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The composite materials are well known by their excellent combination of high structural stiffness and low weight. Their inherent anisotropy allows the designer to tailor the material in order to achieve the desired performance requirements. Thus, it is of fundamental importance to develop tools that allow the designer to obtain optimized designs c...
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... an impact experimental test, it was determined the FRFs (Frequency Response Function) which relate the response given by the specimen when loaded with a signal, allowing for the determination of the natural frequencies and the damping factors, as shown in Fig. 3. This was done by fixing the laminate specimen in a rigid support (1) with one of its side free to vibrate, as a cantilever beam. The impact hammer (3) was used to give the input load (pulse) to the specimen, and the Spectral Analyser was set from 0 Hz to 400 Hz. This output was captured by the accelerometer (2) and together with the ...
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... it was investigated the most attractive points to excite (input) and to get the response (output) in the specimens. Due to their high flexibility it was selected the points 1 (input), 2 and 3 (output) for the determination of two FRFs (H 21 e H 31 ), as shown in Fig. 3. Since the specimens are very flexibility and light, special care should be given to choose the accelerometer to avoid undesirable influences on the measurements. After the measurement of the FRFs (Amplitude and Phase), the natural frequencies were evaluated through program FREQ developed by Lirani (1978) and improved by Baptista ...
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... proving that the stacking sequence has influence on the dynamic behavior of the structure. This was expected since from the Classical Laminate Theory (CLT), the final laminate stiffness is a result of the stacking sequence. It is noticed also that the mode shape related to the vibration at plane (1-2) did not appear, since the experimental set up (Fig. 3) does not allow this measurement. Also in some cases, t he accelerometer was close to a nodal line making it difficult to get the results. Another point to be noticed was that the expected higher frequency of the case 1 on the mode on torsion did not appear clearly. This may be caused by some influence of the 5 th mode (4 th flexural ...
Citations
... M.Topcu et al. [3] studied the dynamic behavior of the laminated composite beam made from woven glass fibre/epoxy prepreg by different three modal analysis techniques theoretically, numerically and experimentally. V.Tita, J. de Carvalho and J. Lirani [4] studied the dynamic behavior of beams were made using the hand-lay-up process. The mechanical properties of the composite were calculated analytically using the simple rule-of-mixtures. ...
In modern engineering applications such as aerial vehicles, composite structures are widely implemented due to their high structural stiffness and very low weight-to-lift ratio. They also enable designers to control their mechanical properties as well as the manufacturing method and fabrication quality to achieve the required structural performance. However, various manufacturing methods and the fabrication process can be considered production imperfections. In this study, an assessment of the fabrication quality for a typical composite structure is implemented. As considered for airplane wings and helicopter blades, a high aspect ratio structure is implemented as a case study. This structure is composed of laminated woven carbon fiber/epoxy resin fabricated using the vacuum bagging production method. To characterize the mechanical properties of the proposed structure, a mechanical tensile test is carried out. An experimental modal analysis via roving hammer test is implemented to examine the dynamic behavior of the proposed structure. To assess the quality of manufacturing and fabrication quality, the obtained natural frequencies are compared with the ones computed using a numerical technique using the Finite Element Method (FEM). The analytical problem using MATLAB had been established to emphasize the experimental results. Results showed that good manufacturing quality is achieved by using the vacuum bagging production method. Also, the experimental results agree well with both the numerical and theoretical results, Which indicates good manufacturing quality.
... They considered the cantilever configuration and found that the E-glass epoxy offers better vibration characteristics compared to the fiber reinforced particle and steel cantilevers. Tita et al [23] conducted an experimental analysis to understand the dynamic characteristics of fiber reinforced composite beams. They considered various stacking sequence for the number of beams and observed that the change in stacking sequence can make a structure made of fiber reinforced composite material more stiff for the same mass, geometry and boundary conditions. ...
... Material properties Glass Epoxy composite[23] ...
