Constitutive modeling of UV-curing printed polymer composites

紫外固化印刷聚合物复合材料的本构建模

• 批准号: 406819523
• 负责人: Professor Dr.-Ing. Alexander Lion
• 金额: --
• 依托单位: Institut für Mechanik (LRT-4)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/406819523?language=en
• 关键词: Constitutive; modeling; UV; curing; printed

3D-printing is an innovative technique to manufacture three-dimensional objects with complex shape. Processed materials are metals, ceramics or polymers depending on the working principle of the printer. During the point- or layer-wise printing the material experiences a transition from a liquid to a solid and a temperature change accompanied by changes in the thermomechanical and caloric material behavior. The process leads to gradients in the material properties and to residual stresses which influence the mechanical behavior and the shape of the structure in desired or undesired manners. Since the processed materials are inelastic these effects depend on time and temperature and on the parameters of the printing and post-treatment process. Due to the lack of understanding, missing constitutive models and simulation tools, such problems are usually faced by costly trial-and-error methods. To keep the costs in view, this project is focused to 3D-printing of filler-modified polymers which are exothermally curing under UV radiation. Our main objectives are to understand, to model, to simulate and to optimize the printing and post-printer processes of filler-modified polymer structures. Therefore, the experiments start with investigations of the UV-induced curing of filler-modified and unfilled polymers: calorimetric, rheometric and volumetric experiments under UV- and temperature-control are planned. Printed and post-treated tensile bars of composites are analysed in dependence on the process-parameters like temperature, UV-intensity, layer thickness or time-scales. Using the data of the unfilled polymer, a degree of cure-dependent model of thermoviscoelasticity will be developed. It describes curing-induced changes in the material properties, is fitted to the experimental data and implemented into a finite element code. A differential equation with UV intensity-dependent parameters is developed to describe the evolution of the degree of cure. If the glass transition temperature of the fully cured polymer is above the curing temperature, diffusion control is taken into account. The distribution and the geometry of the filler particles in printed samples are studied by electron microscopy and the influence of the filler to the material behavior of the composites by mechanical testing. Merging this information, a reference volume element is created whose homogenized behavior is computed under further assumptions with the finite element implementation of the thermoviscoelastic model for the matrix and compared with experiments.Lastly, the simulation chain is applied to simulate the printing process and the post treatment of lattice structures. At different times during the post treatment, the measured and simulated geometries and residual stresses are compared. If the validation is successful, the simulation chain provides optimal process parameters minimizing residual stresses and keeping the printed shape stable and within admissible tolerances.

3D打印是一种制造复杂形状三维物体的创新技术。根据打印机的工作原理，处理的材料是金属、陶瓷或聚合物。在点式或层式打印过程中，材料会经历从液体到固体的转变以及伴随着热机械和热量材料行为变化的温度变化。该过程会导致材料特性的梯度和残余应力，从而以期望或不期望的方式影响结构的机械行为和形状。由于加工的材料是非弹性的，这些影响取决于时间和温度以及印刷和后处理过程的参数。由于缺乏理解、缺少本构模型和仿真工具，此类问题通常需要通过成本高昂的试错方法来解决。为了控制成本，该项目专注于填料改性聚合物的 3D 打印，这些聚合物在紫外线辐射下放热固化。我们的主要目标是了解、建模、模拟和优化填料改性聚合物结构的印刷和后印刷工艺。因此，实验从研究填料改性和未填充聚合物的紫外线诱导固化开始：计划在紫外线和温度控制下进行量热、流变和体积实验。根据温度、紫外线强度、层厚度或时间尺度等工艺参数对印刷和后处理的复合材料拉伸棒进行分析。使用未填充聚合物的数据，将开发一定程度的固化相关的热粘弹性模型。它描述了固化引起的材料性能变化，适合实验数据并实施为有限元代码。开发了具有与紫外线强度相关的参数的微分方程来描述固化程度的演变。如果完全固化的聚合物的玻璃化转变温度高于固化温度，则需要考虑扩散控制。通过电子显微镜研究打印样品中填料颗粒的分布和几何形状，并通过机械测试研究填料对复合材料材料行为的影响。合并这些信息，创建一个参考体积单元，在进一步假设下使用矩阵热粘弹性模型的有限元实现来计算其均质行为，并与实验进行比较。最后，应用模拟链来模拟打印过程和后期处理晶格结构的处理。在后处理的不同时间，对测量的和模拟的几何形状以及残余应力进行比较。如果验证成功，模拟链将提供最佳工艺参数，最大限度地减少残余应力并保持打印形状稳定且在允许的公差范围内。