Plastic kinking in polymer matrix composites and interface debonding in metal matrix composites.

摘要

This thesis deals with mechanical failure in unidirectional fiber composites. It is written in two parts the first addresses plastic kinking in carbon fiber/polymer matrix composites, and the second concerns interface debonding in ceramic fiber/metal matrix composites.Part I. Plastic kinking. Plastic kinking is the dominant compressive failure mechanism in ductile polymer composites. It occurs in three distinct stages kinking initiation, transient kinking and band broadening. Plastic kinking is controlled by their shearing properties, because the composites are soft in shearing. Based on this observation each stage of plastic kinking is modeled analytically. The model for transient kinking involves a new kinematics of band rotation and widening with increasing fiber rotation within the band. The peak stress and band broadening stress are predicted the latter is the lower bound of the first. The effects of initial fiber misalignment and shearing response are investigated. A bridging law for kink band propagation is obtained from micromechanics analysis of plastic kinking. It is used to analyze kink band propagation and the propagation stress is predicted between peak stress and band broadening stress. All three stresses are useful parameters in structure design.Part II. Interface debonding. Interface debonding occurs in