Stress transfer around a broken fiber in unidirectional fiber-reinforced composites considering matrix damage evolution and interface slipping

Abstract

A shear-lag model is applied to study the stress transfer around a broken fiber within unidirectional fiber-reinforced composites (FRC) subjected to uniaxial tensile loading along the fiber direction. The matrix damage and interfacial debonding, which are the main failure modes, are considered in the model. The maximum stress criterion with the linear damage evolution theory is used for the matrix. The slipping friction stress is considered in the interfacial debonding region using Coulomb friction theory, in which interfacial clamping stress comes from radial residual stress and mismatch of Poisson's ratios of constituents (fiber and matrix). The stress distributions in the fiber and matrix are obtained by the shear-lag theory added with boundary conditions, which includes force continuity and displacement compatibility constraints in the broken and neighboring intact fibers. The result gives axial stress distribution in fibers and shear stress in the interface and compares the theory reasonably well with the measurement by a polarized light microscope. The relation curves between damage, debonding and ineffective region lengths with external strain loading are obtained. stress transfer, shear-lag, damage evolution, fiber composite PACS: 62.20.Mk, 46.50.+a, 81.05.Qk

Methods and models for fibre–matrix interface characterisation in fibre-reinforced polymers: a review

“…Following the initial shear-lag analysis, the extended SLMs include models with a matrix carrying tensile stress [116], elastoplastic matrix [117,118], debonded fibre–matrix interfaces [119,120] and matrix with linear damage evolution along with interfacial slipping [121]. The shear-lag analyses have also been supplemented with fibre-strength statistical models [120,122,123] to predict composite failure.…”

Fibre-direction strain measurement in a composite ply under quasi-static tensile loading using Digital Volume Correlation and in situ Synchrotron Radiation Computed Tomography

“…Remote from local discontinuities/cracks, microstructural anomalies and/or other sources of strain gradients, it may be expected that the Voigt [60] isostrain assumption applies to the material and the strains reported by DVC are a good estimate of both fibre and matrix deformation; with the latter being the dominant contributor, as it contains the fiducial markers used to achieve reliable correlation (Appendix A). However, immediately adjacent to fibre breaks, steep strain gradients are expected, and may be influenced by the following mechanisms, or combinations thereof: (1) matrix plastic yielding [21], [22], [23] (2) fibre-matrix interfacial debonding (with slippage) [22], [23], [61], [62], [63], [64] (3) matrix microcracking [64], [65], [66], [67], and (4) fibre unloading and spring-back [3], [68], [69], [70]. The relative displacement of the edge-enhanced fibre ends [42] is also expected to contribute to the measured strain field.…”

“…Nonetheless, surface experiments (e.g. based on Raman spectroscopy [22], [23] and/or photoleasticity [61], [62], [63], [64]) report that such damage mechanisms take place under specimen tensile loading, albeit in model microcomposites with a sparse fibre distribution. Whether the knowledge from microcomposites can be reliably transferred to macro-composites containing bundles of fibres remains unknown [1].…”

“…In terms of the underlying micromechanics, two factors are identified as potential contributors to growth in the strain transfer length with increasing applied load: (1) plastic yielding of the matrix, and (2) progressive propagation of fibre-matrix interface debonding, which both exert similar effects on the strain transfer [1], [21], [22], [23], [61], [62], [63], [64]. This is supported by the sharper gradients at the break plane associated with a higher load, which suggests that local damage is evolving.…”

Application of electric resistance method in characterizing the ability of load transfer of interphase in single-fiber composite

“…It directly influences the stress transfer and distribution between the fiber and matrix of the composite material so as to affect its mechanical properties. By traditionally supervising the molding process first and then analyzing the thermal residual stress 5,6 and damage 7 of the composite material with the interphase, it is hard to get the transfer properties of the interphase. Many evaluations have been applied to the interface performance evaluation.…”