Hierarchical Materials
Hierarchical materials are a class of materials with emergent, holistic properties from the structural layout of simple materials across multiple length scales. The most common examples of hierarchical materials come from nature.[1]. Muscle fibers and cellular structures exhibit multilayer architecture that promotes robust environmental interactions. Muscle fibers span five unique length scales: macroscopic organ level to nanoscale myosin and actin ordering. Synthetic hierarchical materials are much more difficult to achieve due to processing challenges, so two to three length scales are more common, such as in carbon fiber composites and ceramic nanolattices[2]. There are a few synthetic examples of robust materials that span five or more length scales, though. Current research focuses on designing manufacturing techniques that afford structural design across multiple length scales [3]
Hierarchical materials display superior mechanical responses than their components. Well-defined structures across multiple length scales control the distribution of mechanical stresses, ensuring high strength. They also tend to avoid catastrophic failure because there is inherent redundancy built into the structural form via fibers, so cracks cannot propagate as easily. Instead, a crack breaks one fiber and undergoes fiber pullout. This process blunts the crack tip, lowers the stress concentration, and requires a higher stress to continue cracking.
Most materials suffer from mechanical property tradeoffs. For example, traditional materials are either strong or tough, but not both. Compliance and strength are inversely related, too. However, hierarchical materials attempt to break those boundaries and improve both properties simultaneously. Individually, one length scale may have a structure that is incredibly strong and inflexible. However, combining the stiff structure with a compliant one dramatically improves the net stiffness and compliance[4]
References
- ↑ Wegst, Ulrike G. K.; Bai, Hao; Saiz, Eduardo; Tomsia, Antoni P.; Ritchie, Robert O. (January 19, 2015). "Bioinspired structural materials". Nature Materials. 14 (1): 23–36. Bibcode:2015NatMa..14...23W. doi:10.1038/nmat4089. PMID 25344782 – via www.nature.com. Unknown parameter
|s2cid=ignored (help) - ↑ Meza, Lucas R.; Das, Satyajit; Greer, Julia R. (2014). "Strong, lightweight, and recoverable three-dimensional ceramic nanolattices". Science. 345 (6202): 1322–1326. Bibcode:2014Sci...345.1322M. doi:10.1126/science.1255908. PMID 25214624. Unknown parameter
|s2cid=ignored (help) - ↑ Hua, Mutian; Wu, Shuwang; Ma, Yanfei; Zhao, Yusen; Chen, Zilin; Frenkel, Imri; Strzalka, Joseph; Zhou, Hua; Zhu, Xinyuan; He, Ximin (February 19, 2021). "Strong tough hydrogels via the synergy of freeze-casting and salting out". Nature. 590 (7847): 594–599. Bibcode:2021Natur.590..594H. doi:10.1038/s41586-021-03212-z. OSTI 1774154. PMID 33627812 Check
|pmid=value (help) – via www.nature.com. Unknown parameter|s2cid=ignored (help) - ↑ Jia, Zian; Yu, Yang; Wang, Lifeng (April 15, 2019). "Learning from nature: Use material architecture to break the performance tradeoffs". Materials & Design. 168: 107650. doi:10.1016/j.matdes.2019.107650 – via ScienceDirect. Unknown parameter
|s2cid=ignored (help)
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