Preparation And Mechanical Properties Of 3D Printed Fiber-reinforced Composites/Structures

In the fields of aerospace and construction engineering,fiber-reinforced composite materials and lattice structures are widely used due to their high specific strength and high rigidity.Traditional preparation methods,such as winding and injection molding,have the disadvantages of long manufacturing time and cumbersome manufacturing process.Therefore,scholars propose to use 3D printing technology to manufacture fiber-reinforced composite materials,but the strength of the samples using nylon(PA)and polylactic acid(PLA)as raw materials is low,and it is affected by printing process parameters during the molding process The mechanical properties of the prepared samples vary greatly.In order to solve the above problems,this paper uses 3D printing technology to prepare tensile,fracture and lattice structure samples using PLA,PA and glass fiber / nylon(GF/PA)as raw materials,and studies their mechanical properties,using scanning electrons.A microscope(SEM)is used to study the cross-section of the sample and analyze the influence mechanism of different process parameters and raw materials on the mechanical properties of the sample.Using digital image correlation method(DIC)as an auxiliary method,the displacement field and strain field of the sample under different loads are calculated to reveal the failure mechanism of 3D printed composite materials and structures.The specific contents of the research are as follows:1.Use 3D printing technology to prepare PA and GF/PA composite material specimens,and study their tensile mechanical properties,and analyze the effects of different process parameters and raw materials on the mechanical properties of 3D printed composite materials.The research results show that as the printing temperature increases,the tensile strength and elastic modulus of the 3D printed composite materials increase first and then decrease.As the printing speed increases,the tensile strength and the elastic modulus of the 3D printed composite materials increase.When glass fiber is added to the PA material as the reinforcing phase,the tensile strength and elastic modulus of the 3D printed composite sample are increased compared to when the glass fiber is not added.2.Use 3D printing technology to prepare samples with PLA,PA and GF/PA as raw materials,study their static fracture performance under three-point bending load,use SEM to analyze the fracture morphology of the samples,and monitor with digital image correlation methods The deformation evolution of the specimen during the loading process reveals the fracture failure mechanism of 3D printed composites and the effect of process parameters on it.Experimental results show that as the printing temperature and printing speed increase,The fracture toughness of the 3D printed composite material decreased,and the fracture toughness of the 3D printed PA composite material with glass fiber was reduced compared with the sample without glass fiber.3.Use 3D printing technology to prepare lattice structure samples with different process parameters and raw materials,and conduct experimental and finite element simulation studies on their quasi-static compression mechanical properties.The research results show that with the increase of printing temperature and speed,the yield strength and plastic platform stress of lattice structure samples decrease.When the PA material is added with glass fiber,the yield strength,plastic plateau stress and densification strain show a downward trend,with a decrease of 68.75%,68% and 33.3%,respectively.But repeated loading performance increased.The finite element simulation results show that in the initial stage of compression,the mechanical properties of the lattice structure are linear elastic.When the ring of lattice structure reaches the ultimate strength in the compression process,the load value tends to be stable.As the loading displacement increases,the ring at the upper and lower ends of the structure is damaged due to too much deformation,and the load is transferred to the middle ring part so that it appears to be under constant pressure.When the lattice structure is destroyed,all the rings are squeezed together,the structure is in the densification stage,and the pressure bearing capacity increases sharply.4.Developed a continuous fiber-reinforced thermosetting composite 3D printer based on FDM technology,including print heads,fiber bundle delivery tubes,epoxy resin storage devices,control systems,and XY motion mechanisms,which can realize continuous fiber-reinforced thermosetting composite 3D printing of plates and structure parts.The results show that the mechanical properties(tensile strength and elastic modulus)of 3D printed continuous carbon fiber reinforced thermosetting composites are significantly better than 3D printed fiber reinforced thermoplastic composites and 3D printed short carbon fiber reinforced composites.Through the SEM fracture analysis,it can be seen that the interface between the fiber and the matrix of the 3D printed fiber-reinforced thermosetting composite material is better,and the failure mode is mainly fiber fracture.