说明：  使用umat计算蔡吴失效准则，计算失效指数If，弹性模量和强度参数见表3.1.
(Compute the Tsai-Wu failure index IF on each layer of Example 3.8 (p. 151) using a UMAT subroutine, available in umatS8R5.for. The elastic moduli and strength values for the lamina are given in Table 3.1)