Large Scale Integrated Composite Airfoil Fabrication
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Solution Overview
Problem
The fabrication of large-scale composite airfoils faces challenges such as increased part count, labor costs, weight, susceptibility to lightning strikes, and dimensional control issues due to the use of fasteners, as well as complex and costly tooling requirements, which complicate the integration and final curing processes, and limit early detection of nonconformities.
Innovation Solution
The method employs pre-cured skins and spar webs assembled with uncured spar chords using simple and inexpensive tooling, allowing for co-bonding and reduced autoclave pressure application, minimizing vacuum bagging and tooling complexity, enabling early non-destructive inspection and net trimming of parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mechanical assembly using fasteners is used to build up composite airfoil structures, then multiple composite components can be assembled, but part count increases, labor costs increase, weight increases, and susceptibility to lightning strikes increases
Solution Approach 1:
The patent merges multiple separate composite components (skins, spars, ribs) into a single integrated composite structure through co-bonding. The skin and spar are formed as one continuous piece using a match-cut technique, eliminating the need for separate fasteners and reducing part count while maintaining assembly capability.
2Quantity of substance
If large scale integration of composite structures is used to reduce part count, then fastener-related disadvantages are reduced, but tooling complexity increases, work in process increases, and freezer storage space increases
Solution Approach 1:
The patent segments the manufacturing process into distinct phases: pre-curing the skin and spar separately using simple tooling, then integrating them through co-bonding. This allows each component to be manufactured independently with minimal tooling requirements, reducing overall tooling complexity while achieving large scale integration.
Solution Approach 2:
The skin and spar are pre-cured separately before final integration. This preliminary action allows components to be prepared in advance using simple tooling, reducing the complexity of the final assembly process and eliminating the need for complex integrated tooling.
3Manufacturing precision
If matched die tooling is used to achieve desired dimensional control of large scale integrated structures, then dimensional accuracy is improved, but tooling cost and complexity increase
Solution Approach 1:
The patent uses a match-cut technique where the skin is formed with a cut pattern that precisely matches the spar geometry. This copying approach ensures dimensional accuracy through the precision of the cut pattern rather than requiring complex matched die tooling, maintaining manufacturing precision while reducing tooling complexity.
4Productivity
If large area vacuum bagging is used for large scale integrated structures, then final cure is achieved, but labor intensity increases and bag leak detection becomes difficult
Solution Approach 1:
The patent segments the curing process so that the skin and spar are pre-cured separately using small vacuum bags, then only the integration area requires vacuum bagging during co-bonding. This dramatically reduces the total vacuum bagging area and associated labor intensity while maintaining final cure capability.
5Difficulty of detecting and measuring
If NDI operations are carried out only after final cure, then inspection is possible, but early detection of parts requiring rework is not possible, resulting in expensive repairs or scrapping
Solution Approach 1:
The patent performs NDI operations on the skin and spar components before final integration and curing. This preliminary inspection allows early detection of defects that require rework, preventing waste of time and resources on defective components that would otherwise be discovered only after expensive final curing.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An airfoil (110) is fabricated by assembling cured skins (114) with spars (116,118) having cured spar webs (116) and uncured spar chords (118). The skins are bonded to the spars by curing the spar chords.