Study On Low-velocity Impact And Compression After Impact Of Braided CFRP/PMI Sandwich Composite Short Beams

As a novel composite structure,carbon fiber reinforced polymer foam sandwich composite structure has the advantages of light weight,high strength,high specific energy absorption and strong corrosion resistance.It has been widely applied in automobile,ship,aerospace,sports equipment and other fields.The continuous braided closed circular structure has excellent global continuity,and the foam core has load transfer effect,which can effectively enhance the impact resistance and damage tolerance of sandwich composite structure.In practical engineering application,sandwich composite structure is subject to unavoidable external impact,such as lowspeed impact load during daily service and maintenance process,which causes fiber fracture,matrix cracking,core damage,interface failure and so on,and this may lead to the decline of structural strength and stiffness and affects the safety of subsequent use of sandwich composite structure.Therefore,it is of great significance to study the low velocity impact response and after impact residual properties of sandwich composite structures.Three kinds of circular braided carbon fiber reinforced polymer(CFRP)/ polymethacrylimide foam(PMI)composite short beams were designed and fabricated.The lateral low velocity impact resistance and axial compression performance after impact were studied by using the method of finite element analysis and experimental test.The main research work is as follows:(1)This paper introduced the design and fabrication process of braided sandwich composite short beams,and carried out lateral low velocity impact test and lateral quasi-static three-point bending test.And collectsed high-speed photographic images and micro focus CT threedimensional scanning data,the test results of dynamic and quasi-static mechanical response curve,progressive deformation,internal and external damage morphology were obtained.(2)The finite element models of sandwich composite short beams were established by using finite element analysis software Abaqus to,including CFRP layers and PMI foam mandrels.Based on the external damage morphology,internal damage morphology and mechanical response process,the finite element simulation results were compared with the experimental results to verify the effectiveness of this model,and the failure mechanism of local elements was further explained according to the finite element simulation results.(3)The effects of internal structure and low velocity impact damage on the lateral mechanical response and internal/external damage morphology of CFRP/PMI sandwich composite short beam were analyzed.The axial compression processes of samples after impact were characterized by combining acoustic emission detection system and infrared thermal imaging technology.Further more,the effects of internal structure and low velocity impact damage on residual properties were analyzed,and the progressive failure process of CFRP/PMI sandwich composite material short beam under axial compression were revealed.