Comparison of progressive damage between thermoset and thermoplastic CFRP composites under in-situ tensile loading

The in-situ damage progression in three carbon fibre reinforced cross-ply composite systems under tensile loading is examined, namely, carbon IM7/epoxy, carbon IM7/PEEK and carbon AS4/polyamide. Epoxy is a thermoset polymer while polyether ether ketone (PEEK) and polyamide are thermoplastic. The thermoset composite is manufactured in an autoclave using matrix pre-impregnated with unidirectional carbon fibres, while the thermoplastic composites are manufactured using laser-assisted automated tape placement (LATP). A tensile microtester is mounted in a scanning electron microscope to observe the damage mechanisms in-situ under tensile loading. X-ray computed tomography scans are also carried out to examine porosity in the material systems. IM7/epoxy and IM7/PEEK displayed similar damage mechanisms: transverse cracking in 90° plies followed by fibre breakage in the 0° plies at the fillets and interlaminar fracture. AS4/polyamide displayed a different mechanism with fibre fracture appearing first in the 0° plies, followed by transverse cracking and interlaminar fracture. The effect of autoclave treatment on the materials manufactured by LATP has also been examined.