Carbon-Carbon Brake Disk Preforms With Higher Fiber Volume Uniformity
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Solution Overview
Problem
Aircraft brake systems using carbon/carbon composites exhibit varying wear characteristics and friction coefficients due to the materials and heat treatments employed, leading to inconsistent performance.
Innovation Solution
A method involving the stacking of non-crimp, multi-axial stitch-bonded textile fabric layers made from oxidized polyacrylonitrile fibers, needling to form a uniform preform, carbonizing without compression weights, and densifying with a carbon matrix using chemical vapor infiltration to produce carbonized preforms with increased fiber volume ratio and reduced standard deviation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If cross-lapping process is used to form non-woven fabric layers, then manufacturing flexibility is improved, but fiber volume uniformity deteriorates
Solution Approach 1:
The patent segments the preform fabrication into distinct stages: forming uniform textile fabric layers with controlled fiber placement, stacking multiple layers, and applying controlled needling. This segmentation allows each stage to be optimized independently, maintaining manufacturing flexibility while achieving uniform fiber volume throughout the final preform.
Solution Approach 2:
The patent performs preliminary actions by pre-forming uniform textile fabric layers with controlled areal weight and fiber orientation before stacking. The needling process is also applied as a preliminary action to interlock layers before carbonization, ensuring uniform fiber volume is established early in the manufacturing process rather than relying on post-processing adjustments.
2Quantity of substance
If compression weights are applied during carbonization, then fiber volume ratio increases, but manufacturing complexity increases
Solution Approach 1:
The patent implements self-service by designing the needling process to inherently achieve the desired fiber volume ratio and preform density without requiring external compression weights during carbonization. The mechanical interlocking of fibers through needling creates a self-supporting structure that maintains its volume during the carbonization process, eliminating the need for additional compression equipment and weights.
3Strength
If needling density is increased to improve fiber bonding, then preform strength increases, but manufacturing time increases
Solution Approach 1:
The patent applies parameter changes by optimizing the needling density to a specific range (0-50 penetrations/cm²) that achieves sufficient fiber bonding and preform strength without excessive manufacturing time. This parameter optimization balances the competing requirements of strength and production efficiency, identifying the point where additional needling provides diminishing returns relative to the time invested.
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 carbon-carbon composite brake disks with improved mechanical properties and friction coefficients, achieving a higher fiber volume ratio and reduced wear rate, while maintaining ergonomic benefits and reducing manufacturing time and costs.
Implementation Method 1
carbonizing the fibrous preform
Implementation Method 2
densifying the fibrous preform with a carbon matrix
Data Source
Figure 1
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AI summary
A method (500) of making a carbonized preform for a carbon-carbon composite brake disk may comprise: stacking (504) a plurality of textile fabric layers, each textile fabric layer in the plurality of textile fabric layers including oxidized polyacrylonitrile (PAN) fibers, each textile fabric layer in the plurality of textile fabric layers being more uniform than a typical fabric layer formed from cross-lapping; each fabric layer being thinner than a typical fabric layer from cross-lapping, needling the plurality of textile fabric layers to form a needled non-woven board; cutting (508) a fibrous preform from the needled non-woven board; and carbonizing (510) the fibrous preform. The resultant non-woven carbonized preform maintains a higher fiber volume and more consistent properties throughout than what would otherwise be achieved using a typical fabric layer from cross-lapping.