The Numerical Simulation On Composite Materials Interface Crack Propagation Mechanism

With the development of process equipment along the large-scale and high parametric direction, manufacturing materials of process equipment is faced with technical challenges, and multi-layer composite materials become the preferred material to solve this engineering problem. Composite interface is the link of connecting each phases of multi phases multi-layer composite materials; also the bridge of passing mechanics and special features, the interface fracture failure will directly affect the final comprehensive performance of composite materials. Thus prerequisites of design and safety assessment technology for advanced metal composite process equipment is to establish the relevance theory of a composite interface micro structure, performance and service conditions-the internal stress and deformation of the crack micro-region--interface Fracture. Therefore, the relevance theory has been systematically studied by means of extending finite element numerical simulation method in this paper, the interface crack propagation law of composite pressure vessels with Initial interface cracks has been cleared. The formation mechanism of the interface crack propagation has been revealed. The life extension technology theoretical foundation of composite pressure vessel with the initial interface cracks has been laid. This research has the following innovative results.The comparative analysis of extended finite element numerical simulation and experimental study on the initial crack propagation of the traditional single-layer material pressure vessel show that the XFEM method can be used to simulate pressure vessel crack extension process, and can accurately capture the morphology and direction of crack extension, and the simulation results can coincide with experimental results. Experimental studies have shown the XFEM method can be used for the dynamic simulation of crack propagation for pressure vessel shell under complex stress state in this paper.The influence law of the material performance, service conditions and the initial crack morphology on the interface crack propagation of the composite pressure vessels with initial interface crack has systematically been studied and the relevance relationship of a composite interface micro structure, performance and service conditions-the internal stress and deformation of the crack micro-region--interface fracture was established, the formation mechanism of the interface crack propagation has been revealed, the theoretical foundation has been laid for the design and safety assessment of composite pressure vessels.The Interface crack of the composite pressure vessels with initial interface crack significantly elliptical morphology extended, and crack expend in the small elastic modulus material along the direction of deviating from the material interface, Interface crack driving force derived from the internal stress of the interface crack micro-region, The Internal stress distribution in interface crack front shows bimodal distribution patterns along the interface circumferential direction, bimodal vertices represent interface crack front position, the distance between the bimodal vertices and the maximum internal stress of the crack micro-region increases with increasing of temperature which show Layered interface crack front, expands along the interface circumferential direction, and crack growth rate increases.The technical methods was put forward in which the remaining life of composite pressure vessel with the initial interface cracks is improved by means of adding functionally graded buffer layer in layered interface, the relevance relationship of a micro structure of functionally graded interface, performance and service conditions-the internal stress of the crack micro-region--interface fracture was established, the mechanism on improving remaining life of the composite pressure vessel with the initial interface cracks by means of adding functionally graded buffer layer in layered was revealed, The life extension technology theoretical foundation of composite pressure vessel with the initial interface cracks has been laid.