纤维增强聚合物复合材料注塑成型理论与实验研究

发布时间：2018-06-06 05:45

本文选题：纤维增强聚合物 + 注塑成型　；参考：《南昌大学》2017年博士论文

【摘要】：本文针对纤维增强聚合物复合材料注塑成型技术的若干关键问题进行深入研究,以期获得相关成型理论知识,指导提升成型制品质量。本文主要研究内容概要如下:1.搭建了纤维增强聚合物复合材料注塑成型实验装置,设计加工了较复杂结构的注塑成型模具,完成了注塑成型实验装置的安装和调试,并进行了相关实验研究;基于较全面考虑注塑成型过程中形成的残余应力场、温度场、纤维增强聚合物复合材料的非均匀各向异性热力学属性,建立了纤维增强聚合物复合材料注塑成型流动和热应力分析的三维耦合有限元总翘曲变形预测模型。模拟算例与实验结果对比表明:注塑件翘曲变形朝着无加强筋一侧,形成中间低四周高的“拱形”结构,预测值与实验结果变化趋势一致,运用该模型能提升翘曲变形的预测精度,表明该预测模型的有效性。2.围绕注塑成型过程中聚合物熔体模腔充填和纤维取向的核心问题,从粘性流体动力学理论出发,分析纤维增强聚合物复合材料注塑成型熔体流动基本控制方程;针对长纤维增强聚合物复合材料注塑成型的特点,研究注塑成型过程中的纤维分布规律,着重分析和探讨主要工艺参数对纤维分布的影响机理;基于复合材料力学性能均匀化理论,建立长纤维增强聚合物复合材料的非线性弹塑性本构模型,结合耦合有限元分析方法,研究了不同本构模型对翘曲变形计算结果的差异,分析主要纤维参数对翘曲变形的影响规律。研究结果表明:(1)注射时间对纤维取向分布的影响最为显著,浇口附近是长短纤维共存区,近壁面附近纤维较长;随着注射时间的减小或模具温度的升高,纤维取向值和纤维长度均减小;随着熔体温度的升高,纤维取向值减小,但纤维长度则先减小后增大;随着保压压力的增加,纤维长度减小,保压压力对纤维取向的影响与速度/压力转化有关。以上结果与文献结论总体一致。(2)基于弹性和弹塑性本构模型计算的注塑件翘曲变形形状均为中间高四周低的“拱形”结构,前者比后者的最大翘曲变形量小约18%,模拟结果与理论分析相符;随着纤维初始长度、长径比和纤维含量的增加,最大翘曲变形量均随之减小。3.基于有限元数值模拟技术,综合考虑壁面滑移速度和压力对粘度的影响,建立了薄壁注塑流动三维数值模型,通过实验结果对比,验证数值模型的可靠性,考察是否考虑壁面滑移对熔体模腔充填速度分布的影响,分析壁面滑移和粘度的压力依赖性对薄壁模腔熔体充填的影响,从理论上分析和解释其影响机理。数值模拟与实验结果对比表明:只有同时考虑壁面滑移和粘度的压力依赖性才能更好地预测薄壁注塑成型流动过程,忽略壁面滑移或粘度的压力依赖性,对薄壁注塑成型过程均有不同程度的影响。上述研究有助于对薄壁注塑成型理论及较之传统注塑成型固有特性的认识提供理论参考。4.在三维薄壁注塑流动数值模型得到验证的基础上,研究壁面滑移和粘度的压力依赖性,对纤维增强聚合物复合材料薄壁注塑成型纤维取向和翘曲变形的影响,分析不同模型简化条件对数值模拟结果的影响,并从理论上探明其影响机理,研究主要注塑成型工艺参数对纤维增强聚合物复合材料薄壁注塑件的纤维取向分布,以及最大翘曲变形量的影响。研究结果表明:(1)通过与实验结果对比,考虑壁面滑移和粘度压力依赖性的三维数值模拟,能较好地扑捉厚度方向的纤维取向分布,忽略壁面滑移或压力对粘度的影响,对纤维取向分布均有不同程度的影响,基于常规Hele-Shaw薄壁近似计算的芯层纤维取向分布与实际差异较大。(2)注射速率对纤维取向的影响最大,熔体温度次之,模具温度、保压压力和保压时间对纤维取向的影响较小。(3)随着注射速率,熔体温度,模具温度的增加,最大翘曲变形量均随之增大,但注射速率达到一定值后影响减小;随着保压压力的增加,最大翘曲变形量减小;保压时间对最大翘曲变形量的影响较小。
[Abstract]:In this paper, some key problems in the injection molding of fiber reinforced polymer composites are studied in order to obtain relevant theoretical knowledge and guide the quality of molding products. The main contents of this paper are as follows: 1. the experimental device for the injection molding of fiber reinforced polymer composites is set up, and the design and processing are more complex. The injection molding mold of mixed structure has completed the installation and debugging of the injection molding experimental device, and carried out the related experimental research. Based on the comprehensive consideration of the residual stress field, the temperature field and the non-uniform anisotropy of the fiber reinforced polymer composites, the fiber reinforced polymer complex is established. The three dimensional coupled finite element warpage prediction model is used to predict the flow and thermal stress of the injection molding. The comparison of the simulation examples and the experimental results shows that the warpage of the injection parts is facing the non reinforcement side, forming a "arch" structure with low middle height in the middle, and the prediction value is in accordance with the experimental results, and the model can be used to improve the warpage. The prediction accuracy of the curved deformation indicates that the validity of the prediction model is.2. around the core problem of the filling and fiber orientation of the polymer melt in the injection molding process. Based on the viscous fluid dynamics theory, the basic control equation of the melt flow in the injection molding of the fiber reinforced polymer composite is analyzed. The distribution of fiber in the injection molding process is studied, and the influence mechanism of the main process parameters on the fiber distribution is analyzed and discussed. The non linear elastoplastic constitutive model of the long fiber reinforced polymer composites is established based on the homogenization theory of the mechanical properties of the composite materials, and the coupled finite element analysis is combined with the coupled finite element analysis. Method, the difference of warpage calculation results of different constitutive models was studied, and the effect of main fiber parameters on Warpage was analyzed. The results showed that: (1) the effect of injection time on fiber orientation distribution was the most significant, near the gate