Sacrificial Mould for Shrinkage Control in Pre-ceramic Composite Manufacturing
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Solution Overview
Problem
Current methods for manufacturing thermostructural composite articles from preceramic prepreg materials face significant challenges due to dimensional shrinkage during the ceramization process, which complicates the production of complex shapes and is costly, especially when using steel moulds that deform and corrode over time.
Innovation Solution
A method utilizing a sacrificial mould produced by lamination with the component, employing conventional prepregs like carbon fibre or basalt fibre to maintain shape during pyrolysis, avoiding shrinkage and deformation, and allowing for the use of preceramic polymers like poly-dimethylsiloxane without additives, which reduces costs and maintains thermomechanical integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If steel moulds are used to maintain form during ceramization, then dimensional stability is improved, but manufacturing cost increases and the moulds suffer from deformation and corrosion
Solution Approach 1:
The patent employs a disposable paper mould instead of expensive steel moulds. The paper mould is discarded after a single use, eliminating the high manufacturing costs and maintenance issues of steel moulds. This disposable approach resolves the contradiction by providing adequate dimensional stability for one-use applications without the excessive cost and durability problems of reusable steel moulds.
Solution Approach 2:
The paper mould acts as an intermediary between the preceramic prepreg and the final ceramic component. It provides the necessary form and dimensional stability during ceramization, then is easily removed after serving its purpose. This intermediary role allows the use of low-cost materials while achieving the required manufacturing precision.
2Manufacturing precision
If preceramic polymers with additives are used to reduce shrinkage, then dimensional stability is improved, but material cost increases
Solution Approach 1:
The paper mould provides preliminary counter-action to the shrinkage of preceramic polymers during ceramization. By being pressed against the prepreg, it mechanically opposes the dimensional reduction, compensating for the natural shrinkage tendency without requiring expensive shrinkage-reducing additives in the polymer itself.
Solution Approach 2:
The paper mould creates a negative copy or impression of the desired final component shape. The prepreg is formed to match the mould's geometry, and after ceramization, the component retains this shape. This copying approach allows accurate shape reproduction without modifying the preceramic polymer composition with costly additives.
3Ease of manufacture
If conventional prepregs are used without sacrificial mould, then production cost is reduced, but dimensional shrinkage of 50% occurs during ceramization
Solution Approach 1:
The sacrificial paper mould serves as an intermediary that temporarily provides dimensional stability during ceramization. It is pressed against the conventional prepreg to prevent shrinkage, then removed after the ceramic component is formed. This allows the use of inexpensive conventional prepregs while achieving the required dimensional accuracy.
Solution Approach 2:
The paper mould is applied to the prepreg before ceramization to preliminarily establish the desired shape and prevent shrinkage. This preliminary action of constraining the prepreg in the correct geometry allows conventional materials to produce precise components without requiring expensive shrinkage-resistant materials.
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 enables the production of articles with complex shapes without shrinkage or deformation, maintaining the desired geometry and thermomechanical properties up to high temperatures, while reducing production costs and avoiding the limitations of traditional steel moulds.
Implementation Method 1
Preceramic polymers are polymers that can be converted into ceramic by means of a pyrolysis heat treatment at a temperature generally ranging from 600 to 1300°C
Implementation Method 2
a sacrificial mould, produced by lamination on another mould, together with the component to be manufactured
Data Source
AI summary
A method to manufacture an article made of a thermostructural composite starting from a preceramic prepreg and comprising the steps of: - preparing a prepreg multilayer material, in which at least one layer of preceramic prepreg is arranged between at least two layers of conventional prepreg; - cross-linking, during which the conventional prepreg and the preceramic prepreg are cross-linked; - ceramization, during which said prepreg multilayer material resulting from the cross-linking step undergoes a temperature that is greater than the one of the cross-linking step and is such as to cause the ceramization of said preceramic prepreg; - removal, during which said layers of conventional prepreg are removed.