Aramid fibers; a multifunctional sensor for monitoring stress/strain fields and damage development in composite materials

A multifunctional non-destructive technique, based on the Raman response of aramid fibers, is employed for (a) assessing the interface integrity and the overall stress distribution in a unidirectional Kevlar 29®/epoxy composite (b) measuring the stress concentration and its development with applied load in Kevlar 49®/epoxy composites incorporating a circular notch and finally, (c) determining the strain arising in 0° plies due to partial and full crack growth within the θ° plies in multidirectional 0°/θ°/0° composites. It is shown that this technique can be used effectively to study the damage development in composite materials that arise from the presence of different length scale discontinuities.