Issabayeva Zhamila, Shishkovsky Igor
Center for Materials Technologies, Skolkovo Institute of Science and Technology, 121205 Moscow, Russia.
Polymers (Basel). 2023 Feb 25;15(5):1162. doi: 10.3390/polym15051162.
In this study, the mechanical as well as thermomechanical behaviors of shape memory PLA parts are presented. A total of 120 sets with five variable printing parameters were printed by the FDM method. The impact of the printing parameters on the tensile strength, viscoelastic performance, shape fixity, and recovery coefficients were studied. The results show that two printing parameters, the temperature of the extruder and the nozzle diameter, were more significant for the mechanical properties. The values of tensile strength varied from 32 MPa to 50 MPa. The use of a suitable Mooney-Rivlin model to describe the hyperelastic behavior of the material allowed us to gain a good fit for the experimental and simulation curves. For the first time, using this material and method of 3D printing, the thermomechanical analysis (TMA) allowed us to evaluate the thermal deformation of the sample and obtain values of the coefficient of thermal expansion (CTE) at different temperatures, directions, and running curves from 71.37 ppm/K to 276.53 ppm/K. Dynamic mechanical analysis (DMA) showed a similar characteristic of curves and similar values with a deviation of 1-2% despite different printing parameters. The glass transition temperature for all samples with different measurement curves ranged from 63-69 °C. A material crystallinity of 2.2%, considered by differential scanning calorimetry (DSC), confirmed its amorphous nature. From the SMP cycle test, we observed that the stronger the sample, the lower the fatigue from cycle to cycle observed when restoring the initial shape after deformation, while the fixation of the shape did not almost decrease with each SMP cycle and was close to 100%. Comprehensive study demonstrated a complex operational relationship between determined mechanical and thermomechanical properties, combining the characteristics of a thermoplastic material with the shape memory effect and FDM printing parameters.
在本研究中，展示了形状记忆聚乳酸（PLA）部件的力学以及热机械行为。通过熔融沉积成型（FDM）方法打印了总共120组具有五个可变打印参数的部件。研究了打印参数对拉伸强度、粘弹性性能、形状固定率和回复系数的影响。结果表明，挤出机温度和喷嘴直径这两个打印参数对力学性能影响更为显著。拉伸强度值在32兆帕至50兆帕之间变化。使用合适的穆尼-里夫林模型来描述材料的超弹性行为，使我们能够很好地拟合实验曲线和模拟曲线。首次使用这种材料和3D打印方法，热机械分析（TMA）使我们能够评估样品的热变形，并获得不同温度、方向和运行曲线下热膨胀系数（CTE）的值，范围从71.37 ppm/K到276.53 ppm/K。动态力学分析（DMA）表明，尽管打印参数不同，但曲线特征相似，数值偏差为1%-2%。所有具有不同测量曲线的样品的玻璃化转变温度范围为63-69℃。通过差示扫描量热法（DSC）测得的材料结晶度为2.2%，证实了其非晶态性质。从形状记忆聚合物（SMP）循环测试中，我们观察到，样品越强，变形后恢复初始形状时每次循环观察到的疲劳越低，而形状固定率几乎不会随每个SMP循环降低，接近100%。综合研究表明，在确定的力学和热机械性能之间存在复杂的操作关系，将热塑性材料的特性与形状记忆效应和FDM打印参数结合在一起。
