Holmes, John W.6; Liu, Liu7; Sørensen, Bent F.1; Wahlgren, Søren5
1 Department of Wind Energy, Technical University of Denmark2 Composites and Materials Mechanics, Department of Wind Energy, Technical University of Denmark3 Beihang University4 Beijing Institute of Technology5 Risø National Laboratory for Sustainable Energy, Technical University of Denmark6 Beihang University7 Beijing Institute of Technology
An experimental apparatus utilizing double cantilever beam specimens loaded with uneven bending moments was developed to study the mixed-mode fatigue crack growth in composites. The approach is suitable when large-scale bridging of cracks is present. To illustrate the testing method, cyclic growth of delaminations in a typical fibre-reinforced polymer composite was investigated under a constant cyclic loading amplitude. Pure mode I, mode II and mixed-mode crack growth conditions were examined. The results, analysed using a J-integral approach, show that the double cantilever beam loaded with uneven bending moments configuration provides a robust approach to investigate the fatigue crack growth of composites for pure mode and mixed-mode cracking. A steady-state crack growth regime was observed for mode I and mixed-mode loading. For mode II loading, steady-state was absent, and a progressively decreasing crack growth rate observed. In addition to details concerning the equipment, a general discussion of the development of cyclic bridging laws for delamination growth in the presence of large-scale bridging is provided.
Journal of Composite Materials, 2014, Vol 48, Issue 25, p. 3111-3128