Dual-Layer Thermoplastic Casing for Impact Resistance
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Solution Overview
Problem
Existing manufacturing processes for rigid hollow protection casings, such as helmets and body armors, cannot effectively incorporate long reinforcing fibers due to distribution challenges, leading to irregular surfaces and increased production costs.
Innovation Solution
A dual-layered thermoplastic casing design, where a first layer composed of a matrix with long-fiber fabric is combined with a second exterior layer of a different thermoplastic material, ensuring even fiber distribution and improved surface finish, with long fibers like fiberglass, carbon, or aramid fibers making up 45-65% of the first layer and the second layer covering imperfections and enhancing abrasion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If long reinforcing fibres are included in the thermoplastic matrix, then the impact resistance and strength of the casing are improved, but the fibres cannot be correctly distributed in the mould by injection process
Solution Approach 1:
The casing is divided into two separate layers: a first layer containing the long-fibre fabric reinforcement and a second outer layer without fibres. This segmentation allows the fibrous layer to be manufactured separately and then bonded to the outer layer, solving the distribution problem while maintaining strength benefits.
Solution Approach 2:
The long-fibre fabric layer is embedded within the thermoplastic matrix of the first layer, creating a nested structure where the fibres are contained and properly positioned within the mould cavity before the outer layer is formed.
2Ease of manufacture
If an outer layer formed by short fibres is used, then the mould can be easily filled by injection process, but the surface finish becomes irregular and uneven requiring sanding and polishing
Solution Approach 1:
The fibrous reinforcement is extracted from the outer surface layer and placed exclusively in the inner first layer. This removes the cause of surface irregularities while preserving the structural benefits of fibre reinforcement in the load-bearing layer.
Solution Approach 2:
The fibrous reinforcement is localized to the first inner layer where it provides structural strength, while the second outer layer is made of smooth thermoplastic material specifically for achieving a high-quality surface finish without fibres.
3Strength
If long-fibre fabric layer is included in the casing, then the strength and impact resistance are improved, but the production cost increases due to sanding and polishing steps
Solution Approach 1:
By segmenting the casing into two layers with fibres only in the inner layer, the need for post-manufacturing surface treatment is eliminated, reducing production costs while maintaining the strength benefits of fibre reinforcement.
Solution Approach 2:
The fibres are taken out from the outer surface and confined to the inner layer, eliminating the need for sanding and polishing operations and thereby reducing manufacturing costs while preserving structural integrity.
4Strength
If a single layer with long fibres is used, then the impact resistance is improved, but the abrasion resistance and surface finish deteriorate
Solution Approach 1:
Different layers are assigned different qualities: the first inner layer contains fibres for impact resistance while the second outer layer is fibre-free smooth thermoplastic material optimized for abrasion resistance and surface finish.
Solution Approach 2:
The casing uses a composite structure with two distinct layers: a fibrous composite inner layer for structural strength and impact resistance, and a smooth thermoplastic outer layer for abrasion resistance and aesthetic finish.
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 allows for enhanced impact resistance and reduced material usage while maintaining or exceeding the performance of single-layer casings, with a smoother surface finish and improved abrasion resistance without the need for additional polishing, thereby reducing production costs and enhancing the casing's overall durability.
Implementation Method 1
a thermoplastic material is employed that solidifies by the application of heat, so that after the moulding the shell hardens
Implementation Method 2
other layers of softer or deformable material, such as foam or padded elements, intended to absorb as much energy as possible from the impact and to deform to increase the deceleration distance
Data Source
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AI summary
The rigid hollow protection casing (30) includes a first rigid layer (10) composed of a matrix of a first thermoplastic material (11) including in its interior at least one long-fibre fabric layer (12) selected from fibreglass, carbon fibre and/or aramid fibre and comprising between 45% and 65% of the total weight of the first layer (10); a second overlapping rigid layer (20) exterior to the first layer (10), the second layer (20) being entirely composed of a matrix thereof or of a second thermoplastic material (21), the second layer (20) comprising between 2% and 10% of the total weight of the casing (30).