The application of a ply-refinement technique to the analysis of microscopic deformation in interlaminar-toughened laminates with transverse cracks

Predictions of a stress-transfer model proposed by McCartney for calculating the stress and displacement distributions in a symmetric laminate having cracks in 90° plies are compared with experimental results. A ply-refinement technique is used where each ply of the laminate is subdivided into layers having the same properties in order that through-thickness variations of the stress and displacement components can be taken into account. The transverse crack-opening displacement and shear deformation near ply interfaces are calculated and compared with the corresponding experimental results. Cross-ply laminates made of two material systems are used in the experiment. One is interleaved CFRP, T800H/3631-FM300, with epoxy resin (FM300) layers about 100 μm thick between 0 and 90° plies. The other is toughness-improved CFRP, T800H/3900-2, with selectively toughened interlaminar layers about 30 μm thick at all the ply interfaces. It is found that the new model with the ply-refinement technique is more accurate than a previous approximate analysis.