Carbon Fiber Preform Differential Needling for Faster Densification
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Solution Overview
Problem
Current methods for manufacturing carbon-carbon composite materials, such as brake discs, face challenges in achieving optimal interlaminar shear strength and friction performance due to limitations in fiber distribution and densification processes, which affect the efficiency of subsequent processing cycles like CVD/CVI.
Innovation Solution
The technique involves creating a porous preform with varying needled fiber number densities (NFND) in different regions of the composite, where higher NFND in core regions enhances interlaminar shear strength and thermal conductivity, while lower NFND in exterior regions facilitates efficient densification by allowing greater diffusion of carbonaceous gases during CVD/CVI processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If uniform needling is applied throughout the preform, then interlaminar shear strength is improved, but densification efficiency during CVD/CVI processing deteriorates
Solution Approach 1:
The patent applies differential needling with varying needle densities in different regions of the preform. The core region receives higher needling density to maximize interlaminar shear strength, while exterior regions receive lower needling density to maintain porosity and facilitate efficient carbonaceous gas diffusion during CVD/CVI processing. This local differentiation resolves the contradiction by optimizing each region's properties according to its functional requirements.
2Strength
If higher needled fiber number density is used in core regions, then mechanical properties are improved, but processing complexity increases
Solution Approach 1:
The patent segments the preform into distinct regions (core and exterior) with different needling characteristics. This segmentation allows independent optimization of each region's fiber distribution and density, enabling the core to achieve superior mechanical properties while keeping the overall processing approach systematic and manageable through region-based control.
3Productivity
If lower needled fiber number density is used in exterior regions, then densification efficiency is improved, but interlaminar shear strength deteriorates
Solution Approach 1:
The patent recognizes that exterior regions have different functional requirements compared to core regions. By applying lower needling density specifically to exterior regions, the patent maintains adequate porosity for carbonaceous gas diffusion and densification efficiency, while accepting that these regions will have lower interlaminar shear strength than core regions. The overall component strength is dominated by the optimized core region.
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 approach improves the interlaminar shear strength and friction performance of carbon-carbon composite materials by optimizing fiber distribution and densification, ensuring efficient processing and enhanced mechanical properties.
Implementation Method 1
a plurality of needled fibers, where at least some needled fibers of the plurality of needled fibers extend through two or more layers of the plurality of layers
Implementation Method 2
lower NFND in exterior regions facilitates efficient densification by allowing greater diffusion of carbonaceous gases during CVD/CVI processing
Implementation Method 3
densified using one or more of several processes, including chemical vapor deposition/chemical vapor infiltration (CVD/CVI)
Data Source
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AI summary
A carbon-carbon composite preform including a plurality of layers including carbon fibers or carbon-precursor fibers, the layers include a first exterior layer defining a first major surface, a second exterior layer defining a second major surface, and at least one interior layer disposed between the first exterior layer and the second exterior layer, the at least one interior layer having a peripheral region that forms a portion of an outer surface of the preform. The preform includes needled fibers, where at least some needled fibers extend through two or more layers. The preform has an exterior region and a core region, where the exterior region includes at least the peripheral region of at least one interior layer. The needled fibers define a first needled fiber number density (NFND) in the exterior region and a second greater NFND in at least a portion of the core region.