Prediction of the mechanical properties of three-dimensionally braided composites

This paper describes research concerning the mechanical properties of three-dimensionally braided composite materials. A fiber-inclination model is developed and extended to predict strength. The analysis is based upon the transverse isotropy of unidirectional laminae and the Tsai-Wu polynomial failure criterion. In addition, tensile performance tests were conducted on 4-step composite specimens of three types of braid pattern (1 x 1, 3 x 1 and 1 x 1 x 1/2F). A comparison between theoretical and experimental results is also made. The results show that the braider angle has a significant influence on tensile modulus and strength. The transverse angle has an obvious influence upon Poisson's ratio and axial yarns can improve the tensile properties of braided composites. (C) 1997 Elsevier Science Limited.