@article{adekunle_li_vallabh_seyam_2024, title={Assessment of Adhesion in Woven Fabric-Reinforced Laminates (FRLs) Using Novel Yarn Pullout in Laminate Test}, volume={8}, ISSN={["2504-477X"]}, url={https://doi.org/10.3390/jcs8070242}, DOI={10.3390/jcs8070242}, abstractNote={Fiber-reinforced laminates with flexibility (FRLs) are becoming increasingly crucial across diverse sectors due to their adaptability and outstanding mechanical attributes. Their ability to deliver high performance relative to their weight makes them indispensable in lighter-than-air (LTA) applications, such as aerostats, inflatable antennas, surge bladders, gas storage balloons, life rafts, and other related uses. This research delved into employing woven fabrics as the reinforcement material and explored how their specific parameters, like fiber type, fabric count (warp thread density × weft thread density), fabric areal density, and fabric cover influence the bonding and mechanical properties of laminates. A thorough analysis encompassing standard T-peel (ASTM standard D1876) and a newly proposed yarn pullout in laminate test were conducted on laminates fabricated with various woven reinforcements, each with its unique specifications. The T-peel test was utilized to gauge the adhesive strength between FRL components, offering crucial insights into interfacial bonding within the laminates. Nevertheless, challenges exist with the T-peel test, including instances where the adherents lack the strength to withstand rupture, resulting in unsuccessful peel propagation and numerous outliers that necessitate costly additional trials. Thus, our research group introduced a novel yarn pullout in laminate test to accurately assess adhesion in FRLs. This study uncovered correlations between both adhesion tests (T-peel and yarn pullout in laminate), indicating that the innovative yarn pullout in laminate test could effectively substitute for characterizing adhesion in FRLs. Furthermore, the findings unveiled a complex relationship between woven fabric specifications and laminate properties. We noted that variations in fiber type, yarn linear density, and adhesive type significantly impacted adhesion strength. For instance, Kevlar exhibited markedly superior adhesion compared to Ultra-High Molecular Weight Polyethylene (UHMWPE) when paired with Thermoplastic Polyurethane (TPU) adhesive, whereas UHMWPE demonstrated better adhesion with Ethylene Vinyl Acetate (EVA). Moreover, the adhesion quality lessened as fabric count increased for the same adhesive quantity. These discoveries carry practical implications for material selection and design across industries, from automotive to aerospace, offering avenues to enhance FRL performance.}, number={7}, journal={JOURNAL OF COMPOSITES SCIENCE}, author={Adekunle, Feyi and Li, Ang and Vallabh, Rahul and Seyam, Abdel-Fattah M.}, year={2024}, month={Jul} }
 @article{li_vallabh_bradford_kim_seyam_2022, title={Development of hull material for high-altitude airship: A parametric study}, volume={41}, ISSN={0731-6844 1530-7964}, url={http://dx.doi.org/10.1177/07316844211054852}, DOI={10.1177/07316844211054852}, abstractNote={ The development of hull material with ideal properties to meet all the operation requirements has posed the greatest challenge to flying the airship at high altitude for extended periods. Materials developed in our previous study with a laminated structure achieved high strength-to-weight ratio and excellent gas barrier property at a relatively low total weight. To optimize this novel design and obtain a more comprehensive understanding of the laminate properties, a parametric study involving lamination process parameters (temperature and time), and laminate structural parameter (reinforcement fabric construction), was conducted. The effects of lamination parameters on tensile, peel, tear and helium permeability tests were carried out to assess the laminates. It was found that the tensile strength of the laminate is predominantly determined by the fabric reinforcement material properties. The peel and tear strength results showed that increasing the lamination temperature from 185 °C to 200 °C improved respective strength values. Additionally, the analysis of failure modes and tear propagation suggested that laminate samples with progressive failure have better tear resistant property over those with brutal failure. Extremely low helium permeability was achieved, yet the gas barrier property was not affected by the lamination process parameters and fabric type. }, number={11-12}, journal={Journal of Reinforced Plastics and Composites}, publisher={SAGE Publications}, author={Li, Ang and Vallabh, Rahul and Bradford, Philip D and Kim, David and Seyam, Abdel-Fattah M}, year={2022}, month={Jan}, pages={444–458} }
