缝合碳纤维泡沫夹芯复合材料低速冲击及损伤检测

研究了低速冲击对缝合与未缝合碳纤维泡沫夹芯复合材料冲击性能及损伤的影响；采用落锤冲击试验机对缝合和未缝合夹芯复合材料板分别进行了不同冲击能量下的冲击实验，得出冲击力和冲头位移分别随时间变化的曲线；采用水浸超声波扫描成像系统对冲击后的复合材料板进行损伤检测，得出夹芯复合材料板内部损伤情况。结果表明，在相同冲击能量下，缝合碳纤维复合材料板的冲击力较未缝合的要大，但冲头接触时间要短；此外，缝合碳纤维泡沫夹层复合材料板比未缝合的损伤面积要小，这说明缝线能有效的抑制冲击载荷下复合材料板内损伤扩散，减小分层损伤面积，提高复合材料板的抗冲击性能;缝合的抑制损伤效果在表面层和最内部层效果显著，而在中间层缝线的效果一般。

Low-velocity Impact and Damage Detection on Stitched Carbon Fiber Foam Sandwich Composites

In this paper, the effect of low velocity impact on the impact properties and damage for the stitched and unstitched carbon fiber foam sandwich composites was investigated. An impact test was first carried out on the stitched and unstitched sandwich composite panels by using a drop hammer impact tester at impact energy of 10 and 20 J, and the plots of the impact force and displacement as a function of time were obtained. Then, an immersion ultrasonic scanning imaging system was used to detect the damage of the composite panels after impact test, and the internal damage information of the panels was achieved. The results indicated that the impact force of the stitched composite panel was larger than that of the unstitched one under the same impact energy, whereas its punch contact time was shorter. Moreover, the damage area of the stitched composite panel was smaller than that of the unstitched one. This indicates that the delamination damage area was reduced and the impact resistance of the composite panel was improved, because the stitching could effectively inhibit the damage diffusion inside the composite panels under the impact load. The effect of stitching on the inhibition damage is significant in the impacted surface and innermost layers but that is normal in the middle ones.