Study On Melt Impregnation Of Ultrasonic Assisted Fiber Reinforced Polypropylene Composites

Fiber-reinforced thermoplastic composites are widely used in construction,electronic appliances,transportation and petrochemical industries due to their advantages of creep resistance,short molding cycle,simple equipment,low cost,easy repair and recyclability.How to further improve the mechanical properties of the established composite system is a major problem faced by fiber-reinforced thermoplastic composite materials.Its breakthroughs mainly focus on the quality of the prepreg,the quality of the interface and the final forming process.This paper starts from the research of the quality of the prepreg and the interface.For the melt impregnation process,the main problem is that it is difficult for the high-viscosity thermoplastic resin to completely impregnate the fiber,and the fiber is easily broken during the impregnation process.The impregnation degree and fiber breakage rate are often difficult to reconcile in the production process.In this paper,starting with this problem,applying ultrasound to the degree of impregnation of the fiber-reinforced thermoplastic composite material on the curved runner melt impregnation mold,the preliminary experimental exploration of the ultrasonic process parameters(frequency,power,action distance)by designing the DOE experiment,The transfer function was analyzed,and the optimized process parameters were obtained with ultrasonic frequency of 20KHz,power of 1000W,and action distance of 2mm.At this time,the porosity is 3.72%and the fracture rate is 2.67%.By comparison,it is found that after applying ultrasound,the increased degree of impregnation is higher than the increase in breaking rate,which is beneficial to improve the quality of impregnation.By combining Darcy’s law and the acoustic law of the ultrasonic field,a related impregnation model was established and verified through experiments.The results show that the ultrasonic frequency has little effect on the porosity;the greater the ultrasonic power and the smaller the ultrasonic action distance,the better the degree of fiber impregnation.Through the analysis of the stress of the fiber during the impregnation process,the Weibull distribution function is used to describe the fiber breakage and modeling.The results show that the ultrasonic frequency has little effect on the breaking rate;the greater the ultrasonic power and the smaller the ultrasonic action distance,the higher the breaking rate of the fiber.Finally,the effects of the resin matrix and compatibilizer on the performance of the composite material were studied.For the matrix:the lower the viscosity,the better the realization of the impregnation and infiltration process.The interface between the Bx3920 matrix and the fiber is the best.Its tensile strength,bending strength,bending modulus and impact strength are compared with the ZSH composite system.,Respectively increased by 15.54%,8.69%,4.97%and 4.5%.For the compatibilizer:the higher the functional group content of the effective graft component of the MAH in the compatibilizer,the better the interface bonding,the higher the mechanical properties,and the highest tensile strength,flexural strength,flexural modulus and impact strength respectively 67.6%,63.2%,11.3%and 34.0%.