Research On Heating And Cooling Process Of Thermoplastic Composite Fiber Placement

Thermoplastic composite has broad prospects in aerospace field due to itsadvantages of high specific strength, high specific modulus, no reflecting theelectromagnetic wave and high designability. Fiber reinforced thermoplasticcomposite placement is an important auto consolidation process. It offers thepotential to significantly reduce consolidation process time and increase productionrate when processing of large parts. The temperature and its lasting time exactlyaffect the final part quality because the thermoplastic composite is so sensitive totemperature. Thus, it has important theoretical significance and practical value instudying the heating and cooling process in the thermoplastic composite fiberplacement.In this work, the effects of heating and cooling process parameters on productquality and consolidation efficiency from different perspectives based on thecharacter of the fiber placement. First, after the basic process is determined, a2-dimension heat transfer model is developed. The boundary conditions aretransfered to the differential equation and the problem can be analyzed with finiteelement method. The problem is solved in the ANSYS software to obtain thetemperature distribution in the substrate and the prepreg.Next, through analyzing the heat transfer in the substrate and the prepreg, thesafe temperature and the maximum roller velocity are determined. The inconsistencyof heating at the edge and center of the prepreg caused by circular heat source isanalyzed. The rule that not only the center of the prepreg can not be heated todegradation temperature, but also the edge must be raised to melting temperature isproposed. The effects of roller velocity, heating length, heating temperature,different heating length on the substrate and prepreg, different heat source type onthe temperature distribution are analyzed. These parameters are limited by bondingtime, bonding length, glass temperature, melting temperature, the numbers of theplies above the glass temperature.Then, because the prepreg is easy to be raised to higher temperature, only thesubstrate need to be preheated. Through analyzing the effect of the preheating ontemperature distribution in the substrate, it can decrease the temperature gradient inthe top surface of the substrate. Thus, a higher roller velocity can be applied. Thepreheating temperature, preheating position and preheating length are also analyzed.Finally, The crystallinity is discussed qualitatively based on the cooling time. Ifa low heating temperature is used at low roller velocity and a high heating temperature, at high low roller velocity, a larger crystallinity degree can beobstained.