Composite Spar Fitting Integration Without Riveting Or Bulking
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Solution Overview
Problem
The integration of metallic interface fittings into composite aircraft wing spars is hindered by time-consuming riveting operations, increased mass, galvanic corrosion, sealing issues, and bulking effects, making it difficult to achieve co-consolidation and uniform resin filling.
Innovation Solution
A method involving partial polymerization of a laminate preform fitting, followed by layup and complete polymerization with a composite profile, using a tooling system to maintain dimensional stability and facilitate integration, allowing for automated manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metallic interface fittings are assembled to the composite spar by riveting, then the fittings can be connected to the spar structure, but the assembly time increases and the mass of the assembly increases
Solution Approach 1:
The patent merges the metallic fitting and composite spar into a single integrated component by embedding the metallic fitting within the composite preform before curing. This eliminates separate riveting operations and creates a monolithic structure where the metallic fitting becomes an intrinsic part of the composite spar, thereby reducing assembly time while maintaining connection reliability.
Solution Approach 2:
The metallic fitting is positioned and secured within the composite preform before the curing process begins. This preliminary placement ensures the fitting is correctly positioned and prevents movement during curing, eliminating the need for post-assembly riveting operations and reducing overall assembly time.
2Reliability
If metallic interface fittings are assembled to the composite spar by riveting, then the fittings can be connected to the spar structure, but the mass of the assembly increases
Solution Approach 1:
By merging the metallic fitting with the composite spar into a single integrated component, the patent eliminates the need for separate fasteners and rivets that would add additional mass. The integrated structure uses the composite material itself as the bonding medium, reducing overall assembly mass while maintaining connection reliability.
3Reliability
If metallic parts contact with composite parts reinforced by electrically conductive fibers, then galvanic coupling occurs leading to corrosion, but adding a glass fiber ply to prevent corrosion increases the number of operations
Solution Approach 1:
The patent uses an intermediate layer of non-conductive composite material (such as glass fiber or polymer matrix) between the metallic fitting and the carbon fiber-reinforced composite spar. This intermediary layer prevents direct electrical contact between the metallic fitting and conductive carbon fibers, thereby eliminating galvanic coupling and corrosion risks without requiring additional protective operations.
4Strength
If fittings are integrated between two flanges linked to 3 sides of the profile, then the structural stiffening function is achieved, but the integration into composite preform becomes difficult due to bulking effects
Solution Approach 1:
The metallic fitting is positioned and secured within the composite preform before the curing process begins. This preliminary placement allows the fitting to be correctly positioned and prevents movement during curing, accommodating the bulking effect that occurs during polymerization while ensuring the fitting remains properly positioned for structural stiffening.
Solution Approach 2:
The patent accounts for parameter changes during the curing process, particularly the volume expansion (bulking) of the composite preform. By designing the tooling and fitting positioning to accommodate these parameter changes, the patent enables successful integration of the metallic fitting while maintaining the required structural stiffening function.
5Ease of manufacture
If resin injection techniques are used to integrate fittings into composite profiles, then integration is achieved, but the process becomes complex requiring expensive toolings and difficult automation
Solution Approach 1:
The metallic fitting is positioned and secured within the composite preform before the curing process begins. This preliminary placement eliminates the need for complex resin injection techniques and expensive specialized toolings, as the fitting is already in its final position and will be bonded during the standard curing process, thereby simplifying the manufacturing process and enabling easier automation.
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 efficient, automated integration of composite fittings with the spar, reducing weight, eliminating corrosion risks, and ensuring precise assembly without bulking issues, while maintaining tooling consistency throughout the process.
Implementation Method 1
partial polymerization of a laminate preform fitting (110) to obtain a dimensionally stable fitting (110)
Implementation Method 2
a fibrous reinforcement impregnated with a thermosetting resin
Data Source
AI summary
The invention pertains to a method for integrating a fitting fitted between two wings of a composite profile comprising the steps of: obtaining a preform of a fitting impregnated with a thermosetting resin, comprising two flanges and a rib; pre-curing the laminate preform of the fitting to obtain a partial polymerization of the preform; laying up a laminate preform of the profile so that fibers impregnated with a thermosetting resin included in two of the wings of the laminate preform of the profile are laid up over the two flanges of the preform of the partially polymerized fitting; and completely polymerizing an assembly comprising the laminate preform of the profile and the laminate preform of the partially polymerized fitting while maintaining into contact the flanges of the laminate preform of the fitting with the wings of the laminate preform of the profile.