Auxetic Energy-Absorbing Material for Local Impact Densification

Solution Overview

Problem

Current impact protection solutions, such as rigid exterior shells and foam pads, are either uncomfortable or provide inadequate protection due to limited energy absorption and increased peak impact forces, as they often fracture and move away from the impact site, reducing their effectiveness.

Innovation Solution

A flexible energy absorbing system is developed by incorporating a strain rate sensitive material with re-entrant geometry and a tensile layer, which locally densifies at the impact site, preventing material movement and enhancing energy absorption characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If flexible energy absorbing material is used, then comfort and flexibility are improved, but impact protection performance deteriorates due to material fracture and movement away from impact site

Engineering Contradiction:

Improvecomfort and flexibilityVSAvoidimpact protection performance

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The energy absorbing material is pre-configured with re-entrant geometry (auxetic structure) before impact occurs. This preliminary structural configuration enables the material to locally densify at the impact site upon impact, preventing material movement and fracture while maintaining flexibility and comfort during normal wear.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The material's density parameter changes locally at the impact site through the re-entrant geometry mechanism. Upon impact, the material transitions from a low-density flexible state to a high-density protective state at the contact area, while remaining flexible elsewhere, thus resolving the contradiction between comfort and protection performance.

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If material compression is limited to plateau region, then energy absorption is improved, but protection fails when further compression occurs due to bottoming out and fracture

Engineering Contradiction:

Improveenergy absorptionVSAvoidresistance to fracture

Core Design Contradiction:

Loss of energyVSStrength

Solution Approach 1:

The re-entrant geometry creates local quality differences within the material structure. At the impact site, the material locally densifies to provide high strength and fracture resistance, while other areas maintain their original low-density, high-energy-absorption characteristics. This spatial differentiation allows the material to simultaneously absorb energy and resist fracture.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The auxetic structure is pre-configured to enable controlled local densification before impact occurs. This preliminary structural arrangement ensures that when impact happens, the material can transition to a denser state at the impact site to prevent bottoming out and fracture, while maintaining energy absorption capacity in non-impact areas.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If re-entrant geometry is introduced, then local densification at impact site is achieved, but device complexity increases

Engineering Contradiction:

Improveimpact resistanceVSAvoidstructural complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The re-entrant geometry creates local quality differences within the material structure. At the impact site, the material locally densifies to provide high strength and fracture resistance, while other areas maintain their original low-density, high-energy-absorption characteristics. This spatial differentiation allows the material to simultaneously absorb energy and resist fracture.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The auxetic structure is pre-configured to enable controlled local densification before impact occurs. This preliminary structural arrangement ensures that when impact happens, the material can transition to a denser state at the impact site to prevent bottoming out and fracture, while maintaining energy absorption capacity in non-impact areas.

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The system significantly improves impact resistance and comfort by maintaining material at the impact site, reducing peak transmitted forces and enhancing energy management, as demonstrated by reduced back face signatures and improved performance in impact tests.

Implementation Method 1

a material coated, impregnated, and/or combined with a strain rate sensitive substance and formed so as to define repeating adjacent cells, each cell having a re-entrant geometry configured such that, upon impact, the material locally densifies at the impact site

Methodology Applied

Scientific EffectStrain rate sensitivity:

Implementation Method 2

each cell having a re-entrant geometry configured such that, upon impact, the material locally densifies at the impact site

Methodology Applied

Scientific EffectRe-entrant geometry densification: Auxetic Structures

Data Source

PatentUS11746849B2Energy absorbing system

Publication Date: 2023.09.05 RHEON LABS LTD

AI summary

A flexible energy absorbing system comprising a material coated, impregnated and/or combined with a strain rate sensitive substance is disclosed. It is formed so as to define repeating adjacent cells, each cell having a re-entrant geometry such that, upon impact, the material locally densifies at the impact site.