Failure phenomena in multi-fibre model composites .1. An experimental investigation into the influence of fibre spacing and fibre-matrix adhesion

Multi-fibre model composites were used to study the fracture process of carbon/epoxy composites in uniaxial tension. The investigations were focused on experimentally determining the influence of interfibre spacing and fibre-matrix adhesion on the amount of fibre-fibre interaction taking place, i.e. fibre failure due to increased stress concentrations caused by a fracture site in an adjacent fibre, visible through the alignment of fracture sites. In addition to in situ microscopic observations, a quantitative criterion for fibre-fibre interaction was employed. Results showed that, in case of good fibre-matrix adhesion, fibre-fibre interaction takes place at interfibre spacings of less than nine diameters. Furthermore, it was found that the level of fibre surface treatment significantly influences the amount of aligned fracture sites.