Wang Xue, Zhao Liping, Fuh Jerry Ying Hsi, Lee Heow Pueh
Department of Mechanical Engineering, National University of Singapore, Singapore 117575, Singapore.
National Metrology Centre, 1 Science Park Drive, Singapore 118221, Singapore.
Polymers (Basel). 2019 Jul 5;11(7):1154. doi: 10.3390/polym11071154.
Additive manufacturing (commonly known as 3D printing) is defined as a family of technologies that deposit and consolidate materials to create a 3D object as opposed to subtractive manufacturing methodologies. Fused deposition modeling (FDM), one of the most popular additive manufacturing techniques, has demonstrated extensive applications in various industries such as medical prosthetics, automotive, and aeronautics. As a thermal process, FDM may introduce internal voids and pores into the fabricated thermoplastics, giving rise to potential reduction on the mechanical properties. This paper aims to investigate the effects of the microscopic pores on the mechanical properties of material fabricated by the FDM process via experiments and micromechanical modeling. More specifically, the three-dimensional microscopic details of the internal pores, such as size, shape, density, and spatial location were quantitatively characterized by X-ray computed tomography (XCT) and, subsequently, experiments were conducted to characterize the mechanical properties of the material. Based on the microscopic details of the pores characterized by XCT, a micromechanical model was proposed to predict the mechanical properties of the material as a function of the porosity (ratio of total volume of the pores over total volume of the material). The prediction results of the mechanical properties were found to be in agreement with the experimental data as well as the existing works. The proposed micromechanical model allows the future designers to predict the elastic properties of the 3D printed material based on the porosity from XCT results. This provides a possibility of saving the experimental cost on destructive testing.
增材制造（通常称为3D打印）被定义为一类技术，它通过沉积和固结材料来创建三维物体，这与减材制造方法相反。熔融沉积建模（FDM）是最流行的增材制造技术之一，已在医疗假肢、汽车和航空等各个行业中得到广泛应用。作为一种热加工工艺，FDM可能会在制造的热塑性塑料中引入内部空隙和孔隙，从而导致机械性能的潜在下降。本文旨在通过实验和微观力学建模研究微观孔隙对FDM工艺制造的材料机械性能的影响。更具体地说，通过X射线计算机断层扫描（XCT）对内部孔隙的三维微观细节，如尺寸、形状、密度和空间位置进行了定量表征，随后进行实验以表征材料的机械性能。基于XCT表征的孔隙微观细节，提出了一个微观力学模型来预测材料的机械性能与孔隙率（孔隙总体积与材料总体积之比）的函数关系。发现机械性能的预测结果与实验数据以及现有研究结果一致。所提出的微观力学模型使未来的设计师能够根据XCT结果的孔隙率预测3D打印材料的弹性性能。这为节省破坏性测试的实验成本提供了可能性。
