Crashworthiness and Impact Energy Absorption Study Considering the CF/PA Commingled Composite Processing Optimization

The processing of the thermoplastic composites can cause matrix thermo-oxidative degradation. Understanding the level of thermo-oxidative degradation, as well as the thresholds of temperature and processing time, allows the manufacture of high performance composites with higher crashworthiness. This study evaluated the matrix thermo-oxidative degradation by Friedman's isoconversional kinetic model to a carbon fiber/polyamide (CF/PA) commingled fabric. In addition, the CF/PA commingled composite was manufactured by consolidation under pressure at 240°C, 250°C, 260°C, 270°C and 280°C to observe the influence of the matrix thermo-oxidative degradation on its energy absorption capacity. Impact test and compression after impact (CAI) determined the energy absorbed by the CF/PA commingled composite at different processing temperatures. The results demonstrated that the matrix thermo-oxidative degradation affected the energy absorption capacity of the CF/PA composite when the processing temperature exceeded 260°C, which is in accordance with the prediction of the degradation study. Therefore, the optimal processing cycle occurs at 260°C for 20min. When it processed in temperatures above 260°C, the CF/PA commingled composite reduces in 0.14J/°C the energy absorption ability due to the matrix degradation in high temperatures, leading to a considerable reduction on crashworthiness and its performance.

热塑性复合材料的加工过程易引发基体热氧化降解。明晰该降解程度以及对应的温度与加工时长阈值，有助于制备耐撞性能更优异的高性能复合材料。本研究采用弗里德曼等转化率动力学模型（Friedman's isoconversional kinetic model），针对碳纤维/聚酰胺（carbon fiber/polyamide, CF/PA）混纺织物的基体热氧化降解情况展开评估。此外，研究团队通过加压固结工艺，分别在240℃、250℃、260℃、270℃及280℃下制备了CF/PA混杂复合材料，以观测基体热氧化降解对其吸能能力的影响。通过冲击试验与冲击后压缩（compression after impact, CAI）试验，测定了不同加工温度下CF/PA混杂复合材料吸收的总能量。研究结果表明，当加工温度超过260℃时，基体热氧化降解会对CF/PA复合材料的吸能能力产生负面影响，这与降解研究的预测结果一致。因此，最优加工工艺为260℃下保温20分钟。当加工温度高于260℃时，由于高温下基体发生降解，CF/PA混杂复合材料的吸能能力每升高1℃便会降低0.14J，进而导致耐撞性能与综合使用性能大幅下降。