The effect of residual stress on transverse cracking in cross-ply carbon-polyetherimide laminates under bending

Transverse cracking in cross-ply laminated composite beams is investigated as a function of the level of thermal residual stresses. A range of residual stresses was obtained by varying the lay-up of the beam considered. Carbon-and glass-reinforced polyetherimide was chosen for their capacity to produce high levels of thermal stress. The experimental work focussing on the occurrence of the first transverse crack in 5 types of laminated beam is reported. The data obtained is analysed using both continuum mechanics and fracture mechanics principle. The results show that for this particular case, the first transverse crack can be described with a maximum stress criterion. The authors also suggest that the data obtained can be used to define a critical energy release rate for the occurrence of a transverse crack in mode I. The experimental data also show a relation between the critical energy release rate and the strength transverse to the fibres.