Shock Response of Composite Materials Subjected to Aggressive Marine Environments

Abstract

The marine community has an interest in using composite materials for the construction of vehicles and other marine structures. The use of composite materials is appealing due to their abilities in keeping naval vehicles in stealth. These structures are subjected to aggressive marine environments during their service life, such as high salinity water and ultraviolet radiation that can degrade their performance over time. These effects are of particular concern when composite vehicles are subjected to shock and blast loading. Therefore, there is a need to investigate how composite materials that have been exposed to marine environments respond to shock events, and how these responses differ from an equivalently loaded virgin structure. An experimental investigation was conducted to understand the mechanical response of carbon/epoxy composites subjected to long-term exposure of aggressive marine environments. In order to simulate marine environments, an elevated temperature, salt water solution was created. The material was submerged in a 3.5%, 65°C salt solution for 0, 30 and 60 days. The temperature was maintained at 65°C to accelerate diffusion of water into the epoxy, thus accelerating the weathering process. Accelerated weathering simulates years of actual service life in short time. The specimens were then subjected to a controlled and concentrated air blast loading using a shock tube. High speed photography coupled with 3D DIC is utilized to provide full field displacements, strain, and velocities of shock tube specimens during in air shock loading. The specimens for all of the weathering cases recovered elastically after the shock event. The large difference in displacements between the non-weathered and weathered specimens is due to the degradation of the material from water absorption. This confirms that submergence in extreme marine environments degrades the material and diminishes the material properties.