Strain-Responsive Armor Fabrics for Lower BFD at Reduced Weight
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Solution Overview
Problem
Current soft body armor systems made from woven fabrics face challenges in achieving low back face deformation (BFD) while maintaining ballistic resistance, often requiring high weight density and compromising on comfort due to the use of high-stiffness impregnated layers and non-woven laminates.
Innovation Solution
Incorporating a low glass transition temperature viscous polymer adhesive with strain-responsive properties, such as ethylene/methyl acrylate copolymer, into the fabric layers to reduce basis weight and enhance ballistic performance by maintaining flexibility and self-healing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high weight density woven fabric systems are used to achieve low BFD, then ballistic protection performance is improved, but wearer comfort deteriorates due to excessive weight
Solution Approach 1:
The patent changes the physical state of the adhesive from solid to viscous liquid with low glass transition temperature, allowing the fabric to achieve low BFD with reduced weight by utilizing the strain-responsive flow behavior of the liquid polymer at impact conditions
Solution Approach 2:
The patent creates a composite fabric system combining woven aramid fibers with viscous liquid polymer adhesive, where the polymer impregnates the fabric structure to provide both flexibility during normal wear and rigidification upon ballistic impact
2Reliability
If solid adhesive impregnation is used to reduce BFD, then ballistic performance is improved, but penetration resistance deteriorates due to high stiffness and processing conditions
Solution Approach 1:
The patent changes the adhesive state from solid to viscous liquid, enabling impregnation at lower temperatures and pressures that preserve fiber integrity and ballistic properties while still achieving low BFD through strain-responsive behavior at impact
Solution Approach 2:
The patent uses a small amount of viscous polymer adhesive (1-8% by weight) that flows and distributes throughout the fabric structure, providing adequate bonding and impact response without the excessive stiffness of solid adhesive systems
3Reliability
If non-woven laminated structures are used to reduce BFD, then ballistic protection is improved, but basis weight increases compromising lightweight design
Solution Approach 1:
The patent utilizes the strain-responsive viscosity change of the liquid polymer to achieve low BFD in a woven fabric structure without adding substantial weight, as the polymer remains flexible during normal wear but rigidifies upon impact
Solution Approach 2:
The patent creates a lightweight composite by impregnating woven aramid fabric with viscous liquid polymer, combining the high strength of the fiber structure with the strain-responsive behavior of the polymer to replace heavier non-woven laminates
4Reliability
If high stiffness impregnated layers are used to control BFD, then ballistic performance is improved, but flexibility and comfort deteriorate during normal use
Solution Approach 1:
The patent employs a dynamic material system where the viscous liquid polymer transitions from a flexible state during normal wear to a rigidified state upon ballistic impact, providing both comfort and protection as needed
Solution Approach 2:
The patent exploits the temperature and strain-rate dependent viscosity of the liquid polymer to achieve flexibility at ambient conditions and stiffness at impact conditions, resolving the flexibility-protection tradeoff
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 solution achieves a 20% reduction in basis weight with improved BFD and V50 performance, maintaining flexibility during normal use and stiffening upon impact, resulting in higher projectile blunting and damage resistance comparable to non-woven systems with increased comfort.
Implementation Method 1
Fabrics with strain-responsive viscous liquid polymers
Data Source
AI summary
A penetration resistant article with an area density less than 1.5 lb/ft2 made of a plurality of fibrous fabric layers that have applied thereto about 1 to 8 percent by weight of a polymer having a glass transition temperature in the range of minus 40 to about 0° C. and a zero shear melt viscosity 2×106 to about 1013 poise at 20° C.