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A Study on Different Failures of Composite Materials
— Composites are the important engineering materials made from two or more different materials, which has significantly different physical and chemical properties and which also remain distinct and separated at the microscopic level within finished structure. This material provides better mechanical properties than the parent metals. Composite materials have shown boundless engineering application where strength to weight ratio, cost effectiveness and ease of fabrication are mainly required. Composites include a wide range of the products for different application ranging from aerospace, sports, electronics industries, construction, automobile components, furniture and insulation panels made from different fibers, and textiles. It is observed that many defects which may arise from composite materials in fibers, matrix and lamina. These defects, if they exist include misalignment of fibers, cracks in matrix, non uniform distribution of the fibers in the matrix, voids in fibers and matrix, delaminated regions, and initial stress in the lamina as a result of its manufacture and further treatment. These defects tend to propagate as the lamina is loaded creating an accelerated rate of failure. This paper presents a study and analysis of different failures commonly seen in different composite materials.
A Review Of Failure Of Composite Materials
2012
Composite materials are ideal for aerospace applications due to their high strength to weight ratio and their excellent fatigue resistance. Fiber reinforced Composite is widely used in light weight structures for different applications. The main properties that describe a composite material are the engineering constants and the strength properties of a single unidirectional lamina that make the laminated structure. The experimental evaluation of these properties is quite costly and time consuming because they are functions of several variables such as the individual constituents of the composite, fiber volume fraction, packing geometry and fabrication processes. Hence, analytical models to predict these properties were developed by researchers to aid the design of composites. In recent years numerous failure theories have been proposed and are available to the composite structural designer. Object of this review is to gather the available guide lines for theoretical models of failur...
A Survey of Macroscopic Failure Criteria for Composite Materials
Journal of Reinforced Plastics and Composites, 1984
Popular failure criteria of fiber-reinforced composite materials are described and compared. These criteria are empirical and should only be judged from the standpoint of the fitness to data and the ease of application. The criteria for orthotropic plies of unidirectional composites are extensions of those for isotropic materials. The quadratic criteria are considered to be the most suitable for both isotropic and composite materials. Macroscopic criteria are essential for design and for providing guidelines for materials improvements. Strictly speaking, failure criteria for multidirectional laminants are valid up to the first-ply failure envelope; i.e., before transverse cracking and delamination occur. Finally, conditions for fully optimized ply properties are easily derived from the quadratic failure criterion.
A comparative study of failure criteria applied to composite materials
International Journal for Simulation and Multidisciplinary Design Optimization, 2008
This article presents an analytical and numerical investigation of the failure loads, successive failures and failure modes of laminated beams. Two simulations were developed to model various composites behaviours under transverse static loading. Progressive failure analysis has been carried out in linear and elastic range. For the two simulations, the first order shear deformation theory with shear correction factor and the finite element method have been used respectively. The main objective of this paper is to evaluate the overall damage and successive failure for different laminates obtained by failure criteria and then to conduct a comparative study of the commonly used failure criteria. Various failure criteria have been studied to predict the load, when the weakest lamina fails under flexural bending test. After the failure of the weakest ply, the stiffness is reduced to account for fibre or matrix failures. The failure criteria are tested with various stiffness reduction models. Comparisons are made between the failure loads, successive failures, failure modes, macroscopic curves and the total behaviour curves obtained by the various failure criteria used.
Journal of Composite Materials-2013-Kaddour-925-66
This article draws to a conclusion the results from the co-ordinated study known as the Second World-Wide Failure Exercise (WWFE-II). It contains an objective assessment of the performance of 12 leading failure criteria for predicting the response of fibre-reinforced polymer composites when subjected to 3D states of stress. Twelve challenging test problems (Test Cases) were defined by the organisers of WWFE-II, encompassing a range of materials (polymer, glass/ epoxy, carbon/epoxy), lay-ups (unidirectional, angle ply, cross ply and quasi-isotropic laminates) and various 3D stress states (various triaxial strength envelopes, through-thickness and shear loading, and stress-strain curves). A systematic comparison has then been conducted between 'blind' predictions (i.e. without access to the experimental results beforehand) made for each Test Case by the originators of each theory and previously obtained experimental results for each Test Case. In-depth quantitative and qualitative ranking procedures have been employed to identify the strengths and weaknesses of each theory, and the overall effectiveness of each theory as a potential design tool. The theories are grouped according to their degree of maturity and ability to predict accurately the 3D behaviour of composites. The results from this study provide unique information to the community, the intent being that it will form a guide for the selection of the most appropriate failure theory for use in a given design situation.
