Composite Fan Blade Root Bonding for CTE-Mismatched Rotors

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The challenge lies in developing a robust attachment method for composite structures, such as fan blades, to metallic or composite rotors, where differences in material properties, particularly coefficients of thermal expansion (CTEs), compromise the connection between components of varying materials.

Innovation Solution

A method involving coating a portion of the composite structure with metal and applying an intermediate material with a CTE between the two structures, followed by bonding using techniques like transient liquid phase (TLP) or partial transient liquid phase (PTLP) bonding, to create a durable attachment while accommodating thermal expansion mismatches.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If composite materials are used for fan blades to reduce weight, then weight is reduced and specific strength is improved, but attachment reliability to metallic rotors deteriorates due to different coefficients of thermal expansion

Engineering Contradiction:

Improveweight of fan bladeVSAvoidattachment reliability

Core Design Contradiction:

Weight of moving objectVSReliability

Solution Approach 1:

The patent applies an intermediate material layer between the composite fan blade and metallic rotor to serve as a mediator that accommodates the different coefficients of thermal expansion. This intermediate layer absorbs thermal stresses that would otherwise compromise the attachment reliability, enabling successful bonding of dissimilar materials while maintaining both weight reduction benefits and connection reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs composite material structures for the fan blade (such as carbon fiber reinforced polymers) that provide high specific strength and weight reduction. By combining composite materials with metallic materials through the intermediate bonding layer, the system achieves both the weight benefits of composites and the reliable attachment to metallic rotors.

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If different materials are used for fan blades and rotors to optimize individual component performance, then component performance is improved, but bonding robustness deteriorates due to material property differences

Engineering Contradiction:

Improvematerial selection flexibilityVSAvoidbonding robustness

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The intermediate material acts as a mediator that enables bonding between dissimilar materials (composite fan blades and metallic rotors) that would otherwise be difficult to bond directly. This intermediate layer accommodates differences in material properties including thermal expansion coefficients, surface characteristics, and chemical composition, thereby maintaining bonding robustness while preserving material selection flexibility.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent utilizes parameter changes in the intermediate material properties (such as thermal expansion coefficient, viscosity, and bonding temperature) to optimize the bonding process. By selecting an intermediate material with appropriate parameters that bridge the gap between composite and metallic materials, the system achieves robust bonding while maintaining the ability to independently optimize fan blade and rotor materials.

Inventive Principle:

Principle #35Parameter changes

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 enables effective bonding of composite fan blades to metallic or composite rotors, enhancing wear resistance and maintaining structural integrity despite differing material properties, allowing for independent material selection for each component.

Implementation Method 1

differences in the coefficients of thermal expansion (CTEs) can compromise the connection between the fan blades and the rotor

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

bonding the intermediate material to the first and second structures

Methodology Applied

Scientific EffectTransient liquid phase bonding:

Data Source

PatentUS10968758B2Attachment of structures having different physical characteristics

Publication Date: 2021.04.06 RTX CORP

AI summary

A rotor assembly for a gas turbine engine is disclosed. The assembly includes: a composite fan blade, the fan blade including a root; a metallic rotor including a slot for receiving the root; the root being at least partially coated with a metal to form a metal-coated portion; the metal-coated portion of the root being at least partially covered with an intermediate material; and the root, metal-coated portion and intermediate material being received in the slot and bonded to the rotor.