Polyethylene Composite Sheet Ballistic Resistance
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Solution Overview
Problem
Existing composite sheets used in ballistic resistant articles face challenges in processing robustness, dimensional stability under extreme temperature fluctuations, and quality consistency, leading to defects such as bubbling and displacement during manufacturing.
Innovation Solution
A composite sheet comprising at least two adjacent fibrous monolayers of unidirectionally aligned high tenacity polyethylene fibers, with fiber orientation differing by 80° to 90°, embedded in a matrix of ethylene homopolymer or copolymer with specific density and melt flow index ranges, enhancing processing robustness and ballistic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If composite sheets with improved ballistic performance are used, then ballistic resistance is improved, but processing robustness deteriorates and manufacturing complexity increases
Solution Approach 1:
The invention changes the chemical composition parameter of the matrix material from conventional polymers to specifically polyethylene with 2-10 wt% silica particles. This parameter change improves ballistic resistance while maintaining processing robustness, as the silica-modified polyethylene matrix provides both enhanced mechanical properties and favorable processing characteristics.
Solution Approach 2:
The invention uses a composite matrix material consisting of polyethylene combined with silica particles. This composite approach allows the matrix to simultaneously provide the flexibility needed for easy processing and the strength required for high ballistic performance, resolving the contradiction between ease of manufacture and ballistic resistance.
2Manufacturing precision
If compression processes are extended to improve quality, then manufacturing precision is improved, but production time increases
Solution Approach 1:
The invention modifies the matrix material composition by adding silica particles to polyethylene, which changes the rheological and thermal properties of the material. This parameter change enables faster compression cycles while maintaining high quality consistency, as the modified matrix provides better flow characteristics and faster setting time.
Solution Approach 2:
The silica-modified matrix material allows the compression process to be completed more rapidly by improving material flow and consolidation speed. The enhanced processing characteristics enable the process to 'rush through' the critical compression phase faster while still achieving defect-free quality, reducing production time without sacrificing manufacturing precision.
3Strength
If fiber alignment is optimized for ballistic performance, then strength is improved, but processing difficulty increases
Solution Approach 1:
The invention changes the matrix material parameters by incorporating silica particles into polyethylene, which modifies the material's viscosity and flow characteristics. This parameter change facilitates easier fiber alignment during processing while maintaining the high ballistic performance achieved through optimized fiber orientation, thereby reducing process control complexity.
Data Source
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AI summary
The invention relates to a composite sheet comprising at least two adjacent fibrous monolayers of unidirectionally aligned high tenacity polyethylene fibers, whereby the direction of orientation between the polyethylene fibers of said two fibrous layers differs by at least 80° and up to 90°, the fibers having a tenacity of at least 1.5 N/tex, said fibers being in a matrix comprising a homopolymer or copolymer of ethylene and wherein said homopolymer or copolymer of ethylene has a density as measured according to ISO1183 of between 870 to 980 kg/m3, said composite sheet having an areal density of between 50 and 500 g/m2 wherein the composite sheet has an areal density normalized in-plane shear force measured at 25°C evaluated according to the bias extension test method of at least 0.40 N.m2.g-1 at 10 mm clamp displacement.