Failure phenomena in two-dimensional multi-fibre microcomposites, Part 2: A Raman spectroscopic study into the influence of inter-fibre spacing on stress concentrations

Raman spectroscopy is used to determine the influence of inter-fibre spacing on the stress concentration factor (SCF) resulting from a fibre break in a two-dimensional (2-D) carbon/epoxy microcomposite. Microcomposites with an inter-fibre spacing varying from 0.8–19.0 fibre diameters (f) have been investigated. The SCF was found to decrease from a value of 1.26 at an inter-fibre spacing of 0.8f to a value of 1.06 at an inter-fibre spacing of 10.4f. The experimentally found variation of SCF with inter-fibre spacing was compared to some analytical models available in the literature. It was found that none of the models is able to describe the experimental data adequately. The effect of the SCF on the failure process is also discussed. At relatively small inter-fibre spacings the SCF is sufficiently high to cause further fibre failure in neighbouring fibres resulting in alignment of fibre breaks. At increasing inter-fibre spacing the decrease in SCF results in a decreasing influence of the initial fibre break on the progressive fibre failure process and the failure process becomes more random.