Stiffness degradation in cross-ply laminates damaged by transverse cracking and splitting

In contrast to the few existing theoretical models (Highsmith and Reifsnider, ASTM STP 1986;907:233-251; Hashin, Trans ASME J Appl Mech 1987;54:872-879; Daniel and Tsai, Comp Eng 1991;1(6):355-362; Tsai and Daniel, Int J Solid Structures 1992;29(24)3251-3267; Henaff-Gardin et al., Comp Structures 1996;36:113-130; 1996;36:131-140), based on the consideration of a repeated laminate element defined by the intersecting pairs of transverse cracks and splits, the new approach for evaluating the stiffness degradation in [0m/90n]s laminates due to matrix cracking both in the 90° (transverse cracking) and 0° (splitting) plies employs the Equivalent Constraint Model (Fan and Zhang, Composites Science and Technology 1993;47:291-298). It also uses an improved 2-D shear lag analysis (Zhang et al., Composites 1992;23(5):291-298; 1992;23(5):299-304) for determination of stress field in the cracked or split lamina and In-situ Damage Effective Functions for description of stiffness degradation. Reduced stiffness properties of the damaged lamina are found to depend explicitly upon the crack density of that lamina and implicitly upon the crack density of the neighbouring lamina. Theoretical predictions for carbon and glass fibre reinforced plastic cross-ply laminates with matrix cracking in the 90° ply revealed significant reduction in the Poisson's ratio and shear modulus due to additional damage (splitting) in the 0° ply.