Low temperature transitions in fibre reinforced polymers

The results of an investigation into the effect of absorbed moisture on the low temperature transitions of several polymer composite systems are reported. The longitudinal shear modulus and loss factor were measured over a range of temperature, from -150 to +20 degreesC, both before and after conditioning in a hot, wet environment. In all cases, the presence of absorbed water had a plasticising effect, lowering the temperature at which the transition took place and increasing the peak loss factor. Even allowing for differences in measurement frequencies, the transition temperatures of the composites were found to be greater than those of the corresponding matrix resins. This suggests that the resin in the composite did not necessarily have the same properties as the bulk unreinforced resin. (C) 2001 Elsevier Science Ltd. All rights reserved.