Müller Miroslav, Šleger Vladimír, Kolář Viktor, Hromasová Monika, Piš Dominik, Mishra Rajesh Kumar
Department of Material Science and Manufacturing Technology, Faculty of Engineering, Czech University of Life Sciences Prague, Kamycka 129, 165 00 Prague-Suchdol, Czech Republic.
Department of Mechanical Engineering, Faculty of Engineering, Czech University of Life Sciences Prague, Kamycka 129, 165 00 Prague-Suchdol, Czech Republic.
Polymers (Basel). 2022 Mar 23;14(7):1301. doi: 10.3390/polym14071301.
Additive production is currently perceived as an advanced technology, where intensive research is carried out in two basic directions-modifications of existing printing materials and the evaluation of mechanical properties depending on individual production parameters and the technology used. The current research is focused on the evaluation of the fatigue behavior of 3D-printed test specimens made of pure PLA and PLA reinforced with filler based on pinewood, bamboo, and cork using FDM (fused deposition modeling) technology. This research was carried out in response to the growing demand for filaments from biodegradable materials. This article describes the results of tensile fatigue tests and image analysis of the fracture surface determined by the SEM method. Biodegradable PLA-based materials have their limitations that influence their applicability in practice. One of these limitations is fatigue life, which is the cyclic load interval exceeding 50% of the tensile strength determined in a static test. Comparison of the cyclic fatigue test results for pure PLA and PLA reinforced with natural reinforcement, e.g., pinewood, bamboo, and cork, showed that, under the same loading conditions, the fatigue life of the 3D-printed specimens was similar, i.e., the filler did not reduce the material's ability to respond to low-cycle fatigue. Cyclic testing did not have a significant effect on the change in tensile strength and associated durability during this loading interval for PLA-based materials reinforced with biological filler. Under cyclic loading, the visco-elastic behavior of the tested materials was found to increase with increasing values of cyclic loading of 30%, 50% and 70%, and the permanent deformation of the tested materials, i.e., viscoelastic behavior (creep), also increased. SEM analysis showed the presence of porosity, interlayer disturbances, and at the same time good interfacial compatibility of PLA with the biological filler.
增材制造目前被视为一项先进技术，人们在两个基本方向上开展了深入研究，即对现有打印材料进行改性，以及根据个体生产参数和所使用的技术评估机械性能。当前的研究重点是使用熔融沉积建模（FDM）技术，对由纯聚乳酸（PLA）以及用松木、竹子和软木制成的填料增强的PLA制成的3D打印试样的疲劳行为进行评估。这项研究是为了响应对可生物降解材料制成的长丝不断增长的需求而开展的。本文描述了拉伸疲劳试验的结果以及通过扫描电子显微镜（SEM）方法确定的断口表面的图像分析。基于可生物降解PLA的材料存在一些限制其实际应用的因素。其中一个限制因素是疲劳寿命，它是指超过静态试验中确定的拉伸强度50%的循环载荷区间。对纯PLA和用天然增强材料（如松木、竹子和软木）增强的PLA的循环疲劳试验结果进行比较表明,在相同的加载条件下，3D打印试样的疲劳寿命相似，即填料并未降低材料对低周疲劳的响应能力。对于用生物填料增强的基于PLA的材料，在该加载区间内，循环测试对拉伸强度的变化和相关耐久性没有显著影响。在循环加载下，发现测试材料的粘弹性行为随着循环加载值分别为30%、50%和70%的增加而增加，并且测试材料的永久变形，即粘弹性行为（蠕变）也增加。扫描电子显微镜分析表明存在孔隙率、层间干扰,同时PLA与生物填料具有良好的界面相容性。
