Composite Fan Blade Leading Edge Sheath for Core Retention

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Solution Overview

Problem

Existing methods for forming leading edge sheaths in composite fan blades, such as leading edge deposition processes and direct laser metal sintering, have limitations in terms of structural integrity and retention of the core within the sheath under high-temperature and pressure conditions in gas turbine engines.

Innovation Solution

The method involves additively manufacturing a core and securing it to a mandrel, followed by electroforming a leading edge sheath directly onto both, and then removing the mandrel using wedges to facilitate retention, with local thickening of the sheath to enhance core retention and bonding a blade body to the core and sheath for structural integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If leading edge deposition processes or direct laser metal sintering are used to form the leading edge sheath, then the blade can be manufactured with complex geometry, but the structural integrity and retention of the core within the sheath under high-temperature and pressure conditions deteriorates

Engineering Contradiction:

Improvecomplex geometry capabilityVSAvoidstructural integrity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent employs a composite structure consisting of a metal leading edge sheath (electroformed from copper alloy or stainless steel) encapsulating a ceramic core (alumina or zirconia). This composite construction combines the strength and ductility of metal with the high-temperature resistance of ceramic, resolving the contradiction between geometric flexibility and structural integrity under thermal stress

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The ceramic core is nested within the metal sheath, creating a nested structure where the inner core provides thermal insulation and the outer sheath provides mechanical strength. This nesting arrangement allows the blade to maintain complex geometry while ensuring structural integrity through the protective metal enclosure

Inventive Principle:

Principle #7Nested doll (Nesting)

2Weight of moving object

If the core is additively manufactured with complex internal structures, then the blade weight is reduced and strain capabilities are improved, but the retention of the core within the sheath under operational conditions deteriorates

Engineering Contradiction:

Improveblade weightVSAvoidcore retention

Core Design Contradiction:

Weight of moving objectVSReliability

Solution Approach 1:

The metal sheath is locally thickened at the leading edge region where thermal and mechanical stresses are highest. This localized reinforcement ensures secure retention of the additively manufactured core with its complex internal structures, while maintaining overall weight efficiency by not thickening the entire blade structure

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The core is pre-manufactured using additive manufacturing techniques to achieve complex internal geometries and weight optimization before being encapsulated in the metal sheath. This preliminary fabrication allows for optimized weight and strain capabilities while the subsequent sheathing process ensures secure retention under operational conditions

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If the leading edge sheath is formed by conventional deposition methods, then the manufacturing process is simpler, but the durability and performance under high-temperature and pressure conditions deteriorates

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoiddurability

Core Design Contradiction:

Ease of manufactureVSDuration of action of stationary object

Solution Approach 1:

The conventional mechanical deposition process is replaced with electroforming, an electrochemical process that deposits metal onto the core and mandrel assembly. This substitution enables the formation of a dense, defect-free metal sheath with superior mechanical properties and durability under high-temperature and pressure conditions, while maintaining manufacturing efficiency

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 a lightweight composite fan blade with improved strain capabilities and structural soundness, enabling effective retention of the core within the sheath under high-temperature and pressure conditions, enhancing the durability and performance of the fan blades.

Implementation Method 1

electroforming a leading edge sheath directly onto the core and the mandrel

Methodology Applied

Scientific EffectElectroforming: Electrodeposition

Data Source

PatentUS11713680B2Composite fan blade

Publication Date: 2023.08.01 RTX CORP

AI summary

A blade fabrication method is provided and includes additively manufacturing a core, securing the core to a mandrel, electroforming a leading edge sheath directly onto the core and the mandrel and removing the mandrel from the core and the leading edge sheath.