Multiscale Parameters Identification And Ply Optimization Of Automotive CFRP Roof Panel

Lightweight design is one of the key technologies in energy-saving and environmental protection for automobile.Continuous carbon fiber fabric reinforced polymer(CFRP)composite is widely used as a lightweight material for its high specific stiffness/strength and good design-ability.However,the mechanical properties of CFRP are more complex to estimate than metallic materials for its complex spatial structure and the difference of constituents.For application of CFRP widely,it is necessary to investigate its mechanical properties deeply and systematically.Firstly,CFRP plate was manufactured by vacuum assisted resin infusion(VARI).Uniaxial tensile test,in-plane shearing test and scanning electron microscope(SEM)for damage region in tensile specimens were conducted according to the related standard.CFRP shows three different stages under in-plane shear loading:elastic response stage,elastoplastic transition stage and crack propagation and expansion stage.Moreover,load increases approximate linearly with the movement of crosshead and the CFRP shows brittle fracture characteristics at the end of uniaxial tensile test.Secondly,based on rule of mixtures and semiempirical formula,the elastic properties of carbon fiber tow of microscale were studied and the analyzed and the error is within the allowable range as compared with the test results.Then,mesoscale numerical analysis of representative volume element(RVE)was performed based on the results of microscopic scale analysis.The elastic mechanical response of RVE was analyzed by changing the volume fraction of carbon fibers.The results show that the transverse/longitudinal elastic modulus of RVE is sensitive to the volume fraction of carbon fibers and it increases linearly with the increase of the fiber volume fraction.Other elastic constants have the same growth trend,but the sensitivity is relatively lower.At last,a multi-level optimization of CFRP automotive roof panel was performed based on the results of multiscale analysis.The optimization constraints were stiffness and manufacture process of CFRP roof panel.Through multi-level optimization,optimal thickness of each layers and stacking-sequence were achieved and the CFRP roof panel designed in this study achieved a weight reduction of 59.3%.Then,resin flow simulation was performed to predict filling time.Also,the results were examined by manufacturing test.