Airfoil Sheath and Tip-Cap Joint for Continuous Stiffness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Gas turbine engine airfoils face challenges in maintaining structural integrity and reducing delamination due to foreign object debris (FOD) impacts, particularly in composite materials used for fan blades, which can lead to strain and stress concentrations.
Innovation Solution
The airfoil design incorporates a composite layup with a sheath and tip cap structure, featuring staggered joints and interleaved interface members that provide continuous stiffness and reduce structural discontinuities, enhancing the airfoil's resistance to FOD impacts by encapsulating the airfoil body and minimizing inter-laminar stress concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a composite layup is used for the airfoil body, then weight is reduced, but structural integrity and resistance to delamination under FOD impact deteriorates
Solution Approach 1:
The airfoil body uses a composite layup of carbon fiber reinforced polymer plies, while the sheath and tip cap use a different composite material system. This combination allows the airfoil to maintain lightweight characteristics while the sheath provides enhanced protection against FOD impacts, preventing delamination of the composite structure.
Solution Approach 2:
The sheath and tip cap act as protective shells that encapsulate the airfoil body, providing a sacrificial layer that absorbs FOD impact energy before it reaches the critical composite airfoil structure, thereby preventing delamination while maintaining the overall lightweight design.
2Ease of manufacture
If joints are used to connect sheath and tip cap, then manufacturing complexity is reduced, but structural discontinuities and stress concentrations increase
Solution Approach 1:
The protective structure is divided into separate sheath and tip cap components that can be manufactured independently and then assembled to the airfoil body. This segmentation enables easier manufacturing and assembly while the interleaved interface members ensure structural continuity at the joints.
Solution Approach 2:
Interleaved interface members act as intermediaries between the sheath and tip cap, creating a mechanically integrated connection that eliminates structural discontinuities. These interface members distribute loads across the joint region, preventing stress concentrations while maintaining the segmented manufacturing approach.
3Reliability
If the sheath and tip cap are made from a different composite material, then protection against FOD impact is improved, but device complexity increases
Solution Approach 1:
Different composite material properties are applied to different regions: the sheath and tip cap use a composite material optimized for FOD impact resistance, while the airfoil body uses a composite layup optimized for aerodynamic performance and structural strength. This local differentiation provides targeted protection without requiring the entire structure to use complex materials.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An airfoil (164) for a gas turbine engine (20) according to an example of the present invention includes, among other things, an airfoil section (165) extending between a leading edge (LE) and a trailing edge (TE) in a chordwise direction (X) and extending between a tip portion (170) and a root section (168) in a spanwise direction (R). The airfoil section (165) defines pressure and suction sides (PS, SS) separated in a thickness direction (T). A sheath (174) extends in the spanwise direction (R) along at least one of the pressure and suction sides (PS, SS) of the airfoil section (165). A tip cap (176) extends in the chordwise direction (X) along the at least one of the pressure and suction sides (PS, SS). The sheath (174) includes a first set of interface members (174C). The tip cap (176) includes a second set of interface members (176C) interleaved with the first set of interface members (174C) to establish at least one joint (178) along an external surface (ES) of the at least one of the pressure and suction sides (PS, SS). A method of assembly for an airfoil (64) is also disclosed.