Search Results (44)

This study systematically investigates the high-velocity impact response and energy absorption characteristics of carbon fiber-reinforced plastic (CFRP)—aluminum foam (AlF) hybrid composite structures, aiming to address the growing demand for lightweight yet high-performance energy-absorbing materials in aerospace and protective engineering applications. Particular emphasis is placed on elucidating the influence of key geometric and material parameters, including the aspect ratio of the columns and the relative density of the AlF core. Experimental characterization was first performed using a split Hopkinson pressure bar (SHPB) apparatus to evaluate the dynamic compressive behavior of AlF specimens with four different relative densities (i.e., 0.163, 0.245, 0.374, and 0.437). A finite element (FE) model was then developed and rigorously validated against the experimental data, demonstrating excellent agreement in terms of deformation modes and force–displacement responses. Extensive parametric studies based on the validated FE framework revealed that the proposed CFRP-AlF composite structure achieves a balance between specific energy absorption (SEA) and peak crushing force, showing a significant improvement over conventional CFRP or AlF. The confinement effect of CFRP enables AlF to undergo progressive collapse along designated orientations, thereby endowing the CFRP-AlF composite structure with superior impact resistance. These findings provide critical insight for the design of next-generation lightweight protective structures subjected to extreme dynamic loading conditions. Full article

Crash boxes play a crucial role in mitigating force during vehicle collisions by absorbing impact energy. Additive manufacturing (AM), particularly Fused Deposition Modeling (FDM), has emerged as a promising method for their fabrication due to its design flexibility and continuous advancements in material development. This study investigates the crash performance of tapered crash box configurations, each manufactured using two FDM materials: Carbon Fiber-Reinforced Polylactic Acid (PLA-CF) and Polylactic Acid Plus (PLA+). The specimens vary in wall thickness and taper angles to evaluate the influence of geometric and material parameters on crashworthiness. The results demonstrated that both specific energy absorption ($SEA$) and crush force efficiency ($CFE$) increase with wall thickness and taper angle, with PLA-CF consistently outperforming PLA+ in both metrics. ANOVA results showed that wall thickness is the most influential factor in crashworthiness, accounting for 73.18% of $SEA$ variation and 58.19% of $CFE$ variation. Taper angle contributed 13.49% to $SEA$ and 31.49% to $CFE$, while material type had smaller but significant effects, contributing 0.66% to $SEA$ and 0.11% to $CFE$. Regression models were developed based on the experimental data to predict $SEA$ and $CFE,$ with a maximum absolute percentage error of 4.97%. These models guided the design of new configurations, with the optimal case achieving an $SEA$ of 32.086 ± 0.190 kJ/kg and a $CFE$ of 0.745 ± 0.034. The findings confirm the potential of PLA-CF in enhancing the energy-absorption capability of crash boxes, particularly in tapered designs. Full article

The ballistic performance of fiber-reinforced polymer composites (FRPC) is influenced by the adhesive’s mechanical properties, such as stiffness, toughness, and energy dissipation. However, the specific contributions of these properties remain unclear. This study explores how varying the hard segment (HS) content in water-based polyurethane (WPU) impacts the thermal, mechanical, and ballistic performance of FRPCs. By increasing HS content, the storage modulus and tensile strength of WPU improved, while elongation at break decreased, transitioning the adhesive from soft and ductile to rigid and brittle. Quasi-static tests, ballistic experiments, and SEM analysis were conducted on UHMWPE fiber-reinforced WPU-HS% composites. Results reveal that adhesives with high hardness and modulus hinder fiber deformation, reducing energy dissipation and causing severe delamination, which diminishes ballistic performance. Conversely, soft and ductile adhesives allow deformation alongside fibers during bullet impact, suppress delamination, and absorb more kinetic energy while transferring load. Among the tested formulations, WPU with 45% HS content exhibited the best balance of mechanical properties, achieving the most significant improvement in ballistic performance by enhancing energy absorption and minimizing damage. This study establishes a clear relationship between WPU properties and composite protective behavior, providing insights for designing high-performance ballistic materials. Full article

