Laminated Windshield Structure for Lower Pedestrian Impact
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Solution Overview
Problem
Increased windshield rigidity, while effective against chipping, results in higher impact on pedestrians during collisions, necessitating a design that allows for easier cracking when a heavy object collides with it.
Innovation Solution
A windshield configuration featuring a first and second glass sheet with an intermediate film, where a partial region has a lower fracture stress, incorporating an easily breaking means, and a thicker shielding layer on one glass sheet to reduce impact force upon collision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the rigidity of a windshield is increased to countermeasures against chipping, then the resistance to chipping is improved, but the impact force on pedestrians during collision increases
Solution Approach 1:
The windshield incorporates a partial region with different properties (lower fracture stress) than the main body. This partial region is specifically designed to have reduced rigidity and lower fracture stress compared to the surrounding areas, allowing it to crack easily during pedestrian collisions while the rest of the windshield maintains high rigidity for chipping resistance
Solution Approach 2:
The windshield is divided into functionally distinct regions: a main body region with high rigidity for overall structural strength and chipping resistance, and a separate partial region with lower fracture stress specifically positioned to facilitate easy cracking during pedestrian impacts. This segmentation allows each region to fulfill its specific function independently
2Strength
If the fracture stress of the glass sheet is increased to improve strength, then the overall strength is improved, but the ease of cracking during collision decreases
Solution Approach 1:
The glass sheet has non-uniform fracture stress distribution, with a partial region having specifically reduced fracture stress (e.g., 60 MPa or less) compared to the main body. This local quality variation enables the partial region to crack easily under impact while the rest of the glass sheet maintains high fracture stress for overall strength
Solution Approach 2:
The fracture stress parameter is deliberately modified in the partial region through various methods (laser treatment, sandblasting, altered by heat treatment) to create a localized area with lower fracture stress values, while the main body retains its original high fracture stress characteristics
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 windshield can be easily cracked upon collision, reducing the duration and intensity of the impact on pedestrians, thereby enhancing safety by lowering the rigidity and fracture stress in critical areas.
Implementation Method 1
an intermediate film disposed between the first glass sheet and the second glass sheet and joining the second surface of the first glass sheet and the third surface of the second glass sheet to each other
Implementation Method 2
a thickness of the shielding layer laminated on the partial region is larger than a thickness of the shielding layer laminated on the other region
Data Source
AI summary
This windshield comprises: a first glass panel having a first surface and a second surface; a second glass panel having a third surface and a fourth surface; and an intermediate film that is disposed between the first glass panel and the second glass panel, and that joins the second surface of the first glass panel to the third surface of the second glass panel. The failure stress of at least one region of the glass panel which is the inner panel is configured so as to be less than the failure stress of another region.