Semi-permeable Membrane for Ceramic Matrix Composite Fabrication
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Solution Overview
Problem
The traditional process for forming ceramic matrix composite materials using fiberglass bleeder stacks is challenging to scale up and difficult for complex or closed geometries, leading to non-homogeneous parts with mechanical property inconsistencies due to excess matrix removal and volatile escape issues.
Innovation Solution
A semi-permeable membrane made of porous plastic is applied over a stack of composite plies pre-impregnated with ceramic matrix, allowing for easier formation of complex shapes and retaining matrix material while enabling volatile gas escape during curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a thick fiberglass bleeder stack is used to remove excess matrix, then the target fiber volume fraction is achieved, but the part becomes non-homogeneous with mechanical property inconsistencies
Solution Approach 1:
A porous membrane is introduced as an intermediary layer between the composite plies and the bleeder stack. This membrane selectively allows volatiles to pass through while retaining matrix material, thereby controlling the removal process to maintain part homogeneity and mechanical property consistency throughout the structure
Solution Approach 2:
The invention utilizes a porous membrane with specific pore sizes that allow volatile gases to escape during autoclave processing while preventing the loss of liquid matrix material. This selective permeability ensures uniform fiber volume fraction and consistent mechanical properties across the entire part
2Reliability
If a thick fiberglass bleeder stack is used to allow volatile escape, then volatiles can escape during autoclave processing, but the process becomes difficult to scale up for thicker parts
Solution Approach 1:
The porous membrane serves as an intermediary that provides a controlled pathway for volatile escape without requiring a thick bleeder stack. This enables scaling to thicker parts while maintaining effective volatile removal and process reliability
3Manufacturing precision
If a thick fiberglass bleeder stack is used for matrix removal, then excess matrix is removed to achieve target fiber volume fraction, but the process is difficult for curved and complex structures
Solution Approach 1:
The invention replaces the rigid, thick fiberglass bleeder stack with a thin, flexible porous membrane that can easily conform to curved and complex geometries. This thin film approach maintains manufacturing precision for fiber volume fraction while dramatically improving ease of manufacture for complex structures
Solution Approach 2:
The invention changes the physical parameters of the matrix removal system by transitioning from a thick, rigid fiberglass structure to a thin, flexible porous membrane. This parameter change enables the process to accommodate complex geometries while maintaining control over fiber volume fraction
4Reliability
If a thick fiberglass bleeder stack is used for matrix removal, then volatiles can escape, but significant bulk/thickness is added making closed geometries difficult
Solution Approach 1:
The porous membrane acts as an intermediary that provides volatile escape pathways without adding significant bulk. This thin membrane maintains reliability for volatile removal while minimizing impact on part geometry and enabling closed shape fabrication
5Reliability
If a semi-permeable membrane is used instead of fiberglass bleeder stack, then matrix material is retained and part homogeneity is improved, but the membrane must be precisely designed to retain ceramic particles
Solution Approach 1:
The invention employs a porous membrane with carefully controlled pore sizes that are smaller than the ceramic particles to be retained but large enough to allow volatile passage. This porous structure achieves part homogeneity through a relatively simple design approach
Solution Approach 2:
The invention controls the pore size parameter of the membrane to create a selective barrier that retains ceramic particles while allowing volatiles to escape. This single parameter control achieves the desired functionality without excessive design complexity
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 approach results in more uniform ceramic composite parts with reduced scrap material and improved mechanical properties, enabling the fabrication of complex geometries with less consumable material usage.
Implementation Method 1
The semi-permeable membrane may include a semi-permeable plastic sheet having a plurality of pores large enough to allow volatile gasses to escape therethrough during curing but equal to or smaller than the solid ceramic particles or clusters of the solid ceramic particles suspended in the ceramic matrix in order to retain matrix in the composite
Implementation Method 2
The semi-permeable membrane comprises a porous plastic material and may have a thickness of approximately 0.002 to 0.008 inches
Data Source
AI summary
A method of fabricating a ceramic matrix composite material into a part, including applying a semi-permeable membrane over a stack of composite plies pre-impregnated with ceramic matrix. The semi-permeable membrane comprises a porous plastic material and may have a thickness of approximately 0.002 to 0.008 inches. The method may include compressing the semi-permeable membrane and the stack together and heating the semi-permeable membrane and the stack to cure the stack into the composite part. The semi-permeable membrane may be a porous plastic having pores large enough to allow volatile gasses to escape therethrough during curing but equal to or smaller than solid ceramic particles or clusters of the solid ceramic particles suspended in the ceramic matrix. The composite plies may contain approximately 35 percent to 45 percent of the ceramic matrix by weight relative to an overall weight of the stack of the composite plies pre-impregnated with the ceramic matrix.