Tamer Hamouda

Effect of resin type on the signal integrity of an embedded perfluorinated polymer optical fiber

Polymer optical fibers (POF) hold many advantages for embedded sensing, such as their low cost, flexibility, high tensile strain limits and high fracture toughness. POF sensors may therefore be integrated into fiber reinforced composite structures for monitoring structural behavior. Since POFs do not require a protective coating, it is critical to verify that the resin system does not have a negative impact on the noise level or performance of POF sensors during composite manufacture. This study measured the effect of vinylester and epoxy resin systems on the signal loss of embedded perfluorinated, graded index POFs. Photon-counting optical time domain reflectometry (OTDR) was used to monitor the signal attenuation and backscattering level of the POFs throughout the resin curing cycle. Fourier transform infrared spectrometry (FTIR) and cross section analyses using scanning electronic microscope (SEM) images were also conducted to investigate whether the resin system caused chemical and physical changes of the POF. This study showed that vinylester resin caused a significant increase in the backscattering level of POF sensors and therefore induced high fiber signal losses. On the other hand, the POF treated with epoxy showed no change in backscattering level, indicating that no chemical or physical change had occurred to the POF.

Smart textiles: evaluation of optical fibres as embedded sensors for structure health monitoring of fibre reinforced composites

Silica optical fibres (SOF) are established for the use of communicating digital data and numerous applications including structure health monitoring. However, SOFs exhibit drawbacks such as brittleness, low strain and signal attenuation due to bending. These drawbacks limit the use of SOF as embedded sensors for monitoring composite structures’ internal health. Unlike SOFs, the relatively newly developed polymer optical fibres (POF) do not possess such drawbacks and they are able to monitor the health of fibre-based composite structures. Bending in optical fibres is a major concern since this causes signal attenuation at bending points. Integrating optical fibres into a woven preform requires bending because of the crimping that occurs as a result of weave interlacing. The main objective of this research was to evaluate the effect of the macrobending of optical fibres on signal power integrity. The goal is to design optical fibre sensors embedded in woven preforms that have high sensitivity for monitoring the health of composite structures. Newly developed Graded Index Perfluorinated POF (GI-PF-POF) and two types of SOFs were evaluated in a three-point macrobending test bed using a laser light source. A systematic experimental design was executed to evaluate the optical fibres’ signal loss as a result of the bending radius, bending deflection and wrap angle of optical fibre around the middle rod of the test bed. The results showed that POF provides higher signal sensitivity and greater robustness against signal attenuation under bending when compared to SOF. The work also unveiled the bending radius of optical fibres at which minimum or no signal loss occurred. This finding is essential for designing embedded optical fibre sensors with high sensitivity.

Spinning of Polyacrylamidoximes by Solution Blowing Technique: Synthesis and Characterization

A novel route for the production of polyacryloamidoxime nano-fibers is described. The innovative solution blowing spinning technique is used for the production of polyacryloamidoxime nano-fibers. The polyacryloamidoxime was prepared by the amidoximation of the acrylonitrile groups in a non-aqueous medium (DMF) using the least possible amount of hydroxylamine. A comparison study was performed to evaluate the effectiveness of the amidoximation reaction in aqueous or non-aqueous media. As the presented method is acquiring only 0.5 g/g hydroxylamine, at 50 °C for 7 h to achieve 63.1 % conversions, also solution blowing is an alternative technique for manufacturing of micro- and nano-fibers. The morphological structure, the chemical nature as well as the dyeability of the obtained fibers are illustrated. The obtained nano polyacryloamidoxime fibers show superior adsorption ability toward copper ions. Results showed that the present work presents a promising synthesis root for spinnable polyacryloamidoxime.

Polymer optical fibers integrated directly into 3D orthogonal woven composites for sensing

This study demonstrates that standard polymer optical fibers (POF) can be directly integrated into composites from 3D orthogonal woven preforms during the weaving process and then serve as in-situ sensors to detect damage due to bending or impact loads. Different composite samples with embedded POF were fabricated of 3D orthogonal woven composites with different parameters namely number of y-/x-layers and x-yarn density. The signal of POF was not affected significantly by the preform structure. During application of resin using VARTM technique, significant drop in backscattering level was observed due to pressure caused by vacuum on the embedded POF. Measurements of POF signal while in the final composites after resin cure indicated that the backscattering level almost returned to the original level of un-embedded POF. The POF responded to application of bending and impact loads to the composite with a reduction in the backscattering level. The backscattering level almost returned back to its original level after removing the bending load until damage was present in the composite. Similar behavior occurred due to impact events. As the POF itself is used as the sensor and can be integrated throughout the composite, large sections of future 3D woven composite structures could be monitored without the need for specialized sensors or complex instrumentation.

Thermal insulation properties of hybrid textile reinforced biocomposites from food packaging waste

Due to the significant and harmful effect of the global warming on our communities, health, and climate, the usage of thermal insulation material in building is must to decrease the energy consumption and to improve energy efficiency. On the other hand, the utilization of waste and biomass resources for developing new bio-based composite materials is attracting much attention for the environmental and socioeconomics. Therefore, in this study, thermal insulation bio-based composite panels from Tetra Pak® waste and wool fiber waste with different ratios were manufactured. Likewise, other sandwich bio-based composite panels were manufactured using Tetra Pak waste as a core material with glass woven fabric and jute wove fabric as skin materials. Thermal conductivity and thermal resistance results showed a significant improvement on thermal insulation properties of the developed biocomposite panels compared to the control samples made of plain Tetra Pak®.

Investigating the loss of an embedded perfluorinated optical fiber for different resin’s gel time

This work aims to find out the gel time that may not cause damage to the physical properties of the polymer optic fiber (POF). Effect of gel time of vinylester resin on signal attenuation of POF was studied. The resin gel time was controlled by mixing different ratios of Methylethylketone peroxide (MEKP), Cobalt Naphthenate-6 %, and Dimethylaniline at 18 °C. OTDR was used to measure backscattering level and signal loss during the resin curing process. Optical imaging was conducted on POF cross section before and after resin treatment to investigate the effect of resin gel time on its physical properties. Results showed that POF signal was affected by resin gel time. Increasing gel time caused drop of the backscattering level of the POF. It was found that 15 minutes gel time had no significant effect on POF signal integrity. Gel time 45 minutes or longer cause severe physical damage to the POF.