Slow crack growth in laminate composites via in-situ X-ray tomography and simulations

To assist in damage tolerant analyses for composites, a compact tension T650/5320 laminate composite was characterized via in-situ X-ray tomography during cyclic loading. A 3D image processing analysis of the fatigue crack growth illustrated the various damage mechanisms, including intralaminar cracking (dominant) and delamination facilitating ply cross-over. A finite element analysis was conducted to compute the change in stored energy per cycle, dU/dN, which showed that the experimentally observed intralaminar crack growth rates, per ply, collapsed to a single dU/dN curve, where direct observations of fiber bridging were associated with a reduction in crack growth rate for the influenced ply. •In-situ X-ray tomography was conducted on a [-45/+45/-45]s composite.•3D image processing enabled visualization of the fatigue crack growth mechanisms.•Crack growth rates correlated with direct observations of active damage mechanisms.•A finite element analysis calculated the change in energy per cycle in each ply, dU/dN.•The per ply crack growth rates versus dU/dN curves were consistent.