Mode-II fatigue fracture of wood-composite bonded interfaces

In this paper, the shear mode (mode-II) fatigue fracture of wood-FRP bonded interfaces using a unique linear tapered end-notched flexure (TENF) specimen is presented. A tapered beam on elastic foundation (TBEF) model developed for design and analysis of the TENF specimens is first reviewed. A combined analytical and experimental fracture mechanics method is developed to evaluate the fatigue fracture behavior of wood-FRP bonded interfaces under mode-II constant cyclic loading conditions. By applying the compliance method with the unique feature of TENF specimen (i.e., a constant compliance rate change) and modifying the original Paris Law equation, the fatigue fracture behavior of wood-FRP interface under Mode-II loading is effectively evaluated. The possible effects of loading variables (i.e., load ratio, waveform, and frequency) on crack propagation rate are investigated. Both the load ratio and frequency have shown pronounced influences on crack propagation rate; while the waveform has negligible effect. A modified Paris Law equation is proposed to include both the frequency and load ratio effects. The present method can be used for other similar studies of interface fracture of dissimilar materials, and the finding of this study can eventually lead to the development of design guidelines for hybrid material bonded interface.