Automated RTM for Arcuate Honeycomb Rub Strips
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Solution Overview
Problem
Conventional rub strip manufacturing processes result in non-uniform surface finishes and numerous voids due to the difficulties in handling and curing epoxy resin on a paper-like honeycomb core, leading to distorted cells and defects, which affect airflow in turbine engines.
Innovation Solution
An automated resin transfer molding process using a system with a computer-controlled injection machine, vacuum pump, and mold design with projections to evenly distribute resin across the core, ensuring complete filling and minimizing voids, and using glass fabric and peel ply fabric to improve bonding and surface quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hand spreading and troweling epoxy resin is used to fill honeycomb core cells, then the rub strip can be manufactured, but the surface finish becomes non-uniform and voids are created
Solution Approach 1:
The patent replaces the manual mechanical system of hand spreading and troweling with an automated resin injection system. The injection system delivers resin through needles into the honeycomb core cells, eliminating the variability of manual application and achieving uniform surface finish and complete cell filling without voids.
Solution Approach 2:
The patent introduces an intermediary resin injection system that acts as a mediator between the epoxy resin and the honeycomb core. The injection system includes resin reservoirs, pumping means, and needle assemblies that precisely deliver resin to each cell, ensuring uniform distribution and eliminating the defects associated with direct manual application.
2Quantity of substance
If thick epoxy resin is applied by hand to ensure sufficient filling of honeycomb core cells, then cell filling may be achieved, but pockets of air remain within the cured epoxy
Solution Approach 1:
The patent replaces manual resin application with an automated injection system that precisely controls resin delivery. The system uses pumping means to deliver resin through needles directly into each honeycomb core cell, ensuring complete filling without trapping air pockets, and achieves reliable void-free cured epoxy.
Solution Approach 2:
The patent applies preliminary action by injecting resin into the honeycomb core cells before curing occurs. The injection system delivers the exact amount of resin needed to fill each cell completely, preventing air pocket formation from the outset rather than attempting to correct voids after curing.
3Ease of manufacture
If honeycomb core is handled during manual resin application, then resin can be spread across the surface, but the paper-like core becomes deformed resulting in distorted or broken cells
Solution Approach 1:
The patent replaces manual resin spreading that requires handling the honeycomb core with an automated injection system. The needles deliver resin directly into each cell without requiring physical contact or manipulation of the core structure, preventing deformation and maintaining cell integrity throughout the manufacturing process.
4Area of stationary object
If epoxy is applied across large rub strip surface area by hand, then complete coverage can be achieved, but some portions cure before others are applied leading to bonding defects
Solution Approach 1:
The patent uses preliminary action by injecting resin into each honeycomb core cell individually and simultaneously across the entire rub strip surface area. This ensures that all portions receive resin at the same time and cure uniformly, preventing bonding defects that occur when some areas cure before others are applied in manual processes.
Solution Approach 2:
The patent segments the resin application process by using multiple injection needles that can be positioned to target individual honeycomb core cells or groups of cells. This segmentation allows simultaneous resin delivery across the large surface area, ensuring uniform curing throughout the entire rub strip.
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 process produces rub strips with improved surface finish and reduced voids, enhancing airflow and extending the lifespan of turbine engine components by ensuring uniform resin distribution and preventing core distortion during curing.
Implementation Method 1
directing liquid resin into the mold cavity at a pressure and a flow rate such that the cells of the honeycomb structure are prevented from rupturing
Implementation Method 2
vacuum pump
Implementation Method 3
curing the liquid resin
Data Source
AI summary
A method of making a rub strip includes resin transfer molding an arcuate composite structure. The resin transfer molding step includes inserting a honeycomb core into a mold cavity having an arcuate base so that the honeycomb core assumes an arcuate shape. The resin transfer molding step further includes directing liquid resin into the mold cavity to form the composite structure comprising the liquid resin and the honeycomb core, and curing the liquid resin for a sufficient period of time. The resin transfer molding step further includes removing the composite structure from the mold. The method further includes repeating the resin transfer molding step until a sufficient number of arcuate composite structures are produced. The method further includes coupling a plurality of the arcuate composite structures together to form the rub strip.