VARTM Distribution Medium for Composite Impregnation
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Solution Overview
Problem
The challenge in vacuum-assisted resin transfer moulding (VARTM) is the difficulty in achieving complete impregnation of fibre materials with resin, leading to dry spots and air pockets, which complicates the manufacturing of large composite structures like wind turbine blades, increasing impregnation and curing times.
Innovation Solution
The method involves using a mould with a rigid part and a flexible vacuum bag, along with a distribution medium and resin inlet channels to optimize resin distribution, including a centrally positioned upper distribution medium and optionally a lower distribution medium, to reduce impregnation time and prevent air pockets, and a plate-like distribution medium to minimize stress on the fibre laminate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If vacuum outlets are positioned to overlap fibre zones, then resin distribution is improved, but air pockets cannot be removed from intermediate zones
Solution Approach 1:
The vacuum bag is divided into multiple independent vacuum outlets, each responsible for specific zones. The first vacuum outlet serves the first fibre zone, the second vacuum outlet serves the second fibre zone, and the third vacuum outlet specifically serves the intermediate zone. This segmentation allows each outlet to independently manage resin distribution and air removal in its designated area without interfering with other zones.
Solution Approach 2:
The intermediate zone acts as an intermediary region between the first and second fibre zones. By positioning the third vacuum outlet to overlap with this intermediate zone, the system creates a mediator pathway that facilitates air pocket removal from areas that would otherwise be inaccessible when using only two vacuum outlets positioned over fibre zones.
2Manufacturing precision
If staff repair dry spots by standing on the vacuum bag, then dry spots can be addressed, but fibre material may deform and structure may weaken
Solution Approach 1:
The vacuum bag is designed with multiple vacuum outlets positioned before the impregnation process completes. This preliminary positioning of vacuum outlets prevents dry spots from forming in the first place by ensuring continuous vacuum coverage across all zones including intermediate areas, eliminating the need for subsequent repair operations that would require staff to stand on the vacuum bag.
3Reliability
If traditional vacuum bagging is used, then mould cavity can be sealed, but complete impregnation of large structures takes excessive time
Solution Approach 1:
The vacuum bag is segmented into multiple vacuum outlets distributed across different zones of the mould cavity. This segmentation creates multiple parallel vacuum pathways that simultaneously draw resin through different regions of the fibre material, significantly reducing the overall impregnation time for large composite structures while maintaining reliable mould cavity sealing.
Solution Approach 2:
The vacuum outlets are positioned to overlap with fibre zones in the vertical dimension, creating a three-dimensional vacuum distribution network. This spatial arrangement optimizes resin flow paths and accelerates impregnation by utilizing vertical pressure gradients in addition to horizontal resin distribution.
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 significantly reduces the time required for complete impregnation, minimizes the formation of air pockets, and decreases the likelihood of buckling effects, thereby optimizing the production of large composite structures by allowing for faster production and lower production costs.
Implementation Method 1
By generating a vacuum, typically 80 to 95% of the total vacuum, in the mould cavity between the inner side of the mould part and the vacuum bag, the liquid polymer can be drawn in and fill the mould cavity with the fibre material contained herein.
Implementation Method 2
During the process of filling the mould, 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 via the inlet channels
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
AI summary
Provided is a composite structure having a longitudinal direction and a transverse direction, having a longitudinally extending fiber insertion having a plurality of fiber layers, a first surface, a second surface, a first side, and a second side; a fiber insertion first zone at the first side of the fiber insertion; a fiber insertion second zone at the second side of the fiber insertion; an intermediate zone separating the first zone and the second zone; a distribution medium adjacent at least one of the first side and the second surface of the intermediate zone, the distribution medium comprising a resin distribution network; and a cured resin impregnating at least the resin distribution network and the fiber insertion.