Multilayer Foam Sheet Structure for Shear Strength and Flexibility
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Solution Overview
Problem
Foam sheets used in electronic devices require improved flexibility and mechanical strength in the shear direction, as well as enhanced level-difference conformability and gas sealability to address issues with uneven displays and gas-purged environments.
Innovation Solution
A multilayer foam sheet comprising a base layer and a surface layer, with specific properties such as low-speed shear modulus, compressive strength, and moisture permeability, to enhance flexibility, mechanical strength, and gas sealability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the expansion ratio of foam is lowered to improve mechanical strength in the shear direction, then the mechanical strength is improved, but the flexibility decreases
Solution Approach 1:
The invention uses a composite structure consisting of a base layer and a surface layer with different properties. The base layer provides flexibility while the surface layer provides mechanical strength in the shear direction, resolving the contradiction between flexibility and shear strength through material composition rather than uniform expansion ratio control.
2Reliability
If a conventional foam sheet is used for sealing the outer periphery of a hard disk housing, then sealing is provided, but gas sealability and level-difference conformability are insufficient
Solution Approach 1:
The invention applies local quality by giving different layers different properties: the base layer is designed with high elasticity and low shear modulus to conform to level differences, while the surface layer is designed with high mechanical strength and gas impermeability to provide reliable gas sealing. This resolves the contradiction between conformability and sealability through spatial differentiation of material properties.
Data Source
AI summary
Provided is a multilayer foam sheet excellent in flexibility and mechanical strength in the shear direction.A multilayer foam sheet of the present invention is a multilayer foam sheet including: a base layer including a foam layer, and a surface layer including a foam layer or a resin film and laminated on at least one side of the base layer directly or with another layer interposed therebetween, a low-speed shear modulus being 50 MPa or more, and a 25% compressive strength being 125 kPa or less.