Carbon Fiber Bundle Flaw Control Filtration
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Solution Overview
Problem
Existing methods for producing high-strength carbon fibers fail to effectively control flaws within a specific range, leading to reduced tensile strength in carbon fiber bundles, particularly in resin-impregnated strands, and often require lengthy electrolytic treatments that can form brittle layers, making industrial application challenging.
Innovation Solution
A carbon fiber bundle is manufactured with a controlled ratio of flaws on fracture surfaces and a specific single-fiber diameter, where the ratio of flaws 50 nm or more on fracture surfaces is 35% or less, and the single-fiber diameter is 4.3 μm or more, using a method that includes filtration and heat treatment processes to minimize flaws and maintain high tensile strength without fiber fining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If intense electrolytic treatment is applied to remove flaws, then the tensile strength is improved, but a brittle layer is formed on the fiber surface and the treatment time becomes excessively long
Solution Approach 1:
The patent applies preliminary filtration actions during the spinning process to prevent flaw formation in the first place. By filtering the spinning solution through filters with specific pore sizes (0.5-5 μm) and filtering the coagulation bath liquid through filters with pore sizes (0.1-1 μm), the invention removes potential flaw sources before they can affect the carbon fiber, eliminating the need for subsequent intense electrolytic treatment.
2Strength
If multiple-stage filtration with small opening filters is used to reduce flaws, then the tensile strength is improved, but the filter clogs rapidly and requires frequent replacement
Solution Approach 1:
The patent segments the filtration process into two distinct stages with different filter pore sizes. The first stage uses filters with larger pore sizes (0.5-5 μm) for the spinning solution to remove larger particles, while the second stage uses filters with smaller pore sizes (0.1-1 μm) for the coagulation bath liquid to remove finer particles. This segmentation allows each filter to operate within its optimal range, preventing rapid clogging while effectively reducing flaws.
3Strength
If the single-fiber diameter is reduced to reduce flaw surface area, then the tensile strength is improved, but the fiber becomes more susceptible to handling damage and processing difficulties
Solution Approach 1:
The patent changes the parameter of fiber diameter to a specific range (4.3 μm or more) that optimizes the balance between strength and processability. By controlling the diameter within this range, the invention reduces the surface area where flaws can occur (improving strength) while maintaining sufficient fiber robustness for handling and processing (maintaining ease of manufacture).
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 results in a high-quality, high-strength carbon fiber bundle with enhanced tensile strength and reduced flaw presence, improving the composite properties without the need for intense electrolytic treatments or excessive filtration, which can be industrially viable.
Implementation Method 1
filtering a spinning solution through a filter having an opening of 5 μm or less
Implementation Method 2
the stabilized fiber bundle is heated in an inert atmosphere at a temperature of at least 1000° C. to undergo carbonization
Implementation Method 3
the bundle is heated in an oxidizing atmosphere at a temperature of 180 to 400° C. so that it is converted into a stabilized fiber bundle
Data Source
AI summary
A carbon fiber bundle is characterized in that a ratio (n/N) of a number n of pairs wherein a flaw of 50 nm in size or more is present on at least one of the fracture surfaces forming the pair to a total number N of pairs of fiber fracture surfaces selected at random after performing a single fiber tensile test for a gauge length of 10 mm is 35% or less, and in that a single-fiber diameter d is 4.3 μm or more.