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The compressive response of polymer matrix fiber reinforced unidirectional composites (PMC's) is investigated via a combination of experiment and analysis. The study accounts for the nonlinear constitutive response of the polymer matrix material and examines the effect of fiber geometric imperfections, fiber mechanical properties and fiber volume f...
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... typical σ -ε curve of a carbon fiber composite is shown in Figure 3 for the case cor- responding to a fiber volume fraction 10 percent. The σ -ε curve is very irregular, because the carbon fiber composite fails in a progressive manner, quite different from the catastrophic failure of the glass fiber composites. ...
Citations
... Aramid fiber reinforced composites has high strength, with excellent impact energy absorption properties. The compressive failure mechanism in laminated composite materials is involved, sudden and catastrophic as it involves multiple modes of failure like fiber kinking, splitting, buckling, and delamination [7][8][9] . Defang Zhao et al. 10 investigated the flexural properties and failure behavior of CF/PA6 plain-woven laminates with different layers fabricated by the hot compression technique. ...
The mechanical properties and failure behavior of aramid/epoxy composites are studied under static loading conditions. Plain and twill weave fabric structures are used as preform for composite preparation. The hot-pressing molding is applied to prepare laminated composite plates. To find the effect of the fabric weaving patterns on the mechanical performance of the laminated composites, modulus of elasticity, tensile strength, compression strength, short beam shear strength, and flexural strength are investigated by the Universal Testing Machine (UTM) according to ASTM standards. It is found that twill fabric-reinforced composite shows better mechanical performance because yarns long floating length and uniform resin impregnation. An optical microscope image revealed the fracture mechanism under different loading conditions. Delamination is the most common failure mode under any static loading conditions due to aramid fiber and matrix low interfacial bonding.
... Although composite materials have excellent mechanical properties, their fracture mechanism characteristics are still not very developed [3]. The composite fracture characteristics have been extensively investigated regarding the debonding, delamination, and fibre compressive kinking mechanism [4][5][6]. Otherwise, the effects of geometry design parameters have been studied and can be found in some literature. Feraboli et al. [7] investigate the effect of geometry design parameters on the crush behaviour of the carbon fibre epoxy tubes and C-channels. ...
During an evacuation, the tsunami lifeboat should be able to withstand the possible external loads that might be occurred, such as collisions, violent crashes, and capsizing events. Special structural reinforcement and improvement, such as a crash absorber, are attached to prevent damage due to the impact load. Therefore, this article focuses on the crushing behaviour of the tsunami lifeboat crash absorber made of the multi-cell glass fibre-reinforced composite panel. The effect of the cross-section geometry design of the cell on the damage mechanism and energy absorption behaviour was investigated. The explicit dynamic finite element method was used to identify the multi-cell configuration’s crashworthiness performance. Experimental studies such as tensile and three-point bending tests were conducted to define the material properties and validation of the FE model. The simulation results showed that the explicit dynamic finite element method has effectively estimated the crash absorber crushing damage. The circular cross-section has shown the most significant crash absorption capability compared to the others, namely the honeycomb, the square, and the triangular cell. Furthermore, the 4CSM laminate type has revealed a lower energy absorption than the 4WRC45 and 4WRC laminates. Otherwise, the study exhibits that the cross-sectional geometry and the laminate type significantly influence the crash absorber performance for improving the tsunami lifeboat crashworthiness.
... Fleck et al. 13 proposed a bending theory incorporating the finite fiber bending resistance to predict the post-peak response. Lee and Waas 14 and Kyriakides et al. 15 analyzed it broadly. Sun and Wanki Jun, 16 DeMorais and Marques, 17 and Chung and Weitsman 18 further studied the bending theory. ...
A micromechanics based analytical model under combined loading for unidirectional composites has been developed. The peak compressive load predicted from the combined loading analytical model is compared with the experimental results of carbon epoxy pultruded rod having a volume fraction 60%. The specimens were subjected to torsional load under rotational control and longitudinal compressive load using displacement control. The model captures the compressive strength of the composite subjected to remotely applied shear stress. It is observed that the peak compressive strength of the composite decreases linearly with an increase in shear stress. The analytical modeling results are in good agreement with the experiment data. The analytical model and the experimental results are used to find the effect of shear stress on longitudinal compressive loading. The peak compressive strength caused in the presence of applied shear stress and compressive load and the effect of shear on the compressive strength are predicted using a 2D analytical model in this study. The model results are confirmed using experimental data from combined loading.
