Abstract

The main objective of this paper is to develop a method to predict the crack length and crack growth rate in unidirectional carbon fiber/epoxy composite as a function of temperature variation. In order to measure the crack length and crack growth rate, a new analytical method by applying experimental procedure data is developed. By the novel analytical method, relations are achieved to predict the crack length and crack growth rate in unidirectional carbon fiber/epoxy composite. Finally, by using these relations, comparison between crack length and crack growth rate between two thermal fatigue experiments is done. The results have shown that the crack growth rate in bidirectional carbon fiber/epoxy composite is very higher that in unidirectional carbon fiber/epoxy composite. Investigations regarding the achieved results have shown that the higher crack growth rate is due to the mismatch between the coefficients of thermal expansion in two directions of bidirectional carbon fiber/epoxy composite. The two different coefficients of thermal expansion may cause stress concentration in the inter-laminar plies of the composite and therefore may cause higher crack growth rate.

Key words: Crack growth rate, thermal fatigue, temperature variation, carbon fiber, epoxy, composite material.