Hassan M. El-Dessouky

On the digital holographic interferometry of fibrous material, I: Optical properties of polymer and optical fibers

Abstract Digital holographic interferometry (DHI) was utilized for investigating the optical properties of polymer and optical fibers. The samples investigated here were polyvinylidene fluoride (PVDF) polymer fiber and graded-index (GRIN) optical fiber. The phase shifting Mach–Zehnder interferometer was used to obtain five phase-shifted holograms, in which the phase difference between two successive holograms is π/2, for each fiber sample. These holograms were recorded using a CCD camera and were combined to gain the complex wavefield, which was numerically reconstructed using the convolution approach into amplitude and phase distributions. The reconstructed phase distribution was used to determine the refractive index, birefringence and refractive index profile of the studied samples. The mean refractive index has been measured with an accuracy up to 4×10−4. The main advantage of DHI is to overcome the manual focusing limitations by means of the numerical focusing. The results showed accurate measurements of the optical properties of fibers.

An interferometric prediction of the intrinsic optical properties for cold-drawn iPP, PTFE and PVDF fibres

Interference polarizing (Pluta and Interphako) microscopes have been used to measure the birefringence and refractive indices during the cold-drawing of isotactic poly(propylene) (iPP), poly(tetrafluoroethylene) (PTFE) and poly(vinylidene fluoride) (PVDF) fibres. The intrinsic birefringence (Δn0) and refractive indices (niso, and ) of iPP, PTFE and PVDF fibres were interferometrically predicted using affine and pseudo-affine models. In terms of these intrinsic values, a new way of calculating the orientation parameter is discussed. A selection of microinterferograms is given for illustration.

Comparative study on interferometric techniques for measurement of the optical properties of a fibre

The spectral dispersion curve and the refractive index profiles of polypropylene fibre are determined. Multiple-beam Fizeau fringes, a two-beam interference Pluta microscope, a manual variable wavelength system and the automatic variable wavelength interference technique (VAWI) are used to compare the results. A comparison of the optical properties measured using these four techniques is outlined. Also, the advantages, accuracy and limitations of these techniques are dealt with. Microinterferograms are illustrated.

Influence of temperature on the optical and structural properties along the diameter of optical fibres

Multiple-beam Fizeau fringes technique with an opto-thermal device is used to study the effect of temperature on the optical properties of Philips graded-index optical fibres. The refractive index profile of the optical fibre is measured at different temperatures. From these profiles the opto-thermal coefficient, the profile shape parameter α, the cladding/core maximum refractive index difference Δn and some guidance parameters of the optical fibre that play an important role in communication are determined. The variation of oscillation and dispersion energies along the diameter of the optical fibre (energy profile) are calculated at different temperatures. An empirical formula of the energy profile is obtained. Microinterferograms are given for illustrations.

Influence of temperature on the optical and structural properties along the diameter of: I. Polymer fibres

A modified heating device connected to a wedge interferometer is designed to study the influence of temperature on the optical and structural properties along the diameter of undrawn polypropylene fibres. To determine the optical orientation function profile, a model that divides the circular cross section into very small circular zones is suggested. The refractive indices and optical orientation function of each zone are considered assuming there is a constant fully oriented birefringence throughout the fibre. This investigation provides useful information about the structural properties of polypropylene fibres and throws light on its opto-thermal behaviour. The investigation is carried out using multiple-beam interference Fizeau fringes in transmission. Microinterferograms are given for illustration.

A novel non-crimped thermoplastic fabric prepreg from waste carbon and polyester fibres

A biaxial non-crimped fabric, 400 ± 10 g/m2, +45°/−45° lay-up protocol, was made from a unidirectional tape comprised of a 60/40 wt% carded blend of virgin waste carbon fibres, 60 mm chopped length, and polyester resin fibres, 60 mm staple length. The non-crimped fabric was used as a thermoplastic prepreg to produce laminated composite panels. The prepreg exhibited a high degree of drapeability. The physical and mechanical properties of composite samples were determined; the density, void contents, tensile and flexural strengths and moduli were found to be 1.5 g/cm3, 10%, 180.7 MPa, 260.5 MPa, 34.2 GPa and 30.4 GPa, respectively. Modification of the consolidation process and the use of finer polyester fibres should decrease the void content. It was concluded that waste carbon fibres can be converted into flexible/drapeable dry prepreg materials, potentially useful for the manufacturing of thermoplastic composite products by hot press compaction.

Determination of the intrinsic birefringence of polymeric fibres

Abstract The intrinsic (maximum observable) birefringence Δnmax at complete orientation of the assembly is determined for polypropylene (PP) and polyethylene (PE) fibres. This is quantified by determination of the molecular orientation parameter of the fibre at a given value of the draw ratio using mathematical expressions. Also, a new approach is suggested for determining the unknown initial value of the draw ratio for given fibres. The double-beam polarizing (Pluta) microscope with a drawing device attached is used for this purpose. Illustrations using microinterferograms, graphs and tables are shown.

Treatment of polylactic acid fibre using low temperature plasma and its effects on vertical wicking and surface characteristics

The improvement of wicking rate of fabric made from the biodegradable polymer (polylactic acid) by low temperature plasma was investigated using oxygen as the gas treatment. The substrate was subjected to various treatment conditions including, treatment time, power and pressure. According to the modified Washburn equation, the modifications to the wicking rate of the fabric were evaluated by studying the vertical wicking behaviour, in relation to the surface topography and chemical composition, which were examined by scanning electron microscopy and X-ray photoelectron spectroscopy.

Factorial Optimization of the Effects of Melt-Spinning Conditions on As-spun Aliphatic-Aromatic Copolyester Fibers I. Spin Draw Ratio, Overall Orientation and Drawability

According to our previous studies [1,2], the optimum melting conditions have been achieved and lower melt flow index grade has been utilized in this work. In order to characterize the melt-spun AAC fibers, spin-draw ratio, optical birefringence and drawability were measured. The statistical optimization of fiber properties helps to produce the most satisfactory properties in the final fibers as an environmentally friendly attractive alternative to commercial chemical fibers. The importance of this model is in controlling the production process to optimize and enhance fiber properties, which may improve the quality and cost of biodegradable fibers.

Electrically conductive recycled carbon fibre-reinforced thermoplastic composites

Polypropylene (PP) thermoplastic composites were fabricated using recycled carbon fibres (rCFs; recovered from composite parts) and waste CFs (wCFs; generated during post-manufacturing processes). Both staple CFs (average 60 mm long) were blended with staple PP resin fibres (60 mm long) and then converted into yarns prior to the composite fabrication using hot-pressed moulding technique. It is found that the composites fabricated from wCFs contained longer CFs (40 mm long) and exhibited better electrical and mechanical properties (conductivity: 10.75 × 103 S m−1; tensile strength 160 MPa and modulus 45 GPa) compared with the composites fabricated from rCFs. It was concluded and recommended that both composite materials could be used as cost-effective and heating elements in lightweight applications.