The effect of notches and specimen geometry on the pendulum impact strength of uniaxial cfrp

Abstract Charpy impact tests have been conducted on a number of composites consisting of uniaxial carbon fibres in an epoxy resin matrix. The specimen geometry has been varied so as to obtain different length-to-depth ratios in the test piece both for plain test pieces and those containing notches. The results show that there is a critical length-to-depth ratio which marks a change of fracture mode from a relatively brittle transverse cracking to a tougher mode involving extensive delamination. The materials are not notch sensitive provided tests are always conducted at similar length-to-depth ratios. The impact performance of the composite and the critical geometric factors are both governed by the elastic strain energy potential of the composite and by its interfacial shear strength.