INTERFACIAL SHEAR-STRESS DISTRIBUTION IN MODEL COMPOSITES, .1. A KEVLAR-49 FIBER IN AN EPOXY MATRIX

The technique of Laser Raman Spectroscopy has been applied in the study of aramid fibres, such as Kevlar 49, and aramid/epoxy interfaces. A linear relationship has been found between Raman frequencies and strain upon loading a single Kevlar 49 filament in air. Model composites of single Kevlar 49 fibres embedded in epoxy resins have been fabricated and subjected to various degrees of mechanical deformation. The transfer lengths for reinforcement have been measured at various levels of applied tensile load and the dependence of transfer length upon applied matrix strain has been established. Finally, by balancing the tensile and the shear forces acting along the interface, the interfacial shear stress (ISS) distribution along the embedded fibre was obtained.