Static Shear Response of Recycled Carbon Fibre Composites for Structural Applications

The specification and use of recycled carbon fibre composites require the generation of reliable data that gives a comprehensive description of the material. Our research dealt with an experimental study of recycled, discontinuous, needle-punched, non-woven carbon fibre/epoxy composites. The property-constituent relationships of these composites require the adaptation of testing practices, coupled with an understanding of their failure mechanisms. The objective was to define a test protocol to determine their shear load limits. Four interlaminar shear test methods were investigated, namely, Short Beam Shear, Double Notch Shear, Double Beam Shear and Iosipescu Shear. A modified Iosipescu shear specimen provided a stress state in the composite that was much closer to pure interlaminar shear than that observed with other test methods. Identification of the weakest shear plane and re-fabrication of the test geometry enabled consistent interlaminar shear failures using the Iosipescu test method. We found that the shear behaviour was dependent on the internal fibre architecture of our particular material, thus enabling potential optimisation of such composites.