Composite Fan Blade Ply Drop Layout for Bird Impact Resistance
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Solution Overview
Problem
Composite fan blades in turbomachines face challenges in meeting aircraft certification regulations for bird and hailstone impacts while maintaining aerodynamic performance and weight savings.
Innovation Solution
The design of composite fan blades with a greater number of layer exit lines on the lower surface than the upper surface, particularly in specific regions, and strategic placement of terminal portions of incomplete strands to enhance impact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the number of layers is reduced as one approaches the blade tip, leading edge, and trailing edge to achieve decreasing thickness, then the blade weight is reduced and aerodynamic performance is improved, but the resistance to bird and hailstone impacts is insufficient
Solution Approach 1:
The patent applies local quality by differentiating the layer exit line configuration between the lower and upper surfaces of the blade. Specifically, the number of layer exit lines on the lower surface is made greater than on the upper surface in specific regions (between the foot and 30% of blade height, and/or between the foot and 70% of blade height). This creates localized structural reinforcement on the lower surface where impact resistance is most needed, while maintaining reduced thickness and weight in other areas of the blade.
2Strength
If composite blades are made thicker to comply with certification regulations for bird and hailstone impacts, then the impact resistance is improved, but the aerodynamic performance is compromised and weight savings are reduced
Solution Approach 1:
The invention implements local quality by concentrating layer exit lines specifically on the lower surface in regions where impact resistance is critical (0-30% and/or 0-70% of blade height from the foot). This localized reinforcement provides enhanced protection against bird and hailstone impacts without requiring a uniform increase in blade thickness, thereby preserving aerodynamic performance and maintaining weight savings.
Solution Approach 2:
The patent applies asymmetry by creating an unequal distribution of layer exit lines between the lower and upper surfaces of the blade. The lower surface has a greater number of layer exit lines in specific regions compared to the upper surface. This asymmetric configuration optimizes impact resistance where it is most needed (lower surface facing forward impacts) while avoiding unnecessary material addition that would compromise aerodynamics.
Data Source
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AI summary
The disclosed fan blade is composed at least in part of a structure (50) made of composite material comprising a fiber reinforcement (62) and a matrix (64). The fiber reinforcement (62) includes a plurality of plies (66, 68) that are each formed of warp yarns (71) and weft yarns (72). The warp yarns (71) and weft yarns (72) include incomplete yarns (75, 76) that each have a terminal end (78) on the pressure side (40) or the suction side (42). The pressure side (40) and the suction side (42) each have at least one ply drop line connecting the terminal ends (78) of the incomplete yarns (75, 76) of the same ply (66, 68). The number of ply drop lines on the pressure side (40) is greater than the number of ply drop lines on the suction side (42) in a low region of the blade and/or in an extended region of the blade.