Heat Exposure and Its Implications on the Low-Velocity Impact Characteristics of GFRP Laminates

This study investigates how prior heat exposure alters the low velocity impact response of glass fiber reinforced polymer laminates under a constant 16 J impact. Specimens were conditioned at 23.5°C, 50°C, 70°C, and 90°C and then tested. Peak load declined steadily with temperature from 2.040 kN at 23.5°C to 1.535 kN at 50°C to 1.52 kN at 70°C to 1.345 kN at 90°C. Contact duration showed a shallow rise followed by a drop, reported as 8.95 ms at 23.5°C, 9.10 ms at 50°C, 8.45 ms at 70°C, and 8.00 ms at 90°C. Absorbed energy decreased with heat, moving from 15.5 J at 23.5°C to 13.4 J at 50°C to 13.1 J at 70°C to 10.6 J at 90°C. Damage footprints expanded markedly with temperature, with top surface area growing from 152.36 mm2 at 23.5°C to 185.22 mm2 at 50°C to 202.47 mm2 at 70°C to 255.58 mm2 at 90°C, and bottom surface area from 100.24 mm2 to 135.66 mm2 to 155.08 mm2 to 185.09 mm2 over the same temperatures. The combined trends indicate thermally driven matrix softening and viscoelastic effects that reduce load bearing capacity and energy dissipation, shorten the effective contact window, and enlarge subsurface damage. Together these quantitative findings clarify how temperature weakens structural integrity under low velocity impact and provide design relevant guidance for material selection, allowable loads and operational safety margins in components expected to operate in elevated temperature environments, including mobility, aerospace, and energy applications.