Damage mechanics characterization of transverse cracking behavior in high-temperature CFRP laminates

Transverse cracking under tensile loading in high-temperature CFRP, carbon/BMI (bismaleimide), G40-800/5260, has been investigated experimentally. Carbon/epoxy, T800H/3900-2, composite laminates are also examined for comparison. Both material systems have toughened-interlaminar layers. Laminate configurations are [0/90]s, [0/902]s, [±45/90]s and [±45/902]s for G40-800/5260, while [0/90]s and [±45/90]s for T800H/3900-2. In all laminates, the first microscopic damage observed is a 90° ply transverse crack. In [±45/90n]s type laminates, cracking in 45°ply and delaminations are also observed. The cracking behavior is quantified by measuring crack densities as a function of the laminate strain. The difference between the damage progress near the 90° ply transverse crack tips between the material systems are observed. Damage mechanics analysis is used to predict 90° ply transverse cracking based on both the energy and stress criteria. The present analysis can be used as a means of characterization of the transverse cracking resistance of a material, which will be helpful in ranking materials.