粘不粘？有机微颗粒材料抗拉强度的测量
Sticky or not sticky? Measurements of the tensile strength of micro-granular organic materials
摘要：
了解原行星和彗星物质的力学性质对于更好地理解彗星活动和行星形成的早期阶段至关重要。抗拉强度决定了从彗星表面剥离颗粒、卵石和团块所需的压力，也描述了宏观物体在材料失效之前可以承受多大的应变。由于有机物质在太空中无处不在，它们可能在行星形成过程中发挥了重要作用。本工作提供了五种不同的微颗粒有机材料，即腐殖酸，石蜡，褐煤，木炭和石墨的抗拉强度的新数据。这些材料通过所谓的巴西圆盘测试进行研究，并且将所得的拉伸强度值归一化为标准粒度和体积填充因子。我们发现，这些材料的拉伸强度范围超过四个数量级。石墨和石蜡具有比二氧化硅高得多的拉伸强度，而煤具有非常低的拉伸强度值。这项工作表明，有机物质通常并不像人们通常认为的那样比硅酸盐或水冰更粘稠。
英文摘要：
Knowledge of the mechanical properties of protoplanetary and cometary matter is of key importance to better understand the activity of comets and the early stages of planet formation. The tensile strength determines the required pressure to lift off grains, pebbles and agglomerates from the cometary surface and also describes how much strain a macroscopic body can withstand before material failure occurs. As organic materials are ubiquitous in space, they could have played an important role during the planet formation process. This work provides new data on the tensile strength of five different micro-granular organic materials, namely, humic acid, paraffin, brown coal, charcoal and graphite. These materials are investigated by the so-called Brazilian Disc Test and the resulting tensile strength values are normalised to a standard grain size and volume filling factor. We find that the tensile strength of these materials ranges over four orders of magnitude. Graphite and paraffin possess tensile strengths much higher than silica, whereas coals have very low tensile strength values. This work demonstrates that organic materials are not generally stickier than silicates, or water ice, as often believed.
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