Fan Blade Titanium Sheath Adhesive Fabric Stackup
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Solution Overview
Problem
The existing techniques for isolating a titanium sheath from an aluminum fan blade in gas turbine engines are inadequate in preventing galvanic corrosion, particularly with the increased size and weight of fan blades due to gear reduction systems.
Innovation Solution
A sandwich structure is introduced between the titanium sheath and the aluminum fan blade body, comprising an outer adhesive layer, an intermediate woven fiberglass fabric layer, and an inner adhesive layer, which are pressed together in an autoclave to create a strong bond and prevent corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a scrim material is placed between the titanium sheath and aluminum blade to prevent galvanic corrosion, then corrosion protection is improved, but the structural integrity and bonding strength deteriorate
Solution Approach 1:
The patent introduces an intermediate isolation layer composed of non-conductive adhesive material between the titanium sheath and aluminum blade body. This intermediary layer serves dual functions: it prevents galvanic corrosion by electrically isolating the dissimilar metals while simultaneously providing adequate bonding strength to secure the sheath to the blade, resolving the contradiction between corrosion protection and structural integrity
Solution Approach 2:
The isolation layer is formed as a composite structure combining non-conductive adhesive material with reinforcing fibers or mesh. This composite construction provides both the electrical insulation needed to prevent galvanic corrosion and the mechanical strength required for structural integrity, effectively resolving the contradiction between corrosion protection and bonding strength
2Power
If the fan blade diameter is increased through gear reduction, then thrust capability is improved, but weight increases
Solution Approach 1:
The fan blade is constructed using composite materials, combining titanium sheath at the leading edge with aluminum blade body, joined through a specialized isolation layer. This composite construction optimizes the weight-strength balance, allowing larger blade diameters for increased thrust while minimizing weight through strategic material selection and distribution
3Reliability
If titanium sheath is used at the leading edge instead of aluminum, then corrosion resistance and strength are improved, but weight and cost increase
Solution Approach 1:
The patent applies titanium sheath only at the leading edge of the fan blade where corrosion resistance and strength are most critical, while the rest of the blade body remains aluminum. This localized application of premium material provides necessary protection and strength where needed while minimizing overall weight and cost, resolving the contradiction between enhanced reliability and weight reduction
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 solution effectively isolates the titanium sheath from the aluminum fan blade body, preventing galvanic corrosion and reducing weight while maintaining structural integrity and insulation.
Implementation Method 1
The sandwich includes an outer adhesive layer adjacent the sheath, an intermediate fabric layer and an inner adhesive layer adjacent the body
Implementation Method 2
which are pressed together in an autoclave to create a strong bond
Data Source
AI summary
A blade comprises an airfoil extending from a trailing edge to a leading edge. The airfoil includes a body formed of an aluminum containing material. A sheath is at the leading edge and is formed of a titanium containing material. A sandwich is positioned intermediate the sheath and the airfoil body, the sandwich including an outer adhesive layer adjacent the sheath, an intermediate fabric layer and an inner adhesive layer adjacent the body. A gas turbine engine is also disclosed.