Propagation Path of Interlaminar Cracks in Continuous Fiber-Reinforced Plastics under Remote Mode I Loading.

Abstract

The propagation path of cracks in continuous fiber-reinforced plastics (FRP) under remote mode I loading was studied. Two FRP models are used in the two-dimensional boundary element analysis:the inhomogeneous FRP model which has a laminated structure composed of matrix and fiber, and the three-layered FRP model in which a thin matrix layer is sandwiched between homogenized FRP plates. The matrix stress intensity factors and the non-singular T-stress, Tm, were calculated for a crack parallel to the fiber direction in a matrix layer of these models. When the residual stress in the matrix layer is negligible, Tm is negative for typical FRP composites. For long cracks, the absolute value of Tm for the inhomogeneous FRP model is larger than that for the three-layered FRP model, and the ratio of these values is independent of fiber properties. A crack is predicted to propagate along the centerline of the matrix layer of FRP composites without the matrix residual stress because of a negative Tm value and the sign of the mode II matrix stress intensity factor. The effects of the residual stress, the height of the cracked matrix layer, and the crack length on the crack propagation path were discussed on the basis of the results of the present analysis.