Composite Bonding Evaluation Using Alternating-Current Signals
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Solution Overview
Problem
Current non-destructive techniques cannot effectively detect a 'kissing bond' in composite joint structures, which reduces adhesion due to surface contaminations, and existing methods that can detect it, like laser techniques, destroy the bonding interface, making it impossible to ensure reliability in adhesive-only joint structures, particularly in critical applications like aircraft.
Innovation Solution
A joint evaluation method using an alternating-current signal with frequencies between 100 MHz and 10 GHz to measure current and voltage, calculating an evaluation value based on electrical characteristics like dielectric constant, polarizability, or capacitance, and comparing it to a preset criterion to assess the joint state without damaging the bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a non-destructive technique using ultrasound waves is used to inspect the joint state, then the inspection is non-destructive and can be performed on products, but it cannot detect kissing bonds caused by surface contaminations
Solution Approach 1:
The patent replaces the mechanical ultrasound wave-based inspection system with an electrical measurement system. By applying an alternating current signal to the adhesive layer and measuring its electrical characteristics (impedance, capacitance, conductance), the system can detect kissing bonds that ultrasound cannot detect, while remaining non-destructive to the joint structure
Solution Approach 2:
The patent changes the measurement parameter from mechanical (ultrasound wave reflection) to electrical (impedance, capacitance, conductance of the adhesive layer). This parameter change enables detection of chemical adhesion defects at the molecular level without requiring physical gaps or mechanical wave reflection, thereby detecting kissing bonds that were previously invisible to non-destructive inspection methods
2Reliability
If a laser technique is used to detect kissing bonds, then the detection capability for chemical adhesion defects is improved, but the bonding interface is destroyed making product inspection impossible
Solution Approach 1:
The patent replaces the laser-based detection method with an electrical measurement method. Instead of using laser energy that destroys the bonding interface, the patent applies low-power alternating current signals to measure the electrical characteristics of the adhesive layer, achieving kissing bond detection without causing any damage to the joint structure
Solution Approach 2:
The patent introduces electrical signals as an intermediary to detect the state of the adhesive layer. By measuring electrical parameters (impedance, capacitance, conductance) through electrodes applied to the surface, the system can infer the chemical adhesion state without directly interacting with or damaging the bonding interface, unlike laser methods that require direct energy interaction
3Ease of manufacture
If adhesive-only joints are used in structure materials, then the ease of manufacture and joint simplicity are improved, but the reliability cannot be ensured due to inability to detect kissing bonds
Solution Approach 1:
The patent enables the adhesive layer to 'self-reveal' its bonding state through its inherent electrical characteristics. By measuring the electrical parameters (impedance, capacitance, conductance) of the adhesive layer itself, the system can detect kissing bonds without requiring additional sensors, markers, or complex inspection procedures, thereby maintaining manufacturing simplicity while ensuring reliability
Solution Approach 2:
The patent introduces electrical measurement as an intermediary inspection method that can be integrated into the manufacturing process. By applying electrodes to the surface and measuring electrical characteristics during or after assembly, the system can verify joint quality without rework or additional manufacturing steps, maintaining ease of manufacture while ensuring reliability through detectable electrical signatures of proper bonding
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
This method allows for non-destructive evaluation of the joint state, enabling accurate assessment of chemical bonding strength and ensuring reliable joint structures without destroying the interface, thus preventing the use of adhesive-only joints in critical applications.
Implementation Method 1
calculating an evaluation value related to a given electrical characteristic from a current value and a voltage value obtained by the measurement
Implementation Method 2
The given electrical characteristic is at least one preliminarily selected from the group consisting of a dielectric constant, polarizability, capacitance, alternating-current resistance, and phase difference
Data Source
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AI summary
The purpose of the present invention is to provide a method for evaluating the bonding state of a bonding section by inspecting a kissing bond using a non-destructive method. Disclosed is a bonding section evaluation method for evaluating the bonding state of a bonding section of a composite material that has the bonding section where a material to be bonded and another material to be bonded are bonded to each other with an adhesive therebetween. In the method, an alternating current signal is applied to the bonding section, a current and a voltage are measured by changing the frequency, evaluation values relating to predetermined electric characteristics are derived on the basis of the current value and the voltage value, which have been obtained by the measurement, the evaluation values are compared with reference relating to the predetermined electric characteristics, and the bonding state of the bonding section is evaluated according to the deviation quantities of the evaluation values from the reference.