Influence of mechanical pre-strain under varying temperatures on flexural performance and failure of 3D-printed carbon fiber sandwich structures

Abstract

3D-printed sandwich composites offer lightweight solutions for aerospace, automotive, and defense applications; however, their flexural response under combined pre-strain (PS) and temperature remains insufficiently understood. This study systematically investigates the effects of PS (50, 70, and 75% of ultimate deformation) and temperature (room, high ∼ 50 °C, and low ∼ − 20 °C) on flexural strength (FS), energy absorption (EA), failure mechanisms, and residual properties of a 3D-printed continuous carbon-fiber-reinforced thermoplastic (CFRTP) corrugated-core sandwich structure. PS-free specimens exhibited a three-stage failure consisting of interfacial cracking, core cracking, and skin buckling. Lower PS (50%) caused minor reductions in FS and EA, whereas higher PS (70–75%) accelerated crack initiation, promoted dual-sided core crushing and skin instability, and reduced FS from 29.16 MPa to 25.5 MPa and EA from 30.4 J to 21 J. Under coupled PS and temperature, elevated temperature significantly amplified PS-induced degradation and weakened adhesive shear resistance, resulting in early interfacial cracking and unstable fracture. In contrast, low temperature increases stiffness, shifted failure toward skin cracking with distributed core damage, and substantially preserved FS and EA (residual FS ≈89–100% and residual EA ≈62–63%). These results demonstrate that low-temperature effectively mitigating PS degradation and enhance reliability for demanding structural applications.