Research On Compression After Impact Properties Of Three Dimensional Interlaminar Orthogonal Composites

Fabric composite material is a new type of material with higher specific modulus and strength,but its disadvantage is poor out of plane properties.It is very easy to cause internal damage due to out-of-plane low-speed impact.Fabric structure is one of the main influencing factors on the impact resistance and damage resistance of composite materials.At present,researchers generally evaluate the impact resistance and damage resistance of composite materials through compression after impact,impact tension after impact and bending after impact.Firstly,this article weaved three required fabric structures(unidirectional,plain,and three-dimensional interlaminar orthogonal fabrics)and prepared fabric composites.Subsequently,low-speed impact experiments and compression after impact experiments were conducted on the sample at three energy levels.Then,the experimental curves of the three-dimensional interlayer orthogonal composite material are compared with the other two composite materials and its lowspeed impact and compression after impact response are analyzed.Finally,a mesoscale three-dimensional interlaminar orthogonal finite element model was established for simulation analysis.The main research content is as follows:(1)Low speed impact experiments were conducted on composite materials to investigate the influence of three-dimensional fabric structure on impact response.The results indicate that the three-dimensional composite specimens with resin rich areas are more prone to matrix damage compared to the unidirectional and plain composite specimens under low energy level impact.Under high-energy impact,the bundled yarn in the three-dimensional composite sample can effectively suppress the generation and propagation of delamination.Compared with the other two samples,three-dimensional composite materials exhibit better impact resistance at high energy levels.(2)The compression properties of 3D fabric structure after impact were analyzed by compression after impact experiments.The results indicate that fabric structure can affect the damage forms and residual strength of composite materials.When threedimensional composite materials are subjected to high-energy impact,the binding yarn in the three-dimensional composite material fixes the yarn as a whole,suppressing the generation of damage,and has higher residual strength compared to the other two composite materials.(3)A three-dimensional interlaminar orthogonal finite element model was established at a mesoscale to simulate low-speed impact and compression after impact experiments.The model includes resin matrix and impregnated reinforced yarn.The damage of resin matrix is simulated by using ductility and shear damage criteria and the damage of impregnated reinforced yarn is simulated using three-dimensional Hashin criteria.Finally,the simulation results were compared with experimental results to verify the reliability of the finite element model.The compression after impact damage forms and mechanisms of three-dimensional interlaminar orthogonal composite materials were analyzed through computer tomography(CT)technology and simulation results.It shows that the compression damage of three-dimensional interlaminar orthogonal fabric composites is mainly caused by bundled yarns,with the bundled yarn area being the most severely damaged.When composite materials are subjected to compressive load after impact,the lining warp yarns in the impact area are first damaged,followed by gradual damage to the yarns on both sides.The stress distribution of the three types of yarns is different and the stress distribution of the warp lining yarn will be affected by the adjacent bundled yarns,changing from uniform distribution to high and low distribution.