Wind Turbine Blade Spar Cap Curved Strip Bonding
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Solution Overview
Problem
Modern wind turbine blades experience 'planking' issues due to flat, planar spar cap strips not conforming to the chordwise curvature, resulting in uneven adhesive bond lines and resin-rich areas, which complicates the manufacturing process and affects the structural integrity.
Innovation Solution
The method involves arranging peripheral strips inclined relative to intermediate strips in the spar cap, with the shear web flange's primary bonding surface matching the chordwise width of the intermediate strips within a +/-20% tolerance, and optionally including secondary bonding surfaces inclined to match the peripheral strips, to ensure a uniform adhesive bond line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If flat, planar strips are used to form spar caps, then the manufacturing process is simplified and strips are cheaper to produce, but planking occurs resulting in uneven adhesive bond lines and resin-rich areas
Solution Approach 1:
The patent applies curvature to the spar cap strips by forming them with a pre-curved cross-section that matches the blade's chordwise curvature. This allows the strips to conform to the curved mold surface without creating gaps (planking), thereby achieving uniform adhesive bond lines while maintaining manufacturing simplicity through pultrusion of pre-curved sections.
Solution Approach 2:
The patent changes the geometric parameters of the strips by providing them with a pre-curved cross-sectional shape rather than being flat and planar. This parameter change (from flat to curved) enables the strips to conform to the blade curvature, eliminating planking and ensuring uniform adhesive distribution while still allowing efficient pultrusion manufacturing.
2Device complexity
If wider strips are used to reduce the number of strips in the spar cap, then the structural complexity is reduced, but the planking effect increases resulting in larger gaps and more uneven bond lines
Solution Approach 1:
By providing strips with a pre-curved cross-section that matches the blade's chordwise curvature, the patent enables wider strips to be used without increasing planking. The curved geometry allows the entire width of the strip to conform to the curved mold surface, maintaining uniform gap distribution and adhesive bond line thickness even with fewer, wider strips.
3Strength
If excess adhesive is used to fill large gaps between flange base and spar cap, then the bond strength is improved, but the manufacturing precision and control of bond line thickness deteriorates
Solution Approach 1:
The pre-curved cross-section of the strips eliminates large gaps between the flange base and spar cap by ensuring continuous contact across the bonding surface. This geometric solution provides uniform adhesive distribution and consistent bond line thickness without requiring excess adhesive, thereby maintaining both bond strength and manufacturing precision.
Data Source
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AI summary
A wind turbine blade mould extending longitudinally in a spanwise direction and transversely in a chordwise direction is provided and a spar cap (134, 136) is laid the mould. The spar cap comprises a plurality of strips (138) extending longitudinally in the spanwise direction and arranged side-by-side in the chordwise direction, said strips comprising one or more intermediate strips (158) arranged between peripheral strips (160, 162) which are inclined relative to the intermediate strips. A shear web (126) comprising a flange (130a) extending longitudinally in the spanwise direction is provided, the flange comprising a base (144) defining a primary bonding surface (164). A chordwise width of the primary bonding surface corresponds substantially to a chordwise width of the intermediate strips of the spar cap. The primary bonding surface of the flange is bonded to the one or more intermediate strips of the spar cap.