Effects of Microwave-Assisted Cross-Linking on the Creep Resistance and Sensing Accuracy of a Coaxial-Structured Fiber Strain Sensor

Nanocomposites have been widely studied for sensor applications because of their high design flexibility. However, the creep behavior of polymeric materials is a crucial issue of nanocomposite-based strain sensors in terms of sensing accuracy in high-temperature environments, which acts as a bottleneck for the use of nanocomposites in embedded type sensors for monitoring the curing reactions and structural health of composite. Herein, we suggest a microwave-assisted cross-linking method for enhancing the reliability of polymer-based coaxial-structured fiber strain sensors in high temperatures. A dry-jet wet-spun ultra-high molecular weight polyethylene core fiber with a microwave post-treatment in a peroxide bath provided superior strength (2.1 GPa), modulus (69 GPa), and enhanced creep resistance (>94%). By using a creep resistance-enhanced core fiber, coaxial-structured fiber strain sensors, which have multi-layer structured shell parts, could be fabricated via the simple dip-coating method. The fabricated coaxial-structured fiber strain sensor showed a high gauge factor (4.12 with strain range of 0%–1%), a low-temperature sensitivity coefficient (−6.5 × 10⁻⁴), and an improved sensing accuracy (<3% error at 80 °C) in high-temperature environments. From these results, it can be confirmed that the microwave-assisted cross-linking method is very promising for use in nanocomposite-based strain sensors for various application fields.