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.