Stiffness Changes in Fiber-reinforced Polymeric Matrix Laminates Caused by Intralaminar Damage

In the present paper the damage of fiber-reinforced polymeric matrix laminates is considered with the aim to examine their mechanical properties. The damage mode in the form of intralaminar cracks (“primary matrix cracking”) is described in terms of second order, symmetrical damage tensor by Vakulenko and Kachanov. It allows for considering the orientation of the defects, which is determined by the orientation of the constituent layers. The crack discontinuity parameter is estimated in frame of the linear elastic fracture mechanics. To describe the changes of the mechanical properties of a body, namely longitudinal Young modulus and Poisson ratio, caused by the damage the constitutive relations by Adkins, based on the theory of irreducible integrity basis and polynomial functions are employed. Theoretical results obtained due to above procedure are compared with the experimental results for carbon/epoxy laminates of cross and angle-ply stacking sequences.