NANOINDENTATION PROPERTIES OF PLASTIC OPTICAL FIBER INTERPHASE

Plastic optical fiber (POF) is a medium that can transfer light from one place to another place based on the total reflection theory according to the difference of refraction indices between fiber core and fiber cladding. When POF is utilized as the lighting element in textile structure (knits and jacquard wovens) in soft shining textiles which can active emit light, the mechanical properties should be taken into account since the bends in macro or micro leads to optical attenuation. Both POF core and POF cladding are made from polymeric materials and devoted to mechanical properties and illumination performance, which make the interphase properties between fiber core and fiber cladding critical in mechanical deformation, strength distribution and fracture mechanism. The interphase properties in POF were investigated by nanoindentation testing with various nanoindentation depths and spacings. 10-15 nanoindents in a line through the interphase zone were carried out from fiber cladding to fiber core. The hardness and elastic modulus in the transition region were measured and analysed. The results indicate that POF cladding is evidently softer than POF core due to the lower hardness. There is a gradient in the values of hardness and elastic modulus of cladding and core. The interphase width is estimated effectively with the minimal nanoindentation depth and sensitive spacing value, and is in the range of 800-1600 nm when the nanoindentation depth is 40 nm and spacing is 400 nm.