Combined Investigation on Durability and Dynamic Failure of Advanced Naval Materials.

摘要

Durability and dynamic failure properties are critical parameters for naval composite ships in seawater. However, previous approaches and measurements have significantly underestimated the actual durability of a composite structure inside seawater. For a composite ship, a rectangular composite specimen only represents a part of an infinite large panel, and has one external face exposed to seawater. During underwater explosion, this front surface is subjected to shock loading first. For the whole life cycle of a composite ship, since only the front surface of a composite panel is directly exposed to seawater, property degradation and damage from the front surface will be a major issue to determine the durability and life of the composite ship structure. However, almost all previous experiments ignored this single-surface environment effect . For example, Karasek et al. (1995) have evaluated the influence of temperature and moisture on the impact resistance of epoxy/graphite fiber composites. They found that only at elevated temperatures, moisture had a significant effect on damage initiation energy and that the energy required to initiate damage was found to decrease with temperature. Impact damage resistance and tolerance of two high performance polymeric systems was studied after exposure to environmental aging. For cross-ply laminates, the post-impact tensile strength values fell significantly (by maximum 70 75% of original composite strength) depending on aging time, environment and impact velocity. Sala (2000) found that barely visible impact damage, due to the impact of 1 J/mm (for 2.2-mm laminate thickness) increased the moisture saturation level from 4.8% to 6% for aramid fiber-reinforced laminates and enhanced the absorption rate.