Impact Loading Behavior of Large-Scale Two-Way Sandwich Panels with Natural Fiber–Reinforced Polymer Faces

Abstract

This paper presents experimental and numerical studies on sandwich panels with flax fiber–reinforced polymer (FFRP) faces and polyisocyanurate (PIR) foam cores. The panels are subjected to two-way bending under impact loads at the center, simulating applications like building cladding systems exposed to wind-borne debris. Nine large-scale panels were fabricated and subjected to impact loads; 412 tests were performed. Each panel was 1,220 mm × 1,220 mm with a nominal thickness of 80 mm. The main test parameters were core-to-face thickness ratio based on one, two, or three FFRP layers (core-to-face thickness ratios of 65.1, 32.6, and 21.7) and impact energy (50%, 70%, and 95% of failure energy). For each face thickness, three identical panels were fabricated and tested. The impact tests were performed using a 140-mm-diameter drop weight ranging from 10.5 to 20 kg, with a varying height of up to 3,250 mm. The results showed that the panels are susceptible to internal damage accumulating after impacts, such as core shear failure. Analyses of the test data showed that the impulse duration of a panel increased with an increase of damage. A finite-element model was also developed to predict the behavior of these panels under low-energy impacts. The model accounted for the nonlinear behavior of both the FFRP faces and foam cores. The model was used to perform a parametric study to examine the effect of core thickness, face thickness, and core density. It showed that impulse duration and maximum deflection increased with a decrease in face thickness, core density, and core thickness.