Research on high-temperature mechanical behaviour of carbon/phenolic composites under ultra-high heating rates

Fibre-reinforced resin matrix composites exhibit excellent resistance to ablation, thermal insulation and mechanical properties at high temperatures, making them widely used in aerospace engineering. Needle-punched reinforced carbon/phenolic composites are the most commonly used structural material for solid rocket engine nozzles. However, during the working process of the engine, the mechanical behaviour under ultra-high heating rates is difficult to characterise due to extreme loads. Therefore, in this study, specimens were carbonised before testing, and an electric heating testing machine was combined with an infrared thermal imager and digital image correlation system to characterise the mechanical behaviour of carbon/phenolic at ultra-high heating rates. The results indicate that at a heating rate of 200°C/s, the compressive modulus increases linearly with temperature, reaching 63.1 GPa at 1400°C. The maximum compressive strength is 61.9 MPa at 1400°C, while the minimum is 27.4 MPa at 600°C. Referring to the high-temperature damage constitutive model, a pyrolysis damage high-temperature strengthening constitutive model was constructed, accurately describing the in-plane compression mechanical behaviour of carbon/phenolic composites.