Delamination Induced by Low-Velocity Impact and Influence of Water Absorption on Delamination and CAI of FRPs.

Abstract

An investigation of water absorption effects on the impact fracture mechanism and compression after impact (CAI) behavior was conducted using carbon fiber reinforced thermoplastic matrix composite (AS-4/PEEK) and aramid fiber reinforced epoxy matrix composite (K-49/828), which have a quasi-isotropic stacking sequence of [0°/±45°/90°]2s. The impact tests were carried out using a falling weight tester. Impact-induced internal damage was observed with a scanning acoustic microecope (SAM). The delamination area was evaluated by the subtraction method. The delamination area of AS-4/PEEK was much smaller than that of a CF/epoxy composite (MM-1/982X), and no influence of water absorption was observed. In contrast, that of K-49/828 was the largest, and the impact-load-induced delamination area was increased by water absorption. In the case of AS-4/PEEK the compressive strength of the impacted specimen at 3 J was the same as that of a virgin specimen, and no influence of water absorption was observed. Impact energy affected the CAI strength of K-49/828 as much as that of MM-1/982 X. The fracture surface was closely examined using a scanning electron microscope, and the fracture mechanisms were discussed.