Composite Turbine Blade Root Laminate Design for Strength
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Solution Overview
Problem
The use of composite materials in turbine blades leads to a reduction in strength at the blade root due to ply drops, which are regions with no reinforced fibers and high stress concentrations, increasing the risk of breakage.
Innovation Solution
A composite blade design featuring a first laminate extending along the longitudinal direction in the airfoil, a second laminate extending along an opposite inclination direction in the blade root, and a third laminate positioned between them, with reinforced fibers continuously extending from the airfoil to the blade root, and the third laminate's fibers aligned to intersect the first and second laminates, effectively distributing stress and reducing the strength reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If composite layers are expanded outward in the blade root region, then the blade root thickness is increased, but the distance between reinforced fibers is increased and strength is reduced
Solution Approach 1:
The blade root region is divided into multiple laminate sections (first laminate, second laminate, third laminate) with different fiber orientation patterns. This segmentation allows each section to contribute differently to strength and thickness, resolving the contradiction by localizing the thickness increase to specific areas while maintaining fiber density in critical load-bearing zones.
Solution Approach 2:
Different regions of the blade root are assigned different laminate configurations: the first laminate has fibers extending along the longitudinal direction for strength, while the second laminate has fibers inclined outward to increase thickness. This local differentiation allows the blade root to achieve both increased thickness and maintained strength in critical areas.
2Strength
If short composite layers are provided between layers along the thickness direction, then the reduction in strength is suppressed, but ply drops are formed which are regions with low strength
Solution Approach 1:
The harmful ply drops are extracted and relocated to the outer peripheral region of the blade root, separated from the high-stress central loading path. By positioning ply drops where stress is lower, the overall reliability is improved while still allowing short composite layers to be used for thickness buildup.
Solution Approach 2:
The third laminate acts as an intermediary structure between the first and second laminates, providing a transition zone that connects the differently oriented fiber systems. This intermediary laminate ensures continuous load transfer and prevents stress concentration at the interfaces between laminates with different fiber orientations.
3Weight of moving object
If composite material is used for turbine blade, then weight is reduced, but ply drops form in the blade root causing high stress concentration and breakage risk
Solution Approach 1:
The invention uses composite materials with strategically designed laminate structures to achieve both weight reduction and strength maintenance. By combining multiple laminate types with different fiber orientations and properties, the blade achieves optimal weight-to-strength ratio while managing the ply drop issue through careful laminate arrangement.
Data Source
AI summary
A composite blade is formed by laying up composite layers in which reinforced fibers are impregnated with resin, and has a blade root and an airfoil extending from the blade root in a longitudinal direction. The composite blade includes a first laminate of the composite layers extending along the longitudinal direction in the airfoil and extending along a first inclination direction inclined toward a direction intersecting the longitudinal direction in the blade root; a second laminate of the composite layers extending along the longitudinal direction and contacting the first laminate in the airfoil, the second laminate extending along a second inclination direction inclined toward a direction opposite to the first inclination direction in the blade root and being separated from the first laminate; and a third laminate of the composite layers provided between the first and second laminates in the blade root.