Understanding fiber coating process: Instability development and drop shape analysis

Fibers are often coated by drawing them through a complex fluid to provide them with a thin layer of coating/finish chosen say to provide chemical and mechanical protection to fiber or an anti-static layer or as in composites to alter surface characteristics of the fiber or simply to impart color. A fluid film on a fiber is generally unstable, and it spontaneously undulates and breaks into a periodic array of drops. This instability simply results due to surface tension of the fluid and is known as Rayleigh instability for pioneering work done by Lord Rayleigh in 1882 and can be easily observed by noticing how water beads up on a spider web. We are investigating the the instability development by analyzing droplet formation and droplet shapes for a variety of complex fluids.