Study On Shear Instability Of Carbon Bar Grating Reinforced Rubber Composite Material

For carbon bar gratings reinforced rubber composite material,the main purpose of its design is to adapt to the structure of large deformation,such as: variant aircraft through shear deformation to achieve large changes in the area of the wing.Because rubber skin material thickness is small,resistance to bending stiffness is very small,susceptible to fold under shear deformation instability phenomenon,and engineering will fold instability appear generally considered to be a failure mode of the structure,so for the carbon bar gratings reinforced rubber composite material,it is particularly important to improve the ability to resist folding for the optimal design of carbon bar gratings reinforced rubber composite material.First,three kinds of basic mechanical tests are carried out on rubber matrix,(Uniaxial tensile,Uniaxial compression,Plane tensile tests)and the test results are fitted with several kinds of commonly used hyperelastic constitutive models.The fitting effect is evaluated based on goodness of fit,similarity between fitting curve and test curve,and relative deviation.The results show that the three types of fitting effect evaluation methods have their own advantages and disadvantages,and the three methods can be used together to evaluate the fitting effect of the hyperelastic model more accurately.Based on the evaluation results,Yeoh is selected as the applicable hyperelastic constitutive model for rubber matrix.Second,shear test is carried out by using the designed test fixture and optical digital speckle measurement method to investigate the deformation response.It includes the initial angle,phenomenon and out-of-plane deformation of the carbon bar grating reinforced rubber composite material.The research indicates that the designed test fixture can complete the application of shear deformation;Optical digital image measurement system GOM/ARAMIS 5M can obtain the initial angle of fold instability,out-of-plane deformation cloud field and out-of-plane deformation amount.Combined with the test curve analysis method,the precise characterization of the initial angle of fold instability can be realized.Last,the basic finite element model is expanded and compared with the experimental results from three aspects: initial angle of fold instability,experimental phenomenon and out-of-plane deformation.The results show that the analysis results of the basic finite element model are in good agreement with the experimental results,and the existing deviations are explained reasonably.Finally,the effects of different initial angles,different thickness of rubber matrix skin,different spacing of fine carbon rods and different spacing of coarse carbon rods on fold instability are discussed.The results show that the changes of various influencing factors have great influence on the initial angle,phenomenon and out-of-plane deformation of fold instability.