... Intra-laminar failure modes can be fiber or matrix-related. Axial tensile failure occurs due to fiber rupture [8,9,10,11,12], whereas fibers fail and form kink bands under compression due to local instability [13,14,15,16,17]. Matrix mode damage and failure comprise cracking due to transverse tension or compression [18,19,20,21,22,23], shear loading [24,25,26] or combined loads. ...
... In total, the proposed set of failure criteria (fiber and matrix modes) requires five constants, which is consistent with the number of elastic constants for a quasi-isotropic material. Fig. 2. 16 shows the inplane failure envelopes of selected failure criteria compared with micro-mechanical studies by Sun et al. (2019). The quadratic stress criterion (identical with Hashin for σ 22 > 0) has been used in previous EST versions. ...
... 16: Ultimate strengths of actual and virtual specimens. ...
As composite materials are increasingly used in the aerospace industry, there is a rising demand for analysis tools of these advanced composite structures. Validated analysis methods and associated software can help reduce and derisk physical testing as well as explore a broader design space. This can lead to faster development cycles and potentially better structural designs. However, the failure mechanisms in a composite structure are highly complex and challenging to predict. Hence, there is still little trust in the current progressive failure analysis tools for composites.
To address this challenge, we have developed a novel high-fidelity framework that addresses many of the modeling challenges such as failure mode interactions, delamination, splitting, crack density, non-linearity and probabilistic modeling. The framework is built on the commercial software Abaqus and utilizes Python scripting and user subroutines to incorporate meshing procedures and user-defined material definitions. The backbone of the model is the semi-discrete modeling strategy that can be seen as a good compromise between continuum and discrete methods. In sum, the proposed enhanced semi-discrete damage model (eSD2M) toolset consists of three main components that work seamlessly together. It comprises a smart meshing strategy with failure mode separation, a new version of the enhanced Schapery theory (EST) with a novel generalized mixed-mode law and a novel probabilistic modeling strategy. These components make the model efficient in capturing failure modes such as matrix cracks, fiber tensile failure and delamination, as well as their interactions with high fidelity, while taking material non-uniformities into account.
The proposed semi-discrete modeling framework was demonstrated with several test cases, comprising various layups, material systems and geometries under quasi-static tensile loading. In this work, we have investigated unnotched and notched cross-ply laminates, scaled open-hole laminates and +/-45 laminates. The eSD2M was not only capable of capturing the complex damage progression, but also provides insights and explanations for some of the failure events observed in the laboratory. Furthermore, the framework efficiently integrates failure mode predictions with probabilistic modeling and enables Monte-Carlo simulations to predict the ultimate failure strength with good accuracy as well as its scatter.
... Aramid fibre-reinforced composites have high strength, and excellent impact energy absorption properties. However, under the compressive loading, it showed sudden and catastrophic failure mechanism as involves multiple failure modes such as fiber kinking, splitting, buckling, and delamination [7][8][9] . Kyriakydes et al. [10] have observed regularly spaced in-plane kink bands with a width of 1~1.5 mm during the composites compression testing. ...
In the present study, the mechanical properties and failure behavior of aramid/epoxy plain and twill weave laminated composites have been investigated. Aramid fiber plain and twill woven fabric and epoxy resin was used to prepreg preparation. The hotpress molding technique and fabric resin(epoxy) prepreg were used to prepare laminated composite plates. This research aims to find the effect of the fabrics weaving patterns on the mechanical performance of the laminated composites. For this purpose, compressive strength, short beam shear strength, and flexural strength were investigated by the Universal Testing Machine (UTM) according to the ASTM standards. All tests were performed in warp directional loading. Finally, the fracture mechanism was observed from the images taken by the optical microscope. According to test results, it was found that twill fabric reinforced composites have better mechanical performance compared to plain fabric composites. Due to the long floating length, low crimp percentage, and uniform resin impregnation was generated in twill fabric composites. On the other hand, plain fabric composites have inadequate mechanical performance because of the high crimp percentage and uneven matrix impregnation at the interlacement region.
... (Rahul et al., 2019). Lee and Waas (1999) have also identified from their experiments that longitudinal fiber splitting, or brooming is the most common form of failure for glass fiber composites in the 10% to 30% fiber volume fraction range. ...
