Transverse compressive behavior of unidirectional CFRP composites under the coupling effects of specimen size and strain rate

Abstract: The transverse dynamic mechanical properties of unidirectional carbon fiber reinforced polymer (CFRP) cables substantially influence their damage evolution under medium-strain-rate loading, such as vehicle collisions. To reveal the impact failure mechanism of CFRP cables, it is necessary to first characterize the transverse dynamic compressive response of unidirectional CFRP at the material level, which is closely related to the specimen size and strain rate effect. In this study, transverse compression tests were conducted on unidirectional CFRP over a strain-rate range from quasi-static to medium-strain-rate loading. Two specimen sizes with aspect ratios of 1 and 2, namely AR1 specimens of 16 mm × 16 mm × 16 mm and AR2 specimens of 8 mm × 8 mm × 16 mm, were considered. The dynamic compression failure process was captured using a high-speed camera, and the effects of strain rate on the initial fracture angle, compressive strength, elastic modulus, and strain energy density were then discussed for both specimen sizes. The results indicate that the transverse compressive performance of unidirectional CFRP specimens is governed by specimen size and strain rate. With increasing strain rate, the compressive strength, elastic modulus, and strain energy density initially increase and then decrease, indicating a distinct strain-rate-dependent transition. AR2 specimens exhibit more pronounced variations in these parameters than AR1 specimens. For both specimen sizes, the initial fracture angle increases with increasing strain rate, although its growth becomes less evident within the nominal strain-rate range of 0.15-0.50/s. Empirical models are further established to describe the relationships between the logarithm of strain rate and the compressive strength, elastic modulus, and strain energy density. These findings provide a material-level basis for understanding the transverse compressive failure mechanism of unidirectional CFRP cables under impact loading.