Testing and characterization of fibers

Abstract Characterizing fibers—both natural and synthetic—is challenging, especially when the fiber diameter can be as small as just a few microns. Nevertheless, mechanical testing at the single fiber scale is the only unambiguous means of characterizing fibers or exploring their morphologies. Traditionally the properties of fibers have been normalized to their linear weight because of the difficulties of measuring fiber cross sections exactly; however, precise measuring techniques are now available, which allow their properties to be expressed in engineering terms familiar to all engineers working on structural materials. Traditional and conventional engineering units will both be found in this book, usually with an explanation of how to convert from one to the other. The identification of the mechanical responses together with understanding the micromechanisms involved are invaluable in guiding the design and use of fibers with advanced properties. The fiber structure can be rather complex and involves multiple characteristic length scales that demand specific techniques, e.g., from spectroscopic techniques to probe molecular or atomic structures, X-ray diffraction to identify crystalline or amorphous domains or both optical and electron microscopy. Tomography techniques are new tools allowing the internal morphology of fibers to be imaged and recent developments in this direction open up previously unimagined prospects of exploring fiber structure.