Hierarchical Impact-Absorbing Material with Fluid-Filled Features
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Solution Overview
Problem
Current impact-absorbing materials used in helmets and protective gear are inadequate in dissipating energy effectively, leading to a high incidence of head injuries in sports and other activities, as they often saturate quickly, causing large stress concentrations and failing to absorb impacts efficiently.
Innovation Solution
A novel impact-absorbing material with a hierarchical structure featuring multiple sizes of stress-concentrating features, where the material proximate to larger features deforms first, followed by intermediate and then smaller features, filled with a fluid to enhance energy dissipation, and a method of manufacturing this material using a mold with specific geometric features and subatmospheric pressure to create a polymer with optimized energy absorption properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional foam materials are used for impact absorption, then the material structure is simple and easy to manufacture, but the energy dissipation capability is insufficient and the material saturates quickly causing large stress concentrations
Solution Approach 1:
The material is segmented into a hierarchical structure with multiple generations of stress-concentrating features (first, second, and third features) at different size scales. This segmentation allows progressive deformation through multiple levels, enhancing energy dissipation while distributing stress concentrations across different spatial scales rather than concentrating them in a single level.
Solution Approach 2:
Different regions of the material are given different local properties through the hierarchical arrangement of stress-concentrating features. The first features (10-200 microns) are distributed throughout the matrix material, while second features (100-2000 microns) and third features (1000-10000 microns) are strategically positioned to create zones of progressive deformation, allowing each region to contribute differently to overall energy absorption.
2Loss of energy
If the material uses a hierarchical structure with multiple sizes of stress-concentrating features, then the energy absorption capability is improved, but the manufacturing process becomes more complex requiring specific mold cavities and curing procedures
Solution Approach 1:
The hierarchical structure of stress-concentrating features is pre-formed within the mold cavity before the final material curing step. The mold cavity is designed with geometric features that directly create the first, second, and third stress-concentrating features during the curing process, eliminating the need for post-manufacturing assembly or complex multi-step fabrication procedures.
Solution Approach 2:
A mold cavity acts as an intermediary tool that translates a relatively simple manufacturing process into a complex hierarchical material structure. The mold cavity with its specific geometric features serves as the mediating element that imprints the multi-scale stress-concentrating features onto the curable compound during curing, simplifying the overall manufacturing approach while achieving structural complexity.
3Loss of energy
If the stress-concentrating features are filled with fluid, then the energy dissipation is enhanced through progressive buckling, but the material requires additional processing steps for fluid infiltration
Solution Approach 1:
The fluid infiltration is performed preliminarily during the material curing process rather than as a separate post-processing step. The curable compound is placed in the mold cavity with the geometric features, allowed to cure for at least five minutes to establish the hierarchical structure, and then exposed to subatmospheric pressure to draw the fluid into the stress-concentrating features, combining structure formation and fluid infiltration in an integrated sequence.
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 material exhibits improved energy absorption capabilities, maintaining efficient load dissipation beyond conventional foam materials, reducing peak stresses and strains, and providing enhanced protection against impacts and blast/shock waves.
Implementation Method 1
providing a compound that is curable to form a polymer, curing the compound for at least about five minutes
Implementation Method 2
The material proximate to the first, second, and third features progressively buckles upon application of the load
Implementation Method 3
Materials capable of absorbing impacts find a wide variety of uses... provide improved dissipation of energy
Implementation Method 4
exposing the mixture in the mold cavity to pressure less than ambient pressure after said permitting
Data Source
AI summary
A compound for protection of an object from a blast or shock wave. The compound include a matrix material and at least a first and second sets of inclusions in the matrix material that differ in size, quantity, shape and/or composition in a direction through the impact-absorbing material, the combination of which contributes to the ability of the material to exhibit at least one property that changes as the inclusions are deformed in response to a blast or shock wave.