Bonded Structure with Embedded Optical Fiber Sensor
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Solution Overview
Problem
Ultrasonic flaw detection inspections for carbon fiber composite materials cannot effectively evaluate bonding strength due to their reliance on time-consuming and labor-intensive processes, and the inability to measure pressure applied during bonding, leading to safety concerns and reliance on fasteners instead of adhesives in critical applications.
Innovation Solution
A bonded structure incorporating a distributed optical fiber sandwiched between members, which converts radial deformation into axial deformation, allowing continuous detection of bonding state through changes in the optical spectrum, enabling precise assessment of bonding quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ultrasonic flaw detection inspection is used to evaluate bond quality, then defects such as voids and peeling can be detected, but bonding strength cannot be evaluated and the process requires considerable time and effort
Solution Approach 1:
The distributed optical fiber sensor is embedded in the adhesive layer before bonding occurs. During the bonding process itself, the sensor continuously monitors pressure distribution and bonding state in real-time. This preliminary monitoring during the actual bonding process eliminates the need for separate post-bonding ultrasonic inspections, significantly reducing inspection time while providing both defect detection and bonding strength evaluation capabilities
2Weight of moving object
If adhesive bonding is used instead of fasteners, then weight reduction and operational efficiency are achieved, but bond quality evaluation becomes necessary and complex
Solution Approach 1:
The adhesive layer itself serves dual functions: it bonds the members together and simultaneously contains the distributed optical fiber sensor that monitors bonding quality. The sensor system is integrated directly into the adhesive layer, making the adhesive layer self-monitoring. This eliminates the need for separate external evaluation systems, maintaining weight advantages while simplifying the overall evaluation system through integration
3Reliability
If fasteners are used instead of adhesive bonding, then safety concerns are addressed, but weight reduction and operational efficiency are compromised
Solution Approach 1:
The distributed optical fiber sensor provides real-time feedback on pressure distribution and bonding state during the bonding process. This feedback enables continuous monitoring of bond quality development, allowing for immediate detection of bonding anomalies. The system provides quantitative data on bonding strength through axial deformation measurement, enabling informed decisions about bond adequacy and enhancing confidence in adhesive joint reliability without requiring fasteners
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
Enables accurate determination of bonding appropriateness, improving safety by allowing for the evaluation of bonding strength and quality in carbon fiber composite materials, reducing reliance on fasteners and enhancing manufacturing efficiency.
Implementation Method 1
the cross-sectional shape of the distributed optical fiber deforms in accordance with the bonding state... the bonding state between the first member and the second member is detected on the basis of the axial deformation in the distributed optical fiber converted from the radial deformation
Implementation Method 2
changes in the optical spectrum in the distributed optical fiber are relatively insensitive to radial deformation in the distributed optical fiber, but very sensitive to axial deformation. Accordingly, in this configuration, by converting radial deformation in the distributed optical fiber into axial deformation, the pressure applied to the distributed optical fiber is detected
Data Source
AI summary
The purpose of the present invention is to provide a bonded structure, a method for manufacturing the same, and a bonding state detection method which are capable of determining whether or not members are bonded together appropriately. A bonded structure 10 includes a laminated sheet 12A, a laminated sheet 12B, an adhesive 14 that bonds the laminated sheet 12A and the laminated sheet 12B together, and a distributed optical fiber 16 sandwiched between the laminated sheet 12A and the laminated sheet 12B. The cross-sectional shape of the distributed optical fiber 16 is deformed in accordance with the bonding state.