Strain-rate-dependent damage and mechanical behavior of pultruded carbon fiber reinforced composite under transverse compression

This study systematically investigates the transverse compressive behavior of pultruded carbon fiber reinforced polymer (CFRP) with a high fiber volume fraction (72 %) across a wide strain-rate range (0.004 s⁻¹ and 254–2084 s⁻¹), using both a material testing system (MTS) and a split Hopkinson pressure bar (SHPB). Full-field deformation and failure progression were captured by high-speed digital image correlation (DIC), while post-failure microstructural features were examined using scanning electron microscopy (SEM). The results reveal a distinct three-stage transition in damage mechanisms: under quasi-static loading, failure is governed by fiber-matrix debonding and matrix brittle cracking; high strain rates promote predominant matrix plastic deformation; and at strain rates above 651 s⁻¹ , failure shifts to a combined mode involving matrix plasticity and fiber fracture. Both transverse compressive strength and elastic modulus exhibit pronounced strain-rate sensitivity, for which dynamic increase factor models were established across the full strain-rate spectrum (0.004–2084 s⁻¹), whereas failure strain remains rate-independent. The energy dissipation density increases with strain rate, but its strain-rate sensitivity diminishes beyond a critical interval (947–1178 s⁻¹), indicating a transition from logarithmic growth to a near steady-state response. Furthermore, a rate-dependent viscoelastic constitutive model, based on the Zhu-Wang-Tang (ZWT) framework, was developed and shown to accurately predict the dynamic compressive response of pultruded CFRP composites.