Cumulative Impact Energy Absorption of Sandwich Panels with Foam Cores and Flax FRP Facings

Abstract

In this paper, the cumulative energy absorption of sandwich panels constructed of foam cores and flax fiber-reinforced bio-based polymer (FFRP) faces is studied. Nine sandwich panels were constructed and tested under varying amounts of impact energy using a drop weight test. The parameters of the study were facing thickness and foam core density. Three different facing thicknesses (one, two, and three layers of a bidirectional flax fabric with a nominal unit weight of 400 kg/m2) and three different core densities (32 kg/m3, 64 kg/m3, and 96 kg/m3) were used. An accelerometer was placed on the bottom face of each specimen and on the drop weight. The data from the accelerometers is used to determine each specimen’s fundamental frequency after each impact to determine the amount of damage in the specimen. To calculate curvature, strain gauges were placed at the center of the top and bottom face at mid-span. Two string-type displacement gauges were placed at mid-span below the specimen, to accurately measure the displacement during the impact event. The data sampling rate was 25 kHz. The information obtained is used to determine the ability of these panels to absorb the energy from multiple impact events. It also helps to establish a fundamental understanding of the behavior of the panels under impact for future research. To date all specimens have been fabricated and one of the specimens has been tested. The results are presented in this paper and more data will be available for presentation during the conference.