Investigation Of The Transverse Impact Damage And Residual Performance For Fabric Reinforced Composite Tube

Carbon fiber reinforced composite tubes possess excellent energy absorption capacities,have been increasingly utilized in energy-absorbing components.However,the composite tubes are susceptible to transverse low-velocity impact loading events during service.The invisible damages caused by the transverse low-velocity impact tend to accumulate rapidly in repeated impact,leading to the significant decline of stiffness and strength in composite tube,which may seriously threaten the structural safety.Therefore,it is necessary to investigate the transverse impact damage and residual performance of composite tubes.In this paper,the manufacturing process and experimental method of carbon braided composite tubes were firstly discussed.Next,the constitutive models were introduced,and the related material parameters were obtained,followed by the development of numerical models for carbon braided tubes under compression after single and repeated impact loading conditions.By combining experimental and numerical analyses,the single impact damage of biaxial braided tubes with different wall thickness and different impact energy was investigated,followed by the evaluation of the effects of impact energy and impact position on the repeated impact response.Subsequently,the biaxial/uniaxial hybrid braided structure was proposed to evaluate the hybrid effects on the single impact resistance.Finally,the axial compression performance and residual crashworthiness after impact of these braided tubes were further investigated.The main research work were summarized as follows:(1)The transverse single impact damages and residual compression performances of biaxial braided tubes were studied by combining experimental and numerical methods.The bending stiffness of braided tube increased with higher wall thickness,suppressing its structural deformation during 5.6 J impact and thus producing an obviously decreased projected delamination area.Confined projected delamination area in 3-and 4-ply thick tube effectively prevented the buckling deformation of tube wall during axial compression,which was on the contrary to 2-ply thin tube.For pre-impact tube,especially with two composite layers,the transition of failure mode reduced the energy absorption of each composite layer compared to intact tube with progressive folding damage mode.(2)Experimental and numerical investigations into the transverse repeated impact damages and residual crashworthiness of biaxial braided tubes.2-ply braided tube produced obvious structural deformation under single impact with different impact energies,leading to delamination-dominated damage behavior.The initial slope and peak load of mechanical response curve were related to the sinking deformation of top part and bulging deformation of both lateral sides for braided tube,respectively.The structural deformation and mechanical response of braided tube subjected to repeated impact with different impact positions were sensitive to the delamination damage induced by single impact.The compression behaviors and residual crashworthiness of braided tubes were dominated by the delamination area and delamination location after 2.0 J repeated impact.The change of failure mode caused obvious decrease in residual crashworthiness of repeated impacted tubes than intact and single impacted tubes.(3)The transverse impact damages and residual compression performances of biaxial/uniaxial hybrid braided tubes were investigated by experimental and numerical methods.Transverse impact,axial compression and compression after impact tests were performed on 3-ply pure biaxial and uniaxial braided tubes(BBB and UUU)and hybrid tubes with biaxial or uniaxial braided different surface and inner layers(BUB and UBU).It was found that the impact response of braided tube was related to its structural deformation resistance,which was determined by the performance of reinforcement layers with different stacking sequence.The advantage of hybrid effect was more obvious at higher impact energy.At impact energy of 15.4 J,the hybrid tube BUB yielded the strongest impact resistance with small structural deformation.The crack propagation characteristics of the reinforcement layers influenced the damage behaviors of braided tube subjected to axial compression,leading to different energy absorption capabilities.Compared to pure biaxial braided tube,the energy absorption of hybrid tubes was obviously increased under compression and compression after 5.6 J impact,due to the splitting behaviors induced by the introduction of the unidirectional layers.The above findings provided theoretical basis and related guidance for the damage tolerance design of carbon fabric-reinforced composite tubes in structural components under transverse impact.