Abstract A hybrid operating room requires a high-stiffness, radiolucent surgical table for real-time imaging during surgery. This study proposes a stiffness-driven structural design framework for carbon fiber-reinforced polymer (CFRP) sandwich panels subjected to cantilever-type bending, with an allowable tip deflection of less than 20 mm. A Timoshenko beam-based analytical model was employed to derive a design window and select a configuration consisting of 3 mm-thick CFRP skins and a 30 mm-thick polymethacrylimide foam core. Under a uniformly distributed load equivalent to 1150 kg, including the prescribed safety factor, both the analytical model and the full-scale finite element analysis predicted a tip deflection of approximately 15.8 mm, satisfying the allowable limit. Structural performance was further assessed using the maximum stress criterion, yielding failure indices of 0.320 under static loading and 0.627 under dynamic impact. The proposed framework provides practical guidelines for designing large-area radiolucent CFRP sandwich structures.
This research focuses on physical and mechanical characterization of a mycelium biocomposite, formed by fungal growth of Pleurotus eryngii on lignocellulosic biomass composed of shredded leaf sheaths of date palm. A scalable laboratory protocol was established to fabricate the composite samples made of fibers with different sizes, including “Small”, “Medium”, and “Large” with average diameter of 0.38, 1.9, and 2.94 mm, and average length of 12.1, 24.3, and 32.3 mm, respectively, along with their compositions. Samples then were tested and evaluated, in accordance with standard materials testing methods, for their flexural and compressive properties, failure modes, and water absorption. Results revealed that using mixed fibers generally improves compressive performance. Specimens made of small+large fibers as well as mixture of small, medium, and large fibers show nearly 30% higher compressive strength compared to those containing only large fibers. Compressive strength (0.4-5 MPa) falls within the range of synthetic foams (0.03-48 MPa). Flexural tests showed that using smaller fibers generally results in higher density, strength, and stiffness, with the small+medium and medium+large specimens achieving 13% and 11% higher flexural strength than medium and large fiber samples, respectively. Water absorption capacity is also influenced by fiber size. During first two hours of immersion, mixed-fiber specimens exhibited highest sorptivity. Similarly, using small fibers in mixed samples enhanced the absorption rate compared to single fiber samples. Quantitative comparisons highlight the potential of mycelium biocomposites as sustainable, inexpensive, and ecofriendly alternatives to synthetic foams.
Abstract Polyacrylonitrile (PAN)-derived carbon nanofibers (CNFs) were fabricated by incorporating shellac, a naturally derived polymer, into PAN precursor solutions, followed by stabilization, carbonization, and CO 2 activation. The resulting shellac/PAN-derived CNFs were characterized for their morphology, pore structure, surface chemistry, and electrochemical performance using a three-electrode configuration. The Brunauer–Emmett–Teller (BET) specific surface area increased markedly with increasing shellac content, from 214.1 m 2 g −1 for the shellac-free activated CNFs to 771.9 and 1059.8 m 2 g −1 for the samples containing 10 and 20 wt.% shellac, respectively. A corresponding increase in total pore volume was also observed. Despite their lower specific surface area, the shellac-free activated CNFs exhibited the highest specific capacitance of 186.5 F g −1 and the highest energy density of 24.6 Wh kg −1 at a current density of 0.5 A g −1 . These results suggest that a substantial fraction of the surface area generated in the shellac-containing samples was not effectively utilized for charge storage. Nevertheless, the sample containing 20 wt.% shellac exhibited a power density comparable to that of the shellac-free sample and retained 97.7% of the initial capacitance after 1000 charge–discharge cycles. These findings demonstrate that shellac effectively promotes the development of micro- and mesopores in PAN-derived CNFs. However, the electrochemical performance of the resulting electrodes is governed by the combined effects of ion-accessible pore structure, surface chemistry, and interfacial characteristics rather than solely by the total BET specific surface area alone.
Abstract Developing high-performance cathodes for alkaline water electrolysis requires the concurrent optimization of active sites, electron-transport pathways, and electrode architecture. In this work, we report a binder-free, free-standing electrode composed of RuO 2 -anchored, NiCo-embedded N-doped carbon nanofibers (RuO 2 -NiCo/NCNF) for the hydrogen evolution reaction (HER) in alkaline media. NiCo layered double hydroxide (LDH), derived from a Co-based zeolitic imidazolate framework (ZIF-67), was incorporated into electrospun polyacrylonitrile nanofibers and converted into a conductive carbon nanofiber network containing embedded NiCo alloy domains through stabilization and carbonization. These domains provide a favorable environment for the subsequent deposition-precipitation of Ru species, thereby enabling the facile introduction of RuO 2 onto the nanofiber surface. In 1.0 M KOH, RuO 2 -NiCo/NCNF exhibited overpotentials of 48 mV at |j| = 10 mA cm -2 and 208 mV at |j| = 100 mA cm -2 , outperforming NiCo/NCNF, RuO 2 -NCNF, pristine NCNF, and a commercial 10 wt.% Pt/C electrode (0.0385 mg Pt cm -2 ) under identical testing conditions. Furthermore, the electrode maintained stable operation for 50 h. This enhanced alkaline HER performance is attributed to the synergistic integration of amorphous hydrous RuO 2 and NiCo within a conductive and mechanically robust nanofiber scaffold, which promotes water dissociation, charge transfer, and active-site accessibility. These results demonstrate a promising strategy for designing durable and efficient free-standing HER electrodes for alkaline water splitting.
Abstract Minimizing aerodynamic drag is essential for improving the efficiency and sustainability of aircraft structures. This study investigates the potential of hydrophobic microtextures fabricated on T300 carbon fiber reinforced polymer (CFRP) using a reverse micro-electro discharge machining process. Pre-patterned copper tools were employed to replicate three distinct surface morphologies: micro-dimples (120 µ m diameter, 18 µ m depth, 200 µ m pitch), parallel grooves (80 µ m width, 22 µ m depth, 150 µ m spacing), and cross-hatched grooves (75 µ m width, 20 µ m depth, 150 µ m pitch) onto CFRP substrates. Surface characterization confirmed accurate geometric replication, with roughness (Ra) ranging from 2.8–4.3 µ m and contact angles of 132–152°, demonstrating a transition from hydrophilic to hydrophobic behavior. Computational fluid dynamics simulations using the SST k – ω turbulence model were performed to evaluate drag reduction at free-stream velocities of 15–60 m s −1 . Results showed reductions in drag coefficient (Cd) of 7% for micro-dimples, 9% for cross-hatched grooves, and up to 12% for parallel grooves, attributed to micro-vortex stabilization and delayed boundary layer separation. Compared with riblet films and superhydrophobic coatings, the proposed method offers comparable aerodynamic benefits with improved structural integration, making it a promising pathway for durable drag reduction in aerospace composites.
