Chinese scholars have made progress in analyzing the novel structure and mechanical properties of natural materials

Figure 1 Ginkgo husk is assembled from stone cells interlocking through "striated holes"

Fig.
2 The unique stone cell "interlock" structure of ginkgo husk gives it excellent specific fracture toughness

Figure 3 "Pores" induce cracks to enter the inside of stone cells and absorb energy through stratification and tearing

With the funding of the National Natural Science Foundation of China (grant numbers: 52125302, 22075009, 51961130388, 21875010 and 51903125), Professor Cheng Qunfeng's research group from the School of Chemistry of Beihang University made progress in analyzing the novel structure and mechanical properties of natural ginkgo husk unique model for bioinspired design", published online in the journal Proceedings of the National Academy of Sciences on November 28
, 2022.
Link to paper: _istranslated="1">.

Natural structural materials, such as wood, bone, abalone shell, etc.
, have excellent mechanical properties, especially resistance to crack propagation
.
The high fracture toughness of such materials is mainly due to the termination effect of micro-nano multi-level substructures on cracks, that is, the efficient external toughening mechanism
.
Most of the mechanical properties of the widely studied natural structural materials are highly anisotropic, which makes it difficult for these materials to resist crack propagation
in all directions.

In view of this, the researchers discovered for the first time the unique structure of "interlocking" ginkgo shell stone cells, which have excellent resistance
to crack propagation in different directions.
Ginkgo husks are tightly bound together by a large number of polygonal stone cells with thick cell walls (Figure 1).

In the inner secondary wall of the stone cells are slender tubes, known as striated pores
, with a radius of about 1.
2 microns.
These striated pores extend from the cavity in the middle of the cell to the intercellular layer, forming a "striated pair" structure with the striated pores of adjacent stone cells, "interlocking" adjacent cell walls
.
This unique structure makes the _K-ICs of the ginkgo husk almost uniform in all directions (Figure 2), and under loading, the striated pore induces the cell wall near the intercellular layer in stone cells to absorb energy through stratification and tearing (Figure 3).

In this work, the peculiar structure of the porous interlocking stone cells of the ginkgo husk was discovered, which gave the ginkgo husk the ability to resist crack propagation in all directions, and provided biomimetic enlightenment
for the construction of polymer nanocomposites with isotropic mechanical properties.