Effects of thermal cycling on damage progress in interlaminar-toughened CFRP cross-ply laminates

Effects of thermal cycling on transverse cracking behavior in interlaminar-toughened CFRP cross-ply laminates are investigated. Material systems used are T800H/3631 carbon/epoxy composite with FM300 epoxy resin film between 0 degrees/90 degrees interface (T800H/3631-FM300) and T800H/3900-2 with polyamide particle-dispersed layers at every ply interface. The laminate configurations are cross-ply (0/90(n)/0) where n = 4, 8 and 12. The laminates are thermally cycled between -70 degrees C and 150 degrees up to 100 cycles. No damage is observed by the thermal cycles. After thermal cycling, the laminates are subjected to static tensile loading at room temperature. The transverse crack density in 90 degrees ply is measured as a function of the laminate strain by using the replica technique. It is found that transverse crack behavior depends on the number of thermal cycles. Transverse crack density increases as the number of thermal cycles increases. Change in thermal residual strain in 90 degrees ply is measured as a function of the number of thermal cycles by measuring the deformation of an unsymmetric laminate. The effects of thermal cycles on the transverse cracking are characterized by a micromechanical model considering the thermal residual stresses.