Thermoplastic Cellular Polymer Foam for Multi-Directional Crash Energy Absorption
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Solution Overview
Problem
Current energy-absorbing foams used in vehicles are expensive, heavy, and require specific orientation for efficient crash absorption, while also being prone to degradation due to friability from vibration and weathering.
Innovation Solution
A thermoplastic cellular polymer foam with a polystyrenic or polystyrenic copolymer structure, containing a blowing agent like carbon dioxide or water, which maintains high compressive efficiency in multiple directions without friability, ensuring effective energy absorption regardless of orientation and resisting degradation over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If closed cell thermoset foams such as polyurethane/polyurea are used for crash mitigation, then crash energy absorption efficiency is improved, but the foam deteriorates over time due to vibration and weathering
Solution Approach 1:
The patent changes the chemical composition parameters by using thermoplastic polymers (polyethylene, polypropylene, polyvinylidene fluoride) instead of thermoset polymers, and adjusts the cell structure parameters to achieve both high energy absorption and resistance to environmental degradation. This parameter change resolves the contradiction between crash efficiency and long-term durability.
2Loss of energy
If anisotropic foams with oriented cells are used to achieve efficient crash absorption, then energy absorption efficiency is improved, but the foam must be oriented properly relative to the impact direction
Solution Approach 1:
The patent creates a foam structure that appears asymmetric in its cell morphology but achieves functional symmetry in performance. The non-uniform cell structure provides high compressive strength in all directions, resolving the contradiction between optimized energy absorption and multi-directional adaptability.
Solution Approach 2:
The foam structure is designed to perform the same energy absorption function effectively in multiple impact directions, making it universally applicable regardless of crash orientation. This multi-functionality resolves the limitation of oriented foams that require specific alignment.
3Ease of manufacture
If conventional thermoplastic foams are used, then cost is reduced, but weight for compressive energy absorbed is greater than desired
Solution Approach 1:
The patent uses composite material structures combining thermoplastic polymers with specific cell configurations to achieve high energy absorption efficiency. The composite approach optimizes the weight-to-energy-absorption ratio while maintaining cost-effectiveness through the use of common thermoplastic materials.
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 foam achieves excellent compressive efficiency and durability, dissipating energy uniformly in various impact directions without degrading from environmental factors, thus providing enhanced safety and cost-effectiveness.
Implementation Method 1
foams that absorb energy not merely by elastically deforming, but by inelastically deforming (i.e., being crushed)
Implementation Method 2
the cellular polymer has an average cell size of at least about 0.75 mm and at least one of CE/CT, CV/CT and CH/CT is from 0.25 to 0.4, said one of CE/CT, CV/CT and CH/CT having a compressive efficiency of at least 70% at a 60% strain
Data Source
AI summary
An improved energy absorbing member comprising, an thermoplastic cellular polymer in contact with a structural element such as a metal guard rail or automotive door, wherein the cellular polymer has an average cell size of at least about 0.75 mm and at least one of CE/CT, CV/CT and CH/CT is about 0.25 to about 0.4 said one of CE/CT, Cv/Ct and CH/CT having a compressive efficiency of at least 70% at a 60% strain, CE, Cv and CH being the compressive strength of the cellular polymer in each of three orthogonal directions E, V and H where one of these directions is the direction of maximum compressive strength in the foam and Cx equals the sum of CE, Cv and CH.