Investigation On The Hot Pressing-injection Process And Mechanical Properties Of Fiber Reinforced Thermoplastic Composite Components

Fiber-reinforced thermoplastic composite components have the advantages of excellent mechanical properties of continuous fiberreinforced thermoplastic composites and short-fiber reinforced thermoplastic composites that are easy to form complex structures,and have been more and more applied in aerospace,automotive and other fields.However,the existing hot pressing-injection molding process of composite components faces problems such as long cycle and poor performance,and the failure process and failure mechanism of the connection interface of composite components are not clear.To this end,this paper takes continuous glass fiber reinforced polypropylene(CGFR-PP)laminate and short glass fiber reinforced polypropylene(SGFR-PP)as the research object,focuses on the hot pressing-injection molding process of CGFRPP/SGFR-PP composite components,establishes the cohesion model of composite components,and studies their bearing performance,failure process and failure mechanism under specific loads.The main research work of this paper is as follows:1.A rapid hot pressing process platform was built to shorten the molding time of U-shaped skeleton to 90 s,and the influence of different surface temperatures,molding pressures and mold temperatures on the shear strength,surface morphology and cross-section geometry accuracy of U-shaped skeleton parts was studied.The results show that with the increase of surface temperature and molding pressure,the shear strength between U-shaped skeleton layers first increases and then decreases,and the surface morphology gradually improves,and with the increase of laminate surface temperature and mold temperature,the U-shaped skeleton molding angle gradually decreases and tends to be stable compared with the design angle.2.The optimization of the injection over-molding process parameters of composite components was carried out,and the results showed that prefabricated parts temperature and packing pressure had a significant impact on the shrinkage deformation of the composite components,but the overall shrinkage deformation value was small;the melt temperature and the holding pressure had a significant impact on the residual stress of the composite components injection molding;the better injection molding process parameters of the composite components were combined as:A4B2C4D2,that is,the melt temperature was 240 °C,the prefabricated parts temperature was 170 °C,the holding pressure was 50 MPa,and the holding time was 20 s.3.The cohesion model of the interface of the composite components is established,the progressive damage and failure process of the bonding interface of the composite components under bending and axial compressive loads is analyzed,and the final cracking position is predicted.The results show that under the bending load,the interface damage of the composite components first appears in the middle position of the bottom surface,and then gradually expands to both ends,and the interface failure first occurs in the two sides of the bottom surface near the middle part.under the compression load,the interface damage of the composite components first appears in the middle position of the side,and the failure also occurs here first.This paper studies the hot pressing-injection molding process and mechanical properties of CGFR-PP/SGFR-PP composite components,which provides a new technical approach for automobile lightweighting,and lays a theoretical foundation for the prediction of mechanical properties and interfacial damage failure analysis of thermoplastic composite components.This is of great significance to the engineering application of CFRT/SFRT composite components that require both mechanical properties and complex structural functionality.There are overall 80 figures,22 tables and 99 references.