Carbon-Carbon Friction Material with Perforated Layer Reinforcement
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Solution Overview
Problem
Existing methods for producing carbon-carbon composites for friction units face issues such as low interlayer strength leading to delamination, high production costs due to complex needling technologies, and inhomogeneous material properties due to uncontrolled fiber orientation and dry mixing processes.
Innovation Solution
The method involves pre-perforating carbon fabric layers with holes larger than the fiber diameter, followed by suction of an aqueous suspension containing pitch binder and carbon fibers, which are then compressed and heat-treated to integrate fibers into the fabric layers without needling, ensuring increased interlayer strength and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional layering methods are used to produce carbon-carbon composites, then the production process is simple, but the interlayer strength is low leading to delamination
Solution Approach 1:
The carbon fabric layers are pre-perforated with holes before assembly, creating pathways that enable subsequent infiltration of carbon fibers through the layers during compression. This preliminary action ensures that the fiber reinforcement structure is established before final compaction, resolving the interlayer strength issue without requiring complex post-processing
Solution Approach 2:
The pre-perforated fabric layers create a controlled porous structure with holes having linear dimensions significantly exceeding the carbon fiber filament diameter (L/d > 100). This porous architecture allows aqueous suspension to penetrate and deposit carbon fibers within the layer gaps, forming strong interlayer bonds that prevent delamination
2Strength
If needling technology is used to reinforce carbon-carbon composites, then interlayer connection is improved, but production cost increases significantly
Solution Approach 1:
The mechanical needling process is replaced with a chemical-physical infiltration process where aqueous suspension containing carbon fibers is drawn through the pre-perforated layers by suction. This substitution eliminates expensive needling equipment while achieving comparable or superior interlayer bonding through fiber infiltration and binder consolidation
Solution Approach 2:
An aqueous suspension serving as an intermediary medium carries carbon fibers and pitch binder through the perforated fabric layers. The suspension acts as a vehicle that deposits reinforcing fibers into the layer interfaces and binds them together, achieving reinforcement without direct mechanical needling
3Ease of manufacture
If dry mixing of components is used to manufacture friction materials, then the production process is simple, but fiber grinding and structural inhomogeneity occur
Solution Approach 1:
The mixing process parameters are fundamentally changed from dry mixing to wet mixing using aqueous suspension. This parameter change prevents fiber-grinding mechanical action while enabling uniform distribution of carbon fibers and pitch binder through fluid dynamics, eliminating structural inhomogeneity without sacrificing production simplicity
Solution Approach 2:
Hydraulic principles are applied by using aqueous suspension to transport and deposit carbon fibers and binder materials. The liquid medium enables controlled infiltration through the perforated layers via suction, ensuring uniform material distribution and preventing the fiber damage associated with dry mechanical mixing
4Volume of stationary object
If traditional pyrolytic compaction is used for friction materials, then density is achieved, but production time is long and final density remains low
Solution Approach 1:
Carbon fibers are infiltrated into the fabric layers during the molding stage before pyrolysis, rather than relying solely on slow pyrolytic compaction to achieve density. This preliminary fiber placement and compression significantly reduces the time required for density achievement while maintaining or improving final density values
Solution Approach 2:
The method creates a composite structure by infiltrating discrete carbon fibers into the fabric layers during molding, forming a hybrid architecture that achieves high density more rapidly. The combination of pre-formed fabric and infiltrated fibers creates a denser, more uniform structure that requires less time for pyrolytic compaction
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 enhances the shear strength of the composite material, reduces production costs, and maintains fine structure, achieving interlayer strengths of 25-30 MPa and friction coefficients between 0.3-0.5, with improved wear resistance and a shorter production cycle compared to existing methods.
Implementation Method 1
suction of an aqueous suspension containing pitch binder and carbon fibers
Implementation Method 2
depositing fibers and binder into the holes to integrate layers
Implementation Method 3
dried in a fixed state at the melting temperatures of the pitch binder
Implementation Method 4
pressed at a temperature not less than twice the melting temperature of the pitch binder to the required thickness
Implementation Method 5
the workpieces are carbonized, compacted, heat treated and mechanically processed
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to the field of mechanical engineering, namely to heavily loaded friction units, such as brake systems of sports cars and other ground equipment. The proposed method for producing carbon-carbon material in the form of circular workpieces for use in heavily loaded friction units, contains the following steps: (i) impregnating the carbon fabric with a binder, preferably based on pitches, or in the initial state, exposing the carbon fabric to perforation by forming holes on it with linear size exceeding the diameter of the carbon fiber filament; (ii) assembling a press pack in a perforated sleeve by alternating laying of fabric cuts and sucking through them an aqueous suspension containing a pitch binder powder and carbon fiber filaments with a length of not more than 750 mkm; (iii) compressing the resulting wet press pack in the sleeve by at least ¼ of the original height and drying in a fixed state at the melting temperatures of the pitch binder to constant weight; (iv) pressing the resulting press pack at a temperature not less than twice the melting temperature of the pitch binder; (v) workpiece carbonization; (vi) workpiece compaction; (vi) heat treatment and (vii) mechanical processing in accordance with the drawing.