热塑性树脂及树脂基复合材料多点热成形机制和控形控性方法

Thermoplastic resins and resin-based composite materials have the characters of light weight, high strength, high modulus, resistance to fatigue and corrosion, good formability, and easy to manufacture large-scale overall structure, which has been widely used in the fields of architecture, automobile, aeronautics and astronautics. In order to provide a high quality, efficient, low-cost method for thermoplastic resins and resin-based composite materials with small quantity and many varieties, the multi-point hot forming technology is proposed, which is combined by multi-point forming and hot forming. With the goal of control technology of shape and performance for multi-point hot forming, the mechanisms of discontinuous heat transmission and non-uniform force transmission for multi-point hot forming are carried out for thermoplastic resins and resin-based composite materials. The behaviors, influence factors and variation discipline of non-uniform heat transmission and discontinuous force transmission are explored. The tensile tests of thermoplastic resins and resin-based composite materials are putted forward. The accurate constitutive model of large deformation discontinuous heat transmission, the program of thermoplastic resins and resin-based composite materials, and the equivalent finite element model of non-uniform force transmission are established. The Influence law of punch shape, punch radius, forming temperature, holding time, forming pressure and dwell time on the forming quality and performance of thermoplastic resins and resin-based composite materials are researched, and the control methods of uniform temperature and load are explored.

热塑性树脂及树脂基复合材料具有轻重量、高强度、高模量、抗疲劳、耐腐蚀、工艺性好等特点，容易制造大型整体结构件，在建筑、汽车、航空航天等领域得到广泛应用。为了给小批量、多品种热塑性树脂及树脂基复合材料成形提供一种优质、高效、低价方法，本课题通过将多点成形技术和热成形相结合，提出多点热成形技术。以控形控性多点热成形为目标，开展热塑性树脂及树脂基复合材料多点热成形非连续导热和非均匀传力机制研究，探索多点热成形非连续导热和非均匀传力行为、影响因素及其变化规律；开展热塑性树脂及树脂基复合材料力学性能试验，建立大变形非连续导热条件下的精确本构模型、热塑性树脂及树脂基复合材料程序、以及非均匀传力条件下等效有限元模型；研究冲头形状、冲头半径、成形温度、保温时间、成形压强和保压时间等工艺参数对热塑性树脂及树脂基复合材料多点热成形精度和性能的影响规律，探索其多点热成形均匀控温和加载方法。

针对建筑、汽车、航空等领域对热塑性树脂及树脂基复合材料零件柔性成形方法的迫切需求，开展了多点热成形技术研究。建立了多点热成形非连续导热关系模型和多点热成形非均匀传力关系模型，测得PC和PMMA的玻璃态转变温度，获得其应力松弛曲线、WLF方程参数和应力应变曲线。开展了PC板广义Maxwell模型和PC-DSGZ模型多点热成形对比分析，结果表明PC-DSGZ模型结果与实验结果更接近。建立了树脂板多点热成形等效有限元模型，探讨了成形温度、成形压强、冲头数量和冲头半径对成形精度的影响，结果表明：成形温度越高或成形压强越大，平均形状误差越小；冲头数量越多或冲头半径越大，压痕越轻微。研究了板厚、半径和成形温度对起皱的影响，结果表明:板料越厚、半径越大、成形温度越低，起皱越轻微，获得了不同条件下的无皱曲成形极限。提出了多步多点热成形抑制起皱的方法，结果表明：成形步数越多，最大皱曲量越小。研究了材料、板厚和半径对冷却收缩变形的影响，提出了多点模具型面补偿冷却收缩变形来降低成形误差的方法。探索了多点热成形均匀控温与加载方法，开展了大量多点热成形实验，结果表明：PC板最佳成形温度区间为150℃-160℃、PMMA板最佳成形温度区间为110℃-120℃、Corian板最佳成形温度区间为155℃-165℃。大尺寸PMMA板多点热成形零件无银纹、烧伤、压痕、起皱等缺陷，90%以上区域的误差分布在±1.5mm的区间范围，透光率超过75%。这说明多点热成形技术可用于热塑性树脂及树脂基复合材料控形控性成形，具有广泛的应用前景。