Flexural after impact behaviour of carbon/epoxy and carbon/vinyl-ester composite laminates at elevated temperatures

The Flexural After Impact (FAI) behaviour of epoxy and vinyl-ester based carbon fiber reinforced composite laminates was investigated at elevated temperatures. Carbon/Epoxy (CE) and Carbon/Vinyl-ester (CV) laminates with cross-ply configuration (0/90/90/0)3S were manufactured via a compression moulding technique and subjected to Low-Velocity Impact (LVI) s at ∼1.5 and ∼2.5 m/s under temperatures 30, 60 and 90°C. The flexural behaviour of composite laminates was investigated via three-point bending tests. The non-impacted and impacted CE and CV samples' failure profile during the flexural tests was examined using the real-time Acoustic Emission (AE) monitoring technique via peak frequency analysis of AE events. Flexural after impact strength of CE samples at both the velocities were higher than that of the CV ones. For CE and CV samples, the flexural after impact strength increases at 60°C, and decreases when approaching 90°C. At 90°C, flexural strength degradation was considerably higher in the CE ones because the Co-efficient of Thermal Expansion (CTE) of the epoxy matrix occurs at a much higher rate than the vinyl-ester, which generates higher residual stress at the carbon fiber-epoxy interfaces. Acoustic emission (AE) monitoring allowed to capture the interface among the fiber and matrix due to the exposure temperature and impact velocity.