In the current scenario, the structures made of composites are drawing attention due to their high spring rate, capacity to withstand high force, reinforcement and optimized mass. Up till now, several materials have been designed and manufactured. The components as well as structures made of these composite materials do expose to dynamic loading during their functions which leads to the failure of the respective component/structure. The dynamic characteristics depend on the material properties, physical dimension, no. of layers, orientation of the fibers and end conditions. Here an analysis is performed to determine the vibration characteristics of multilayer composite beams made of glass epoxy composite. The Cantilever boundary condition is considered. Ten layers are considered. Various stacking are considered with the different fiber orientations. The natural frequency of a multilayer composite beam is sensitive to the length and fiber orientations. As the length and number of layer increase, the natural frequency decreases. The natural frequency for fiber orientation at 90 ⁰ is minimum as compared to other fiber orientations irrespective of the length while the natural frequencies for the 0 ⁰ fiber orientation is more compared to other orientations for out of plane vibrations irrespective of the geometrical dimensions. The natural frequencies for other orientations are more compared to 0 ⁰ orientation for specific modes due to high stiffness in the torsional direction.
... The mechanical behavior of the carbon fiber-reinforced polyamide laminated composites was probed experimentally by Botelho et al. [3] by doing tensile, shear and compressive tests on this laminated structure. Also, the influence of fibers' orientation angle on the natural frequencies and modal damping of the fiber-reinforced laminated beams was investigated by Tita et al. [4] in the framework of experimental and theoretical analyses. Again, Nayak et al. [5] carried out dynamic and static analyses on the initially stressed laminated composite plates with finite element formulation based on higher-order theories. ...
The current paper is devoted to investigate the free and forced vibrational responses of the multi-phase angle-ply laminated nanocomposite beam with focusing on the occurrence of resonance phenomenon. The influence of uniform thermal loading and three-parameter Kerr substrate which can affect the resonance behavior of the structure is surveyed. Utilizing a superior nanofiller with the name of Graphene Oxide (GO) together with the macro-scale Carbon Fibers (CFs) will constitute a novel multi-scale hybrid reinforcement for the polymer matrix. The combination of the Halpin–Tsai micromechanical model and extended rule of the mixture is implemented to estimate the effective properties of this multi-scale hybrid nanocomposite. Refined higher-order beam theory is employed to obtain the displacement fields and then with applying Hamilton’s principle, the governing equations are derived and analytically solved via Galerkin's exact solution method. Also, the presented results are validated with reputed works in open literature. Furthermore, some tabulated and graphical results are provided to reveal the effects of various parameters such as fibers’ orientation angle, weight and volume fractions of reinforcements, different boundary conditions, beam’s slenderness ratio, Kerr substrate parameters, excitation frequency and temperature change on the dynamic behavior of the proposed structure.
... Kompozit malzemelerin ve çatlaklı kompozit malzemelerin doğal frekansları üzerine yapılan çalışmalar incelendiğinde; Tita vd. [12] fiber katkılı kompozit kirişlerdeki katman dizilişinin ve fiber açısının, kirişin doğal frekansına olan etkisini incelemişler ve her iki parametrenin de son derece etkili olduğunu vurgulamışlardır. Atlıhan ve Ergene [13] de delaminasyon ve fiber açısının katmanlı kompozit kirişin titreşim davranışını nasıl etkilediğini analitik ve nümerik olarak incelemişler ve fiber açısı 0⁰ ile 59⁰ arasında iken doğal frekans değerlerinin giderek azaldığı, kritik değer olan 59⁰'den sonra ise artış gözlemlendiği ifade etmişlerdir. ...
Günümüzde kompozit malzemeler sırasıyla fiber ve matris malzemesinin sağladığı yüksek dayanım ve hafiflikten dolayı uzay havacılık, otomotiv, savunma, denizcilik gibi bir çok farklı alanda
tercih edilmektedirler. Kompozit malzemeden üretilen yapılarda meydana gelen çatlakların yapının mekanik ve titreşim özelliklerini etkilediği bilinmektedir. Bu çalışmada, % 50 karbon fiber takviyeli polimer (KFTP) kompozit bir kirişte çatlak bulunup bulunmaması, bulunması durumunda ise 1,2,3,4 ve 5 mm derinliğindeki çatlağın ilgili kirişin titreşim davranışlarını nasıl etkilediği Ansys APDL programı kullanılarak sonlu elemanlar analizi yöntemiyle incelenmiştir. Farklı
çatlak derinliğine sahip ve çatlaksız KFTP kompozit kirişler Ansys APDL programında modellenmiştir. Ayrıca, malzeme özellikleri olarak da kompozit malzemelerin karışım kuralı eşitlikleri ile belirlenen malzeme özellikleri sonlu eleman analizlerinde atanmıştır. 200 mm uzunluğunda, 20 mm genişliğinde ve aynı fiber açılarına sahip her biri 0,5 mm kalınlıkta 6 katmandan oluşan toplam kalınlığı 3 mm olan KFTP kompozit kirişler sol kenarından ankastre mesnetlenmiş, sağ kenarı ise serbest uç olarak bırakılmıştır. Ek olarak, 6 katmandan oluşan KFTP kompozit kirişin fiber açıları da 0⁰, 15⁰, 30⁰, 45⁰, 60⁰, 75⁰ ve 90⁰ olacak şekilde değiştirilerek, fiber açısının çatlaklı ve çatlaksız kirişin doğal frekansına olan etkileri de irdelenmiştir. Elde edilen sonuçlara göre, fiber açısının ve çatlak derinliğinin KFTP kompozit kirişlerin doğal frekans değerlerini genel olarak % 10 ile % 20 aralığında değiştirebildiği, doğal frekansların değişiminde çatlak derinliğine nazaran fiber açısının daha etkili olduğu görülmüştür.
