Study on re-entrant hierarchical honeycombs in-plane impact

Area of Science:

• Materials Science
• Mechanical Engineering
• Nanotechnology

Background:

• Hierarchical structures enhance energy absorption in cell materials.
• Negative Poisson's ratio (NPR) materials offer unique deformation and energy absorption capabilities.

Purpose of the Study:

• To improve the mechanical properties and energy absorption of re-entrant honeycomb (RHA) structures.
• To introduce an augmented double arrow honeycomb structure as a substructure within RHA.
• To investigate the energy absorption enhancement through a novel hierarchical design.

Main Methods:

• Derivation of analytical formulas for collapse stress under quasi-static compression using a two-scale method.
• Analysis of failure stress under varying relative densities and impact velocities.
• Development of an analytical formula for RHA stress during dynamic crushing via momentum conservation.

Main Results:

• The augmented RHA exhibits two distinct plateau periods in its stress-strain response.
• Collapse stress in the first plateau period is comparable to first-order re-entrant honeycombs.
• Collapse stress in the second plateau period shows a significant increase of 332%.

Conclusions:

• The proposed hierarchical honeycomb structure with a second plateau period significantly enhances energy absorption.
• This design represents an effective strategy for improving the impact resistance of cellular materials.
• Further exploration can optimize this structure for advanced impact mitigation applications.