Fabrication And Mechanical Properties Of CF/PEEK Composite Lattice Sandwich Structures

Whether in the automotive industry or in the field of aerospace,lightweight structure has become the mainstream of industrial development in order to achieve energy saving and emission reduction under the premise of ensuring safety and reliability.The primary way to realize the lightweight structure is the lightweight of the material.With the continuous exploration of the lightweight and high-strength materials,fiber reinforced resin matrix composites have become one of the best choice materials.Over the past few decades,fiber reinforced thermosetting composites have been widely studied and applied,but fiber reinforced thermoplastic composites have not been greatly developed due to the restriction of high temperature thermoplastic resin moulding process and prepreg impregnation technology.With the continuous improvement of thermoplastic composites prepreg molding technology,fiber reinforced thermoplastic composites have also become a research hotspot.Compared to the traditional fiber reinforced thermosetting composites,fiber reinforced thermoplastic composites have the following performance advantages: higher impact toughness,damage tolerance,flame resistance and water resistance,and it can be stored at room temperature,recyclable and melt welding.In this paper,continuous carbon fiber reinforced high performance polyether ether ketone(CF/PEEK)composite was adopted to study the fabrication technology and mechanical properties of the three-dimensional sandwich structure with truss core.In this paper,a new fabrication process of CF/PEEK composite sandwich structure with truss core is proposed by combining the repeated heating and welding characteristics of CF/PEEK composites.A new hot stamping process has been put forward combining the characteristics of hot pressing deformation of CF/PEEK composites in the fabrication process of lattice core,the traditional embedded assembly technique and the heat-die pressing process have not been adopted.A hot press connection method distinguishing from traditional welding(metal material)and adhesive(thermosetting composites)is proposed on the connection between the facesheets and the cores.The out-of-plane compression property of CF/PEEK composite lattice structure was studied.The theoretical analysis model is established,and the formula of the equivalent compression modulus/strength of the CF/PEEK composite lattice structure under compression load is derived.Besides,the prediction formula of compression strength corresponding to the different failure modes is given.The out-of-plane compression test of CF/PEEK composite lattice structure was carried out.The stress-strain curves of the CF/PEEK composite lattice structures with four kinds of relative density under compression load were obtained.The corresponding failure modes were observed,and the accuracy of the failure mode predicted by the theoretical model was verified.The finite element software ABAQUS is used to simulate out-of-plane compression process of the CF/PEEK composite lattice structure.The simulation results are compared with the experimental results to show that the finite element model well predicted the structural responses of CF/PEEK composite lattice structure under compressive loading.The finite element model is used to investigate the influence of the ply angle of the lattice core on the compression performance of CF/PEEK composite lattice structures.The Instron Dynatup 9250 HV impact testing machine was used to the low velocity impact tests of CF/PEEK composite lattice structures with three kinds of relative density.The structural impact response under different impact energy and impact position was studied.According to the damage of the CF/PEEK composite lattice structures under different impact energy and impact position,the load-time curves and the energy-time curves are analyzed.