Fatigue damage assessment of unidirectional GRP and CFRP composites

Morteza Panbechi, Ryerson University

Date of Award

2005

Degree Type

Thesis

Degree Name

Master of Applied Science (MASc)

Department

Mechanical Engineering

First Advisor

A Varvani-Farahani

Abstract

The present thesis has developed an energy-based critical plane fatigue damage parameter to assess the fatigue damage of unidirectional GRP and CFRP composites. The proposed model is based on the physics and the mechanism of fatigue cracking within three damage regions of the matrix (I), the fiber-matrix interface (II), and the fiber (III) in unidirectional GRP and CFRP composites as the number of cycles progresses. The model involves the shear and normal energies calculated from stress and strain components acting on (i) a relatively ductile matrix, (ii) the matrix-fiber interface, and (iii) the unidirectional brittle fibers. For the regions III, and I the cracking is dominantly based on the maximum shear stress and the maximum normal principal stress, respectively and fatigue damage was assessed based on the Varvani-Farahani damage approach, For region II, the damage progress along the matrix-fiber interface was evaluated based on the Plumtree-Cheng approach.

The proposed fatigue damage analysis has addressed the cracking and damage progress within three regions over the life of unidirectional GRP and CFRP composites and showed a good capability in unifying the experimentally obtained fatigue lives with various off-axis angles and stress ratios as compared with other well-known damage criteria available in the literature.