Development of a Dielectric Sensor System for the On-line Cure Monitoring of Composites

iSens: A Fiber-Based, Highly Permeable and Imperceptible Sensor Design

Embedded sensors are key to optimizing processes and products; they collect data that allow time, energy, and materials to be saved, thereby reducing costs. After production, they remain in place and are used to monitor the long-term structural health of buildings or aircraft. Fueled by climate change, sustainable construction materials such as wood and fiber composites are gaining importance. Current sensors are not optimized for use with these materials and often act as defects that cause catastrophic failures. Here, flexible, highly permeable, and imperceptible sensors (iSens) are introduced that integrate seamlessly into a component. Their porous substrates are readily infused with adhesives and withstand harsh conditions. In situ resistive temperature measurements and capacitive sensing allows monitoring of adhesives curing as used in wooden structures and fiber composites. The devices also act as heating elements to reduce the hardening time of the glue. Results are analyzed using numerical simulations and theoretical analysis. The suggested iSens technology is widely applicable and represents a step towards realizing the Internet of Things for construction materials.

Design and Integration of Flexible Sensor Matrix for in Situ Monitoring of Polymer Composites

Sensory polymer composites are highly desirable for applications such as in situ and real-time production processes and structural health monitoring, and for technologies that include human-machine interfaces for the next generation of Internet of Things. However, the development of these materials is still in its infancy: these materials have been reported, but the large-scale fabrication of polymer composites with versatile and customizable sensing capabilities has yet to be demonstrated. Here, we report on a scalable fabrication strategy that enables such materials by designing and integrating PCB technology-inspired large-area flexible sensor matrices into polymer composites. The integrated sensor matrices successfully monitored in situ the production processes and structural health of an industrial polymer composite: from the application of vacuum, resin flow and polymerization, production defects, and temperature distribution. Our results demonstrate that the proposed strategy is a simple and effective solution as a distributed monitoring platform for polymer composites and shows the potential toward next generation of sensory polymer composites.