Viscoelastic response of carbon fibre reinforced polymer during push-out tests

Push-out is one of the available techniques to assess the bond strength between the reinforcing fibres and the matrix in composite materials. The test is conducted on thin sections of composite, and a small indenter is used to apply increasing load on single fibres while measuring the displacement, until the debonding occurs. This study used push-out tests to assess the debonding mechanism of carbon fibres in an epoxy matrix. The tests were conducted at multiple loading rates (0.1 mN/s, 1 mN/s and 10 mN/s) and temperatures (24 °C and 125 °C). The results were analysed and contrasted with scanning electron microscopy and atomic force microscopy observations. The data showed evidence of push-out events and provided new insights into the contribution of the viscoelastic behaviour of the fibre/matrix interface and/or the matrix. This finding could pave new pathways for improving the bond strength between the carbon fibres and the matrix in composite materials.