Structured Ceramic Friction Layer for Wet Braking Response
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Solution Overview
Problem
Carbon-ceramic brake discs exhibit poor wet response behavior and unstable coefficient of friction when in contact with water or aqueous solutions, leading to a sharp drop in braking performance.
Innovation Solution
A structured ceramic friction layer is developed with a crack pattern formed during cooling, achieved by using an intermediate layer with different thermal expansion coefficients, such as silicon carbide powder or carbon filaments, to create stress relief cracks that enhance the coefficient of friction during wet braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional friction layer is used without structured cracks, then the manufacturing process is simple, but the wet response behavior is poor and the coefficient of friction drops sharply
Solution Approach 1:
The patent changes the physical structure of the friction layer by introducing controlled cracks with specific width (0.01-0.5mm) and depth (0.1-2mm) parameters. These dimensional changes create stress relief structures that improve wet response behavior while maintaining manufacturing feasibility through the intermediate layer approach
Solution Approach 2:
The patent introduces an intermediate layer between the support body and friction layer that serves as a mediator to generate the desired crack pattern. This intermediate layer with different thermal expansion coefficients automatically creates the stress relief cracks during cooling, avoiding direct complex structuring of the friction layer itself
2Reliability
If the friction layer is made homogeneous, then the manufacturing is easier, but the coefficient of friction becomes unstable in wet conditions
Solution Approach 1:
The patent applies local quality by creating cracks only in specific regions of the friction layer where stress relief is needed. The cracks are localized with controlled width and depth, allowing the friction layer to maintain homogeneity in most areas while having structured features where required for wet response performance
Solution Approach 2:
The patent controls the crack pattern by adjusting parameters of the intermediate layer including its thickness (0.1-10mm), material composition, and thermal expansion coefficient. These parameter changes enable precise control over crack formation without requiring complex manufacturing processes for the friction layer itself
3Reliability
If no intermediate layer is used, then the assembly is simpler, but the crack pattern cannot be controlled for wet braking performance
Solution Approach 1:
The intermediate layer serves multiple functions: it acts as an adhesive bond between support body and friction layer, provides thermal expansion differential to generate cracks, and serves as a template for the crack pattern. This multi-functionality justifies the added complexity by eliminating the need for separate crack induction mechanisms
Solution Approach 2:
The intermediate layer automatically generates the desired crack pattern through its own thermal expansion properties during the cooling process after siliconization. The system uses the natural thermal contraction differential to self-create the stress relief cracks without requiring external intervention or additional processing steps
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 method results in a stable braking behavior within 1-3 seconds of contact, with a reduced coefficient of friction by less than 50% compared to dry conditions, and maintains performance without increasing response time as the brake disc ages.
Implementation Method 1
Due to the different thermal expansion of the materials of the carrier body and the friction layer or friction layers fixed on it, a random crack pattern forms during cooling after siliconization
Implementation Method 2
infiltrating the carbonized composite with liquid silicon or a liquid alloy containing at least 50% by mass of silicon to form carbides of silicon
Implementation Method 3
pyrolysis of the composite formed with the exclusion of oxidizing substances with formation of carbon from the organic binder
Data Source
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AI summary
The invention relates to a cylindrical ring-shaped friction disc comprising a support body and at least one friction layer, as well as an intermediate layer arranged between the support body and the friction layer, wherein the intermediate layer has adjacent planar areas with different thermal expansion, a method for its manufacture, and its use as parts of brake and clutch systems, particularly for motor vehicles.