A Inverse Method Of Material Parameters About The CFRP Used In Vehicle

The Carbon Fibre Reinforced Plastics(CFRP) have obvious advantages such as lightweight, high strength, noise damping and ease formed in automotive body panels lightweight design. However, The CFRP used in vehicle was under state of complicated and compound stress when the vehicle collision happened. Accurate mechanical analysis of vehicle body must be obtained on the basis of accurate mechanical parameters of material. As we know, anisotropic parameters of the CFRP much more than metal material, and the traditional electrical measuring method has limited measurement points, also easy influenced by the environment temperature and humidity. So, it could not get the surface's full displacement fields of the tensile test specimen. Therefore, it is necessary to study a wide applicability as a means of identifying the characteristics of composite material parameter. As a result, the following studies are carried out in this dissertation:(1) According to computational inverse technology, this study proposed a new inverse method of material parameters about the CFRP used in vehicle based on digital image correlation technique(DIC), which solves the easily interfered issue at the time of measuring parameters. Firstly, the inverse technique obtains the whole displacement field of the composite specimens by using the test apparatuses of DIC. Secondly, experiment technology and finite element technology are used separately to get structural response of test points, so the test data and simulation data are obtained. Finally, optimize all the parameters which is need to be measured to make simulation data approach to test data gradually, and minimize the least square error equation of them, so the material parameters of specimen will be determined by only once. The paper using the normalization method to reduce the deviation of the optimizing search direction and combines the Genetic Algorithm(GA) with Sequential Quadratic Programming(SQP) to represent the real composite material constitutive parameters, the method has the superior precision and efficiency.(2) This thesis designs a test plan to verify the effect of the inverse method. Simple shape specimen with speckle is created firstly; Secondly, the proposed inverse method and tensile test method are used respectively to obtain the material parameters of the specimen, the experiment shows that the ability of the proposed method is strong to identify material constitutive parameters. Finally, an application example is proposed. In this example, a kind of complex specimen is produced in terms of corrugated plate. The drop weight test is applied to verify the accuracy of the inverse result in the forward.(3) Finally, a surrogate-based method was provided to reduce the amounts of inverse the material parameters. The method using the design of experiment and surrogate-based method with global sensitivity analysis to inverse the parameters in a larger interval range. Besides, the approach could identify complete composite material parameters by once, and has the superior precision and efficiency. So, it has guiding significance that rapid inverse the composites multiple material parameters.