 @article{szőke_devenport_borgoltz_alexander_hari_glegg_li_vallabh_seyam_2022, title={Investigating the Aeroacoustic Properties of Porous Fabrics}, volume={60}, ISSN={0001-1452 1533-385X}, url={http://dx.doi.org/10.2514/1.j061385}, DOI={10.2514/1.J061385}, abstractNote={The aeroacoustic properties of porous fabrics are investigated experimentally with the goal of finding a fabric that serves as an improved interface between wind tunnel flow and quiescent conditions. A total number of eight porous fabrics were investigated, namely, four glass fiber fabrics, two plain-weave Kevlar fabrics, and two modified plain Kevlar fabrics with their pores irregularly clogged. Two custom-made rigs were used to quantify the transmission loss (TL) and self-noise of all fabrics. The pores were found to serve as a low-resistance gateway for sound to pass through, hence enabling a low TL. The TL was found to increase with decreasing open area ratio (OAR), whereas other fabric properties had a minor impact on TL. The thread density was found to be a primary factor in determining the frequency range of porous fabrics’ self-noise, with the OAR potentially playing a secondary role in the self-noise levels. Fabrics with irregular pore distribution showed a more broadband self-noise signature associated with lower frequencies compared to fabrics with periodic pore patterns. Overall, fabrics with an irregular pore distribution or fabrics with increased thread density were identified as two potential ways to obtain superior aeroacoustic behavior compared to commonly used Kevlar fabrics.}, number={6}, journal={AIAA Journal}, publisher={American Institute of Aeronautics and Astronautics (AIAA)}, author={Szőke, Máté and Devenport, William J. and Borgoltz, Aurélien and Alexander, W. Nathan and Hari, Nandita and Glegg, Stewart A. L. and Li, Ang and Vallabh, Rahul and Seyam, Abdel-Fattah M.}, year={2022}, month={Jun}, pages={3651–3660} }
 @article{li_danladi_vallabh_yakubu_ishiaku_theyson_seyam_2021, title={Cellulose Microfibril and Micronized Rubber Modified Asphalt Binder}, volume={9}, ISSN={["2079-6439"]}, url={https://doi.org/10.3390/fib9040025}, DOI={10.3390/fib9040025}, abstractNote={Cellulose microfibrils (CMFs) and micronized rubber powder (MRP) can be derived from low or negative-cost agricultural/industrial waste streams and offer environment-friendly and cost-effective pathways to develop engineering products. This study investigated the efficacy of adding these micromodifiers on the performance characteristics of asphalt binders. In this work, samples were produced using a mixture of slow-setting anionic asphalt emulsion with various combinations of MRP (at 0, 2 and 10 wt %) and four types of CMFs (hydrophobic and hydrophilic with crystalline ratios of 86% and 95%) at 0, 2 and 5 wt %. The performance of modified asphalt samples was assessed by penetration depth (PD), softening point (SP), and penetration index (PI). Linear regression analysis showed that adding CMFs and/or MRP reduced PD and increased SP values. The type of CMFs significantly affected the performance, which becomes more distinct with the increased weight content of CMFs. While hydrophilic CMFs caused increases in SP and PI values, no clear trend was seen to determine the effect of CMF crystallinity. It was also discovered that the combined addition of CMF and MRP achieved similar PI values at lower total weight content compared to using MRP alone.}, number={4}, journal={FIBERS}, publisher={MDPI AG}, author={Li, Ang and Danladi, Abdu A. and Vallabh, Rahul and Yakubu, Mohammed K. and Ishiaku, Umar and Theyson, Thomas and Seyam, Abdel-Fattah M.}, year={2021}, month={Apr} }
 @article{vallabh_li_bradford_kim_seyam_2021, title={Ultra-lightweight fiber-reinforced envelope material for high-altitude airship}, volume={113}, ISSN={0040-5000 1754-2340}, url={http://dx.doi.org/10.1080/00405000.2021.1948695}, DOI={10.1080/00405000.2021.1948695}, abstractNote={Abstract In this work, fiber-reinforced laminates for the envelope (hull) of high-altitude airships were developed using a novel design concept utilizing ethylene vinyl alcohol (EVOH) as the adhesive component layer with high gas barrier properties. The other component layers of the laminates included poly(p-phenylene benzobisoxazole) (Zylon®) fabric, metalized Mylar® (polyester) and metallized Kapton® (polyimide). The envelope materials were developed in two different strength categories. In the first category, three laminate designs were developed with strength ranging from 945–970 N/cm. The second group had one laminate design with a strength of 702 N/cm. These laminates with basis weights ranging from 103–113 g/m2, are the lightest envelope materials developed to date. As a function of their high strength and low basis weights, the new envelope materials have significantly higher specific strength (ranging from 911–925 kN.m/kg) compared to other envelope constructions published in the open literature. Other outstanding properties of the laminates include low helium permeability ranging from 0.4–8.0 cc/m2.24 hr.1 atm, high tear strength, UV and visible light (UV–Vis) resistance, and high creep resistance.}, number={9}, journal={The Journal of The Textile Institute}, publisher={Informa UK Limited}, author={Vallabh, Rahul and Li, Ang and Bradford, Philip D. and Kim, David and Seyam, Abdel-Fattah M.}, year={2021}, month={Jul}, pages={1799–1805} }
