Stitched Composite Preform Tension Control for Mode II Disbond Resistance
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Solution Overview
Problem
Conventional stitching methods for stitched resin-infused composite structures provide minimal resistance to Mode II disbonds and can result in improper stitch orientations, leading to reduced load carrying capability and structural integrity issues.
Innovation Solution
A method and system that determines the dry and debulked thickness of a fabric preform using a computing system to apply a through-the-thickness stitch with a controlled stitch tension, combined with edge-stitching and adaptive pressure to ensure consistent stitch orientation and resistance to Mode II disbonds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional stitching methods are used for composite structures, then the manufacturing process is simple, but the resistance to Mode II disbonds is minimal and stitch orientations become improper
Solution Approach 1:
The system performs preliminary measurement of fabric preform thickness and calculates appropriate stitch tension parameters before the stitching process begins. This pre-planning of stitching parameters ensures proper stitch orientation and resistance to Mode II disbonds from the start, preventing the need for rework or correction.
Solution Approach 2:
The system implements real-time feedback by continuously monitoring the stitching process and adjusting stitch tension dynamically based on measured fabric thickness and debulked thickness. This closed-loop control maintains consistent stitch orientation and improves resistance to Mode II disbonds while adapting to variations in the fabric preform.
2Reliability
If fasteners are used to reinforce bondlines in composite structures, then residual strength is maintained, but weight increases and part counts increase
Solution Approach 1:
The invention extracts and eliminates the need for fasteners by implementing through-the-thickness stitching that directly reinforces bondlines. The stitching system removes the harmful element (fasteners) while maintaining the beneficial function (bondline reinforcement and residual strength retention).
Solution Approach 2:
The system changes the reinforcement method from mechanical fasteners to controlled stitch tension parameters. By adjusting stitch tension based on fabric thickness measurements, the system achieves bondline reinforcement equivalent to fasteners but without the associated weight penalty.
3Productivity
If stitch tension is not controlled during stitching, then the manufacturing process is faster, but stitch orientations become inconsistent and load carrying capability decreases
Solution Approach 1:
The system pre-calculates the appropriate stitch tension based on measured fabric thickness and debulked thickness before stitching begins. This preliminary determination of tension parameters allows the stitching process to proceed at optimal speed while ensuring consistent stitch orientation from the start.
Solution Approach 2:
The system implements dynamic adjustment of stitch tension during the stitching process, adapting to variations in fabric thickness and debulking. This dynamic control maintains consistent stitch orientation throughout the manufacturing process without sacrificing productivity, as the adjustments are made in real-time without stopping production.
Data Source
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AI summary
An example method includes determining, by a computing system, a dry thickness of a fabric preform. The method also includes determining, by the computing system, a debulked thickness of the fabric preform using the dry thickness of the fabric preform. In addition, the method includes determining, by the computing system, a stitch tension using the dry thickness of the fabric preform and the debulked thickness of the fabric preform. And the method includes causing, by the computing system, a stitching machine to apply a through-the-thickness stitch having the stitch tension to the fabric preform.