Towards a Novel Defect Severity Model for Compressive Failure Analysis of Unidirectional Composites

Abstract

Compressive failure of high-performance unidirectional (UD) carbon fibre polymer composites is driven by fibre kinking. Fibre kinking is known to be controlled by the shear strength of the supporting matrix material. Consequently, compressive strength is significantly reduced as the fibre waviness increases, as postulated by Argon in the 1970’s.\xa0 In this paper, additional fibre architectural features affecting the compressive strength of UD composites, and to be considered in strength analyses of UD NCF reinforced carbon fibre composites, are discussed. The current work comprises development and use of a method for characterization of fibre misalignment in CFRP. Transfer of fibre misalignment measurements into finite element models and subsequent compressive strength analyses is conducted. These analyses reveal a very strong relationship between compressive strength and fibre waviness in accordance with Argon’s model. In addition, geometrical features such as the size of zones with large fibre misalignment are also found to influence the compressive strength of the studied composites.