Özen Arda, Ganzosch Gregor, Völlmecke Christina, Auhl Dietmar
Chair of Polymer Materials Science and Technologies, Institute of Material Science and Technology, Technische Universität Berlin, Ernst-Reuter-Platz 1, 10587 Berlin, Germany.
Chair of Continuum Mechanics and Materials Theory, Institute of Mechanics, Technische Universität Berlin, Einsteinufer 5, 10587 Berlin, Germany.
Polymers (Basel). 2022 Aug 26;14(17):3512. doi: 10.3390/polym14173512.
Additive manufacturing is an emerging technology and provides high design flexibility to customers. Fused deposition modeling (FDM) is an economical and promising additive manufacturing method. Due to its many advantages, FDM received great attention in recent years, and comprehensive studies are being undertaken to investigate the properties of FDM-printed polymers and polymer composites. As a result of the manufacturing technology employed in FDM, inner structures are changed with different process parameters, and thus, anisotropic properties are observed. Moreover, composite filaments such as particle- or fiber-reinforced polymers already have anisotropy before FDM printing. In this study, we investigate the effect of different process parameters, namely layer thickness and raster width on FDM-printed copper-reinforced poly(lactic acid) (PLA). Mechanical characterizations with a high-resolution camera are carried out for analyzing the deformation behaviors. Optical microscopy characterizations are performed to observe the mesostructural changes with various process parameters. Scanning electron microscopy (SEM) and an energy-dispersive X-ray spectroscopy (EDS) analysis are conducted for investigating the microstructure, specifically, copper particles in the PLA matrix. A 2D digital image correlation code with a machine learning algorithm is applied to the optical characterization and SEM-EDS images. In this way, micro- and mesostructural features, as well as the porosity ratios of the specimens are investigated. We prepare the multiscale homogenization by finite element method (FEM) simulations to capture the material's response, both on a microscale and a mesoscale. We determined that the mesostructure and, thereby, the mechanical properties are significantly changed with the aforementioned process parameters. A lower layer thickness and a greater raster width led to a higher elasticity modulus and ultimate tensile strength (UTS). The optical microscopy analysis verified this statement: Decreasing the layer thickness and increasing the raster width result in larger contact lines between adjacent layers and, hence, lower porosity on the mesoscale. Realistic CAD images were prepared regarding the mesostructural differences and porosity ratios. Ultimately, all these changes are accurately modeled with mesoscale and multiscale simulations. The simulation results are validated by laboratory experiments.
增材制造是一项新兴技术，为客户提供了高度的设计灵活性。熔融沉积建模（FDM）是一种经济且有前景的增材制造方法。由于其诸多优点，FDM近年来受到了极大关注，目前正在进行全面研究以探究FDM打印聚合物及聚合物复合材料的性能。由于FDM所采用的制造技术，内部结构会随不同工艺参数而改变，因此会观察到各向异性特性。此外，诸如颗粒增强或纤维增强聚合物之类的复合长丝在FDM打印之前就已经具有各向异性。在本研究中，我们研究了不同工艺参数，即层厚和光栅宽度对FDM打印的铜增强聚乳酸（PLA）的影响。使用高分辨率相机进行力学表征以分析变形行为。进行光学显微镜表征以观察不同工艺参数下的细观结构变化。进行扫描电子显微镜（SEM）和能量色散X射线光谱（EDS）分析以研究微观结构，具体而言是PLA基体中的铜颗粒。将带有机器学习算法的二维数字图像相关代码应用于光学表征和SEM - EDS图像。通过这种方式，研究了试样的微观和细观结构特征以及孔隙率。我们通过有限元方法（FEM）模拟准备多尺度均匀化，以捕捉材料在微观和细观尺度上的响应。我们确定，上述工艺参数会显著改变细观结构，进而改变力学性能。较低的层厚和较大的光栅宽度会导致更高的弹性模量和极限拉伸强度（UTS）。光学显微镜分析证实了这一说法：减小层厚并增加光栅宽度会导致相邻层之间的接触线更大，从而在细观尺度上孔隙率更低。针对细观结构差异和孔隙率制备了逼真的CAD图像。最终，所有这些变化都通过细观尺度和多尺度模拟进行了精确建模。模拟结果通过实验室实验进行了验证。
