Abba Mohammed T, Hunger Philipp M, Kalidindi Surya R, Wegst Ulrike G K
The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405, USA.
Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA.
J Mech Behav Biomed Mater. 2015 Mar;55:140-150. doi: 10.1016/j.jmbbm.2015.10.013. Epub 2015 Oct 30.
Functional materials often are hybrids composed of biopolymers and mineral constituents. The arrangement and interactions of the constituents frequently lead to hierarchical structures with exceptional mechanical properties and multifunctionality. In this study, hybrid thin films with a nacre-like brick-and-mortar microstructure were fabricated in a straightforward and reproducible manner through manual shear casting using the biopolymer chitosan as the matrix material (mortar) and alumina platelets as the reinforcing particles (bricks). The ratio of inorganic to organic content was varied from 0% to 15% and the relative humidities from 36% to 75% to determine their effects on the mechanical properties. It was found that increasing the volume fraction of alumina from 0% to 15% results in a twofold increase in the modulus of the film, but decreases the tensile strength by up to 30%, when the volume fraction of alumina is higher than 5%. Additionally, this study quantifies and illustrates the critical role of the relative humidity on the mechanical properties of the hybrid film. Increasing the relative humidity from 36% to 75% decreases the modulus and strength by about 45% and triples the strain at failure. These results suggest that complex hybrid materials can be manufactured and tailor made for specific applications or environmental conditions.
功能材料通常是由生物聚合物和矿物质成分组成的复合材料。这些成分的排列和相互作用常常会形成具有卓越机械性能和多功能性的分级结构。在本研究中，通过手动剪切浇铸，以简单且可重复的方式制备了具有类似珍珠母的砖石结构微观结构的混合薄膜，使用生物聚合物壳聚糖作为基体材料（灰浆），氧化铝薄片作为增强颗粒（砖块）。无机与有机成分的比例从0%变化到15%，相对湿度从36%变化到75%，以确定它们对机械性能的影响。研究发现，当氧化铝的体积分数从0%增加到15%时，薄膜的模量增加了两倍，但当氧化铝的体积分数高于5%时，拉伸强度降低了高达30%。此外，本研究量化并说明了相对湿度对混合薄膜机械性能的关键作用。将相对湿度从36%提高到75%会使模量和强度降低约45%，并使破坏应变增加两倍。这些结果表明，可以制造复杂的混合材料并针对特定应用或环境条件进行定制。
