Composite Airbag Cover Structure for Low Tensile Strength
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Solution Overview
Problem
Existing composite structures for airbag covers lack a balance of low tensile strength, flexibility, and haptics, making them unsuitable for reliable deployment without material weakening or adverse effects on softness and design.
Innovation Solution
A composite structure comprising a polyolefin foam layer, an inner layer with a high content of polypropylene and elastomer particles, and an outer layer with a different polymer composition, all bonded together with a lacquer layer, achieving a tensile strength of less than 5 MPa and resistance to tear of less than 25 N/mm without the need for perforation lines or additives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional materials like PVC or PUR with spacer materials are used for airbag covers, then the material provides sufficient strength and durability, but the material becomes expensive and lacks the required flexibility and softness
Solution Approach 1:
The patent uses a composite structure consisting of a foam layer (providing flexibility and softness) combined with a compact cover layer (providing strength and durability). This composite approach allows the material to meet mechanical requirements without using expensive traditional materials like PVC or PUR with spacer materials, thereby resolving the contradiction between strength and cost-effectiveness.
2Strength
If the airbag cover material is made strong and rigid, then the material provides durability and protection, but the material becomes difficult to tear at predetermined breaking points and loses flexibility
Solution Approach 1:
The patent applies local quality by creating a composite structure where the foam layer provides flexibility and controlled tearability at specific locations (predetermined breaking points), while the compact cover layer provides overall durability and strength. This allows the material to be strong where needed and easily tearable where required, resolving the contradiction between durability and tearing behavior.
3Strength
If the foam layer density is increased to improve structural integrity, then the material becomes stronger, but the material loses softness and flexibility
Solution Approach 1:
The patent resolves this contradiction by combining a foam layer with controlled density (providing softness and flexibility) with a compact cover layer (providing structural integrity and strength). The composite structure allows each layer to perform its specific function optimally, achieving both structural integrity and softness that would be impossible with a single material.
4Strength
If perforation lines or weakening components like microspheres are added to achieve low tensile strength, then the material becomes easier to tear, but the material complexity and manufacturing cost increase
Solution Approach 1:
The patent achieves low tensile strength and easy tearing without adding complexity by optimizing the parameters of the composite structure itself - specifically the density of the foam layer (40 to 150 kg/m³) and the composition of the compact cover layer. This intrinsic parameter optimization eliminates the need for additional weakening components like microspheres or perforation lines, resolving the contradiction between tensile strength and material complexity.
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 composite structure provides a cost-effective, flexible, and tearable airbag cover with improved handling and sewing properties, suitable for complex geometries like U-shapes, and is recyclable, offering a superior alternative to traditional materials like PVC or PUR.
Implementation Method 1
the foam layer consists of or contains a polyolefin foam, the density of the foam layer is 40 to 150 kg/m 3
Implementation Method 2
an inner layer and an outer layer of a thermoplastic compact cover layer, and a lacquer layer in this order
Data Source
AI summary
The invention provides a composite structure containing a foam layer, an inner layer and an outer layer of a thermoplastic compact cover layer, and a lacquer layer in this order, and having a tensile strength according to DIN EN ISO 527-3 at 2000 mm/min and 23 °C of less than 5 MPa in both a first direction and a second direction perpendicular to the first direction, wherein the density of the foam layer is 40 to 150 kg/m3, the inner layer contains particles of an elastomer (polymer (F)) and at least 50 wt% of a thermoplastic polyolefin (polymer (E)) and is directly bonded to the outer layer, the outer layer differs from the inner layer in its composition and contains the following polymers (A) to (C) in a total amount of 100 parts by weight: 25 to 70 parts by weight of particles of an elastomer (polymer (A)), 0 to 40 parts by weight of a low-density polyethylene (polymer (B)), and 20 to 70 parts by weight of a thermoplastic polyolefin (polymer (C)) other than polymer (B). The invention provides the use of the composite structure in car interiors, in particular as airbag cover, a method for the production of the composite structure.