Fugitive Binder Preform for CMC Fiber Placement
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Solution Overview
Problem
The preforming process for ceramic matrix composites often results in inhomogeneity due to non-uniform fiber compaction, poor control over fiber placement, and delamination, especially around tight radii, leading to insufficient control over the skeletal structure and geometry.
Innovation Solution
A method involving the use of a fugitive organic polymer binder to form flexible prepreg sheets, which are then laminated and bonded to create a rigid preform with controlled tow aspect ratios and uniform fiber compaction, followed by pyrolysis to produce a porous preform suitable for further ceramic matrix composite processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If native sizing on fiber is used for wet layup, then the fiber can be laid up into desired geometry, but the preform exhibits inhomogeneity due to non-uniform fiber compaction and poor control over fiber placement
Solution Approach 1:
A fugitive binder is introduced as an intermediary substance between fibers during the preforming process. This binder temporarily holds fibers in the desired configuration, enabling precise fiber placement control. After preforming, the binder is removed (made fugitive), leaving the fibers in the controlled geometry without residual binding effects.
Solution Approach 2:
The patent applies preliminary compaction and binding actions during the preforming stage to establish controlled fiber placement and uniform compaction before subsequent processing. The fugitive binder is applied in advance to ensure uniform distribution and control, then removed later when no longer needed.
2Device complexity
If conventional preforming methods are used, then the process can be performed with simple equipment, but the preform exhibits delamination and insufficient control over skeletal structure
Solution Approach 1:
The fugitive binder serves as a temporary intermediary that provides uniform bonding between fiber layers during preforming, preventing delamination. The binder is designed to be removable after serving its structural support function, maintaining process simplicity while achieving homogeneous preform composition.
Solution Approach 2:
The patent changes the chemical and physical parameters of the binder over time - initially providing strong adhesion for uniform compaction and delamination prevention, then undergoing transformation (removal/pyrolysis) to become fugitive. This parameter change enables both process simplicity and preform homogeneity.
3Shape
If tight radii are formed in preform, then complex geometries can be achieved, but non-uniform fiber compaction occurs around the radii
Solution Approach 1:
The fugitive binder acts as a mediating substance that distributes compaction forces uniformly around tight radii during preforming. It prevents fiber buckling and non-uniform compaction in curved regions, enabling complex geometries while maintaining fiber placement precision. The binder is then removed to leave the complex geometry without compaction defects.
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 enhances the homogeneity and control of fiber placement, allowing for improved preform geometry and skeletal structure, reducing distortions and inhomogeneities, and facilitating more uniform processing into ceramic matrix composites.
Implementation Method 1
the stack is heated to soften the organic polymer and bond together the flexible prepreg sheets into a bonded prepreg structure
Implementation Method 2
The rigid preform is then heated at a sufficient temperature to pyrolyze the organic polymer
Data Source
AI summary
A method of making a fiber preform for ceramic matrix composite (CMC) fabrication comprises laminating an arrangement of fibers between polymer sheets comprising an organic polymer, which may function as a fugitive binder during fabrication, to form a flexible prepreg sheet. A plurality of the flexible prepreg sheets are laid up in a predetermined geometry to form a stack, and the stack is heated to soften the organic polymer and bond together the flexible prepreg sheets into a bonded prepreg structure. Upon cooling of the bonded prepreg structure, a rigid preform is formed. The rigid preform is heated at a sufficient temperature to pyrolyze the organic polymer. Thus, a porous preform that may undergo further processing into a CMC is formed.