Compression testing of pultruded carbon fibre-epoxy cylindrical rods

Abstract

The fibre waviness inherent in conventional prepreg laminatessignificantly reduces their compressive strength. This waviness canbe reduced through the use of unidirectional fibre rods. In thiswork, the development of a new test procedure and specimen design isreported that was used to determine the compressive properties ofpultruted T300/828 and IM7/828 carbon fibre-epoxy unidirectionalrods at room temperature. The IM7/828 system demonstrates a highercompressive strength than the T300/828 composite due to strongerfibres used and fewer manufacturing defects. Since the fibres as intension primarily carry the compressive load, the final fracture ofthe rods occurs when the fibres fail. Post-failure examinationreveals that failure of the fibres is microbuckling-induced. This isa bending failure as a consequence of buckling. Other events such asfibre-matrix debonding (splitting) and matrix yielding do not bythemselves cause the final failure, but they facilitate fibrebuckling by reducing the lateral support for the fibres.Microbuckling failure models are used to predict the compressivestrength of the carbon fibre rods; agreement between theory andexperiment is acceptable.