Dynamic failure of curved interfaces in composite and bonded polymer materials under quasi-static loading
Demirkan Coker (METU), Denizhan Yavas (METU-Ankara), Burak Gozluklu (Turkish Aerospace Industries)
Dynamic Behavior of Materials
Tue 2:40 - 4:00
Salomon 101
Failure of curved weak interfaces is important in bonded joints, curved composite laminates and earthquake faults. Crack growth in curved weak interfaces may occur dynamically as a result of curvature and loading even under quasi-static loading conditions. In this paper, dynamic crack growth along curved interfaces under quasistatic loading is investigated experimentally and computationally in unidirectional graphite-epoxy laminates and in bonded L-shaped PMMA plates. The effect of initial crack length on the stability of the crack growth is examined. In the experimental study, a unique testing fixture with a sliding platform is designed to create a displacement loading perpendicular to one of the arms in a curved beam. The full-field optical techniques of digital image correlation and photoelasticity are used in conjunction with a high speed camera in order to visualize stress and strain fields around the interface crack. In the computational study, debonding at the interface of the curved interface is modeled using dynamic (explicit) finite element analysis in conjunction with Xu-Needleman cohesive zone model with a pure vertical displacement loading to reflect the same loading condition as the experiment. Experimental and finite element analysis results are found to be in agreement in terms of load-displacement behavior, stress distribution, and crack tip speeds. Stable and unstable crack growth regimes, depending on the pre-crack length, are identified in agreement with energy release rate calculations. In the unstable crack growth regime, crack tip velocities at the material wave speeds are observed.