Flexible latex – polyaniline segregated network composite coating capable of measuring large strain on epoxy

A new conductive polymer nanocomposite (CPC) strain sensor, with a segregated network of polyaniline nanoparticles in a poly(vinyl acetate) latex matrix (PVAc–PANI), was created to improve upon existing systems. The strain sensing capabilities of these CPC transducers, attached to epoxy beams, were determined by subjecting them to loading/unloading cycles up to 1% strain (and straining them until the epoxy beam failed (around 5% strain)), in uniaxial  tension. Microstructural images and visco-elastic properties show that these CPC are homogeneous and behave much like neat PVAc. PVAc with 4 wt.% PANI provided the best compromise among high sensitivity, small hysteresis and low noise. These environmentally friendly, flexible and low cost strain sensors are capable of monitoring strain above 5%, with a gauge factor between 6 and 8 (3 times those of classical metallic gauges). Moreover, this technology can be easily scaled up to monitor deformations of large composite structures,
opening up many promising areas (e.g., damage detection for aircraft).