Laminated Glass Strength Control via CTE Mismatch
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Solution Overview
Problem
Existing methods for forming laminated glass sheets in a laminate fusion draw apparatus do not effectively control the final strength properties, as they fail to manage the viscoelastic glass properties and coefficient of thermal expansion (CTE) differences between core and clad glasses, leading to unpredictable strength retention and cutting difficulties.
Innovation Solution
A double fusion process is employed to create a laminated glass sheet by selecting core and clad glass compositions with specific CTE profiles, processing them to achieve desired strength conditions through the glass transition zone, and controlling the cooling rate to manipulate viscoelastic behavior and thermal strain differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If existing methods for forming laminated glass sheets are used, then the glass sheets can be formed in a laminate fusion draw apparatus, but the final strength properties cannot be effectively controlled and strength retention is unpredictable
Solution Approach 1:
The patent applies parameter changes by systematically varying the cooling rate parameter to control the viscoelastic behavior of glass during processing. By changing the cooling rate from 1-15°C per second, the patent achieves control over the final strength properties and strength retention of the laminated glass sheet, transforming an unpredictable process into a controllable one through parameter optimization
Solution Approach 2:
The patent utilizes thermal expansion differences between core and clad glasses by creating a controlled CTE (coefficient of thermal expansion) mismatch. This thermal expansion principle generates thermal strain differences during cooling, which directly influences the final strength properties of the laminate by inducing compressive or tensile stresses in specific layers
2Ease of manufacture
If CTE differences between core and clad glasses are not managed, then the lamination process can proceed, but strength retention becomes unpredictable and cutting becomes difficult
Solution Approach 1:
The patent deliberately creates and manages CTE differences between core and clad glasses to generate controlled thermal strain during cooling. This thermal expansion control enables both improved strength retention through induced compressive stresses and easier cutting by creating a viscoelastic zone where the glass can be more easily separated
Solution Approach 2:
By controlling the cooling rate parameter within the range of 1-15°C per second, the patent optimizes the viscoelastic behavior of the glass during the critical cooling phase. This parameter control simultaneously achieves both goals: maintaining strength through controlled stress development and creating favorable conditions for cutting by managing the glass transition behavior
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
This method results in a strengthened laminated glass sheet with enhanced strength retention and ease of cutting, as demonstrated by maintaining 92% of its strength when reheated, compared to prior art which loses significant strength, and allowing for easier cutting in the viscoelastic zone.
Implementation Method 1
creating or generating a difference in the coefficient of thermal expansion (CTE) between the two different glasses of the core (CTEcore) and the clad (CTEclad)
Implementation Method 2
managing the viscoelastic glass properties of the constituent glasses
Data Source
AI summary
A method for making a glass laminate sheet including:selecting a core glass composition and a clad glass composition combination for a glass laminate structure;determining and comparing the viscosity and coefficient of thermal expansion (CTE) profiles for each of the selected core and the clad glass compositions with each other over a temperature range of interest including the onset of viscoelasticity to ambient temperature; andprocessing the selected core and clad glass composition in a laminate fusion draw apparatus to form a laminate glass sheet in accordance with at least one difference condition for the clad effective coefficient thermal expansion (CTEeff core) and the core effective coefficient thermal expansion (CTEeff core). Another method for making a glass laminate sheet includes controlling the cooling rate to control the resulting strength of the laminate.