Literature review on imperfection of composite laminated plates

A composite material can be defined as a combination of two or more materials that gives better properties than those of the individual components used alone. In contrast to metallic alloys, each material retains its separate chemical, physical, and mechanical properties. The two constituents are reinforcement and a matrix. The main advantages of composite materials are their high strength and stiffness combined with low density when compared to classical materials. Micromechanical approach is found to be more suitable for the analysis of composite materials because it studies the volume proportions of the constituents for the desired lamina stiffness and strength. It is found that the manufacturing processes are responsible of many defects which may arise 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. The above mentioned defects tend to propagate as the lamina is loaded causing an accelerated rate of failure. The experimental and theoretical results in this case tend to differ. Hence, due to the limitations necessary in the idealization of the lamina components, the properties estimated should be proved experimentally.