Blast response of carbon-fiber/epoxy laminates subjected to long-term seawater exposure at sea floor depth pressures

Abstract

An experimental investigation was carried out to determine the long term effects of exposure to a sea-floor depth ocean environment on the blast response of carbon-fiber/epoxy (CFE) laminates. By means of accelerated life testing (ALT), the behavior of laminates with and without exposure to high pressure saline water was explored using an air-blast shock tube facility and 3D-DIC technique coupled with high speed stereo photography. Specimens were tested in the unweathered condition and two durations of exposure: 14 days and 24 days immersed in a 70 °C, 3.5% NaCl solution pressurized to 41.3 MPa in a novel aging facility specifically designed to study the weathering behavior of composite materials at large ocean depths. From a diffusion study utilizing Arrhenius methodology, these cases simulate 8.9 and 15.3 years of service life, respectively. No statistically significant differences between the in-plane tensile elastic modulus, ultimate tensile strength, in-plane shear modulus, and ultimate shear strength were observed between any of the three cases. The flexural modulus of the laminates was observed to decrease by 13.2% and 20.8% for the two weathered cases, respectively. Dynamic air-blast experiments utilizing 3D digital image correlation (DIC) to track out-of-plane displacements revealed only marginal gains in normalized deflection of 5.1% and 2.0% for the two weathering cases, indicating no significant change in blast response with aging.