Laminated Glass with Modulus Contrast for Flaw Resistance
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Solution Overview
Problem
Glass articles, such as those used in smartphones, suffer from mechanical reliability issues due to deep flaws introduced during use, leading to potential breakage, as they are not adequately resistant to indentation and subsequent stress.
Innovation Solution
A laminated glass article is developed with a core layer and cladding layers having a modulus contrast, where the cladding modulus is at least 5 GPa less than the core modulus and a modulus ratio of at least 1.08, enhancing the retained strength by creating compressive and tensile stresses that resist flaw propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer glass structure is used, then the manufacturing process is simple, but the resistance to deep flaws and mechanical reliability are insufficient
Solution Approach 1:
The glass article is divided into multiple layers: a core glass layer and at least one cladding glass layer with different elastic moduli. This segmentation allows each layer to perform different functions - the core layer provides structural integrity while the cladding layer with lower modulus protects against flaw propagation, thereby improving mechanical reliability without requiring a completely new material.
Solution Approach 2:
The patent uses composite glass structures where layers with different elastic moduli are combined. The core glass layer has a higher elastic modulus while the cladding glass layer has a lower elastic modulus, creating a composite material system that leverages the advantages of both high-stiffness and low-stress-concentration properties to resist deep flaws.
2Strength
If the cladding layer has a significantly lower modulus than the core layer, then the retained strength against shallow flaws increases, but the resistance to deep flaws decreases
Solution Approach 1:
The patent optimizes the elastic modulus parameter of the cladding layer, specifying it should be between 0.7 to 0.95 times the modulus of the core layer. This parameter adjustment creates compressive stress in the cladding layer that effectively protects against shallow surface flaws while maintaining adequate resistance to deeper flaws through the core layer's higher modulus.
Solution Approach 2:
Different regions of the glass article are assigned different elastic moduli - the cladding layer has a lower modulus optimized for protecting the surface against shallow flaws, while the core layer maintains a higher modulus for overall structural strength and deep flaw resistance. This local differentiation of material properties optimizes performance for different types of damage.
3Strength
If a modulus ratio of at least 1.08 is achieved, then the retained strength is significantly improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific parameter ranges for the elastic moduli of core and cladding layers, with the cladding layer modulus set at 0.7 to 0.95 times the core layer modulus. This parameter specification achieves the desired modulus ratio (at least 1.08) while providing clear manufacturing guidelines that balance performance requirements with manufacturability.
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 modulus contrast between the core and cladding layers significantly increases the retained strength of the glass article, particularly against shallow flaws, but may decrease resistance to deep flaws, offering improved mechanical reliability and drop performance.
Implementation Method 1
The modulus contrast between the core and cladding layers significantly increases the retained strength of the glass article, particularly against shallow flaws
Data Source
AI summary
A laminated glass article includes a glass core layer having a core modulus Ecore and a glass cladding layer adjacent to the core layer and having a cladding modulus Eclad. Eclad can be at least 5 GPa less than Ecore. A modulus ratio Ecore/Eclad can be at least 1.08. The cladding layer can have a compressive stress resulting from a coefficient of thermal expansion (CTE) contrast between the core layer and the cladding layer and/or subjecting the laminated glass article to an ion exchange treatment to form an ion exchanged region at an outer surface of the cladding layer.