A substantial amount of kenaf fiber research has been carried out recently to incorporate more sustainable materials into the production process. For many years, scientists have studied the properties of kenaf and the hybrid composites it may form. Composites made from kenaf and synthetic fibers were the focus of the majority of the study. Similarly, the researchers discovered mechanical characteristics as a fundamental truth. Despite this, earlier research on particular properties has not permitted using kenaf composites for load-bearing purposes. Nevertheless, kenaf composites can significantly influence car exteriors and other vital applications, even if their impact characteristics are only studied in other materials science disciplines. Due to this, dynamic failure behavior and mechanism of unidirectional kenaf and kenaf/glass hybrid composite compressive response were examined. Therefore, both composite specimens were loaded compressively under static and dynamic loading at a strain rate range of 0.1/s to 1700/s. The results showed that the failure behavior and mechanism of kenaf and kenaf/glass hybrid composite were different under static and dynamic loadings. Shear banding failure occurred at 60 degrees for kenaf composites. In contrast, kenaf/glass composites were fractured longitudinally along the fiber direction under static loading. Glass fibers in hybrid composites were more vulnerable to damage under microscopic analysis because they carried most loads. Consequently, the kenaf fibers in hybrid composites were less damaged than those in kenaf composites, which had fiber breakage, fiber splitting, and fiber-matrix debonding.
... Interestingly, these PET fibers were not fractured at the two ends of a kinked band which is significantly different from conventional polymer composites. In CFRPs or GFRPs, compressive failure in a UD composite was typically characterized by the micro buckling of the fibers forming a band with fractured fibers at two ends [234][235][236][237][238][239]. In addition, Schneider et al. [42] also showed that longitudinal compression can also lead to a large expansion of self-reinforced UD PET composites. ...
Thermoplastic polymer fiber-thermoplastic polymer matrix composites (PPCs) or polymer-fiber-reinforced polymers(PFRPs), often recognized as self-reinforced or single polymer composites, are potential candidates for future advanced polymer composites because of various advantages (e.g., recyclability, formability, low-cost, ultra-lightweight, environmental friendliness, etc.). The manufacturability and mechanical behavior of these composites compared to conventional carbon-/glass-/aramid-fiber-reinforced polymers is of great interest to the composites community, but there are a limited number of studies in this area.
To this end, this paper reviewed fabrication methods with different processing parameters and mechanical behavior of uni-/multi-directional thermoplastic PPCs featuring continuous thermoplastic polymer fibers from limited data in the literature. It was shown that most specific behaviors (normalized by density) of these materials in various loading conditions (e.g., quasi-static tension/shear/flexure, tension-tension fatigue, and out-of-plane impacting, etc.) are comparable to or better than glass-/aramid-fiber-reinforced polymers. Particularly, the specific ductility in the foregoing conditions outperforms all the carbon-/glass-/aramid-fiber-reinforced polymers. Thermoplastic PPCs with remarkable performance can be achieved through several uncomplicated methods (e.g., film stacking, hot compaction, powder and solution impregnations, matrix infusion and injection molding, additive manufacturing, etc.), which have some similarities to the methods used for carbon-/glass-/aramid-fiber-reinforced polymers. Moreover, several opportunities and challenging problems of thermoplastic PPCs were summarized at the end of this review paper. Efficient solutions may require countless efforts in the composites community to further strengthen the performance and understanding of thermoplastic PPCs for wide applications in various engineering fields in the future.
... Micromechanical approaches generally assume a periodic arrangement of alternating fibers and matrix layers in the models. To verify the effects of this idealistic modeling assumption about fiber topology, Lee and Waas [72] modeled non-uniform fiber spacing and found it to have an insignificant effect on the prediction of the compression strength. Following this work, Yerramalli and Waas [136] compared modeling of 2D plane strain and 3D model of a cylindrical specimen. ...
Because of their excellent specific strength and stiffness properties, fiber-reinforced polymers (FRPs) have become increasingly material of choice for advanced industries such as aerospace and wind turbines. One of the design limiting factors in FRPs is their lower compression strength in comparison to their tensile strength. Microbuckling (MB) is the dominant failure mode in unidirectional FRPs under predominant compression loads. The main factors dictating failure under compression dominated loads are the fiber misalignment and the nonlinear material behavior. Because of high sensitivity of MB failure to the fiber misalignment, the MB strength shows uncertainty. To enable reliable failure prediction, a quantification of the strength uncertainty is required. The current investigation aims for a probabilistic prediction of MB failure under axial compression and combined compression-shear loads. Using a newly in-house developed combined loading fixture, a statistically significant number of specimens was tested under aforementioned load cases. Using the experimental strain measurements, a probabilistic failure envelope in strain space is presented. Results of the axial compression load case are interpreted in the context of the notion of the effective misalignment angle using an analytical model. A failure envelope in stress space is derived using an analytical solution for the combined compression-shear load cases and the effective global misalignment angle calculated from the measurements. Other experimental aspects of the problem are also investigated such as the material characterization and measurements of the fiber misalignment. To represent the fiber misalignment in numerical models for the prediction of MB strength while preserving the spatial correlation information, the spectral representation method is employed in this investigation. A large number of realizations were developed based on spectral densities calculated from the measurements of the fiber misalignment. The numerically determined probabilistic failure envelopes in stress and strain spaces are presented with lower percentiles of distributions of failure. The failure enveloped are also compared against classical failure criteria from the literature to highlight the limitations of the classical criteria. Since the sizes of the model and the experimental specimen were different, a comparison of numerically predicted strengths against experimentally obtained results under the axial compression loads was performed on the basis of a scaling law. A discussion on differences in the shape of the failure envelopes is provided. Conclusions are drawn at the end and an outlook for further research on the topic is given.
