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

in contrast to the few existing theoretical models (Highsmith and Reifsnide r, ASTM STP 1986;907:233-251; Hashin, Trans ASME J Appl Mech 1987;54:872-87 9; Daniel and Tsai, Comp Eng 1991;1(6):355-362; Tsai and Daniel, Int J Soli d Structures 1992;29(24)3251-3267; Henaff-Gardin et al., Comp Structures 19 96;36:113-130; 1996;36:131-140), based on the consideration of a repeated l aminate element defined by the intersecting pairs of transverse cracks and splits, the new approach for evaluating the stiffness degradation in [0(m)/ 90(n)](s) laminates due to matrix cracking both in the 90 degrees (transver se cracking) and 0 degrees (splitting) plies employs the Equivalent Constra int 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., Composite s 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 d amaged lamina are found to depend explicitly upon the crack density of that lamina and implicitly upon the crack density of the neighbouring lamina. T heoretical predictions for carbon and glass fibre reinforced plastic cross- ply laminates with matrix cracking in the 90 degrees ply revealed significa nt reduction in the Poisson's ratio and shear modulus due to additional dam age (splitting) in the 0 degrees ply. (C) 2000 Elsevier Science Ltd. All ri ghts reserved.