Fibre break failure processes in unidirectional composites: evaluation of critical damage states

Abstract

Earlier work which successfully modelled the kinetics of fibre breakage in unidirectional composites under monotonic tensile loading has been extended to quantify the kinetics of fibre failure during both monotonic and sustained tensile loading. In both cases, failure was seen to occur when a critical density of large clusters (more than 16 fibres are broken within the representative volume element) of fibre breaks developed. However, in monotonic loading failure occurred very quickly after the first development of these large clusters, whereas under sustained loading the composite could accommodate greater levels of large clusters because of the lower applied load. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'.

A Stochastic Model Based on Fiber Breakage and Matrix Creep for the Stress-Rupture Failure of Unidirectional Continuous Fiber Composites 2. Non-linear Matrix Creep Effects

“…These models do not focus on the nature of the lifetime distribution over time given the applied stress level. Of particular interest are such bundle models under LLS, several of which are discussed in [42][43][44][45][46][47][48][49][50][51][52][53][54][55]. The first two models [42,43] are predecessors to the model we develop later and involve both theory and experiments on the strength and creep-rupture of seven-fiber, micro-composites of carbon fibers in an epoxy.…”

“…In a sequence of papers by Bunsell et al [47][48][49][50][51][52][53][54][55], a model has been developed that considers the lifetime of unidirectional carbon fiber-epoxy composites under sustained loads, and where the main application is filament wound pressure vessels. In [47] the work begins with numerical modeling of the micromechanisms of fiber-to-fiber load transfer resulting from WP fiber failures.…”

“…In later works [51][52][53][54][55], these authors extend their RVE modeling in terms of the formation and evolution of small clusters of breaks called of i-plets of various sizes (e.g., twoplets, four-plets, eight-plets, 16-plets, 32-plets, . .…”

“…The focus is on critical damage states in tension testing [51], sustained loading over time [52], and laminated structures [53]. The work in [54,55] looks deeper into critical damage states in terms of iplets as precursors to imminent failure and on the possibility of determining a lower threshold for applied composite stress below which the lifetime becomes infinite [55]. Overall, the impressive multi-scale model developed in [47][48][49][50][51][52][53][54][55] is computationally intensive so that Monte Carlo replications beyond a few 100 samples are currently impractical.…”

“…The work in [54,55] looks deeper into critical damage states in terms of iplets as precursors to imminent failure and on the possibility of determining a lower threshold for applied composite stress below which the lifetime becomes infinite [55]. Overall, the impressive multi-scale model developed in [47][48][49][50][51][52][53][54][55] is computationally intensive so that Monte Carlo replications beyond a few 100 samples are currently impractical. Except in [55] where 100 replications were performed, the focus was largely on mean lifetime behavior, rather than the form of lifetime distributions, particularly in their lower tails.…”