Statistical inference about stress concentrations in fibre-matrix composites

Abstract

In previous papers about statistical properties of composite materials, assumptions have been made about both the statistical and mechanical properties of the component fibres and matrix, and these have been used to calculate properties of the composite. The results are sensitive to the assumed stress concentration factors and length of stress overload region, and there remains considerable interest in characterizing them. In this paper, it is shown how experimental data on the fibres and composites may be used to make inferences about these properties of the material. The statistical technique employed is numerical maximum likelihood, but this involves detailed combinatorial calculations and is therefore highly computationally intensive. The method is illustrated using experimental data on hybrid composites consisting of carbon fibre tows embedded in glass-epoxy composite, particular emphasis being placed on the consequences of varying the distance between the carbon fibre tows.