Experimental Investigation on the Strain Rate Dependence of Continuous Carbon fibre-reinforced PA6 Under four-point Flexural Loading

Abstract Carbon fibre-reinforced thermoplastics used in structural applications, such as crash-relevant parts, are typically subjected to different strain rate conditions. This requires a deep understanding of their structural behaviour under these conditions. To date, there is limited data on their strain rate dependent behaviour. In this study, four-point flexure tests are used to determine the longitudinal flexural properties and failure behaviour of unidirectional carbon fibre-reinforced polyamide 6 (CF-PA6) material as a function of the applied strain rate. A universal testing machine and a drop tower test setup with two different drop heights were used to investigate the behaviour in quasi-static (1.3 × 10 − 4 1/s) to medium strain rates (7 1/s). Flexural modulus, flexural strength and fracture strain were determined for all strain rates applied, and the fracture morphology was analysed using microscopic images and high-speed camera recordings. Further, Weibull analysis was performed on the flexural strength. The experimental investigation of the flexural properties showed no significant strain rate effect and no trend was observed in the Weibull parameters. Irrespective of the strain rate applied, all specimens tested exhibited a comparable fracture morphology due to a similar failure process of initial compressive failure followed by tensile failure.