Flaw-Bridging in Composite Materials

Abstract

The implicit assumption in the modelling of fibre reinforced materials is that they are defect free. Defects in fibre-reinforced materials can be initated during their service life and can result a variety of damage phenomena. This paper focuses on the mathematical treatment of the case where a defect is present in the matrix of a uni-directionally reinforced composite but the fibres themselves exhibit continuity across the matrix crack. This results in a processes that is referred to as “flaw bridging”. The amplification of the stress intensity factors at the boundary of the matrix crack can be influenced by the bridging action, to the extent that if the the fibres are inextensible, the stress intensity factor can be suppressed. This paper examines the flaw bridging action in a unidirectionally reinforced composite, which can be reduced to the solution of a Fredholm integral equation of the second kind. The mathematical treatment is used to examine the influence of the bridging action on the crack opening mode stress intensity factors at the boundary of a penny-shaped crack.

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