The effect of interphase toughness on fibre/fibre interaction in graphite/epoxy composites: an experimental and modelling study

Abstract

Fibre/fibre interaction in composite materials is a very important micromechanical phenomenon that dictates the composite mechanical behaviour especially the toughness and failure process. A number of models have been developed to predict the fibre/fibre interaction in composite materials, but none of the existing models has considered the effect of interphase toughness on fibre/fibre interaction. In this study, micro-Raman spectroscopy (MRS), with the ability to measure strain in graphite fibres with a spatial resolution of 2 µm, was used to measure fibre/fibre interaction in graphite/epoxy model composites with three different interphases. An energy-based model was used to calculate the strain energy release rate (Gi) for the three interphases used in this study. The three interphases, unsized, sized, and PMMA coated, yielded strain energy release rates of 40, 30, and 10 J m −2 respectively. Using the values calculated for strain energy release rate of the interphase and interfacial crack length, the energy-based model predicated stress concentration factor values in agreement with those experimentally measured.

Raman Spectroscopy of nanomaterials: How spectra relate to disorder, particle size and mechanical properties

“…22 and Ref. [458]), stress concentration factors [454,456e 458,460,462,468]), ineffective lengths 33 (IL) [458], the interfacial fracture energy G i [462] or the Coulombian friction coefficient (the proportionality factor between s radial and t ci ) [415] can be derived.…”

Non-destructive mechanical characterization of SiC fibers by Raman spectroscopy

“…The method is already used on model Carbon/Epoxy composites [35][36][37][38][39][40] and applicability to ceramic-and metal-matrix-composites has been demonstrated recently [41][42][43][44][45][46][47] despite the high consolidation temperatures which can induce significant structural evolution (by fiber/matrix interdiffusions) and complicate the study. Even though bonds anharmonicity is usually considered as a simple perturbation to the harmonic case, it has a very significant influence on the physical behavior of materials.…”

Analysis of Strain and Stress in Ceramic, Polymer and Metal Matrix Composites by Raman Spectroscopy

“…The results, obtained through this method on carbon fibres-reinforced (ªmodelº) polymer matrix composites, have been discussed by Schadler et al, [12,23] Amer et al [35] and Galiotis et al. [36] For a fibre embedded in a transparent matrix (a model composite in many case), the axial strain distribution can be determined by taking Raman spectra of the fibre at different points along its length.…”

“…From the ISS profiles, matrix yielding, interface debonding, frictional load... can be determined. Other measured parameters are Stress Concentration Factors (SCFs; the ratio of the fibre stress divided by sample loading), [35,37±43] the loading length, [36] the interfacial stress G i [35] or the coulombian friction coefficient (the proportionality factor between r radial and ISS). Raman spectroscopy micron scale resolution makes it possible to assess the so called ªenvironment effectº on stress in composites (fibre volume fraction and/or neighbouring damaged fibre, [38±42] cracks/holes, [44] sizing [45] or water absorption).…”

“…Following the pioneer works of Anastassakis and of Gardiner on the study of stressed silicon and oxide films, respectively, [14] Galiotis [11] and Young [10] were the first to demonstrate that the stress-induced-Raman shift could be used to follow the deformation of aramid and carbon fibres in polymer-matrix (model) composites. The results, obtained through this method on carbon fibres-reinforced (ªmodelº) polymer matrix composites, have been discussed by Schadler et al, [12,23] Amer et al [35] and Galiotis et al. [36] For a fibre embedded in a transparent matrix (a model composite in many case), the axial strain distribution can be determined by taking Raman spectra of the fibre at different points along its length.…”