Carbon Fiber Bundle Modulus Control for Stable Processing
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Solution Overview
Problem
Existing carbon fiber bundles with high total fineness face issues with process stability during further processing, such as fuzz and breakage, despite improvements in mechanical properties and productivity.
Innovation Solution
A carbon fiber bundle with a specific relationship between the stress-strain curve nonlinearity and crystallite orientation, produced through a stabilization, pre-carbonization, and carbonization process with controlled stretching ratios and temperatures, ensuring the bundle remains substantially untwisted and has a defined elastic modulus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the total fineness of carbon fiber bundle is increased to improve productivity and reduce cost, then the number of filaments increases and cost reduction is achieved, but the processability deteriorates with increased fuzz and breakage during further processing
Solution Approach 1:
The patent applies parameter changes by precisely controlling the initial elastic modulus within 240-279 GPa and the number of filaments within 24,000-72,000. These specific parameter ranges optimize the balance between productivity (higher filament count) and processability (controlled fuzz and breakage through elastic modulus control). The stabilization process parameters (temperature 200-300°C, atmosphere control) are also optimized to achieve the target elastic modulus range.
2Productivity
If the total fineness of carbon fiber bundle is increased to improve productivity, then more filaments are produced per batch, but the process stability deteriorates with increased breakage during unwinding and travel
Solution Approach 1:
The patent resolves this contradiction by changing the elastic modulus parameter to a specific range (240-279 GPa) that provides optimal flexibility and strength balance. This elastic modulus control, achieved through stabilized process parameters (heating temperature 200-300°C, heating rate 1-10°C/min, atmosphere control), enables high filament counts (24,000-72,000) to be produced with improved process stability, reducing breakage during unwinding and travel.
3Strength
If the elastic modulus is increased to improve strength and rigidity, then mechanical properties are enhanced, but the processability deteriorates with reduced fiber spreadability
Solution Approach 1:
The patent applies parameter changes by defining a specific elastic modulus range (240-279 GPa) that optimizes the balance between strength and fiber spreadability. This controlled elastic modulus, achieved through optimized stabilization processing (temperature 200-300°C, time 1-10 hours, atmosphere control), provides sufficient mechanical strength while maintaining adequate fiber flexibility for spreading and handling during composite manufacturing processes.
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 solution provides a carbon fiber bundle with enhanced strength, elastic modulus, and process stability, suitable for high-fineness applications, reducing fuzz and breakage during further processing.
Implementation Method 1
a stabilization process of heat-treating a substantially untwisted polyacrylonitrile-based precursor fiber bundle having 24,000 to 72,000 filaments at a temperature of 220 to 280° C. in an oxidizing atmosphere
Implementation Method 2
a pre-carbonization process of heat-treating the stabilized fiber bundle obtained in the stabilization process in an inert gas at a maximum temperature of 300 to 1,000° C., and a carbonization process of heat-treating the pre-carbonized fiber bundle obtained from the pre-carbonized fiber bundle in an inert gas at a maximum temperature of 1,000 to 1,600° C.
Data Source
AI summary
In order to provide a carbon fiber bundle excellent in strength, elastic modulus, and process stability when subjected to further processing in spite of having a high total fineness, and a method for producing the carbon fiber bundle, the carbon fiber bundle allows a relationship between a coefficient A obtained from an approximation formula (1) of nonlinearity in a stress σ-strain ε curve in a resin-impregnated strand tensile test in a range of stress of 0 to 3 GPa and an orientation parameter of crystallites Π (%) in wide-angle X-ray diffraction measurement to satisfy a formula (2), an initial elastic modulus of the carbon fiber bundle is 240 to 279 GPa, the number of filaments of the carbon fiber bundle is 24,000 to 72,000, and the carbon fiber bundle is substantially untwisted, in whichε=Aσ2+Bσ+C(1)-410≤(0. 0000832π2 - 0.0184 π + 1. 00)/A≤-310(2)where, A, B, and C are coefficients of a quadratic function of the stress σ and the strain ε, and Π is an orientation parameter of crystallites.