Research On Low Energy Impact Damage And Dynamic Response Of Woven And Laminate Composites

Carbon fibers are characterized by low density,high specific strength and high specific modulus,so composite laminates(CFRP)with them as reinforcement materials are likely to be under complex loading environments during service,and the resulting accumulation of damage will inevitably deteriorate their structural mechanical properties,thus affecting the use and lifetime of the structures.In this paper,the mechanical response of single impact and secondary impact as well as the crack dissipation energy after impact are investigated for composite unidirectional laminated and plain weave structures in the following aspects:(1)Single impact experiments were conducted on three different structural CFRP specimens at different impact energies by the drop hammer method to derive the structural dynamic response and energy absorption as well as damage.A single low-velocity impact finite element model of the composite laminate was developed using ABAQUS software and compared with the experimental results to verify the accuracy of the model.(2)On the basis of(1),secondary impact experiments with the same impact energy and secondary impact finite element simulations were conducted on the above three different structural CFRP specimens to verify the accuracy of the model again and to study and analyze the changes of structural dynamic response,energy absorption and damage of CFRP laminates with the number of impacts.(3)Based on the characteristics that the crack dissipation energy of different structural laminate specimens under two impacts changes with the evolution of damage,we propose to introduce the crack dissipation energy combined with the absorbed energy as the damage index to evaluate the impact damage without damaging the sheet.Finally,the residual compressive strength test was performed to calculate the residual strength after two impacts.The results show that the damage index can characterize the influence of cracks in the overall damage to equivalently evaluate the internal damage of the composite sheet and make the overall damage assessment more accurate.