Post-Impact Flexural Collapse of Composite Sandwich Structures in Low-Temperature Arctic Conditions

Abstract

Drastic reduction of ice over the last thirty years has grown interest in increased use of marine vessels to sail through new routes in arctic regions which are efficient and economical. The major challenge of operating in the polar environment is to avoid any potential impact and subsequent secondary damage by bending in extreme lowtemperature conditions. This study analyses the post-impact bending collapse modes of Divinycell H-100 PVC foam core with woven carbon fiber reinforced polymer (CFRP) face sheets composite sandwich panel. Effects of low temperature and impact energy on collapse modes in 3-point bending have been predicted analytically and validated by experimental results. A series of low-velocity impact tests with 4 J and 8 J impact energy were performed at three different temperatures 23, -30 and -70 °C. Impacted specimens were then subjected to a three-point bending test for identifying flexural collapse modes. Bending characteristics were analyzed on both sides of the specimens (front impact face and back distal face). Analytical results portray that indentation, core shear, face wrinkling are the main competing collapse modes. Results also elucidate that the competing flexural collapse mode strongly depends on pre-bend impact, face sheet thickness, temperature, and bending configuration. Experimental results are further compared and validated with analytical predictions. Experimental results show that thick specimens were collapsed either by indentation or core shear. However, thin specimens at 23 and -30 °C revealed a new mechanism of core tensile failure while debonding was observed at -70 °C. This new observation of core tensile failure is attributed to the reduced tensile properties of the back-face sheet. This work will lead to understanding the post-impact failure modes of composite sandwich structures, which will subsequently lead to an improved design for marine structures and materials that can operate safely and effectively in the Arctic environment.