Karbhari Vistasp M, Acharya Rabina, Hong SoonKook
Department of Civil Engineering, University of Texas Arlington, Arlington, TX 76006, USA.
Department of Mechanical and Aerospace Engineering, University of Texas Arlington, Arlington, TX 76006, USA.
Polymers (Basel). 2023 Apr 29;15(9):2138. doi: 10.3390/polym15092138.
Carbon fiber-reinforced epoxy matrix composites using ambient- and moderate-temperature curing non-autoclave processes have broad applicability in marine, offshore, and naval applications. This research focuses on the characterization of moisture kinetics of ambient cured carbon/epoxy composites subject to immersion in seawater for up to 72 weeks after prior periods of extended thermal aging. A two-stage model is shown to best describe the overall kinetics and response. The level of maximum moisture uptake shows an increasing trend with the temperature and time of prior thermal aging, reaching asymptotic levels at the highest levels. The transition point is seen to represent a shift between the diffusion and relaxation-/deterioration-based dominant regimes, and the ratio of uptake at the transition point to the maximum uptake can be correlated to the relaxation coefficient. Diffusivity, as expected, generally increases with the temperature of prior aging and shows changes based on the level of post-curing and network changes with time. Moisture uptake kinetics and characteristics developed through the sequence of exposures provide a better understanding of phenomena towards the development of a future comprehensive model capable of long-term prediction based on the sequential prior history of exposure to elevated temperatures and immersion in seawater.
采用常温及中温固化非高压釜工艺的碳纤维增强环氧树脂基复合材料在海洋、近海和海军应用中具有广泛的适用性。本研究聚焦于对经过长时间热老化后的常温固化碳/环氧复合材料在海水中浸泡长达72周的吸湿动力学进行表征。结果表明，一个两阶段模型能够最好地描述整体动力学和响应。最大吸湿量水平随先前热老化的温度和时间呈上升趋势，在最高水平时达到渐近值。转变点被视为扩散主导机制与基于松弛/劣化主导机制之间的转变，转变点处的吸湿量与最大吸湿量之比可与松弛系数相关联。正如预期的那样，扩散系数通常随先前老化温度的升高而增大，并根据后固化程度和网络随时间的变化而变化。通过一系列暴露过程所形成的吸湿动力学和特性，有助于更好地理解相关现象，从而开发出一个未来基于高温暴露和海水浸泡的连续先前历史进行长期预测的综合模型。
