Department of Biomechanical Engineering, Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology (TU Delft), Mekelweg 2, 2628 CD, Delft, The Netherlands.
Department of Chemistry, Materials and Chemical Engineering Giulio Natta, Politecnico di Milano, Piazza Leonardo da Vinci, 32, 20133, Milano, Italy.
Sci Rep. 2018 Aug 13;8(1):12052. doi: 10.1038/s41598-018-30012-9.
Biomimetic composites are usually made by combining hard and soft phases using, for example, multi-material additive manufacturing (AM). Like other fabrication methods, AM techniques are limited by the resolution of the device, hence, setting a minimum length scale. The effects of this length scale on the performance of hard-soft composites are not well understood. Here, we studied how this length scale affects the fracture toughness behavior of single-edge notched specimens made using random, semi-random, and ordered arrangements of the hard and soft phases with five different ratios of hard to soft phases. Increase in the length scale (40 to 960 μm) was found to cause a four-fold drop in the fracture toughness. The effects of the length scale were also modulated by the arrangement and volumetric ratio of both phases. A decreased size of the crack tip plastic zone, a crack path going through the soft phase, and highly strained areas far from the crack tip were the main mechanisms explaining the drop of the fracture toughness with the length scale.
仿生复合材料通常通过使用例如多材料增材制造（AM）将硬相与软相结合来制造。与其他制造方法一样，AM 技术受到设备分辨率的限制，因此存在最小长度尺度。该长度尺度对硬-软复合材料性能的影响尚未得到很好的理解。在这里，我们研究了该长度尺度如何影响使用硬相和软相的随机、半随机和有序排列制成的单边缺口试样的断裂韧性行为，其中硬相和软相的比例有五种不同。研究发现，随着长度尺度的增加（40 至 960 μm），断裂韧性下降了四倍。长度尺度的影响还受到两相的排列和体积比的调制。裂纹尖端塑性区尺寸减小、裂纹穿过软相以及远离裂纹尖端的高应变区是解释断裂韧性随长度尺度下降的主要机制。
