Synergistic effects of extreme temperature and prebending on <scp>CF</scp> / <scp>PEKK</scp> composite flexural characteristics

Abstract The mechanical properties of carbon‐fiber‐reinforced polymer composites are highly sensitive to temperature and preloading conditions. The behavior of carbon‐fiber/poly(etherketoneketone) (CF/PEKK) under various temperatures and prebending (PB) conditions is not fully understood. This study examines CF/PEKK's interlaminar shear strength, tensile, Mode II, and bending properties at room temperature (RT, 25°C), low temperature (LT, −60°C), and extreme cryogenic temperature (ECT, −196°C). The combined effects of temperature and PB at 30%, 50%, and 70% of ultimate displacement for 24 and 72 h were analyzed. Results indicate that decreasing temperature increases shear strength, improves tensile properties, and reduces fracture toughness. Bending tests show that strain, yield strength, and yield strain rise significantly from RT to ECT, while the modulus remains similar, but the postyield modulus decreases. Higher PB intensity reduces strength, moduli, and strain. Under combined PB and LTs, CF/PEKK shows a coupled mechanism with PB‐induced microcracks mitigated by low‐temperature failure mechanism. Strength increased by ~20% from RT to ECT, and 30%‐prebent samples retained over 80% residual flexural strength even at LT and ECT. These findings highlight CF/PEKK's excellent bending resistance at extreme temperatures, emphasizing its potential for aerospace applications. Highlights Temperature significantly impacts CF/PEKK composites' mechanical properties. Decreasing temperature increases shear strength and tensile properties. PB‐induced microcracks and low temperatures influence flexural properties. CF/PEKK composites show excellent bending resistance in extreme conditions. High residual strength persists at low temperatures and after prebending.