Layered Carbon Fiber With CNT Core for Uniform Crystallinity

Solution Overview

Problem

Conventional carbon fibers have a temperature gradient during processing, leading to crystallization of carbon on the exterior and amorphous carbon in the center, which reduces modulus and increases weight, making them undesirable for structural applications.

Innovation Solution

A method involving coating carbon nanotube yarn with polyacrylonitrile, followed by carbonization and graphitization processes to form a layered carbon fiber with a crystalline carbon sheath and a carbon nanotube yarn core, addressing the temperature gradient issue and enhancing structural properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional carbon fiber processing is used with extrusion and stretching, then fiber shape is formed and polymer molecules are aligned, but temperature gradient causes exterior carbon to crystallize while center remains amorphous, reducing modulus and increasing weight

Engineering Contradiction:

ImprovemodulusVSAvoidfiber weight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

Carbon nanotubes are pre-aligned into yarn form before the carbonization process, establishing a crystalline structure framework in advance. This preliminary arrangement ensures that the entire fiber cross-section, including the center, develops crystalline properties during carbonization, eliminating the amorphous core problem in conventional fibers.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the fundamental processing parameters by using carbon nanotube yarn as the starting material instead of conventional polymer extrusion. This parameter change allows the fiber to maintain crystalline structure throughout the cross-section during carbonization, achieving uniform modulus properties and reducing weight by eliminating amorphous carbon.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If polyacrylonitrile is extruded into fiber shapes and stretched, then fiber formation and molecular alignment are achieved, but the thick fiber center remains amorphous carbon due to temperature gradient, creating undesirable weight

Engineering Contradiction:

Improvecrystalline structure uniformityVSAvoidfiber weight

Core Design Contradiction:

Manufacturing precisionVSWeight of moving object

Solution Approach 1:

Carbon nanotubes are pre-aligned into yarn form before the carbonization process, establishing a crystalline structure framework in advance. This preliminary arrangement ensures that the entire fiber cross-section, including the center, develops crystalline properties during carbonization, eliminating the amorphous core problem in conventional fibers.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the fundamental processing parameters by using carbon nanotube yarn as the starting material instead of conventional polymer extrusion. This parameter change allows the fiber to maintain crystalline structure throughout the cross-section during carbonization, achieving uniform modulus properties and reducing weight by eliminating amorphous carbon.

Inventive Principle:

Principle #35Parameter changes

3Strength

If conventional carbon fiber processing is used, then fiber formation is achieved, but amorphous carbon in the center does not contribute to modulus while adding weight

Engineering Contradiction:

Improvemodulus contributionVSAvoidfiber weight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

Carbon nanotubes are pre-aligned into yarn form before the carbonization process, establishing a crystalline structure framework in advance. This preliminary arrangement ensures that the entire fiber cross-section, including the center, develops crystalline properties during carbonization, eliminating the amorphous core problem in conventional fibers.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the fundamental processing parameters by using carbon nanotube yarn as the starting material instead of conventional polymer extrusion. This parameter change allows the fiber to maintain crystalline structure throughout the cross-section during carbonization, achieving uniform modulus properties and reducing weight by eliminating amorphous carbon.

Inventive Principle:

Principle #35Parameter changes

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 resulting layered carbon fiber has improved modulus and reduced weight, making it suitable for replacing traditional carbon fibers in structural applications and composite materials, with the carbon nanotube core increasing the fiber's strength and reducing density.

Implementation Method 1

The polyacrylonitrile is converted to crystalline carbon to form a layered carbon fiber with a sheath of the crystalline carbon and a core of the carbon nanotube yarn

Methodology Applied

Scientific EffectCarbonization: Pyrolysis

Implementation Method 2

A sheath of crystalline carbon is formed on the carbon nanotube yarn by performing a graphitization process on the carbon layer

Methodology Applied

Scientific EffectGraphitization:

Data Source

PatentUS10533266B2Layered carbon fiber

Publication Date: 2020.01.14 THE BOEING CO

AI summary

A carbon nanotube yarn is coated with polyacrylonitrile to form a coated carbon nanotube yarn. The polyacrylonitrile is converted to crystalline carbon to form a layered carbon fiber with a sheath of the crystalline carbon and a core of the carbon nanotube yarn.