Composite Fan Rotor Blade with Segmented Metal Sheath
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Solution Overview
Problem
Fan rotor blades in aircraft jet engines face significant bending deformation and stress upon collision with foreign objects, leading to potential detachment of the metal sheath, which can cause damage to other blades and the engine case, necessitating improved impact resistance and weight reduction.
Innovation Solution
A fan rotor blade design featuring a metal sheath that extends from the base end to the tip end, with a flush trailing edge and strategically positioned seam to minimize bending moments, reducing the risk of sheath detachment and incorporating a composite material blade body for weight reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal sheath is provided on the blade body to improve impact resistance, then the resistance to foreign object collision is improved, but the sheath may detach from the blade body due to bending stress during collision
Solution Approach 1:
The sheath is divided into multiple segments along the blade body, with seams positioned at locations where bending moments are minimized. This segmentation allows the sheath to better accommodate bending stresses during foreign object collisions while maintaining overall structural integrity and preventing detachment.
2Weight of moving object
If the blade body is made from composite material to reduce weight, then the overall weight is reduced, but the impact resistance compared to solid metal is reduced
Solution Approach 1:
The blade body is constructed from composite materials (fibers and resin) which provide high strength-to-weight ratio, while a metal sheath is added as a protective layer to enhance impact resistance. This composite structure maintains weight reduction benefits while improving collision resistance.
3Reliability
If the sheath covers the entire blade body to maximize protection, then the impact resistance is improved, but the weight increases
Solution Approach 1:
The sheath is strategically positioned to cover only the critical regions of the blade body that are most susceptible to foreign object collisions, rather than covering the entire blade. This localized approach provides necessary protection while minimizing additional weight.
4Ease of manufacture
If the seam of the sheath is positioned at the leading edge to simplify manufacturing, then the manufacturing ease is improved, but the bending stress concentrates at the seam causing detachment
Solution Approach 1:
The seam position is pre-calculated and pre-positioned at locations where bending moments are minimized based on aerodynamic and structural analysis. This preliminary optimization ensures that the seam is placed in the most favorable location before manufacturing, preventing stress concentration and detachment while maintaining manufacturing feasibility.
Data Source
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AI summary
A fan rotor blade (1) includes a blade body (10) made from a composite material of a resin and fibers, and having a pressure surface (10a) facing one side in a rotation direction and a suction surface (10b) facing the other side in the rotation direction. The blade body is provided with a sheath (20) which is more rigid than the blade body and is fixed to the blade body in a state where the sheath covers a leading edge portion of the blade body, which is located on an upstream side in the direction of intake of external air, and the vicinity thereof. A tip end portion (21b) of the sheath extends from the leading edge portion side of the blade body to a trailing edge portion side of the blade body. An end portion of the tip end portion (21b) of the sheath is flush with the trailing edge portion of the blade body.