Abstract: This article introduces the definition of expanding fiber and the influence on the form of the high-performance fibers, fiber permeability and performance of composite, and calculates the width of expanding the fiber bundle and describes contrastly five kinds of common methods of expanding fiber at present, such as hot rolling, mechanical methods and ultrasonic wave. We explain the equipments and theories of these five expanding fiber methods and the prospect for expanding fiber.

Key words: definition of expanding fiber, fiber bundle, expanding fiber methods, theory of expanding fiber