MICROSCOPIC FATIGUE FAILURE PROCESS IN INTERLEAVED AND TOUGHNESS-IMPROVED CFRP CROSS-PLY LAMINATES

Microscopic damage progress in CFRP cross-ply laminates under tensile fatigue loading was measured by the replica technique, Material system s were interleaved CFRP, T800H/3631-FM300 and toughness-improved CFRP, T800H/3900-2, with selectively toughened interlaminar layers. The dam age parameter, the transverse crack density, was presented. A Paris la w model was proposed, which related the cyclic strain range and the nu mber of cycles at the transverse crack initiation. Based on the experi mental data, a variational stress analysis combined with the modified Paris law was conducted to model the transverse crack multiplication.