Polymer matrix composites have a tendency to absorb measurable moisture in nearly all operating environments. This absorbed moisture either becomes bound to the polymer network via secondary bonding interactions or exists as free water with negligible interactions. Damage creates new internal free volume where water molecules can exist in the latter state. This study introduces a novel basis for non-destructive examination in polymer matrix composites which leverages locally-higher concentration of free water in damaged areas. Experiments involved impact-induced sub-surface damage in a laminate prior to moisture exposure. Polymer-water interaction—determining the free or bound state of water—was characterized by near-infrared spectroscopy and microwave-range relative permittivity. Results show a direct correlation between the extent of local damage and higher relative levels of free water at damage sites.

聚合物基复合材料在几乎所有操作环境中都有吸收可测量水分的趋势。这种吸收的水分要么通过二次键合相互作用与聚合物网络结合，要么以游离水形式存在，且相互作用可忽略不计。损坏会产生新的内部自由体积，其中水分子可以以后者状态存在。这项研究为聚合物基复合材料的非破坏性检查提供了新的基础，该方法利用了受损区域局部较高的游离水浓度。实验涉及在暴露于湿气之前，对层压板中的冲击引起的亚表面损坏。聚合物-水的相互作用（确定水的自由状态或结合状态）的特征在于近红外光谱和微波范围的相对介电常数。