Smart Inlays for Simultaneous Crack Sensing and Arrest in Multifunctional Bondlines of Composites

Area of Science:

• Materials Science
• Mechanical Engineering
• Sensor Technology

Background:

• Adhesive bonds in composite structures require enhanced safety through integrated surveillance.
• Disbond arrest features are crucial for preventing catastrophic failures.
• Existing methods for integrating monitoring systems may compromise bondline integrity.

Purpose of the Study:

• To design and fabricate a smart inlay for permanent bondline surveillance in composite structures.
• To integrate disbond arrest functionality with micro strain sensing capabilities.
• To ensure the integration process does not weaken the bondline.

Main Methods:

• Fabrication of a micro strain sensor system on polyvinylidene fluoride (PVDF) foil.
• Special pretreatment of PVDF to meet thin film sensor requirements.
• Integration of smart inlays into composite materials using standard manufacturing procedures.
• Testing with a covering caul plate to protect sensor grids during curing.
• Mechanical testing under static loading and cantilever bending setup.

Main Results:

• PVDF foil successfully used as a substrate for lithographic micro sensor fabrication.
• Smart inlays endured high-temperature composite manufacturing processes.
• Sensory function was preserved during curing despite substrate melting.
• Integrated sensors detected strain gradients in a cantilever bending test.
• Smart inlays demonstrated high stretchability beyond critical composite elongations.

Conclusions:

• The developed smart inlays form a multifunctional bondline, combining disbond arrest and health monitoring.
• This technology significantly enhances the safety of adhesive bonds in composite structures.
• The integration method preserves bondline integrity and sensor functionality.