Moisture absorption in glass-fibre/epoxy laminates with transverse matrix cracks

Moisture uptake in cross-ply glass-fibre/epoxy laminates containing matrix cracks in transverse plies has been investigated. Experimental results are compared to finite-element calculations and an approximate analytical model . The experimental results show that crack closure may occur early in the a bsorption process. This is confirmed by finite-element calculations which i ndicate that even small amounts of absorbed moisture (average moisture conc entration < 10% of saturation level) may result in crack closure. As a resu lt of crack closure, moisture penetration through the crack channels is pre vented. The experimentally observed small differences in moisture uptake be tween cracked and uncracked laminates thus support the crack-closure hypoth esis. Direct microscopic observations of crack closure versus time furtherm ore confirm the mechanism. A previously developed analytical model has been extended to include the case of crack-closure effects. The model compares favourably with experimental observations. (C) 1999 Elsevier Science Ltd. A ll rights reserved.