Flexible Core Block with Crossed Grooves for Composite Impregnation
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Solution Overview
Problem
The existing VARTM process faces challenges in achieving complete impregnation of fibre materials, leading to dry spots and air pockets, especially in large composite structures like wind turbine blades, which increases impregnation time and curing time, and can result in structural weaknesses and buckling effects.
Innovation Solution
The method involves using core blocks with a resin distribution network of grooves that allow for flexible placement and efficient resin distribution, eliminating the need for separate distribution layers and enabling uniform impregnation, reducing the risk of dry spots and shortening the curing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rigid mould part and resilient vacuum bag are used for VARTM, then the mould cavity can be sealed for vacuum generation, but dry spots and air pockets occur due to incomplete polymer distribution
Solution Approach 1:
The core block integrates both vacuum distribution and resin distribution functions into a single component. The first grooves extend from the first surface to the second surface for vacuum distribution, while the second grooves extend from the second surface to the first surface for resin distribution. This merging eliminates the need for separate distribution layers and vacuum channels, simplifying the device structure while ensuring complete polymer distribution throughout the fibre material.
Solution Approach 2:
The core block is divided into multiple grooves (first grooves and second grooves) that segment the vacuum and resin distribution paths. The first grooves create multiple vacuum outlets distributed across the core block, while the second grooves create multiple resin inlet channels. This segmentation ensures uniform distribution of both vacuum and resin throughout the fibre material, preventing dry spots and air pockets.
2Reliability
If separate distribution layers and vacuum channels are used, then polymer distribution can be improved, but handling and placement becomes more difficult
Solution Approach 1:
The core block combines distribution layers and vacuum channels into a single integrated component that is placed in one operation. The core block with its embedded grooves is positioned between the mould part and vacuum bag, eliminating the need for separate placement of distribution layers and vacuum channels. This significantly simplifies handling and placement operations while maintaining uniform polymer distribution.
3Volume of moving object
If large mould parts are used for wind turbine blades, then the structure size increases, but impregnation time and curing time increase significantly
Solution Approach 1:
The core block uses multiple segmented grooves (first grooves and second grooves) that divide the vacuum and resin distribution into multiple parallel paths. This segmentation allows resin to be distributed simultaneously through multiple channels throughout the large mould cavity, significantly reducing impregnation time. The integrated design also reduces curing time by ensuring uniform resin distribution across the entire volume.
Solution Approach 2:
The grooves extend in multiple directions (first grooves from first surface to second surface, second grooves from second surface to first surface), creating a three-dimensional distribution network. This multi-dimensional approach allows resin to reach all areas of the large mould cavity more efficiently, reducing both impregnation and curing times for large structures like wind turbine blades.
4Reliability
If vacuum pressure is increased to remove air pockets, then air removal may be improved, but fibre material deformation and buckling can occur
Solution Approach 1:
The core block segments vacuum distribution into multiple outlets through the first grooves, creating multiple low-pressure zones distributed throughout the mould cavity. This segmented approach allows air pockets to be removed gradually and uniformly from different locations, avoiding the need for high vacuum pressure that could deform fibre material. The distributed vacuum outlets prevent localized stress concentrations that could cause buckling.
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
This approach facilitates easier handling and more efficient resin distribution, reducing production time and costs by allowing the core blocks to conform to curved surfaces and preventing delamination, thereby enhancing the structural integrity of composite structures.
Implementation Method 1
a vacuum, said vacuum in this connection being understood as an underpressure or negative pressure, is generated via vacuum outlets in the mould cavity, whereby liquid polymer is drawn into the mould cavity
Implementation Method 2
liquid polymer is drawn into the mould cavity via the inlet channels in order to fill said mould cavity
Implementation Method 3
Patent literature discloses examples of the use of a semi-permeable membrane, which increases the area, in which the vacuum is active, and thus reduces the above problems. In this connection the term semi-permeable membrane means a membrane, which is permeable to gasses but impermeable to liquid polymer.
Data Source
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AI summary
A use of a core block for an impregnation process as well as a composite structure comprising such a core block is described. The core block has a first surface and a second surface, and a number of first grooves is formed in the first surface of the core. Furthermore, a number of second grooves is formed in the second surface of the core. The first grooves have a first height (h1) and a bottom, and the first grooves and the second grooves are part of a resin distribution network formed in the core block. The distance (t) between the bottom of the first grooves and the second surface of the core block is of such a size that the core block is flexible along the first grooves. Additionally, the sum of the first height and the second height is larger than the thickness of the core block, and at least one of the first grooves in the first surface of the core block crosses at least one of the second grooves in the second surface of the core block.