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Mechanical properties of Non-self similar Two Hierarchical Bio-inspired Composites

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Mechanical properties of Non-self similar Two Hierarchical Bio-inspired Composites

Aerospace Engineering

Biological composites such as bone, nacre, spider silk, and bamboo are known for their magnificent mechanical properties compared to their constituents at the basic level. Their fine mechanical properties such as high strength and toughness are attributed to various geometric and material properties. Of these, the staggering type and hierarchical structure are two essential geometrical properties responsible for the superior mechanical properties. Bio-inspired composites are artificial composites inspired from the design of biological composites. In our recent study, the mechanical properties of two hierarchical (2H) non-self-similar composites are analysed. The results show that the 2H non-self-similar composites possess much higher toughness than single hierarchical regular staggered (RSM) and stairwise staggered models (SSM) available in the literature. From Figure 2, it can be seen that on using two levels of non-self-similar hierarchy, the toughness can be amplified by a factor of more than 20 while keeping the strength at 20% of the platelet. But, a substantial reduction of elastic stiffness (less than 1% of the platelet stiffness) is observed at these values. A minimum stiffness of 2% of the platelet was kept and it is found that the toughness gain is still greater than 10 times irrespective of the type of staggering at both levels of hierarchy. Moreover, the non-self-similar composites seem to be characterized with much better strength for a similar toughness as that of self-similar 2H composites. Thus, these results indicate that 2H non-self similar composite may be used to obtain excellent toughness combined with good strength.

 

Figure 2: a) Two Hierarchical Regularly Staggered Composite made with Stairwise Staggered Composite as platelet (2H RS); (b) Zoomed view of platelet with Stairwise Staggered Structure; (c) Two Hierarchical Stairwise Staggered Composite made with Regularly Staggered Composite as platelet (2H SR) (d) Zoomed view of platelet with Regularly Staggered Structure; Normalized strength vs normalized maximum toughness for (e) 2H RS model , (f) 2H SR model

Ref: Abhirami, A. J., & Anup, S. (2021). Mechanical properties of unidirectional bio-inspired composites with two non-self-similar hierarchical structures. Mechanics of Materials, 163, 104082.

 

ae7_05052022