Indicator Strip Monitoring for Composite Repair Bond Strength
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current non-destructive test methods for adhesive bonded structures, such as those in aircraft outer skins, fail to accurately assess the residual strength of adhesive joints after repairs, making it difficult to ensure structural integrity.
Innovation Solution
An indication device with an elongate, thin indicator strip applied to the laminate structure near a repair location, which detaches when a predefined residual strength of the adhesive joint is reached, providing visual indication of the adhesive joint's strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-destructive test methods are used to assess adhesive bonded structures, then structural integrity can be evaluated without damage, but the methods fail to accurately assess residual strength of adhesive joints after repairs
Solution Approach 1:
The patent introduces an indicator strip as an intermediary element that mediates between the adhesive joint and the assessment process. The strip is applied over the adhesive joint and contains a breaking point that fails at a specific load, providing visual indication of residual strength without requiring complex non-destructive testing equipment.
Solution Approach 2:
The patent replaces complex non-destructive test methods with a simple mechanical indicator system. Instead of using advanced sensing equipment or complex testing procedures, the solution uses a mechanically-based indicator strip that directly responds to the structural integrity through physical deformation and breaking at a predefined load level.
2Measurement precision
If proof load tests are implemented to determine quality of adhesive joints, then residual strength can be assessed, but it is not possible to perform such tests after repairs are bonded
Solution Approach 1:
The indicator strip is pre-configured with a breaking point at a specific load level before application. This preliminary action allows the strip to automatically indicate when the adhesive joint reaches its residual strength limit, eliminating the need for actual proof load testing after repair while still providing accurate quality assessment.
3Measurement precision
If test specimens are used to determine adhesive joint strength through torsion shear tests, then the state of the adhesive joint can be determined, but the samples are very large and make fastening to aircraft outer skin virtually impossible
Solution Approach 1:
The patent extracts the essential function of strength assessment from large test specimens and concentrates it into a thin indicator strip. By taking out only the necessary indication function and separating it from the bulk material requirements of traditional test specimens, the solution enables implementation on aircraft outer skin where space is limited.
Solution Approach 2:
The indicator strip is implemented as a thin film structure that can be conformally applied to the curved surface of aircraft outer skin. This thin-film approach replaces the bulky test specimens while maintaining the ability to assess adhesive joint strength, enabling deployment in the actual application environment.
4Loss of information
If traditional test methods are used to assess adhesive joints, then strength information can be obtained, but fast and simple visual inspection during maintenance is not possible
Solution Approach 1:
The indicator strip incorporates visual indicators (such as color changes or visible breaking points) that provide immediate, intuitive information about adhesive joint strength. When the strip breaks or changes appearance, it clearly indicates that the residual strength threshold has been reached, enabling rapid visual inspection during maintenance without requiring complex measurement equipment.
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 device allows for simple and reliable visual assessment of the adhesive joint's residual strength, ensuring the repair maintains structural integrity by indicating when the adhesive joint can no longer support the repair patch effectively.
Implementation Method 1
The indicator strip is detachably applied to the outer layer of the laminate structure in the immediate vicinity of the repair location
Data Source
AI summary
An indication device for monitoring the structural integrity of a repair location on a laminate structure, produced from a composite material, of a part of an aircraft outer skin is specified. The indication device has at least one elongate, thin indicator strip. The indicator strip is detachably applied to the outer layer of the laminate structure in the immediate vicinity of the repair location. The indicator strip is designed to indicate a predefined residual strength of an adhesive joint of a repair patch to the surrounding composite material.