Ballistic Helmet Shell Using Optimized Polyethylene Matrix
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Solution Overview
Problem
Existing ballistic-resistant helmets with reduced areal density using HMPE fibers suffer from poor blunt impact performance and low ear-to-ear stiffness, compromising their protective capabilities against lateral compression and back face deformation.
Innovation Solution
A process involving compression molding of a stack of composite sheets with unidirectionally aligned ultra-high molecular weight polyethylene (UHMWPE) fibers and a polyethylene resin matrix, optimized for temperature and pressure conditions to produce a lightweight, high-stiffness, and high-ballistic-performance helmet shell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If HMPE fiber composites are used to reduce helmet weight, then weight is reduced, but blunt impact performance deteriorates
Solution Approach 1:
The invention changes the matrix material parameter from conventional polymers to specifically polyethylene with density 900-970 kg/m³ and melt flow index 0.5-50 g/10min, which optimizes the balance between weight reduction and blunt impact performance by controlling the matrix's mechanical properties while maintaining lightweight characteristics
Solution Approach 2:
The invention uses a composite material system combining HMPE fibers with polyethylene matrix, where the specific combination of high-strength fibers and optimized matrix material achieves both weight reduction and improved blunt impact resistance that neither material could achieve alone
2Quantity of substance
If areal density is reduced by replacing aramid or inorganic fibers with HMPE, then weight is reduced, but ear to ear stiffness deteriorates
Solution Approach 1:
The invention optimizes the polyethylene matrix parameters (density 900-970 kg/m³, melt flow index 0.5-50 g/10min) to achieve the right balance between reducing areal density and maintaining sufficient ear to ear stiffness for lateral compression resistance
3Length of stationary object
If helmet thickness is reduced to achieve light weight, then weight is reduced, but back face deformation performance deteriorates
Solution Approach 1:
The invention employs a composite structure of HMPE fibers embedded in polyethylene matrix that provides high strength-to-thickness ratio, enabling reduced helmet thickness while maintaining or improving back face deformation performance through the synergistic effect of fiber reinforcement and optimized matrix material
Solution Approach 2:
By changing the matrix material to polyethylene with specific properties (density 900-970 kg/m³, melt flow index 0.5-50 g/10min), the invention achieves better energy absorption and deformation characteristics that improve back face performance even at reduced thickness
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 resulting helmet shells exhibit improved ballistic resistance, reduced blunt impact acceleration, enhanced ear-to-ear stiffness, and lower back face deformation, meeting stringent protection standards while maintaining a low areal density.
Implementation Method 1
composite sheets comprising unidirectionally aligned ultra-high molecular weight polyethylene (UHMWPE) fibers and a matrix comprising a polyethylene resin
Implementation Method 2
pressing in a mold a stack comprising a plurality of composite sheets
Implementation Method 3
pressing in a mold a stack comprising a plurality of composite sheets having unidirectionally aligned ultra-high molecular weight polyethylene (UHMWPE) fibers and a matrix comprising a polyethylene resin
Data Source
AI summary
The invention relates to a process for producing a ballistic-resistant curved molded article said process comprising forming a stack of a plurality of composite sheets, pressing the stack comprising the composite sheets at a temperature of between 80° C. to 150° C. and a pressure of between 10 and 400 bar for at least 5 minutes to obtain a curved molded article, cooling the compacted stack to a temperature below 80° C. while maintaining the pressure above 10 bar, releasing the pressure from the cooled curved molded article; wherein the composite sheets comprise unidirectionally aligned high tenacity polyethylene fibers and a matrix comprising a polyethylene resin being a homopolymer or copolymer of ethylene having a density of between 870 to 980 kg/m3 when measured according to ISO1183 and a melt flow index of between 0.5 and 50 g/10 min when measured according to ASTM 1238B-13 at a temperature of 190° C. and a weight of 21.6 kg.