Fabricating Plank Stringers with Variable Profiles
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Solution Overview
Problem
Current methods for fabricating aircraft plank stringers with variable profiles are inefficient due to the difficulty in subdividing the stringers into similarly-shaped charges, leading to increased numbers of charges and layup/stacking operations.
Innovation Solution
An automated fabrication system using an automated tape-laying machine and cutting tool, guided by a computing device, groups plies into charges and lays them up as continuous blankets, which are then cut and stacked to form the plank stringer, accommodating variable profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If plank stringers are subdivided into similarly-shaped charges for fabrication, then the fabrication process becomes standardized and easier to manage, but this approach becomes difficult and inefficient when the plank stringer has variable profiles in vertical and longitudinal directions
Solution Approach 1:
The plank stringer is divided into multiple charges (segments) that can be fabricated separately and then stacked. Each charge maintains a consistent basic shape for standardized fabrication, while the variable profile is achieved through selective ply discontinuation at different charge locations. This segmentation allows standardized manufacturing processes to be applied to each charge while still producing the overall variable profile required by the design.
Solution Approach 2:
Different charges have different local ply configurations - specifically, different numbers and arrangements of plies are used in different charges to create the variable profile. For example, intermediate charges may have fewer plies than end charges, creating the desired height variations along the longitudinal direction. This local differentiation of ply quality allows the standardized charge fabrication process to produce the non-uniform final structure.
2Manufacturing precision
If the number of charges is increased to accommodate profile variations, then the plank stringer can more accurately represent the desired variable profile, but the number of layup and stacking operations increases, reducing manufacturing efficiency
Solution Approach 1:
The stringer is divided into a limited number of charges (e.g., three charges: first, second, and third charges) rather than using many small segments. Each charge is sufficiently large to accommodate the necessary ply variations while maintaining a consistent basic geometry that can be fabricated using standardized processes. This optimal segmentation balances profile accuracy with manufacturing efficiency.
Solution Approach 2:
The ply stacking sequence and orientation are predetermined and planned in advance for each charge location. The fabrication system is pre-programmed with the specific ply configurations for each charge, allowing automated tape laying machines to efficiently deposit the correct ply patterns without requiring complex real-time adjustments. This preliminary planning reduces on-site fabrication complexity and improves productivity.
3Shape
If plies are discontinued within the plank stringer's profile to achieve height variations, then the variable profile is achieved, but the differentiation between individual charges increases, making fabrication more complex
Solution Approach 1:
Different charges have different local ply configurations - specifically, different numbers and arrangements of plies are used in different charges to create the variable profile. For example, intermediate charges may have fewer plies than end charges, creating the desired height variations along the longitudinal direction. This local differentiation of ply quality allows the standardized charge fabrication process to produce the non-uniform final structure.
Solution Approach 2:
Despite the local variations in ply configurations, all charges share a universal basic structure and fabrication approach. The same standardized charge geometry, material types, and general fabrication procedures are used across all charges. This universality allows the fabrication system to handle the complexity of differentiated charges through a consistent, repeatable process framework, reducing overall device complexity.
Data Source
AI summary
A method of fabricating a plank stringer for use in an aircraft includes grouping a plurality of stacked plies of reinforcing material into a plurality of charges, where each charge in the plurality of charges includes a substack of plies. The method also includes grouping the plurality of charges into two or more groups such that, for each charge in a given group, a respective substack of plies includes a sequence of orientation angles with respect to a longitudinal axis of the plank stringer corresponding to the given group. The method also includes laying up each group of charges as a continuous blanket of plies, where each continuous blanket of plies includes the respective substack of plies for each charge in the respective group. The method also includes cutting each continuous blanket of plies into the respective group of charges and stacking the plurality of charges to form the plank stringer.