where, σij denote the stress components and the tensile and compressive allowable strengths for lamina are denoted by subscripts T and C, respectively. XT, YT, ZT denotes the allowable tensile strengths in three respective material directions. Similarly, XC, YC, ZC denotes the allowable compressive strengths in three respective material directions. Further, S12, S13 and S23 denote allowable shear strengths in the respective principal material directions.