydrofoil déformable en composite et contrôlable par le pilotage de la pression interne est fabriqué et testé dans différentes conditions d’écoulement et de pression interne. Il est montré que cet hydrofoil déformable en composite permet, dans une certaine mesure, le contrôle des forces hydrodynamiques ainsi que l’élargissement de son domaine de fonctionnement en fonction de l’angle d’attaque. Le contrôle de la pression permet également de modifier le domaine sub-cavitant de l’hydrofoil déformable. Parallèlement aux expériences, un outil numérique pour l’étude de l’Interaction Fluide Structure (IFS) de ce type de structure composite est développé afin d’aider à la conception des hydrofoils. Les résultats des simulations IFS sont en bon accord avec les campagnes expérimentales.
This work focuses on the frequencies of rotating carbon nanotubes (CNTs)/fiber/polymer/metal laminates (CNTFPMLs) thin circular cylindrical shell. The cylindrical shell is studied on the basis of Love’s first approximation shell theory with simply supported boundary condition. In this manuscript, Eshelby-Mori-Tanaka is used to define the modulus of carbon nanotubes reinforced composites (CNTRCs) cylindrical shell. In addition, fibers can be reinforced using the obtained matrix by means of extended rule of mixture. The influence of various parameters for example characteristics of fiber phase material, such as circumferential and axial wave numbers, lay-ups, metal volume fraction, composite volume fraction and CNTs mass fraction on the frequencies of rotating CNTFPMLs cylindrical shell have been studied. The outputs illustrated by growing rotational speed, the frequencies of CNTFPMLs cylindrical shell change differently for different fiber volume fractions. Also, the backward and forward frequencies of functionally graded (FG)-X and FG-O distributions are more and less than the uniformly distributed (UD) for rotational speed equals to 1, respectively, while this process is reversed for rotational speed equals to 5. In 10 and 20 rotational speeds, while the frequencies of backward and forward modes for FG-X distribution are more and less than the UD , respectively, but this procedure is reversed in FG-O distribution.
Linerless composite cryogenic tank is significant for weight reducing in launch vehicles, and a microscopic-to-macroscopic model is presented in this paper to capture the burst behaviors of the carbon-fiber-reinforced-composite cryotank. The hierarchical framework starts from the material components (carbon fiber and matrix) at microlevel, filament winding layups at mesolevel, and pressure tank at macrolevel. The locally exact homogenization theory is first introduced to generate stiffness degeneration coefficients with matrix crack and fiber fracture failure, which is compared with previous literature and good agreements are obtained. And 1° finite element representative model is then established considering spiral filament winding, and progressive damage analysis is finally conducted based on Hashin and Maximum stress criteria complied with ANSYS Parametric Design Language. In addition, the thermodynamic analysis is demonstrated by considering the integrated design structure with a corrugated sandwich cylindrical shell under multiple physical fields. The proposed multiscale model provides references for fuel cryotank design from a microscopic perspective to predict the burst pressure.
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