T-shaped Stringer Rounded Web End Shaping
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Solution Overview
Problem
Conventional methods for manufacturing T-shaped aircraft stringers result in beaked excess material at the web end, which is not load-bearing and requires damaging machining to correct, and the dark color of composite materials makes impact damage detection time-consuming and inefficient.
Innovation Solution
A method involving a shaping process with a fixed and moveable tool set to form a rounded web end, along with a curing tool adapted to the new geometry, and the inclusion of a lighter-colored impact-detecting strip to identify damage without damaging the structure, reducing manufacturing time and improving impact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional manufacturing method is used to produce T-shaped stringers, then the stringers can be manufactured with standard processes, but the web end has beaked excess material that is not load-bearing and requires damaging machining operations
Solution Approach 1:
The patent applies curvature by rounding the web end of the stringer instead of leaving it with beaked excess material. The shaping tool is configured to form a rounded profile at the web end, which eliminates the need for subsequent machining operations while improving impact resistance by distributing stresses more evenly across the surface.
2Strength
If the web end is rounded to improve impact resistance, then the stringer performs better under impact loads, but the shaping process requires adapted tools and increased manufacturing precision
Solution Approach 1:
The rounding of the web end is performed during the initial shaping operation before curing. The shaping tool is configured with the appropriate profile to form the rounded web end in one pass, eliminating the need for subsequent machining operations and reducing the cumulative precision requirements across multiple operations.
3Shape
If machining is performed to remove excess material, then the web surface becomes horizontal and planar, but the machining operation can damage the web end and creates useless weight loss
Solution Approach 1:
Instead of machining the web end to achieve a planar surface, the patent forms a rounded profile during the shaping operation. This approach accepts the rounded geometry as the final form, which actually improves impact resistance while eliminating material waste associated with machining operations.
4Difficulty of detecting and measuring
If the stringer is painted to enable damage detection, then impact damage can be identified, but the painting process is time-consuming and requires covering other areas
Solution Approach 1:
The patent incorporates a color change mechanism by including a visible indicator strip with a color different from the surrounding composite material at the web end. This allows impact damage to be detected through color contrast without requiring time-consuming painting operations or masking of other areas.
5Difficulty of detecting and measuring
If a lighter-colored strip is added to the web end for damage detection, then impact damage can be efficiently identified, but the manufacturing process requires additional material placement steps
Solution Approach 1:
The indicator strip is integrated into the shaping operation itself. The shaping tool is configured to form the rounded web end while simultaneously positioning and embedding the indicator strip in the appropriate location. This merging of operations eliminates the need for separate strip placement steps and reduces overall process complexity.
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 method produces stringers with a rounded web end that withstands impacts better, reduces manufacturing time, and allows for efficient damage detection, utilizing the material more effectively and eliminating the need for costly and damaging machining operations.
Implementation Method 1
vertically moving the moveable tool at a pre-determined speed to progressively bend the web of the preform
Implementation Method 2
Pressure and temperature higher than those applied during shaping are applied when curing because the purpose is to cure the resin and to get said resin to be redistributed in order to fill the cavities that may exist in the part
Implementation Method 3
Pressure and temperature higher than those applied during shaping are applied when curing
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present invention relates to a method of manufacturing T-shaped stringers (7) made of composite material, comprising a second shaping step for shaping laminates (4) into L-shaped preforms (6), which comprises providing a set of tools formed by a fixed tool (1) comprising a lower portion and an upper portion, and a moveable tool (3) comprising a lower element and an upper element. It also comprises the segment of the laminate (4) intended for the foot of the preform (6) being located between the lower portion and the upper portion of the fixed tool (1), and the segment of the laminate (4) intended for the web of the preform (6) being located between the lower element and the upper element of the moveable tool (3). It further comprises vertically moving the moveable tool (3) to progressively bend the web of the preform (6) supporting it on a vertical wall of the fixed tool (1). The end of its web adopts a rounded shape.