Carbon Fiber Void Control for Strength and Weight Balance
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Solution Overview
Problem
Current carbon fibers with single hollow portions fail to achieve a balance between low specific gravity and high tensile strength and tensile modulus of resin-impregnated strands, and existing methods do not adequately reduce weight while maintaining mechanical properties.
Innovation Solution
Control the tension during the coagulation process in the spinning of polyacrylonitrile-based precursor fibers within a specific range to create carbon fibers with a controlled void content and size, resulting in fibers with high elongation and tensile modulus while being lightweight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a single hollow portion is introduced to reduce specific gravity, then the apparent specific gravity decreases, but the tensile strength and tensile modulus of resin-impregnated strands become insufficient
Solution Approach 1:
The invention introduces multiple voids with specific size ranges (0.5-5.0 μm) distributed throughout the carbon fiber structure, transforming the solid fiber into a controlled porous material. This porous structure reduces the specific gravity while the controlled void distribution and size prevent excessive stress concentration, thereby maintaining adequate tensile strength and modulus of resin-impregnated strands.
Solution Approach 2:
The invention applies local quality by specifying that voids should be distributed in the inner 5 μm from the fiber surface, creating a gradient structure where the surface region has different properties than the core. This localized void distribution optimizes both weight reduction and mechanical performance by concentrating porosity in regions that minimize impact on overall structural integrity.
2Strength
If void amount is extremely reduced to maintain high tensile strength and tensile modulus, then mechanical properties are maintained, but the specific gravity is not sufficiently reduced
Solution Approach 1:
The invention changes the parameters of void characteristics from the conventional approach of simply reducing void amount. Specifically, it controls void size within 0.5-5.0 μm, void content ratio within 0.03-5.0% by area, and aspect ratio within 2.0-50. These parameter optimizations allow significant weight reduction while maintaining mechanical properties, as the specific size and distribution ranges are critical for balancing porosity benefits with structural integrity.
3Weight of moving object
If void content ratio is increased to reduce weight, then specific gravity decreases, but the tensile strength and tensile modulus of resin-impregnated strands deteriorate
Solution Approach 1:
The invention establishes feedback control by defining specific ranges for void content ratio (0.03-5.0% by area), void size (0.5-5.0 μm), and aspect ratio (2.0-50). These ranges are determined based on the balance between weight reduction and mechanical property maintenance. By controlling void parameters within these feedback-defined boundaries, the invention achieves optimal specific gravity reduction while preventing excessive degradation of tensile strength and modulus.
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 method produces carbon fibers with a high tensile modulus and elongation while minimizing weight, effectively balancing mechanical properties and specific gravity, as demonstrated by the controlled void content and size within specific ranges.
Implementation Method 1
a polyacrylonitrile-based spinning dope solution is spun into fiber through a coagulation process to obtain a polyacrylonitrile-based precursor fiber
Implementation Method 2
a polyacrylonitrile-based spinning dope solution is spun into fiber through a coagulation process
Implementation Method 3
a stabilization process of converting a polyacrylonitrile-based precursor fiber into a stabilized fiber under an oxidizing atmosphere
Implementation Method 4
a carbonization process of carbonizing the fiber under an inert atmosphere at 300 to 3000°C
Implementation Method 5
carbonizing the fiber under an inert atmosphere at 300 to 3000°C
Data Source
Figure 1~2
AI summary
The purpose of the present invention is to provide carbon fibres which achieve a high elongation percentage and a high tensile modulus of resin-impregnated strands while being lightweight. Accordingly, these carbon fibres are configured such that: the void content in a cross section of the fibres in the axial direction, said cross section including the long axis of a cross section of the fibres in the radial direction, is at least 0.3% by area, but not more than 5.0% by area; the average aspect ratio of the voids is at least 2.0, but not more than 50; and the average width of the voids in the cross section of the fibres in the radial direction is at least 3 nm, but not more than 100 nm.