What is the elastic limit of silica glass? At what strain level will the fiber immediately fracture?
The theoretical elastic limit for flawless silica glass is approximately 8-10%, meaning it can withstand a strain of 80,000 to 100,000 microstrain before permanent deformation or fracture. However, in practical applications, optical fibers made from silica glass have microscopic flaws on their surface. These flaws act as stress concentrators, significantly reducing the effective fracture strength.
For standard optical fibers, the typical fracture strain is usually in the range of 0.5% to 1% (5,000 to 10,000 microstrain), at which point the fiber will immediately fracture. The precise value depends heavily on the fiber’s surface quality, coating, and the specific loading conditions.
For applications requiring higher strain tolerance, specialized fibers and FBG sensors are available. For instance, OFSCN® High-Strength Fiber Bragg Gratings / Fiber Bragg Grating Strings (Bare) are engineered to achieve a much higher available strain range, typically exceeding 2.5% (25,000 microstrain), by utilizing screened high-strength polyimide-coated optical fibers.
Here are some relevant product images:
https://www.ofscn.org/images/fiber/400-c-fiber.jpg
For more detailed technical parameters, you can refer to: