In-plane Compression Behavior Of Thermoplastic Composite Sandwich Structure

In this paper,the composite honeycomb sandwich structures with/without grille reinforcing were fabricated and investigated.The honeycomb sandwich consisted of unidirectional glass fiber reinforced PP skin and PP honeycomb core,and the PLA grille was fabricated via 3D printing.These sandwich structures have high specific strength and specific stiffness.In addition,they were all composed of thermoplastic materials,which are easy easily to realize recycling.The application of this structure show potentials inautomobile container body,and it is an effective alternative for lightweight,energy-saving and emission-reduction.In this paper,the compression performance of sandwich structure is studied by finite element method and experiment.1.Firstly,the in-plane compression performance of honeycomb sandwich structures with different sizes are studied through experiments.When the fiber orientation of skin is modified,the one-way laying is beneficial for single loading direction,while the cross-laying is more favor of complex working conditions.The experimental results show that 45/-45 pavement is weaker in load-carrying but stonger in energy absorption,Furthermore,the bearing capacity of honeycomb sandwich structure increases with the increase of skin thickness and honeycomb core height.2.Secondly,it is revealed that the in-plane compression force-displacement curve of honeycomb sandwich structure is divided into three stages.The first stage is pre-buckling stage.At this stage,the load increases linearly with the increase of compression displacement.The second stage is buckling stage.At this time,the bearing capacity of honeycomb sandwich structure reaches its limit,resulting in large deformation and irreversible damage of the structure,which makes bearing capacity decreased greatly.The third stages are post-buckling stage,at which time the sandwich structure has been destroyed and the bearing capacity reduced to a lower level,resulting the bearing capacity totally losing.Through the analysis of failure modes of honeycomb sandwich structure,it is found that there are three failure modes:skin fracture,overall buckling and local buckling under different skin layers.Based on the size parameters of sandwich structure,the boundaries of different failure modes of P3 and P4 skin layers are chosen.3.Triggered by bionics principle,the honeycomb sandwich structure is enhanced with grille,and thus the grille-reinforced honeycomb sandwich structure is obtained.The in-plane compression performance test and out-of-plane compression performance test are conducted between thehoneycomb sandwich structure with and without grille-reinforcingt.It is found that the peak bearing capacity and specific strength of the honeycomb sandwich structures reinforced by grilles are significantly enhanced,which exhibite the superiority of the structure.4.Finally,finite element analysis of P4-F2.0-H20,P4-F1.0-H20 and F2.0-H20-D8-G2 sandwich structures are performed.The results show that the failure modes of the three structures are in good agreement with the experimental results,which verifies the validity of the finite element model.In order to sysmatically evaluate the superiority of grid-reinforced honeycomb sandwich structure,two objectives including peak load and weight are optimized.The structure is optimized based on finite element method and response surface method.Firstly,key factors are screened and it is found that the thickness of skin,the height of honeycomb core and the thickness of grille wall have significant effects on the peak bearing capacity.The functional relationship between the peak bearing capacity and key factors is established by response surface method,and the mathematical model of optimization problem is constructed.A series of solutions are obtained by genetic algorithm,which can provide useful information and guildance for the design of grille-reinforced honeycomb sandwich structure.