Research On Temperature Field During Automated Fiber Placement And The Mechanical Properties Of Thermoplastic Composites

Thermoplastic composites will be the development direction for the future composite materials due to its advantages of high toughness and recyclable.The technology of in-situ consolidation is the key point for efficient and inexpensive manufacturing large composite components.Based on the in-situ Automated Fiber Placement(AFP)of thermoplastic composites(TPC),this paper analyzed the key technologies of in-situ consolidation and studied the in-situ AFP of TPC.To develop the principle prototype and realize the technology of in-situ consolidation for AFP of TPC successfully,this paper optimized the fiber tension and the placement speed,realized the dynamic constant tension for the AFP and ensured the quality of components,meanwhile,regulated the speed and the sending fiber to achieve precise positioning security component.Desired quality of composite parts depends intensively on the thermal history of the AFP,so this paper provided a transient two-dimensional temperature field model and the boundary conditions for AFP.The problems of simulating heater moving with the AFP head and the case of layer addition were solved in the ANSYS software to obtain the temperature distribution in the laminate and determine the reasonable temperature range for hot gas at different placing speed.Meanwhile,a real-time temperature measurement system based on WinCC flexible was established,aiming at acquiring and memorizing the temperature and proving the finite element simulation results were correct.Aiming at the processing speed will be changed within the larger scope,this paper proposed an infrared heating technology which was fast response rate and efficient.Based on the analysis of the heat transfer process between the infrared heat source and the layers,the control equation of dynamic temperature was put forward and the matching relationship between the radiation intensity and laying speed was established.Based on the AFP platform,the infrared heating system which adopted the feedforward control method was constructed and the corresponding control strategy was formulated according to the dynamic thermostatic control equation to realize the heating temperature of prepreg controlled accurately.Because of the mechanical properties of thermoplastic composites made by AFP are greatly influenced by its crystallinity,the non-isothermal crystallization kinetics of glass fiber reinforced polypropylene for automated fiber placement was studied with the Avrami equation.To investigate the influence of cooling rate and cooling time on non-isothermal crystallization behavior of matrix material and solve the maximum processing speed at different cooling speed,the non-isothermal crystallization Kinetics model and the heat transfer model were derived and the cooling conditions in the process of automated fiber placement was set up.The prepreg made of polypropylene as matrix and continuous glass fiber as reinforcement was used to produce laminates through the AFP platform.Influences of the processing parameters,such as temperature of hot gas,lay-up pressure of hot roller and cooling roller,and furthermore,their interaction effects on interlaminar shear strength,compress strength and impact strength were analyzed based on the theory of response surface methodology.A quadratic polynomial regression equation was set up to forecast the relationship between the processing parameters and mechanical property.The effectiveness and reliability of regression model were verified through the test analysis such as predicated versus actual.Furthermore,the optimal process parameters of AFP were obtained.To analyze the bonding condition between fiber and resin matrix and the broken morphology this paper observed the broken morphology.