Composite Blade Damping via Viscoelastic Titanium Layer
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Solution Overview
Problem
Current fan blades in turbojet engines, particularly those made of composite materials, face challenges in predicting and mitigating flutter due to complex aerodynamic and mechanical coupling, with inadequate mechanical damping leading to unstable conditions and increased risk of flutter, especially under subsonic conditions.
Innovation Solution
Integration of a viscoelastic material layer between the titanium leading edge and the woven composite blade, replacing the adhesive layer, to enhance mechanical damping and provide protection against flutter and accidental loadings like bird ingestion, while using the titanium leading edge as a counter layer to limit additional parts and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a blade made of composite material is used, then weight is reduced and manufacturing flexibility is improved, but mechanical damping is insufficient leading to increased risk of flutter
Solution Approach 1:
The patent applies composite materials by bonding a metal protection layer (titanium) to the composite blade using a viscoelastic adhesive layer. This creates a multi-layer composite structure where the metal layer provides damping and flutter resistance while the composite blade maintains its weight advantage. The viscoelastic adhesive layer contributes additional damping properties, resolving the contradiction between weight reduction and flutter resistance.
2Strength
If a metal protection layer is added to the leading edge, then mechanical strength and protection are improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges multiple functions into the metal protection layer and adhesive system. The metal layer provides both mechanical strength/protection and vibration damping, while the viscoelastic adhesive simultaneously bonds the metal layer and provides additional damping. This consolidation reduces device complexity compared to adding separate damping components, as the protection layer system fulfills both protective and damping functions.
3Reliability
If the adhesive layer is replaced with viscoelastic material, then mechanical damping is enhanced, but manufacturing process complexity increases
Solution Approach 1:
The patent changes the material parameter of the adhesive layer from conventional adhesive to viscoelastic material. This parameter change enhances mechanical damping and flutter resistance. The viscoelastic material's properties can be tuned to provide optimal damping across different frequency ranges, improving reliability while maintaining manufacturability through established bonding processes.
4Reliability
If damping arrangements are added to the blade, then flutter resistance is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies multi-functionality by designing the metal protection layer and viscoelastic adhesive to serve multiple purposes simultaneously. The metal layer provides both mechanical protection against erosion and vibration damping, while the viscoelastic adhesive provides both bonding and additional damping. This eliminates the need for separate damping components, reducing device complexity and cost while maintaining improved flutter resistance.
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
The viscoelastic material layer significantly improves the harmonic response to aerodynamic excitations, reduces the risk of flutter, and effectively dissipates impact energies during accidental loadings, offering a dual function of vibration damping and impact absorption without adding extra components.
Implementation Method 1
at least one layer 20 of a viscoelastic material is interposed at least in part between said protective element and the blade so as to form with the protective element a vibration damping means on the blade
Implementation Method 2
The principle of operation of the damping system is based on the dissipation of energy by shearing of a suitably placed viscoelastic material
Implementation Method 3
protection along the leading edge... a piece of titanium bonded to the entire surface of the leading edge
Data Source
Figure 1~7
Figure 3~6
AI summary
Damping device for a composite material blade. The present invention relates to a composite material blade comprising a blade (10A) formed of woven filaments impregnated with a thermosetting resin, with a protective element (10B) in the leading edge region of the blade, comprising a rigid blade-shaped portion, said blade being integral with the blade. The blade is characterized in that at least one layer of a viscoelastic material is interposed, at least partially, between said rigid blade and the blade, so as to form, together with the protective element, a means (11, 12, 13) for damping vibrations on the blade.