Hydrothermal in-plane-shear strength of carbon fibre/benzoxazine laminates manufactured out-of-autoclave by liquid-resin-infusion

Benzoxazine's have recently emerged as new candidate resins for elevated temperature structural applications in the aerospace sector offering attractive attributes including infusibility under vacuum, fire-smoke-toxicity performance and room temperature storage/transport. The main objective of this study is to evaluate the hydrothermal in-plane-shear (IPS) strength of carbon-fibre (CF) based laminates manufactured using two benzoxazine (BZ) resin systems (BZ9120 and BZ9130). CF/BZ9130 was evaluated at 160 °C in the wet condition and benchmarked against two commercially available bismaleimide (BMI) resin systems – traditionally considered for wet applications at 160 °C. CF/BZ9120 was evaluated at 120 °C (just below its Tg) in the dry and wet condition and benchmarked against CF/BZ9130. BMI's remain the benchmark for IPS strength at 160 °C (wet) with 64% retention while BZ9130 only retained 48% of IPS strength at 160 °C (wet) and also exhibited excessive elongation. CF/BZ9130 showed good retention at 120 °C (68% wet) outperforming CF/BZ9120 (48% wet). Positively, both BZ systems performed at least as well as the BMI's under ambient conditions.