Non-classical scaling of strength with size in marine biological fibers

TL;DR

This paper reports that marine sponge glass fibers exhibit a non-classical inverse quadratic scaling of strength with size, exceeding traditional expectations and suggesting new avenues for engineering material design.

Contribution

It reveals a novel non-classical size-strength scaling law in marine sponge fibers, supported by experiments and fracture mechanics analysis.

Findings

Strength scales inversely with the square of the specimen size

Maximum tensile strength reaches 1.5 GPa in smallest fibers

Flaw size decreases faster than specimen size, explaining the scaling

Abstract

Intriguing physical phenomena observed in natural materials have inspired the development of several engineering materials with dramatically improved performance. Marine sponge glass fibers, for instance, have attracted interest in recent decades. We tested the glass fibers in tension and observed that the strength of these fibers scales inversely with their size. While it is expected that the strength of a material scales inversely with its size, the scaling is generally believed to be inversely proportional to the square root of the specimen dimension. Interestingly, we found that the marine sponge glass fibers' strength scaled much faster, and was inversely proportional to the square of the specimen dimension. Such non-classical scaling is consistent with the experimental measurements and classical linear elastic fracture mechanics. We hypothesize that this enhanced scaling is due to the flaw size decreasing faster than the size of the specimen. The tensile strength, as a result of non-classical, higher-order scaling, reached a value as large as 1.5 GPa for the smallest diameter specimen. The manufacturing processes through which the spicules are made might hold important lesson for further enhancing the strength of engineering materials.