The Numerical And Experimental Investigation On Low-velocity Impact Response Of Composite Panels:Effect Of Fabric Architecture

Composite reinforced by carbon fiber is a kind of lightweight material with excellent mechanical properties,which is widely used in various engineering fields.In the process of use,the structural components made of carbon fiber composite are vulnerable to low-velocity impact,which leads to internal damage,the reduction of load capacity and potential failure.The fabric structure is an important factor that affects the impact resistance of composite.Therefore,this paper studies the influence of different fabric structures on the damage mechanism of composite materials.In this paper,the effects of fabric structure on the impact resistance of composite are studied by experiments and finite element simulation.Composite materials made of four kinds of fabric reinforcement were prepared by vacuum assistant resin transferring mold.According to the test and simulation results,the strengthening mechanism of z-yarn is studied.In addition,based on the damage mechanism of layered unidirectional fabric and plain woven fabric,the effects of hybridization of layered unidirectional fabric and plain woven fabric on the impact properties of composite were studied.This study is carried out as the following aspects:In Chapter 2,the design of fabric reinforcement structure and the preparation of composite are introduced.First,the structures of layered unidirectional,plain woven and orthogonal woven fabric are described.According to the structure of orthogonal woven fabric,the three-dimensional loom is designed and the weaving principle is expounded.Then the process of preparing composite by vacuum assistant resin transferring mold is described.Finally,the low-velocity impact test platform and the test data processing method are introduced.In chapter 3,the mesoscopic finite element simulation model is established.First,the geometric model of composite panel is established.Then,material properties of the resin and the impregnated yarn were measured.Finally,the damage failure criteria of resin and impregnated yarn are introduced,respectively.In this paper,ductile failure criterion and shear failure criterion were used to simulate the damage initiation and development of resin,and Hashin failure criterion was used to simulate the damage initiation and development of impregnated yarn.In chapter 4,the influence of z-yarn on the impact resistance of composite panel is analyzed.According to the test results,the orthogonal woven composite panel has the minimum post-impact deformation and the least absorption of inelastic energy.Moreover,the main failure mode of its surface is resin cracking,the main failure mode of the impregnated yarn is mainly transverse damage and the interlaminar delamination is restrained by z-yarn.By comparing the finite element simulation results of composite panels reinforced by layered unidirectional and orthogonal woven fabric,it is found that the existence of z-yarn causes discontinuous resin damage in orthogonal woven composite panel instead of delamination in layered unidirectional composite.Thus,impact resistance is improved.At the same time,according to the finite element simulation results,different in-plane structures of layered unidirectional and plain woven fabric lead to different stress propagation modes,which ultimately affects impact response.In chapter 5,the effect of fabric hybridization on the impact resistance of composite panel is analyzed.The damage modes of composite panels reinforced by layered unidirectional,plain woven and hybrid fabric are compared and analyzed.The damage mechanism of layered unidirectional and plain woven composite is further explained.Then,it can be explained that by the addition of quasi-isotropic woven fabric,the hybrid fabric can restrain the occurrence of early lamination damage,which avoids the stress concentration on the sub-layer.As a result,the fracture failure of fiber on the top layer and the bottom layer is relieved.Moreover,the unidirectional fabric is beneficial to stress propagation avoiding the damage concentration.Therefore,the impact resistance of hybrid composite is improved by hybridization of layered unidirectional fabric and plain woven fabric.In chapter 6,the research content of this paper is summarized and the following research is prospected.