The Analysis Of Composite Interface Stress

Composite materials are widely used in aerospace,automotive electronics,medical equipment and other fields because of their excellent properties.When designing composite materials,engineers usually neglect the existence of their interfaces and treat them as a uniform structure to study.Engineering practice shows that the failure of composites is mainly due to the interface delamination caused by the large interfacial stress on the weak interface,which usually starts at the end of the interface.Based on this engineering background,this dissertation establishes a fine finite element numerical calculation model for three common interface models of composite materials in engineering,including isotropic material interface,anisotropic material interface and isotropic material and anisotropic material interface.Through calculation and analysis,the stress distribution law at these three interfaces,especially the stress singularity at the end of the interface,is analyzed.Opposite sex.It provides valuable methods and basis for the safety design of composite materials.The main research work is as follows:For the isotropic material model,the influence of load on interface stress and stress singularity is analyzed.The results show that for the interface normal load,when the geometric structure and constraints are certain,the singularity is the strongest when the load is loaded separately on the upper side of the structure,and the load is the second when the load is loaded separately on the lower side,and the singularity is the weakest when the load is loaded simultaneously on the upper and lower sides.The theoretical method is the closest to the singularity index when loading the load on the upper and lower sides;For the interface tangential load,when the geometry and constraints are fixed,the load acts on the upper side of the structure or simultaneously on the upper and lower sides of the structure,and there is no stress concentration at the interface end;When the load acts on the underside of the structure,there is a stress concentration phenomenon.For the anisotropic materials and isotropic/anisotropic material plane model,the effects of geometry,material parameters and loads on stress singularity and interfacial stress are analyzed,and a premise of not affecting the overall structural strength is proposed.The stress value of the interface large stress region is improved by changing the geometry of the interface junction.The results show that the singularity of both symmetrical and asymmetrical interfaces increases with the increase of bonding angle,and the ratio of tensile modulus of upper and lower materials increases with the increase of singularity.For the interface normal load,when the geometry and constraints are certain,the singularity is the strongest when the load is loaded separately on the upper side of the structure,and the load is the second when the load is loaded simultaneously on the upper and lower sides,and the singularity is the weakest when the load is loaded separately on the lower side.The harmonic smooth curved interface is better than the zigzag interface and the horizontal interface for improving the large stress area on the interface.