Numerical Simulation Study On Mesomechanics Of GFRP Bolt Tension And Curing Process

In GFRP bolt, the main load is undertaken by the fiber and the fiber debonding and the crack propagation are the two main forms of failure around the breakpoint after the fiber fraction failure for the bolt body’s tension. In addition, in the production of GFRP bolt which experiences the curing process of high temperature to low temperature, the thermal residual stress is inevitable when the is experienced. This thesis focuses on the numerical simulation of the fiber pull-out and the bolt body crack extension during the GFRP bolt tensile failure and the thermal residual stress distribution in during the GFRP bolt body’s curing. The numerical simulation of this thesis in which the initial condition, boundary condition, failure criterion, material and state equation of GFRP bolt are established, is carried out by using the general finite element simulation software ANSYS and the independent development program. The main research contents are as follows:In the part of single fiber pull-out, the effect of ideal interface, interface thickness and interface elastic modulus on single fiber pull-out is successfully carried out. The results of the study show that: stress concentration can be found both in the lower end of the deboning point and the upper end surface, and the stress concentration range and degree of the stress concentration of the lower end of the debonding point is greater than the upper end face. As appropriately increasing the thickness and reducing the elastic modulus of the interface layer, the stress distribution of the interface is more uniform, the range and degree of the stress concentration is reduced, and the interfacial deformation ability and the interfacial debonding load is increased. Thus, the brittle failure of the bolt body can be avoided, and the strength and toughness can be improved.In the part of crack propagation of bolt body, the mode of crack propagation after fiber fracture and the law of interfacial strength on the evolution of damage are simulated and analyzed. The results of the study show that: In the case of strong interface, because the crack generated at the breakpoint of the fiber is extended in the matrix along the axis perpendicular to the fiber axis, the stress on the fiber increases rapidly, and the stress concentration of the fiber tends to appear brittle failure; The stress on the broken fiber and the adjacent fiber is quickly restored. In the case of weak interface, because the crack generated at the breakpoint of the fiber is extended along the fiber axis on the interface of the broken fiber and its adjacent matrix, with the fiber debonding, the range and degree of the stress concentration in the adjacent fibers is relatively small. The material showed good toughness, and the stress recovery of the fiber and the adjacent fiber is slow. In the case of medium interface, because both the crack propagation and fiber debonding occur in the fiber breakpoint, the material can maintain a certain strength and a certain toughness.In the part of distribution of thermal residual stress in the bolt body during curing, the influence of technological parameters such as interfacial elastic modulus, curing temperature, fiber elastic modulus, matrix, elastic modulus, fiber volume fraction and other parameters on the thermal residual stress distribution in the GFRP bolt body is simulated. The results of the study show that: the increase of the curing temperature, the fiber elastic modulus, matrix elastic modulus and the fiber volume fraction can increase the thermal residual stress of the GFRP bolt body. As the increasing of the interface elastic modulus, the thermal residual stress concentration in the GFRP bolt body is reduced and transferred to the interface layer. When the difference between the interface elastic modulus and the fiber elastic modulus is small, the thermal residual stress in the GFRP bolt body is greatly reduced.