起圈织物泡沫夹芯复合材料Ⅰ/Ⅱ型断裂韧性研究

Study on TypeⅠ/ⅡFracture Toughness of Loop Fabric Foam Sandwich Composite

夹芯复合材料在受到弯曲、剪切和冲击等载荷作用下易发生脱层损伤。脱层损伤程度与Ⅰ、Ⅱ型断裂韧性密切相关。起圈织物由于在其厚度方向引入环状纤维束,增强了与芯层的结合能力,使其在抗分层方面性能优良。本文主要研究起圈织物泡沫夹芯复合材料的Ⅰ/Ⅱ型界面断裂韧性。根据试验标准分别制作了平纹织物泡沫夹芯复合材料和起圈织物泡沫夹芯复合材料。采用双悬臂梁试验(Double cantilever beam, DCB)和末端缺口挠曲试验(End notch flexure, ENF)对上述试验件的增韧机理进行了研究。研究表明,环状纤维束的引入大大提高了界面性能。起圈结构相较于平纹结构的Ⅰ型断裂韧性G_(ⅠC)提高了434%,Ⅱ型断裂韧性G_(ⅡC)提高了400%。通过建立有限元模型,采用内聚力模型来描述裂纹的扩展,数值结果与试验结果吻合较好。

Sandwich composites suffer from delamination damages under bending,shear,impact and other loads.The degree of delamination damage is closely related to the fracture toughness of typeⅠand typeⅡ.Due to the introduction of ring fiber bundles in its thickness direction,the binding ability of the ring fabric with the core layer is enhanced,which makes it excellent in anti-delamination performance.In this paper,the fracture toughness of typeⅠ/Ⅱinterface of fabric foam sandwich composites is studied.According to the test standard,the plain weave fabric foam sandwich composite and the loop fabric foam sandwich composite are made seperately.The toughening mechanism is studied by the double cantilever beam(DCB)test and the end notch flexure(ENF)test.The results show that the interfacial properties are greatly improved by the introduction of annular fiber bundles.Compared with the plain weave structure,the typeⅠfracture toughness G_(ⅠC) and typeⅡfracture toughness G_(ⅡC) of the loop structure are increased by 434%and 400%,respectively.A DCB finite element model is established and the cohesive force model is used to describe the crack propagation.The numerical results agree well with the experimental results.The finite element model is applied to the study of DCB specimens with different initial crack lengths,which provides a reference for the design of composite materials.