Study On Fatigue Of Polyurethane Foam Sandwich Beam Under Shear Failure Mode

The main advantage of the sandwich plate applied to structure is it has a high stiffness and strength ratio. Sandwich plate have been successfully applied to a variety of different modes of transport,such as:space vehicles,aircraft structures, ships, trains,trucks,cars and centralized box, etc. These vehicles have one thing in common that will withstand repeated dynamic loads, fatigue loads. By the sandwich plate theory knowledge, when the sandwich plate subjected to shear or bending loads, the core is bear the shear load.Today, foam sandwich construction as the main load-bearing components have been widely used. Research on the sandwich structure especially on the surface of the structure is already quite mature, but for the optimizational of the design of the sandwich structure, the research of core of the sandwich structure is essential. In the known literature, the study of fatigue of the polyurethan foam sandwich beam is rare.This paper focuses on fatigue study of polyurethane foam sandwich beam under shear failure mode. By four-point bending failure mode theory of sandwich beam, we design the thickness of surface and core, and the span of the polyurethane sandwich beam to satisfy the shear failure mode B. Using the fatigue testing machine for polyurethane foam sandwich beam under shear failure mode of fatigue are studied. For polyurethane foam sandwich beam test result data, using the three-parameter weibull distribution obtained the P-S-N curve of polyurethane foam sandwich beam under the different survival probability. According to the error factor theory, we calculate the fatigue test error rate of sample size polyurethane sandwich beam with weibull distribution.The fatigue crack growth of Polyurethane foam sandwich beam are studied, using the commercial computational finite element software ABAQUS,the strain energy release rate G1, G2 of polyurethane sandwich beam under different fatigue crack length in the tip is calculated by virtual crack closure technology. In the case of don’t know the material fracture toughness, we propose a calculation method of equivalent strain energy release rate and,according to this method to obtain the equivalent energy release rate. Finally, we obtain the material parameter C,m of polyurethane foam sandwich beam crack propagation rate through Paris formula.