An investigation into the damage development and residual strengths of open-hole specimens in fatigue

• Published in: Composites. Part A, Applied science and manufacturing Applied science and manufacturing, 2015-02, Vol.69, p.266-278
• Main Authors: Nixon-Pearson, O.J., Hallett, S.R.
• Format: Article
• Language: English
• Subjects: A. Carbon-fibre; B. Fatigue; B. Fracture; Brittleness; Crack propagation; Damage; Fatigue failure; Fibre; Laminates; Residual strength; Stacking; Tomography; X-ray computed tomography
• ISSN: 1359-835X; 1878-5840
• DOI: 10.1016/j.compositesa.2014.11.013

An extensive experimental program was carried out to investigate and understand the sequence of damage development throughout the life of open-hole composite laminates loaded in tension–tension fatigue. Quasi-isotropic carbon/epoxy laminates, with stacking sequence [452/902/−452/02]S, [45/90/−45/0]2S and [45/90/−45/0]4S were examined. These were selected on the basis that under quasi-static loading the [452/902/−452/02]S configuration exhibited a delamination dominated mode of failure whilst the [45/90/−45/0]2S and [45/90/−45/0]4S configurations showed a fibre dominated failure mode, previously described as “pull-out” and “brittle” respectively. Specimens were fatigue loaded to 1×106 cycles or catastrophic failure, which ever occurred first. A number of tests were interrupted at various points as the stiffness dropped with increasing cycles, which were inspected using X-ray computed tomography (CT) scanning. A static residual strength program was carried out for run-out specimens of each configuration.