Precured Spar Cap Strip Taper for Uniform Resin Infusion
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Solution Overview
Problem
The manufacturing of large wind turbine blades faces challenges with resin impregnation, leading to dry spots, wrinkles, and structural weaknesses due to increased impregnation time and complexity, especially with the integration of precured parts and varying thicknesses in spar caps.
Innovation Solution
A precured fibrous strip for a load-carrying structure, such as a spar cap, with a tailored taper region featuring varying taper angles and an S-shaped profile to ensure smooth transitions and reduced crack formation, combined with flow-promoting materials to enhance resin distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If vacuum infusion is used to manufacture composite structures with varying thickness, then the aerodynamic shape can be controlled, but dry spots and resin distribution problems occur due to increased impregnation time and complexity
Solution Approach 1:
The spar cap is divided into multiple precured fibrous strips with different thicknesses that are stacked to create the varying thickness profile. This segmentation allows each strip to be pre-manufactured with consistent quality, avoiding resin distribution problems while achieving the desired aerodynamic shape through controlled stacking and resin infusion between layers
Solution Approach 2:
The fibrous strips are precured before final assembly, meaning the resin is already cured in each individual strip. This preliminary action ensures each strip has consistent mechanical properties and dimensional stability before being stacked and infused with resin in the final structure, eliminating dry spots and improving manufacturing precision
2Shape
If precured parts with varying thickness are stacked, then the load-carrying structure achieves desired shape, but wrinkles and resin-rich areas form at interfaces
Solution Approach 1:
The taper regions of the fibrous strips feature curved transitions instead of sharp angles, creating smooth S-shaped profiles. This curvature prevents stress concentration and eliminates the formation of wrinkles and resin-rich areas at thickness transitions, maintaining structural integrity while achieving the desired thickness profile
Solution Approach 2:
Different regions of the fibrous strips have different geometric properties - the taper regions have curved transitions while the mid-sections have constant thickness. This local differentiation of geometric quality allows the structure to achieve varying thickness for aerodynamic shape while maintaining uniform quality at critical interfaces through proper curvature design
3Manufacturing precision
If impregnation time is increased to ensure complete resin distribution, then dry spots are reduced, but manufacturing complexity and time consumption increase
Solution Approach 1:
The resin impregnation is performed preliminarily during the precuring of individual fibrous strips before final assembly. This ensures complete and uniform resin distribution in each strip with controlled, shorter impregnation cycles, while the final stacking requires only minimal resin infusion at the interfaces, significantly reducing total manufacturing time while maintaining high resin distribution uniformity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution reduces resin-rich areas and wrinkles, enhances resin distribution, and minimizes crack formation, improving the structural integrity and manufacturing efficiency of wind turbine blades.
Implementation Method 1
liquid polymer is drawn into the mould cavity via the inlet channels in order to fill said mould cavity. From the inlet channels, the polymer disperses in all directions in the mould cavity due to the negative pressure
Implementation Method 2
a vacuum, said vacuum in this connection being understood as an under-pressure or negative pressure, is generated via vacuum outlets in the mould cavity, whereby liquid polymer is drawn into the mould cavity
Implementation Method 3
a vacuum, said vacuum in this connection being understood as an under-pressure or negative pressure, is generated via vacuum outlets in the mould cavity
Data Source
AI summary
A precured fibrous composite strip for a load-carrying structure for a wind turbine blade has a first longitudinal end and a second longitudinal end, a first side and a second side with a width defined as the distance between the first side and the second side, and an upper surface and a lower surface with a thickness defined as the distance between the upper surface and the lower surface. The strip includes a taper region with a taper length at the first longitudinal end. The taper region tapers in thickness towards the first longitudinal end. The taper region includes a first taper section proximal to the first longitudinal end and having a first average taper angle, a third taper section distal to the first longitudinal end and having a third average taper angle, and a second taper section between the first taper section and the third taper section.