Research On Winding In-situ Curing Process Of Thermoplastic Composites

Carbon fiber reinforced thermoplastic resin matrix composites have become more and more popular due to their in-situ curing,good recyclability,environmental friendliness,and store convenience.They have broad applications in aerospace,transportation,oil and gas pipelines and other civil and military fields.The winding process is an automated method for molding fiber-reinforced composites,and its application to thermoplastic composites tends to achieve efficient,high quality and low cost molding of thermoplastic composites.This paper focuses on the in-situ curing process of thermoplastic composites by winding,aiming to explore the influence of key process parameters on samples' quality.During the winding process of thermoplastic composites,they need to go through resin melting-bonding-curing process,and the temperature field distribution has a crucial influence on interlayer bond strength.In this paper,the thermoplastic winding process was analyzed,the geometric model of the winding process was established,its boundary conditions were set,and the mathematical model of heat transfer in the winding process was established.The UMAT moving heat source subroutine based on Abaqus was developed to establish a three-dimensional transient heat transfer finite element model of the winding process,and the effects of winding speed and number of layers on the temperature distribution were obtained.The correctness of the heat transfer model was verified by monitoring the temperature distribution in winding experiments.A differential tension control system was designed and established for the thermoplastic composite winding equipment.The control model of the system was established,after which the open-loop transfer function of the system was obtained,and the stability and rapidity of the system were analyzed.The classical PID control algorithm and the integral separation nonlinear PID control algorithm were designed respectively,and the effects of the diameter of the material tray and signal fluctuation on the two systems' rapidity and stability were compared and analyzed using different algorithms.The PLC programs of the two algorithms were written and the tension experiments were carried out to verify the effectiveness of the algorithms.For thermoplastic composite materials,non-geodesic winding is prone to loose and tight edges,which leads to defects.Taking the ellipsoidal head pressure vessel as an example,the geodesic winding trajectory of the rotary body was designed.The fourcoordinate and five-coordinate winding trajectory solving models were established to analyze the influence of different number of coordinates on the prepreg winding to avoid the occurrence of winding folds.The orthogonal test was designed by selecting three process parameters: winding speed,heating temperature and winding tension,and nine sets of NOL ring samples were prepared.The interlayer shear strengths of the samples were tested under different process parameters,through which the influence of the process parameters on the performance of the parts was obtained by response surface analysis.The results showed that the effect of winding speed on the interlayer strength was small in the selected parameter range,and the interlayer strength increased with the increase of temperature and tension,but after reaching a certain value,insteadly the layer shear strength decreased when the temperature and tension continued to increase.