Moisture absorption and interfacial failure in aramid/epoxy composites

Raman spectroscopy has been used to monitor strain profiles that developed along Twaron aramid fibres with different surface treatments due to non-mechanical stresses during exposure to moisture at the ambient temperature. Using test specimens of different configurations, two aspects of the hygrothermal ageing could be addressed: (1) the mechanism, rate and extent of the water ingress into composite constituents, and (2) the stability of fibre/matrix interfaces. The diffusion characteristics for the matrix have been found to be in line with data reported in the literature. The diffusion coefficient for the fibre is estimated to exceed that for the matrix. Debonding of fibres which had received a surface treatment indicates a vulnerability of the interfaces in aramid/epoxy composites to hygrothermal effects. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.