Untwisted Carbon Fiber Bundle for Strength-Modulus Balance
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Solution Overview
Problem
Existing carbon fiber bundles face challenges in achieving a balance between high strand strength and elastic modulus, particularly when the single-fiber diameter is large, leading to issues such as insufficient resin impregnation, buckling, and reduced compressive strength, which are exacerbated by twisting and entangling processes.
Innovation Solution
A carbon fiber bundle with an average diameter of 5.7 µm to 6.5 µm, no twist, and specific production methods involving controlled heating and stretching to achieve a strand strength of 4.7 GPa or more and a strand elastic modulus of 320 GPa or more, ensuring balanced physical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If carbon fiber single-fiber diameter is reduced to improve strand strength and elastic modulus, then mechanical properties improve, but resin impregnation property deteriorates
Solution Approach 1:
The patent optimizes the carbon fiber single-fiber diameter within a specific range (5.0 μm to 7.0 μm) to achieve the best balance between strand strength and resin impregnation property. This parameter optimization allows the fibers to maintain high mechanical properties while enabling adequate resin penetration during composite manufacturing.
2Strength
If twisting is applied to improve strand strength and elastic modulus, then mechanical properties improve, but fiber linearity deteriorates causing buckling
Solution Approach 1:
The patent removes the twisting step from the carbon fiber production process, producing straight carbon fibers without helical deformation. This extraction of the harmful twisting element eliminates the cause of buckling while maintaining high strand strength and elastic modulus through alternative means such as optimized fiber diameter and alignment.
Solution Approach 2:
The patent converts the potential harm of fiber deformation into a benefit by deliberately controlling the fiber structure to be straight rather than twisted. This straight fiber configuration prevents buckling under compression while maintaining the mechanical strength needed for high-performance applications.
3Strength
If strong entangling treatment is applied to improve bundle strength, then generation of fluff is reduced, but resin impregnation property deteriorates
Solution Approach 1:
The patent optimizes the entangling treatment parameters to achieve adequate bundle strength without excessive entanglement. By controlling the degree of entanglement within appropriate limits, the patent maintains fiber bundle integrity while preserving sufficient resin accessibility for proper impregnation during composite manufacturing.
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 strand strength and elastic modulus, improving resin impregnation and compressive strength, suitable for thin carbon fiber reinforced composite materials with excellent bending strength.
Implementation Method 1
stabilization treatment by heating a carbon fiber precursor fiber bundle in an oxidizing atmosphere
Implementation Method 2
carbonization treatment by heating the obtained stabilized fiber bundle in a non-oxidizing atmosphere
Data Source
Figure 1
AI summary
Provided are a carbon fiber bundle having a high strand elastic modulus and high strand strength, and having balanced physical properties even when the average diameter of carbon fiber single-fibers is large, and a method for producing the same. The carbon fiber bundle of the present invention has an average diameter of carbon fiber single-fibers of 5.7 µm or more and 6.5 µm or less, substantially no twist, a strand strength of 4.7 GPa or more, and a strand elastic modulus of 320 GPa or more.