Document Type : Research Article
Abstract
Unidirectional composite materials are among the most important composite materials and have many applications in daily life. The angle of the fibers of the lamina is an important factor in controlling properties of the composite materials as well as the sequence of layers. The aim of this study is to obtain the best laminate with good mechanical properties (strength and stiffness) with the selection of the appropriate failure theory. This study was conducted to carbon /epoxy laminate with different angles (0°,25°,30°,50°,60°,75°,90°) by three theories of failure (maximum stress theory, Tsai-Hill theory and Hashin theory). The strength ratio depending on the last ply failure load was found by using MATLAB program of five layers of laminates and by applied the classical laminate theory. Seventy-two combinations of laminates were obtained with not repeating the layers that have the same angles. The theoretical results showed a large deviation between the theoretical and practical results of the laminate [0/30/60/90/50] for the three theories by (24%). While, there was convergent deviation of the laminate [30/90/060/25] by (11.9% and 9.7%). As for the laminate [60/30/0/90/75], the deviation between the theoretical and practical results was according to the Hashin and Tsai Hill theories by (9.7%). As for the deviation in relation to the maximum stress theory was by (24.3%).