Stress Transfer From the Matrix to the Fibre in a Fragmentation Test: Raman Experiments and Analytical Modeling

The stress transfer properties of the fibre/matrix interface in the single fibre fragmentation test were investigated. Two carbon fibre-resin systems involving epoxy-sized and unsized fibres, were examined. Axial fibre stress data at resolutions of the order of one micron, were obtained with the technique of Remote Laser Raman Microscopy. Subsequent analytical modeling of the data was performed using a Bessel-Fourier Series stress analysis approach. The analysis provides a nearly exact solution for the stress field in the fragmentation test and simultaneously accounts for damaged or imperfect interfaces through the use of an interface parameter Ds. All data were fit using a two zone model in order to account for the propagation of interfacial damage as a function of applied strain. The fitting process was used to determine D (i) s , the interface parameter in undamaged zones, D (d) s , the interface parameter in the damage zones near fibre breaks, and ld, the length of the damage zones, all as a function of applied strain. The interface parameter in the undamaged zones, D (i) s , was independent of applied strain. We claim D (i) s is a good property for comparing fibre/matrix interfaces and the most relevant property for predicting the role to the interface in real laminates.