Sacrificial Fiber Channels in Carbon Preforms for Faster Stabilization
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Solution Overview
Problem
In the manufacturing of carbon-carbon composite materials, existing processes face challenges in efficiently managing gas diffusion and porosity within preforms, leading to prolonged stabilization and production times due to limited ingress and egress of gases and volatiles.
Innovation Solution
The introduction of sacrificial fibers that are heated to remove at temperatures between 170° C. and 400° C., creating porosity in the form of channels within the preform, allowing enhanced gas and liquid penetration, and subsequent infiltration of densifying agents to accelerate stabilization and reduce manufacturing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional preform manufacturing processes are used, then the preform structure is formed, but gas diffusion and porosity are limited leading to prolonged stabilization time
Solution Approach 1:
Sacrificial fibers are incorporated into the preform structure before carbonization, creating a preliminary porosity network that will become channels after the sacrificial fibers are removed through heating, thus preparing the structure for enhanced gas diffusion before the actual stabilization process begins
Solution Approach 2:
The invention utilizes porous preform structures created by removing sacrificial fibers, forming a network of channels and pores that significantly enhance gas diffusion rates and allow faster ingress and egress of gases and volatiles during stabilization, directly addressing the limitation of traditional dense preform structures
2Reliability
If preform porosity is increased to enhance gas diffusion, then gas penetration improves, but preform structural integrity may be compromised
Solution Approach 1:
Sacrificial fibers serve as intermediary elements that are temporarily present in the preform structure to define channel locations, providing structural support during preform formation while enabling future porosity creation; these fibers are subsequently removed to create the desired porous structure without compromising the final strength
Solution Approach 2:
The preform is constructed as a composite mixture of carbon fiber precursors and sacrificial fibers, where each component serves a different function: carbon fiber precursors provide structural integrity while sacrificial fibers create the porosity network; after processing, the sacrificial fibers are removed leaving a porous carbon fiber structure with both strength and permeability
3Productivity
If sacrificial fibers are removed to create channels, then porosity and gas flow improve, but additional processing steps are required
Solution Approach 1:
The removal of sacrificial fibers and creation of porosity is merged with the existing carbonization process; the sacrificial fibers are heated to temperatures between 170°C and 400°C during normal preform processing, causing them to decompose and leave channels without requiring separate porosity creation steps
Solution Approach 2:
The sacrificial fibers undergo phase transition through heating and decomposition at temperatures between 170°C and 400°C, transforming from solid fibrous material into gaseous products that escape, leaving behind void spaces and channels in the preform structure; this phase change occurs as part of the standard carbonization process
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 method enhances porosity, facilitating faster diffusion and stabilization, reducing production time and preventing cracks or voids in the final composite, while improving yield rates and mechanical properties.
Implementation Method 1
heating a mixture of fibers comprising sacrificial fibers and a plurality of carbon fiber precursor fibers to a temperature between about 170° C. and about 400° C. to substantially remove the sacrificial fibers from the mixture of fibers
Implementation Method 2
Heating of the sacrificial fibers may result in formation of additional porosity in the form of channels in the workpiece
Implementation Method 3
The rate at which gases may penetrate or evacuate a preform can depend on, among other things, gas diffusion rates and the porosity of the preform
Implementation Method 4
carbonizing the plurality of carbon fiber precursor fibers to form a porous carbon fiber preform
Data Source
AI summary
A technique of heating a mixture of fibers that includes sacrificial fibers and carbon fiber precursor fibers to a temperature between about 170° C. and about 400° C., such that the sacrificial fibers are substantially removed and a plurality of channels remain in a preform precursor, and carbonizing the carbon fiber precursor fibers to form a porous carbon fiber preform. Also disclosed is a technique of heating a mixture of fibers that includes sacrificial fibers and carbon fibers to a temperature between about 170° C. and about 400° C., such that the sacrificial fibers are substantially removed and a plurality of channels remain, and infiltrating a densifying agent into at least the plurality of channels. Also disclosed is an article including a mixture of fibers that includes sacrificial fibers and carbon fiber precursor fibers or carbon fibers.