... Aref and Alampalli [14] implemented fiberreinforced polymers (FRPs) to achieve the vibrational mode shapes of bridges consisted from FRPs. Later, both experimental and theoretical ways are implemented by Tita et al. [15] to examine the dynamic behaviors of FRC beams. Zenkour [16] performed a visco-elastic stability analysis on the FRC plates using both classical and higher order plate theories. ...
Present paper is proposed to capture the influences of carbon nanotubes’ agglomeration on the stability behaviors of multi-scale hybrid nanocomposite beams within the frameworks of refined higher order beam theories for the first time. In this research, a mixture of macroscale and nanoscale fillers will be utilized to be dispersed in an initial matrix to possess a multi-scale hybrid nanocomposite. The equivalent material properties are seemed to be calculated coupling the Eshelby–Mori–Tanaka model with the rule of the mixture to consider the effects of carbon nanotubes inside the probably generated clusters while finding the mechanical properties of such novel hybrid nanocomposites. Furthermore, an energy-based approach is implemented to obtain the governing equations of the problem utilizing a refined higher order beam theorem. Next, the derived equations will be solved in the framework of Galerkin’s well-known analytical method to reach the critical buckling load. It is worth mentioning that influence of various boundary conditions is included, too. Once the validity of presented results is proven, a set of numerical examples are presented to explain how each variant can affect the structure’s stability endurance.
... Natural frequencies along with mode shapes for beams with different end conditions are demonstrated. V.Tita [3] performed dynamic tests experimentally using samples by varying the fiber orientations and order of stacking. From the performed experiments it was found that both fiber orientations and stacking order affected natural frequencies and damping. ...
In the present work formulation of the stiffness matrix is carried out for laminated composites Envelope and core angles are taken with three plies with core thickness and envelope thickness varied for cantilever beam widely used in Aircraft structures. The natural frequency of the structure was found using the stiffness formulated for different orientations of core and envelope angles and its effect is investigated for glass epoxy and graphite-epoxy laminated composite beams keeping the density constant. Natural frequencies decrease when the orientation of laminae (either core or envelope) is increased from 0 0 to 90 0. But increasing the orientation of the envelope has a significant effect on natural frequencies when compared to that of the core angle.
... Higher no. of layer leads to significant improvement in term of flexural strength [6]. 45°/-45° plies have a lower frequency in flexural mode but have a higher frequency in torsion mode, in line with Tita et al [15]. However, 45°/-45° plies, 60°/-60° and 90°/90° ply orientation will be ruled out in composite strut bar optimization process due to inferior performance as compared to steel in static loading. ...
Front strut bar is an automotive part commonly used for McPherson suspension system to minimize load on the strut tower by tying both left and right strut with a single bar. By distributing the force acting on a single strut to both strut tower, the strut bar minimizes the chassis flex which improves ride and handling especially during cornering. Therefore, strut bar should be stiffer but lighter at the same time to reduce vehicle weight towards fuel efficiency and lower carbon emission. This research attempts to design a lightweight carbon fiber reinforced polymer strut bar to replace conventional steel strut bar with equivalent stiffness. For validation, a steel strut bar model is analyzed by conducting experimental modal analysis to determine their natural frequencies and the corresponding mode shapes. These results were compared to simulation results. Later, the dynamic behavior of CFRP and the equivalent mode shapes were analyzed and correlated with static loading test results. Combination of different ply orientation and stack sequence results in the design of an optimized carbon fiber strut bar achieved 48% reduction in weight, up to 40% higher natural frequency while improving or preserving the static and dynamic performances compared to the steel strut bar.