 @article{seyam_vallabh_hassanin_2015, title={Improving UV resistance of fibers: Idealized computational model predicting the distribution of UV blocking cylindrical nanoparticles in protective polymeric layer}, volume={10}, number={1}, journal={Journal of Engineered Fibers and Fabrics}, author={Seyam, A. M. and Vallabh, R. and Hassanin, A. H.}, year={2015}, pages={20–31} }
 @article{vallabh_hassanin_said_seyam_2016, title={Improving high-altitude UV-Vis resistance of PBO braided tendons of NASA's super pressure balloons}, volume={107}, ISSN={["1754-2340"]}, DOI={10.1080/00405000.2015.1077021}, abstractNote={Super pressure balloons (SPBs) are used by the National Aeronautics and Space Administration (NASA) for ultra-long duration ballooning (ULDB) missions which carry various scientific explorations to support space and earth sciences research activities. The resistance to photo-degradation of load-bearing braided tendons of SPBs is critical to the success of ULDB missions. Recognizing the critical need to improve UV and visible light (UV–Vis) protective performance of p-phenylene-2, 6-benzobisoxazole (PBO) braids, North Carolina State University and NASA's Balloon Program collaborated to investigate the effectiveness of sheath extrusion method in improving the UV–Vis resistance of tendons. This study included two PBO tendon types – 48,000 (48k) denier tendons and 72,000 (72k) denier tendons. Using a sheath extrusion method, the tendons were covered with UV protective sheath of low-density polyethylene containing two types of UV inhibitors – TiO2 rutile nanoparticles and PolyOne PE White CC®. Bare and sheathed tendons were subjected to artificial UVB exposure in the lab as well as to both high altitude and ground exposure during flight missions conducted by NASA. Protection against radiation exposure was evaluated by determining the loss of tensile strength after exposure. UV–Vis protection of tendons improved with an increase in sheath thickness as well as UV inhibitor content in the sheath. The results also showed that 72k denier braids had higher resistance against UV degradation compared to 48k denier braids. In-flight exposure results confirmed the comparative UV protective performance of tendons exposed to accelerated artificial UVB exposure in lab. 72k denier tendon covered with sheath containing 10% PE White CC® (sheath thickness of 0.37 mm) experienced the lowest strength loss among all tendon samples to high-altitude exposure during flight missions. The study has also utilized UV–Vis transmittance of the sheath covering the braids as a method of evaluating the performance of the protective sheaths.}, number={1}, journal={JOURNAL OF THE TEXTILE INSTITUTE}, author={Vallabh, Rahul and Hassanin, Ahmed H. and Said, Magdi A. and Seyam, Abdel-Fattah M.}, year={2016}, month={Jan}, pages={136–143} }
 @article{vallabh_ducoste_seyam_banks-leel_2011, title={Modeling tortuosity in thin fibrous porous media using computational fluid dynamics}, volume={14}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-80053462291&partnerID=MN8TOARS}, DOI={10.1615/jpormedia.v14.i9.40}, abstractNote={VALLABH, RAHUL. Modeling Tortuosity in Fibrous Porous Media using Computational Fluid Dynamics. (Under the direction of Dr. Pamela Banks-Lee and Dr. Abdel-Fattah Seyam). Tortuosity factor is often used to characterize the structure of the pore volume in fibrous porous media. This work involves the determination of tortuosity using computational fluid dynamic (CFD) simulation and particle tracking analysis. A new method has been adopted to generate 3-D geometry for modeling fibrous porous structures using ANSYS Parametric Design Language (APDL). Computation fluid dynamics has been used to simulate permeability of modeled 3-D fiberweb structures. The simulated permeability results are in good agreement with the models proposed by other authors. The experimental results were found to be slightly higher compared to simulated results and existing models due to the layered configuration of the samples. Permeability is found to be significantly influenced by fiber diameter, and porosity as well as fiberweb thickness. The relationship between air permeability and fiberweb thickness has been used to develop an indirect method for determination of tortuosity factor. Tortuosity factor has also been determined using a more direct method involving CFD simulation and Particle Tracking analysis. Different models established using the direct and indirect methods of determination show that tortuosity is significantly influenced by porosity, fiber diameter and fiberweb thickness, whereas the models available in the literature express tortuosity as a function of porosity only. Modeling Tortuosity in Fibrous Porous Media using Computational Fluid Dynamics}, number={9}, journal={Journal of Porous Media}, author={Vallabh, R. and Ducoste, J. and Seyam, Abdel-Fattah and Banks-Leel, P.}, year={2011}, pages={791–804} }
 @article{vallabh_banks-lee_seyam_2010, title={New approach for determining tortuosity in fibrous porous media}, volume={5}, number={3}, journal={Journal of Engineered Fibers and Fabrics}, author={Vallabh, R. and Banks-Lee, P. and Seyam, A. F.}, year={2010}, pages={7–15} }