Study On Failure Modes And Residual Strength Of Composite Laminates Under Low-velocity Impact

Composite materials have advantages in many aspects and are more and more applied in various fields.But in the process of use,it is unavoidable to be subjected to low-velocity impact,which causes the internal damage of various modes,and reduces the strength and stiffness of the material.In recent years,the research on the problem of low velocity impact and residual strength mostly adopts the progressive failure analysis method to predict the fracture failure and damage expansion of the material during the whole loading process.For progressive failure analysis methods,it is very important to choose which failure criteria and damage evolution modes.In the process of low velocity impact,the main failure modes of composites are matrix failure and interlayer delamination,ie inter-fiber damage(IFF),and the impact problem is more complicated.The fracture surface of the matrix does not necessarily coincide with the material’s main axis.Therefore,the Puck criterion based on the physical mechanism is used to predict the matrix damage during the impact process.The Selected Range Golden Section Search algorithm(SRGSS)is used to search the fracture surface angle of the matrix,and the strain-based Hashin failure criterion is used to determine the damage of the fiber.At the same time,the bilinear constitutive model is used to simulate the damage evolution process.The progressive failure prediction model presented in this paper is realized by the VUMAT subroutine in ABAQUS.The compression simulation of the composite laminates validates the effectiveness of the damage constitutive model,so that the complex low-velocity impact and static compression after impact can be analyzed.First,the low velocity impact and post impact compression test of T700/ epoxy composite laminates are carried out.The damage size,damage form and damage distribution are obtained.The influence law of impact energy on damage morphology and residual compression strength after impact is discussed.The damage propagation rule is obtained and the failure mechanism under low-velocity impact and compression load after impact is analyzed.Second,the strain-based Hashin failure criterion,the physical-mechanismbased Puck criterion and the bilinear damage evolution rule are introduced into the VUMAT subroutine to establish a three-dimensional finite element model of the composite laminate under low-velocity impact and simulate various in-plane damage forms of composites under impact loading.And the cohesive force elements are used to simulate interlayer damage.Then the simulation results are compared with experimental data to verify the validity of the model.Finally,various types of damage caused by impact are introduced into the nondestructive laminates in the form of predefined fields.The finite element model of the impact-damaged laminates subjected to static compression loading is established.The compression simulation is performed to analyze the damage propagation law and residual compression strength.Through the comparison between the experiment and the simulation,the validity of the model is further verified,and the full-scale analysis of the composite laminate from low-velocity impact to post-impact compression is realized.