was long short fiber coexistence area, fiber near the near wall surface was longer, with the injection time decreasing or With the increase of die temperature, the fiber orientation value and fiber length decrease. With the increase of the melt temperature, the fiber orientation value decreases, but the fiber length decreases first and then increases. With the increase of pressure pressure, the fiber length decreases, and the influence of the pressure on the fiber orientation is related to the speed / pressure transformation. The above results are generally with the literature conclusion. (2) the warpage shapes of injection molded parts based on elastic and elastoplastic constitutive models are all "arch" structures with low middle and low middle, the former is about 18% smaller than the latter, and the simulation results agree with the theoretical analysis. With the increase of fiber initial length, length diameter ratio and fiber content, the maximum warpage deformation is all followed. .3. based on the finite element numerical simulation technology and considering the influence of the wall slip velocity and pressure on the viscosity, a three-dimensional numerical model of the thin wall injection flow is established. By comparing the experimental results, the reliability of the numerical model is verified. The effect of the wall slip on the velocity distribution of the melt cavity filling is considered, and the wall slip and the wall slip are analyzed. The effect of pressure dependence of viscosity on melt filling of thin-walled mold cavity is analyzed and explained theoretically. The comparison between numerical simulation and experimental results shows that the pressure dependence of wall slip and viscosity can be better predicted by considering the pressure dependence of wall slip and viscosity at the same time, and the pressure dependence of wall slip or viscosity is ignored. This study provides a theoretical reference for the theory of thin-walled injection molding and the understanding of the inherent characteristics of the traditional injection molding. Based on the verification of the numerical model of three-dimensional thin wall injection flow, the pressure dependence of the slip and viscosity of the wall is studied and the fiber reinforced.4. is reinforced. The influence of the fiber orientation and warp deformation on the thin wall injection molding of polymer composites is analyzed. The influence of different model simplification conditions on the numerical simulation results is analyzed, and the influence mechanism is explored theoretically. The fiber orientation distribution and the maximum warping of the main injection molding process parameters to the fiber reinforced polymer composite thin wall injection molding parts are studied. The results show that: (1) by comparing with the experimental results, the three-dimensional numerical simulation of wall slip and viscosity pressure dependence can be used to catch the fiber orientation distribution in the thickness direction better, neglecting the effect of wall slip or pressure on the viscosity, and to varying degrees of influence on the fiber orientation distribution, based on the conventional Hele The orientation distribution of core fiber in the -Shaw thin wall approximate calculation is different from the actual difference. (2) the injection rate has the greatest influence on the fiber orientation, the melt temperature is the second, the mold temperature, the pressure holding pressure and the holding time have little effect on the fiber orientation. (3) the maximum warping deformation increases with the injection rate, the melting temperature and the mold temperature. It is large, but the effect decreases after the injection rate reaches a certain value, and the maximum warpage deformation decreases with the increase of pressure protection pressure, and the influence of pressure holding time on the maximum warpage is less.
【学位授予单位】：南昌大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ327;TB332

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