الفهرس 
General Introduction And Previous workOnly 14 pages are availabe for public view
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Abstract
A general introduction is given in chapter 1 with a review of the previous work. Moreover, chapter 2 introduces the physical concepts of viscoelasticity and creep behaviour of polymers. The accuracy of strain measurements of polymeric fibres under creep extension is an important issue. Chapter 3 presents a modified creep device including a digital ruler which allows the online measurement of the fibre’s length during creep experiments. The modified creep device was used for studying the effect of creep straining on the optical and structural properties of polymeric fibres for relatively long times (~15000 seconds). A novel optical setup based on Fizeau system is introduced in chapter 4, named double-arm multiple beam Fizeau system. This novel optical setup allows the simultaneous recording of two interference patterns in the same frame; one pattern for light waves with electrical vector vibrating parallel to the fibre axis, and the other pattern if for the perpendicular direction of vibrations. This allows online birefringence measurements and other optical parameters of fibres depending on the double-refraction phenomenon. This, double-interferogram is separated into two independent interference patterns using a new colour-separation algorithm, proposed in this thesis to overcome some difficulties facing other colour separation techniques. Finally, the novel optical setup was combined with the creep device attached to the digital ruler for investigating the variations of the optical properties of polymeric fibres during creep experiments for short times (~1000 seconds), at which relaxation process occurs. Accurate fringes analysis is a very important task for investigations involving optical interferometry. Chapter 4 gives an account for a source of error arises when analysing multiple-beam patterns. Inverse interferogram was proposed to overcome such error and enhance the accuracy of the evaluated phase values of multiple-beam interference patterns. Also in this chapter, a modified method for reconstructing the refractive index distribution in three-dimensions is introduced. Finally, double-arm multiple-beam Fizeau system combined with the modified creep device was used for investigating the necking phenomenon observed during creep experiments. The obtained double-interferograms were separated using our proposed algorithm. The separated multiple-beam patterns were analysed by first obtaining the inverse interferogram of these patterns, then different phase measuring techniques were used to retrieve the phase values. The distribution of the three-dimension refractive indices is calculated using our modified method.