Abstract

Polymer-matrix tapered composite laminates with internal taper are considered in the present thesis. Appropriate finite element models for the tapered laminates are developed using quadratic isoparametric elements. Both the rectangular and triangular isoparametric elements are employed in the model in order to obtain accurate solutions. Singularity elements are used to model the vicinity of the crack tip in the laminate. Appropriate computational methods including the displacement extrapolation method and virtual crack extension method are employed for the determination of the following fracture parameters: stress intensity factor, energy release rate, and J-integral. In order to determine the response to random excitation, the normal mode method is employed in conjunction with the finite element method. The associated computer programs are developed using FORTRAN ® and MATLAB ® programming languages. The fracture behavior and the dynamic response to stationary random excitation of different types of internally tapered laminate are investigated based on the finite element model. The locations of delamination initiation are predicted based on the stress analysis results and the Von Mises failure criterion. The energy release rates and J-integral values corresponding to the delamination at the critical location of the laminate are computed. The effects of taper angle and the laminate configuration on the fracture behavior and the random vibration of the laminate are determined. The probability of failure is then calculated and the use of this information in determining the location of failure initiation is demonstrated.