Composite Stringer Forming with Displaceable Die Portions
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Solution Overview
Problem
The fabrication of composite blade stiffeners, such as I-stringers, is labor-intensive and costly due to the need for multiple tools and labor-intensive hand layup techniques, especially when forming highly contoured stringers that require localized contouring to conform to aircraft skins, which often results in ply wrinkling.
Innovation Solution
A method and apparatus that uses simplified tooling to form a single composite charge into a desired stringer configuration, including press forming a flat composite charge into a die set to create a stringer with an I-shaped cross section, allowing for contouring along its length using ply drop-offs or pad-ups, and utilizing a die set with displaceable die portions and a punch to apply pressure, optionally with heating to facilitate forming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hand layup techniques are used to form highly contoured stringers, then ply wrinkling is minimized, but labor intensity and cost increase
Solution Approach 1:
The die set is divided into multiple displaceable die portions that can independently move to accommodate complex contours. This segmentation allows the tooling to adapt to highly contoured surfaces while maintaining automated forming processes, resolving the contradiction between surface quality and manufacturing efficiency.
Solution Approach 2:
The die portions are made displaceable rather than fixed, allowing dynamic adjustment during the forming process. This enables the tooling to conform to complex contours and prevent ply wrinkling while maintaining automated high-speed production, eliminating the need for labor-intensive hand layup.
2Shape
If multiple separate charges are combined to fabricate blade stringers, then desired stringer configuration is achieved, but tooling complexity and manufacturing time increase
Solution Approach 1:
Multiple separate charges are merged into a single integrated composite charge that is formed in one operation. The die set is configured with multiple cavities that simultaneously form different portions of the stringer (flanges, web, bulb) from a single charge, eliminating the need for multiple tools and assembly steps.
Solution Approach 2:
The die set is designed as a universal tooling system that can form complete I-stringers with complex configurations in a single operation. The multi-functional die set eliminates the need for multiple specialized tools, reducing tooling complexity while achieving the desired stringer shape.
3Shape
If multiple separate charges are assembled to form blade stringers, then desired stringer configuration is achieved, but manufacturing flow time increases
Solution Approach 1:
The entire stringer configuration is prepared in advance as a single integrated charge rather than assembling multiple separate charges during production. This preliminary preparation eliminates assembly time and reduces manufacturing cycle time while maintaining the desired complex stringer configuration.
Solution Approach 2:
Multiple forming operations that would be performed sequentially on separate charges are merged into a single simultaneous forming operation. The die set forms all portions of the stringer (flanges, web, bulb) in one cycle, dramatically reducing manufacturing flow time.
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 reduces tooling costs and manufacturing flow times by eliminating the need for multiple charges and assembly, while minimizing ply wrinkling and improving the efficiency of forming contoured stringers with localized features.
Implementation Method 1
The method may further comprise locally heating the bulb to a forming temperature before the bulb is press formed within the recess
Implementation Method 2
a stringer hat is formed by press forming the composite charge into a cavity formed by the die set. A stringer base is formed by press forming the composite charge against the dies. The die set is used to compress the stringer hat into a stringer web
Implementation Method 3
Press forming the charge into the cavity in the die set is performed using a punch
Data Source
AI summary
Method and tooling apparatus for forming a composite charge into a stringer having an I-shaped cross-section. A substantially flat composite charge is placed on a die set and pressed formed into a die set cavity to form a stringer hat. A stringer base is formed by press forming the composite charge against the die set. The die set is used to compress the stringer hat into a stringer web having a bulb on one end thereof. A stringer cap is formed by press forming the bulb within a recess in the die set.