Dynamic intralaminar fracture toughness characterisation of unidirectional carbon fibre-reinforced polymer composites using a high-speed servo-hydraulic test set-up

This paper presents an experimental investigation on the intralaminar fibre-dominated fracture of unidirectional (UD) IM7/8552 carbon-epoxy composites, loaded under quasi-static (QS) and intermediate strain rates (IR). Dynamic tensile testing is carried out using a previously proposed test methodology involving a high-speed servohydraulic test machine, equipped with a slack adapter, and Digital Image Correlation (DIC), with the aim of providing an alternative means to Split-Hopkinson pressure bar testing for the characterisation of similar composite materials at intermediate-to-high strain rates. Three sizes of Double-Edge Notched Tension (DENT) specimens are tested at QS and IR to obtain the mode I intralaminar fracture toughness. The results of the fracture toughness tests compare well with literature data, supporting the proposed methodology. This study is a first step towards standardising a more easily accessible test method for characterising the mechanical properties of fibre-reinforced polymer (FRP) composites over a broad range of dynamic strain rates.