Compressible Mandrel for Hollow Wind Turbine Spar Beam Removal
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Solution Overview
Problem
Conventional methods for manufacturing hollow composite structures, such as wind turbine rotor blades, face challenges in removing rigid mandrels due to size constraints, especially as wind turbines and blades increase in size, leading to difficulties in manufacture and transportation.
Innovation Solution
A method using a mandrel formed from compressible material with a rigid neutral state, which maintains shape during fiber reinforcement layup and curing, and is then compressed and withdrawn through a smaller opening by applying a vacuum, allowing for the production of hollow composite structures like tapered box-beam spar beams without the need for complex inflatable mandrels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a rigid mandrel is used to define the hollow space in conventional manufacturing processes, then the composite structure can be produced with proper shape and rigidity, but the mandrel becomes difficult to remove from the composite structure when the opening is smaller than the mandrel dimensions
Solution Approach 1:
The mandrel transitions from a static rigid state during molding to a dynamic compressed state for removal. The compressible material allows the mandrel to change its physical state - maintaining rigidity when needed for shape definition, then becoming compressible for easy removal through the opening.
Solution Approach 2:
The physical parameters of the mandrel are changed - specifically its compressibility and volume. By using compressible material, the mandrel's density and shape parameters can be altered after molding, enabling it to be compressed to a smaller size that fits through the opening for removal.
2Ease of operation
If an expandable mandrel with flexible material is used to enable mandrel removal, then the mandrel can be collapsed and removed through small openings, but the flexible material deforms during the casting process
Solution Approach 1:
The mandrel provides dynamic rigidity - being rigid during the molding process to maintain shape precision, then becoming compressible for removal. This temporal separation of rigidity and flexibility resolves the contradiction between shape stability and ease of removal.
Solution Approach 2:
The mandrel is designed with compressible material from the beginning, preparing it in advance to provide rigidity during molding while retaining the capability for later compression and removal, rather than requiring post-molding modifications.
3Power
If wind turbine rotor blades increase in size to improve power generation efficiency, then more power can be generated, but difficulties arise in integral manufacture and conveyance and transport of the blades
Solution Approach 1:
The blade manufacturing process is segmented into sections that can be manufactured separately and assembled later. The improved mandrel removal process enables this segmentation by allowing complex hollow structures to be manufactured with ease of demolding, facilitating modular construction for larger blades.
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
Enables the efficient production of hollow composite structures, such as spar beams for wind turbine blades, by allowing the mandrel to be easily removed from the structure, reducing manufacturing complexity and costs, and facilitating the assembly of larger wind turbine blades.
Implementation Method 1
Subsequent to curing, the method includes drawing a vacuum on the mandrel to compress and reduce the size of the compressible material
Data Source
AI summary
A method for producing a hollow composite structure, such as a spar beam for use in a wind turbine blade, includes placing fiber reinforcement material around a mandrel within a mold, and curing the fiber reinforcement material. The mandrel is formed from a compressible material having a rigid neutral state with a rigidity to maintain a defined shape of the mandrel during lay up and curing of the fiber reinforcement material. Subsequent to curing, a vacuum is drawn on the mandrel to compress the compressible material so that the compressed mandrel can be drawn out through an opening in the composite structure, the opening having a size such that the mandrel could not be withdrawn through the opening in the rigid neutral state of the mandrel.