Relationships between microstructures and fracture energies in carbon fibre/PEEK composites

Abstract

The aim of this investigation was to characterize the fracture surfaces of a series of similar composites, and to relate the features observed to the fracture modes. The materials used in this study were based on the ICI material APC-2, being uniaxially aligned composites of carbon fibre in a matrix of poly-ether-ether-ketone, peek. The fracture method chosen for this comparative study was to propagate cracks in the weakest plane of the materials, so that the samples split under the wedging action of a blade driven into the material. The fracture surfaces are thus representative of cracks propagating parallel to the fibres and normal to the prepreg layers. Fracture energies were obtained from analysis of the geometry of the crack without the need for any load measurements using a specially developed technique, the razor blade test 1,2. The fracture surfaces were prepared from the slivers of material split off in the test, and were examined in the scanning electron microscope ( sem). They were thus taken from the same region of material which yielded the data on fracture energy. The principal microstructural factors identified as being significant were the matrix ductility and the fibre/matrix adhesion.