Study On Low Velocity Impact And Residual Compressive Strength Of Composite Honeycomb Sandwich Structures

Composite honeycomb sandwich structure is widely used in aircraft,automobile,ship and other transportation fields because of its advantages of light weight,high specific strength and specific stiffness.Honeycomb sandwich structures may be subjected to static and dynamic loads in practice.In particular,the low-velocity impact load will cause invisible internal damage to the structure,thus causing safety risks.In practical application,low-velocity and heavy load impact may occur.Therefore,it is necessary to carry out in-depth research on the damage mechanism and compression failure mechanism of honeycomb sandwich structure under low-velocity and heavy load impact.In this paper,the impact damage and residual compression strength of the sandwich structure composed of hybrid skin of carbon fiber and glass fiber and Nomex honeycomb were studied.The main contents of the study are as follows:Based on the constitutive relation of anisotropic materials,the failure theory of fiber tension and compression and matrix tension and compression of composite materials are studied.Strain is used to define the damage initiation criterion because strain is continuous compared with stress in numerical simulation.The interlaminar failure criterion is introduced to predict the delamination damage of composite materials.By studying the damage initiation criteria and damage evolution of composite materials,a three-dimensional progressive failure model which can accurately predict the impact damage of composite materials is established.It provides a theoretical basis for subsequent impact and compression simulation after impact.Based on the establishment of a three-dimensional progressive failure model,the effects of different impact energies and boundary conditions on the failure mode,impact force,energy absorption and dissipation of sandwich structures under low-velocity and heavy load impact are studied.At the same time,the accuracy and reliability of the simulation results are verified.The effect of skin thickness and impactor diameter on the impact resistance of sandwich structure is further discussed by using the validated simulation model.The specimens before and after impact were subjected to in-plane and out-plane compression tests.The influence of impact energy and boundary conditions on the residual compressive strength of sandwich structure is discussed by recording the ultimate compressive load at failure.The failure mechanism and deformation process of sandwich structure under in-plane compression load are discussed by damage accumulation analysis method.In this paper,the damage impedance and damage tolerance of hybrid composite honeycomb sandwich structures subjected to low-velocity and heavy load are systematically discussed by finite element simulation and experiment.The effects of boundary conditions and related impact parameters on the failure mode,impact force,energy absorption and dissipation of the sandwich structure are analyzed.It provides reference for reasonable evaluation of damage characteristics of honeycomb sandwich structure and optimization design.