Mechanical properties and failure behaviour of carbon fibre-reinforced polymer composites under the influence of moisture

The effect of moisture on the mechanical properties and the failure behaviour of fibre-reinforced polymer composites was investigated. Moisture was introduced into the specimens by immersion in distilled water. Three materials were investigated, which were all reinforced with continuous carbon fibres. Two thermosetting matrices (unmodified and toughness-modified epoxy) and one thermoplastic matrix (polyetheretherketone) were used. The results showed that the absorbed moisture decreases those properties of both epoxy-based composites which were dominated by the matrix or the interface. The influence of water on the fibre-dominated values, as well as on the properties of the thermoplastic material, was not detectable. The distinct fall of the matrix- and interface-based values due to moisture can be ascribed to the weakening of bonding between fibre and matrix and softening of the matrix material. (C) 1997 Elsevier Science Limited.