Temperature effects on the low-velocity impact of FML panels: experimental and numerical analyses.

Abstract

This study aims to evaluate the impact damage of FML panels under the effects of elevated temperatures. Low-velocity impact tests were conducted experimentally on FML panels at impact energy levels of 5, 8, 10, 12, 13.5 and 15 J at room temperature. Finite element models of the FML with quarter and half symmetry were then developed using explicit nonlinear code LS-DYNA and validated against experimental results. The quarter model was sufficiently validated as it simulates identical results compared with the half model. The quarter and half models produced maximum percentage differences of 11.92 and 15.25% respectively in terms of the total energy absorption, along with respective 5.68 and 5.57% for the peak load. Thereupon, combined analysis on the same impact energy levels and temperatures of 30, 50, 70, 90 and 110°C were performed by employing the FE quarter model. The results indicate that an increase in temperature significantly affects the low-velocity impact response and impact resistance of FML. Load-displacement and deflection responses show pronounced loss of stiffness, toughness and resilience with increasing temperature. From 30 to 110°C, the energy restitution coefficient (ERC) decreases by roughly 0.2 while the load-bearing capacity drops by 45 to 50%. The degradation of FML is progressive in that it is less significant at a lower temperature range of 30 to 70°C yet severe at a higher temperature range of 70 to 110°C. Evidently, the impact damage of FML panels may be more severe in critical applications involving ranges of high temperatures.