缝合增强复合材料层合板层间断裂韧性研究

Study on Interlaminar Fracture Toughness of Stitched Composite Laminates

为了提高复合材料层合板抵抗分层的能力,引入缝合技术来提高层合板的层间断裂韧性。采用自主研发的单线弯针缝合设备来缝合干纤维,通过真空辅助树脂灌注技术(VARI)固化成型,脱模后制成缝合层合板试样。通过对试样进行双悬臂梁(DCB)试验研究了缝合密度对缝合层合板I型层间断裂韧性G IC的影响规律,并探究了缝线失效形式和层间断裂韧性间的联系。采用端部缺口弯曲(ENF)试验研究了缝合密度和缝线直径对缝合层合板Ⅱ型层间断裂韧性G IIC的影响机理。结果表明:缝合能够显著阻碍层间裂纹的扩展,随着缝合密度的增加,层合板I型层间断裂韧性均有不同程度的提高,Ⅱ型层间断裂韧性表现出先略微降低而后上升的变化趋势;层合板层间断裂韧性随缝线直径的增大而增大。试验发现,缝线主要存在断裂与拔出两种失效形式,缝线断裂比例越高,相应的G IC也越高。

In order to prevent delamination failure of composite laminates,stitching technology is introduced to improve the interlaminar fracture toughness of laminates.The self-developed stitching machine is used to stitch dry fibers,then the stitched preform is cured and formed by vacuum assisted resin infusion(VARI)technology,and the stitchedlaminates samples are prepared after demoulding.The effect of stitching density on the mode I interlaminar fracture toughness G IC of laminates was researched by DCB test,and the relationship between the failure mode of suture and interlaminar fracture toughness was explored.The effect of stitching density and suture diameter on laminates modeⅡinterlaminar fracture toughness G IIC was investigated using ENF test.The results show that:stitching can significantly hinder the propagation of interlaminar cracks.With the increase of stitching density,the mode I interlaminar fracture toughness of laminates increases significantly,and the modeⅡinterlaminar fracture toughness shows a trend of slightly decreasing at first and then increasing.The interlaminar fracture toughness increases with the increase of suture diameter.The test found that there are two types of suture failure:fracture and pullout.The higher the proportion of suture fracture,the higher the corresponding G IC.