Composite Tape Layup Guard Bands for Undetected Gap Anomalies
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Solution Overview
Problem
Existing manufacturing processes for composite parts, such as aircraft panels, fail to accurately account for anomalies like whiskers and missing fiber due to poly backing, leading to unnecessary rework and potential nonconformance, as automated optical inspection systems often miss these issues.
Innovation Solution
A method and system using a two-stage hurdle model and bootstrapping to simulate anomaly data, calculating guard bands that account for undetected whiskers and missing fiber, ensuring compliance with manufacturing requirements with a known confidence level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If automated optical inspection systems are used to inspect preform layers, then inspection speed and automation are improved, but measurement precision deteriorates because the systems cannot detect undetected anomalies like whiskers and missing fiber
Solution Approach 1:
The inspection approach is segmented into two stages: automated optical inspection for rapid screening of obvious defects, and statistical guard band analysis for accounting for undetected anomalies. This segmentation allows each method to operate in its optimal domain while compensating for the other's limitations.
Solution Approach 2:
A statistical guard band model acts as an intermediary between the automated inspection system and the final quality decision. The model incorporates anomaly data from historical processes to compensate for the inspection system's inability to detect certain defects, thereby bridging the gap between automated screening and precise quality assurance.
2Manufacturing precision
If strict specification limits are enforced based on automated inspection results, then manufacturing precision is improved, but productivity deteriorates due to unnecessary rework of parts that would have been acceptable
Solution Approach 1:
The guard band is calculated in advance based on historical anomaly data and inspection system characteristics. This preliminary statistical adjustment allows the inspection criteria to be optimized before production, preventing overly strict rejection criteria that would cause unnecessary rework while ensuring adequate quality control.
Solution Approach 2:
The inspection acceptance criteria are adjusted by incorporating a statistical guard band parameter that accounts for undetected anomalies. This parameter modification transforms the rigid specification limit into a more nuanced acceptance threshold that balances quality assurance with production efficiency.
3Reliability
If retroactive rework is performed on parts with detected anomalies, then product quality is improved, but loss of time increases due to post-inspection rework
Solution Approach 1:
The guard band calculation and anomaly modeling are performed preliminarily based on historical data, allowing the inspection system to be properly calibrated before production begins. This prevents the need for time-consuming retroactive rework by ensuring that inspection criteria accurately reflect actual quality risks from the outset.
Data Source
AI summary
Techniques for manufacturing a composite part using a tape laying process are presented. The techniques can include: laying up a preform layer from composite tape; inspecting the preform layer for gaps; comparing the gap measurement with a gap guard band, where the gap guard band is determined by: obtaining anomaly data that includes measurements of fiber that has not been deposited on a respective preform during prior preform lay-up processes; fitting a multi-component model to the anomaly data; simulating a preform manufacture based on the multi-component model; calculating summary statistics on gap width accounting for undetected anomalies; and determining a guard band based on the summary statistics on gap width accounting for undetected anomalies and based on a manufacturing requirement; determining that the preform layer complies with the manufacturing requirement; repeating the laying up, the inspecting, the comparing, and the determining; and heating the preform to form a composite part.