... Prashanth Turla (2014) stated that there is negligible variation in ILSS values of carbon and glass epoxy reinforced composite. V. Tita (2003) gives importance of composite applications and manufacturing of composite materials by hand lay up method. ASTM D2344/D 2344M-00 (2006) provides standard specimen and testing configurations and guidelines to conduct a short beam shear test. ...
Present work study the short beam strength of
glass reinforced / epoxy composite materials. The
composite materials are well known by their excellent
combination of high structural stiffness and low weight.
Their inherent anisotropy allows the designer to tailor the
material in order to achieve the desired performance
requirements. The composite lamina is prepared by hand
molding using mixture of Epolam resin and Epolam
hardener. Laminates are prepared with different
thicknesses. Short beam shear tests are carried out with
three point bending test as per ASTM D2344 standards.
Interlaminar shear stresses of samples are evaluated. The
Effect of Fiber laminate thicknesses on shear properties are
observed. .This paper examines the influence of thickness
on ILSS properties of laminated composites. many
structures used in Automobile, Aerospace, Naval and other
Transportation vehicle structural parts are subjected to
various kinds of loads. These structures are further
subjected to bending loads causing Shear stress in the
structures. The purpose of this work is to experimentally
analyze the progressive failure process of laminate
composites subjected to shear loads, Shear loading causes
stresses in the composites, which vary through the
thickness. Shear properties evaluated are Shear strength
and stiffness of the composites system appropriate
conclusions was drawn. Analytical model is developed and
experimental results are validated with the help of
laminated beam theory.
... Vibration analysis of the composite beams is one of the ways of identifying the undetected delamination occurring in layered composite beams [2].In the research, natural frequencies were found to be decreasing with delamination in the beam due to its influence of structural stiffness. Due to the presence of interlaminar shear stresses and deformations, the transverse stiffness [3] of a fiber composite beam under vibrational environment is less compared to its longitudinal stiffness, which promotes fatigue failures. The usage of natural fiber reinforced composite beams is liable to be influenced by its highly anisotropic nature [4] on the weaker stiffness to transverse loadings. ...
High stiffness and high strength to weight ratio are the attributes which make composite a preferred material over any other conventional materials in many engineering applications. The ease of engineering desired material properties by controlling the physical and structural parameters has made it highly preferred while selecting materials for light weight but high strength and durable applications. In this present study a completely new approach is tested with the objective to enhance the strength of a layered composite beam with the use of roller clamps. Authors have not found any other researcher who has initiated any approach in this regard. A roller clamp is used to provide uniform force in the transverse directions of the beam across its width in a line. The free vibration of the clamped cantilever beam is studied and compared its values with the unclamped one. The location of clamp is also varied to observe its effect on the natural frequency. Simulated results for clamped free beams are validated with the published literatures which establishes the acceptability of the design model. The response of clamped beam has shown interesting results indicating an increase in stiffness compared to unclamped beam. The location of clamp also indicates increasing tendency as it gradually move from fixed end to the free end. This approach can be very much useful for enhancing the composite beam stiffness which got degraded due to climatic conditions, impact, delamination or any other reason.
... Aref and Alampalli (2001) implemented fiber reinforced polymers (FRPs) to achieve the vibrational mode shapes of bridges consisted from FRPs. Later, both experimental and theoretical ways are implemented by Tita et al. (2003) in order to examine the dynamic behaviors of FRC beams. Zenkour (2004) performed a viscoelastic stability analysis on the FRC plates using both classical and higher-order plate theories. ...
Application of a newly developed refined higher-order beam theory in the thermal buckling problem of a multiscale hybrid nanocomposite beam is shown here with respect to effect of nanofillers aggregation for the first time. In this research, a mixture of macro and nanoscale fillers will be utilized to be dispersed in an initial matrix to possess a multiscale hybrid nanocomposite. The equivalent material properties are seemed to be calculated coupling the Eshelby-Mori-Tanaka model with the rule of mixture to consider the effects of CNTs inside the probably generated clusters while finding the mechanical properties of such novel hybrid nanocomposites. Furthermore, an energy based approach is implemented to obtain the governing equations of the problem utilizing a refined higher-order plate theorem. Next, the derived equations will be solved in the framework of Galerkin’s well-known analytical method to reach the critical buckling load. It is worth mentioning that influence of various boundary conditions is included. Once the validity of presented results is proven, a set of numerical examples are presented to explain how each variant can affect the buckling behaviors of the structure.
