Mode-II Interlaminar Fracture Toughness of Carbon/Epoxy Laminates

The interlaminar fracture behaviour of unidirectional carbon/epoxy composites has
been studied under flexural loading by using end-notched flexure (ENF) specimens.
GIIc values were calculated as total fracture toughness energy at the maximum
load sustained by the materials as the delamination extended. The results showed
that high temperature moulding systems (XHTM45) have the highest GIIc values well
above 1000 J/ m2 . For medium temperature systems (MTM), GIIc has also increased
significantly after post cure. For compression strength after impact (CSAI), the behaviour
to a certain extent is related to that found for GIIc tests. Comparison of the GIIc values with
CSAI also indicated a relationship between two test results. SEM Micrographs revealed
their excellent delamination resistance as good crack stoppers with the evidence of
strong fibre/matrix interface. Dynamic mechanical analysis (DMA) indicated the
increased Tg and modulus retention of the LTM and MTM prepregs after post-curing at
elevated temperatures. The failure mechanisms seem to be different for different tough
matrix materials and appear to be strongly dependent on the cure and post-curing conditions.
This is particularly noticeable for curing at 135°C and 80°C of medium and low
temperature moulding systems.

Citation:
Saidpour, H., Barikani, M. and Sezen, M. (2003) ‘Mode-II Interlaminar Fracture Toughness of Carbon/Epoxy Laminates’ Iranian Polymer Journal, 12 (5), pp. 389-400..