Composite Part Assembly Using a Machinable Insert Interface
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Solution Overview
Problem
The integration of ceramic matrix composites in aeronautical turbomachines faces challenges due to high manufacturing tolerances, making precise assembly and replacement of parts difficult, especially when combined with metal parts, as traditional matching techniques are costly, non-interchangeable, and risk damaging the composite fibers.
Innovation Solution
A method involving a machinable metal insert with a cylindrical portion and shoulder is used to precisely position and bond a ceramic matrix composite part to another part, allowing for defined dimensions and easy replacement, where the insert is brazed to prevent corrosion and maintain material integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional matching technique is used to assemble CMC parts with metal parts, then assembly precision can be achieved, but production cost increases and part interchangeability is eliminated
Solution Approach 1:
A metal insert is introduced as an intermediary component between the CMC part and the metal part. The insert is fitted into a housing drilled in the CMC part and can be precisely machined to ensure accurate positioning. This mediator allows standard machining techniques to achieve precision without requiring expensive matching procedures on the CMC parts themselves.
Solution Approach 2:
The assembly system is segmented into three independent components: the CMC part with its housing, the machinable metal insert, and the metal part. This segmentation allows each component to be manufactured separately with standard tolerances, and the precision is achieved through the machinable insert interface rather than requiring precision on the CMC part itself, enabling interchangeability and reducing costs.
2Manufacturing precision
If CMC part is machined directly to achieve precise dimension, then assembly precision is improved, but composite fibers are exposed and mechanical properties are impaired
Solution Approach 1:
The metal insert serves as a protective intermediary that prevents direct machining of the CMC part. The insert is fitted into a housing drilled in the CMC part, and all precision machining is performed on the metal insert rather than the composite. This protects the CMC fibers from exposure while still achieving the required dimensional precision for assembly.
Solution Approach 2:
A housing is drilled in the CMC part in advance to accommodate the metal insert. This preliminary action creates a protective cavity that allows the CMC part to maintain its integrity while the metal insert provides the machinable surface for precise positioning and assembly operations.
3Reliability
If CMC part is assembled with another CMC or metal part using matching technique, then assembly is achieved, but part replacement and repair become difficult and expensive
Solution Approach 1:
The metal insert provides universal interfaces for assembly - it can accommodate various metal parts with standardized fastening methods (screws, rivets, or welding). The insert acts as a universal adapter that maintains assembly stability while enabling easy replacement of the metal part or the entire assembly, as the CMC part with its housing and insert can be reused with different metal components.
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 high-precision assembly and easy replacement of parts with minimal material risk and cost, maintaining the mechanical properties of the composite while accommodating manufacturing tolerances, thus facilitating efficient and cost-effective production and repair.
Implementation Method 1
the insert is fastened by means of a washer that is brazed to the face on the opposite side from the shoulder
Implementation Method 2
as the metal insert expands more strongly than the CMC composite, it is sufficient to install and fit the washer hot
Implementation Method 3
The metal, on cooling, contracts and the CMC plate is pinched between the washer and the shoulder upon cooling
Data Source
AI summary
A method for bonding a first part made of a composite to a second part to a predetermined dimension is disclosed. The method includes placing an insert into the first part, a first surface of the insert protruding beyond the predetermined dimension; machining the insert until the first surface is at the predetermined dimension; placing the second part on the insert; and fastening the second part via the insert. The use of an insert makes it possible to produce, with high precision, a reproducible assembly, which can still be dismantled.