Void reduction during composites manufacturing is critical for successful processing. In this study, we perform a parametric study to determine the mechanisms of interply void evolution in unidirectional prepregs during vacuum bag-only cure and to identify the key factors that affect interply air removal. We employ an in situ visualization setup for direct, real-time observation of air removal for prepregs during cure. Results showed that super-ambient dwell at 50℃ effectively promoted interply air removal in unidirectional prepregs, reduced vacuum quality (80% vacuum) had negligible effects on part quality, and that an increase in moisture content of the laminate notably increased void content. Prepreg moisture content was tracked by the inspection of laminate water content at different times during the cure cycle, and the data was combined with a diffusion-based analytical model to predict void size and to improve the understanding of void evolution mechanisms. Results indicated that moisture content of the laminate decreased markedly as cure progressed, providing insights into bubble behavior (expansion and shrinkage) observed during cure. The modified model predictions aligned with experimental data, especially during the second stage, confirming that the observed void growth results from moisture diffusion.

中文翻译：

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材料和工艺参数对单向预浸料真空袋固化过程中空隙演变的影响

复合材料制造过程中的空隙减少对于成功加工至关重要。在这项研究中，我们进行了一项参数研究，以确定在仅真空袋固化过程中单向预浸料中层间空隙演变的机制，并确定影响层间空气去除的关键因素。我们采用原位可视化设置直接、实时观察固化过程中预浸料的空气去除情况。结果表明，50℃超环境停留有效地促进了单向预浸料中层间空气的去除，降低真空质量（80%真空）对零件质量的影响可以忽略不计，层压板水分含量的增加显着增加了空隙率。通过检查固化周期中不同时间的层压板含水量来跟踪预浸料含水量，并将数据与基于扩散的分析模型相结合，以预测空隙大小并提高对空隙演化机制的理解。结果表明，随着固化的进行，层压板的水分含量显着降低，从而深入了解固化过程中观察到的气泡行为（膨胀和收缩）。修改后的模型预测与实验数据一致，特别是在第二阶段，证实观察到的空隙增长是水分扩散的结果。