Failure modes of fibre reinforced composites: The effects of strain rate and fibre content
Journal of materials science, 1998
The many aspects of high speed response of fibre reinforced composite materials have received the attention of a large number of investigators. Nevertheless, the understanding of the mechanisms governing failure under high speed loadings remain largely unknown. The effect of rate and fibre content on failure mechanisms was investigated by viewing fractured surfaces of tensile specimens using a scanning electron microscope (SEM). Tensile tests were conducted on a woven glass/epoxy laminate at increasing rates of strain. A second laminate (with random continuous glass reinforcement) was tested in tension at varying fibre volume fractions in order to ascertain the relationship between fibre content and failure mechanisms. The results suggest a brittle tensile failure in fibres of the woven laminate. In addition, the matrix was observed to play a greater role in the failure process as speed was increased, resulting in increased matrix damage and bunch fibre pull-out. The results also indicated that increasing the fibre volume fraction increased the likelihood of a matrix dominated failure mode.
Matrix failure in composite laminates under tensile loading
Composite Structures, 2016
The failure envelope of the matrix in composite laminates under tensile loads has not received much attention in literature. There are very little to no experimental results to show a suitable failure envelope for this constituent found in composites. With increasing popularity in the use of micromechanical analysis to predict progressive damage in composite structures, it is important that matrix behaviour under tension is modelled correctly. In this paper, the authors present and test a new biaxial specimen design to investigate tensile matrix failure in composite structures. Through the use of micromechanical analysis, the authors developed a method in which the matrix stresses at failure can be extracted. Comparing to the existing off-axis test, it was shown that the presented specimen design and test methodology can improve the accuracy of the obtained matrix failure stresses, i.e., the matrix failure envelope for EP280 resin. Additionally, the results indicate that matrix failure takes place earlier than that predicted by von-Mises failure criterion and that the 1st Stress Invariant criterion can better predict matrix failure under tensile loading.
In polymer matrix composites (PMCs) manufacturing processes can induce defects , e.g., voids, fiber misalignment, irregular fiber distribution in the cross-section and broken fibers. The effects of such defects can be beneficial or deleterious depending on whether they cause failure suppression or enhancement by localized deformation processes e.g., crazing, shear yielding and fiber-matrix debonding. In this study, a computational approach is formulated and implemented to develop solutions for general boundary-value problems for PMC microstructures that accounts for micromechanics-based constitutive relations including fine scale mechanisms of material failure. The defects considered are voids, and the microstructure is explicitly represented by a distribution of fibers and voids embedded in a polymer matrix. Fiber is modeled as a linearly elastic material while the polymer matrix is modeled as an elastic-viscoplastic material. An improved macromolecular con-stitutive model that accounts for rate, pressure and temperature dependence on yielding, small-strain softening and large-strain hardening. Damage is simulated by implementing a new micromechanical craze model, developed to account for craze initiation, growth and breakdown. Critical dilatational energy density criterion is utilized to predict fiber-matrix debonding through cavitation induced matrix cracking. An extensive parametric study is conducted in which the roles of void shape, size and distribution relative to fiber in determining damage initiation and evolution are investigated under plane strain tension. Results show there are significant effects of voids on microstructural damage as well as on the overall deformational and failure response of composites.
Effect of Defects on Progressive Failure Behavior of Plain Weave Textile Composites
Materials, 2021
Various types of internal defects occur during manufacturing and handling of composite materials. It is practically impossible to manufacture composite structures without defects, making it crucial to understand the effect of defects on their failure behavior to maintain structural safety. In this work, the effect of pre-defects on the failure behavior of plain weave textile composites was studied. Unit cell configurations with symmetric, in-phase, and shifted fiber tow arrangements were considered. Inter-laced warp and fill tows and matrix pockets of plain weave unit cells were modeled in three-dimensional finite elements, and cohesive elements were inserted between all bulk elements to account for the fracture modes of the fiber and matrix direction failure of warp and fill tows, matrix pocket failure, and interface failure. Unit cell models containing pre-defects of voids, tow-matrix pocket separation, warp-fill tow separation, and cracks in the warp and fill tows were analyzed, ...