... Budiansky and Fleck [6] took the strain hardening effect of the matrix into consideration when analysing the fibre kinking. Lee and Waas [7] studied the compressive strength and failure modes of a unidirectional glass fibre reinforced polymer (GFRP) and carbon fibre reinforced polymer (CFRP). A finite element (FE) model was presented to study the effect of initial misalignment angles of the fibres. ...
... Later, splitting was identified in the compressive failure mechanisms of the carbon fibre reinforced composites by Oguni and Ravichanran [11]. Lee and Waas [7] investigated the effect of different fibre volume fractions on the compressive failure mechanisms of unidirectional glass fibre and carbon fibre composites. A combined fibre kinking and splitting failure mode was reported at different fibre volume fractions. ...
This paper presents an experimental investigation on the mechanisms of damage onset and evolution in unidirectional PEEK/AS4 carbon fibre reinforced thermoplastic (CFRTP) composites subjected to off-axis compressive loadings. A test fixture was designed to prevent buckling, splitting, and end collapsing of the specimens during the test. A series of compression tests were conducted with specimens of various off-axis angles. The displacement and strain fields of all specimens during the tests were evaluated by the digital image correlation (DIC) method. In combination with the DIC results, the influence of the off-axis angles on the failure mechanisms and nonlinear stress–strain responses were analysed. The corresponding failure mechanisms were examined by scanning electron microscopy (SEM). The fracture angles of the tested specimens were evaluated and analysed according to Puck’s theory. The off-axis compression failure envelope based on LaRC05 and Hashin criteria was presented and compared to the experimental results. It was shown that the LaRC05 criterion can provide accurate predictions when the off-axis angle is larger than 15°. The complex failure mechanisms were analysed to better understand the effect of ductility of the thermoplastic matrix to the composites. The series of tests provide an experimental failure envelope in combined stress states and can be used for the evaluation of failure theories and the criteria of thermoplastic composites.
... Yerramalli and Waas (2003) from their experiments showed a deterioration in compressive strength of UD glass/carbon hybrid composites at all hybrid ratios for a total fiber volume fraction of 30%. Also, they observed a change in failure mode from carbon fiber kinking (Lagoudas and Saleh, 1993;Budiansky and Fleck, 1994;Hsiao and Daniel, 1996;Yerramalli and Waas, 2004;Davidson and Waas, 2016) to longitudinal splitting Waas, 2002a, 2003;Lee and Waas, 1999) when the glass fiber content increased. Pan and Postle (1996), reported a negligible influence of the matrix properties on hybrid tensile strength. ...
... The elastic properties of the constituents of the hybrid composite (Lee and Waas, 1999 (Cavalcanti et al., 2019). The influence of stacking sequence is also observed in the case of hybrid synthetic/natural fiber composites (Mohanavel et al., 2021). ...
... where glass fibers surrounded by carbon and vice versa ( Fig. 1a& b respectively), an unsymmetrically distributed glass and carbon fibers shown in Fig. 1c and an intermingled glass and carbon random fiber distribution (Fig. 1d). Radius of the glass fiber (r g ) is 0.01205 mm and the carbon fiber (r c ) is 0.0025 mm (Lee and Waas, 1999). The kinking analysis methodology is followed in the current work similar to that of the literature (Yerramalli and Waas, 2004;Koppisetty et al., 2019). ...
The sensitivity of the in-situ resin response in the composite to the variability in fiber distribution combined with the changes in hybrid fiber ratio and total fiber volume fraction are studied using finite element analysis. Highly stiff carbon fibers and less stiff glass fibers are arranged differently in the micromechanical composite models to represent various fiber distributions. The results from the post buckling analysis indicate that the in-situ resin behavior could be altered with varying the fiber distribution in the composite. This significantly affected the hybrid composite performance under compression loading. In the case of symmetric fiber arrangement, the respective positions of glass and carbon fibers determined the onset and progress of local resin plasticity. When both the fibers were off centre, relatively there was an early collapse of the hybrid composite. A qualitative match in the prediction of compressive strength of hybrid composites with available experimental data in literature is also presented.
