Damage Resistant Glass Laminate with Compressive Stress
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Solution Overview
Problem
Conventional glass substrates used in automotive exterior applications are prone to breakage due to mechanical impacts and deep flaws, leading to significant failure rates and limited mechanical reliability, which is exacerbated by stringent regulatory requirements.
Innovation Solution
A glass substrate design featuring a glass clad layer fused to a glass core layer, where the clad layer has a lower coefficient of thermal expansion than the core layer, with compressive stress extending from the surface to a depth of at least 10% of the substrate's thickness, and incorporating boron oxide (B2O3) in the clad composition to manage tensile stress and enhance mechanical reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional glass substrates are used in automotive exterior applications, then manufacturing simplicity is maintained, but mechanical reliability and resistance to breakage deteriorate due to significant failure rates from mechanical impacts and deep flaws
Solution Approach 1:
The patent applies composite materials by fusing a glass core layer with a glass clad layer having different chemical compositions and coefficients of thermal expansion. The clad layer contains boron oxide (B2O3) at concentrations between 10-50 wt%, creating a composite structure that combines the benefits of both layers to achieve improved mechanical reliability and impact resistance while maintaining manufacturing feasibility
Solution Approach 2:
The patent implements local quality by creating a layered structure where the clad layer has specific local properties (lower CTE, higher B2O3 content) that differ from the core layer. This local differentiation allows the clad layer to provide enhanced protection against mechanical impacts and deep flaws while the core layer maintains structural integrity
2Strength
If the glass clad layer has a lower coefficient of thermal expansion than the glass core layer, then compressive stress is generated to prevent crack propagation, but tensile stress in the core layer increases which may lead to breakage
Solution Approach 1:
The patent applies parameter changes by carefully controlling the coefficient of thermal expansion (CTE) difference between the clad and core layers, and by optimizing the boron oxide content in the clad layer (10-50 wt%). These parameter adjustments enable the generation of beneficial compressive stress in the clad layer while limiting excessive tensile stress development in the core layer, achieving an optimal balance for crack resistance
Solution Approach 2:
The patent implements beforehand cushioning by pre-establishing compressive stress in the clad layer through the CTE differential during manufacturing. This pre-compressive stress acts as a cushioning effect that counteracts subsequent tensile stresses from mechanical impacts, preventing crack propagation before failures can occur
3Reliability
If compressive stress extends deeper into the substrate (greater than or equal to 10% of total thickness), then resistance to mechanical impacts improves, but manufacturing control and stress distribution become more difficult
Solution Approach 1:
The patent applies parameter changes by optimizing the boron oxide content in the clad layer (10-50 wt%) and controlling the CTE differential between layers to achieve the desired compressive stress depth. These parameter adjustments enable compression extending to at least 10% of total thickness while maintaining manufacturability through established glass forming processes
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 significantly reduces crack propagation and improves mechanical reliability, enabling the glass substrate to withstand deeper impacts without shattering, while maintaining strength and resistance to thermal cycling.
Implementation Method 1
The glass core layer comprises a core glass composition having an average core coefficient of thermal expansion (CTEcore) and the glass clad layer comprises a clad glass composition having an average clad coefficient of thermal expansion (CTEclad) that is less than the CTEcore
Data Source
AI summary
A glass substrate comprises a glass clad layer fused to a glass core layer. The glass core layer comprises a core glass composition having an average core coefficient of thermal expansion (CTEcore) and the glass clad layer comprises a clad glass composition having an average clad coefficient of thermal expansion (CTEclad) that is less than the CTEcore. A maximum tensile stress in the glass core layer is less than 15 MPa.