Mozafari Hozhabr, Dong Pengfei, Hadidi Haitham, Sealy Michael P, Gu Linxia
Department of Mechanical & Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.
Materials (Basel). 2018 Dec 20;12(1):1. doi: 10.3390/ma12010001.
The objective of this study is to characterize the micromechanical properties of poly-l-lactic acid (PLLA) composites reinforced by grade 420 stainless steel (SS) particles with a specific focus on the interphase properties. The specimens were manufactured using 3D printing techniques due to its many benefits, including high accuracy, cost effectiveness and customized geometry. The adopted fused filament fabrication resulted in a thin interphase layer with an average thickness of 3 µm. The mechanical properties of each phase, as well as the interphase, were characterized by nanoindentation tests. The effect of matrix degradation, i.e., imperfect bonding, on the elastic modulus of the composite was further examined by a representative volume element (RVE) model. The results showed that the interphase layer provided a smooth transition of elastic modulus from steel particles to the polymeric matrix. A 10% volume fraction of steel particles could enhance the elastic modulus of PLLA polymer by 31%. In addition, steel particles took 37% to 59% of the applied load with respect to the particle volume fraction. We found that degradation of the interphase reduced the elastic modulus of the composite by 70% and 7% under tensile and compressive loads, respectively. The shear modulus of the composite with 10% particles decreased by 36%, i.e., lower than pure PLLA, when debonding occurred.
本研究的目的是表征由420级不锈钢（SS）颗粒增强的聚左旋乳酸（PLLA）复合材料的微观力学性能，特别关注其界面性能。由于3D打印技术具有诸多优点，包括高精度、成本效益和定制几何形状等，因此使用该技术制造试样。所采用的熔融沉积成型工艺形成了平均厚度为3 µm的薄界面层。通过纳米压痕试验表征了各相以及界面的力学性能。通过代表性体积单元（RVE）模型进一步研究了基体降解（即粘结不完善）对复合材料弹性模量的影响。结果表明，界面层使弹性模量从钢颗粒到聚合物基体实现了平滑过渡。10%体积分数的钢颗粒可使PLLA聚合物的弹性模量提高31%。此外，相对于颗粒体积分数，钢颗粒承担了37%至59%的外加负载。我们发现，在拉伸和压缩载荷下，界面降解分别使复合材料的弹性模量降低了70%和7%。当发生脱粘时，含10%颗粒的复合材料的剪切模量降低了36%，即低于纯PLLA。
