EXPERIMENTAL CHARACTERIZATION OF MICROSCOPIC FAILURE PROCESS UNDER QUASI-STATIC TENSION IN INTERLEAVED AND TOUGHNESS-IMPROVED CFRP CROSS-PLY LAMINATES

The microscopic failure process in CFRP cross-ply laminates under quas i-static tensile loading has been investigated at ambient temperature and 80 degrees C. Material systems considered were interleaved T800H/3 631-FM300 and toughness-improved T800H/3900-2 with selectively toughen ed interlaminar layers. In situ observation of the microscopic failure process was conducted by using an optical microscope (OM) and a scann ing acoustic microscope (SAM) with an 'instrumented tensile loading de vice' together with the replication technique. The transverse crack de nsity was measured as a function of the applied laminate strain. On th e basis of the above data, a variational stress analysis and a probabi listic approach were used to calculate the transverse crack density as a function of laminate strain. Failure mechanisms after transverse cr acking were also discussed. (C) 1997 Elsevier Science Limited.