In the current energy transition procedure, the application prospect of hydrogen as a clean energy material has attracted much attention. However, the widespread use of hydrogen is also accompanied by safety hazards, and how to detect hydrogen safely and efficiently has become a research focus. In this paper, we propose a fiber-optic hydrogen sensor based on the thermo-optic effect and nanomaterials, which combines the unique advantages of fiber-optic grating and platinum-loaded tungsten trioxide and is capable of detecting hydrogen concentration with high sensitivity. The principle of this sensor is to absorb hydrogen molecules by nanomaterials and trigger the exothermic effect, which leads to grating period change and refractive index change in the fiber, thus modulating the resonant wavelength of grating. By monitoring the wavelength drift in real time, the hydrogen concentration can be accurately detected. The experimental results show that the sensor can provide high sensitivity, fast response, wide detection range, and miniaturized design, which are suitable for hydrogen detection in complex environments. In addition, its dual-channel operational method further improves detection accuracy and environmental adaptability. This work provides technical support for safe hydrogen detection, which is suitable for hydrogen production, storage, industrial safety and environmental monitoring. Full article

Dynamic manipulation of light in optical fibers has attracted extensive interest due to its compatibility with various fiber-optic systems. The integration of two-dimensional (2D) materials on the surface of optical fibers is an effective method to manipulate light beams. However, it is still a huge challenge to acquire dynamic modulation for light signals in fiber. In this work, we develop electrically manipulable in-line multilayer graphene (MLG) devices by integrating a graphene-based lithium-ion (Li-ion) battery on a side-polished fiber. Through charge and discharge processes with a current of 400 µA, the output power of a 1550 nm laser can be cyclically tuned in the range of ~120 and ~240 µW with a response time of about 1.8 min. After 100 cycles of testing, the modulation power of the laser system remains nearly unchanged, exhibiting good stability. The optical modification of MLG is due to the shift of Fermi energy (E_f), which results from charge transfer between Li and graphene layers. Therefore, the light in the fiber can be modulated due to the change in the optical absorbance of MLG. Our findings imply potential value in fabricating fiber-intergraded 2D intercalation materials with high tunability. Full article

Lightweighting is a critical focus in the transportation sector, directly enhancing efficiency and significantly reducing costs. In electric vehicle (EV) design, the body surrounding the battery must effectively absorb impact, especially during crashes. This study aims to improve the crash performance of the side profiles in the battery box of an M1 category vehicle. It is based on the crash test in Annex 8D of the ECE R100 regulation. In this study, the safe displacement at which the battery will not deform is set as 20 mm, and the maximum force and energy absorption at this displacement are compared. In total, 33 different electric and hybrid vehicle models were benchmarked in this study. L-shaped geometry and aluminum materials are generally preferred; this study focuses on using glass-fiber-reinforced polymer (GFRP) pultruded profiles to make batteries more durable and lighter. The GF800 material was selected for its superior mechanical strength among glass fiber composites. A virtual tensile test verified its properties. A unique hybrid model combining honeycomb and auxetic geometries was developed, showing a crash performance improvement of ~360% over honeycomb structures and ~88% over auxetic structures. Through multi-objective optimization using artificial neural networks (ANNs), 27 models were analyzed, leading to an optimized design. The final design resulted in the battery box side profile being 23.9% lighter and 38.6% cheaper, and exhibiting a performance 3% higher. This study demonstrates significant advancements in EV safety and cost efficiency, highlighting the practical benefits of innovative material and design approaches. Full article

Q-switched fiber lasers have become reliable light sources for generating high-energy pulses, which can be passively modulated by saturable absorbers with excellent nonlinear optical properties. The composite combining Ag and MXene exhibits a broadband nonlinear response and high modulation depth, making it a promising candidate for saturable absorbers in pulsed lasers. Herein, we demonstrate a Q-switched Tm:Ho co-doped fiber laser centered at 2 µm, where the Ag/MXene composite serves as a saturable absorber to generate pulses. The typical spectrum, pulse train, and radio frequency spectrum of Q-switched pulses were observed, in which the 60 dB signal-to-noise ratio was higher than that of 2 µm Q-switched fiber lasers based on other materials, demonstrating the stability of the output pulses. Additionally, the long-term stability of the laser was evaluated over 2 h, where the well-maintained central wavelength and output power also indicated the robustness of the Q-switched laser. Furthermore, the influence of the pump power on the parameters of Q-switched pulses was also investigated, which is conducive to control the output characteristics of lasers. Specifically, the pulse width of the Q-switched pulse decreased, while the repetition rate, output power, and single pulse energy all increased with the increase in pump power. These experimental results demonstrate the ability of Ag/MXene as a saturable absorber and show its potential for generating high-performance pulses in ultrafast lasers. Full article

Based on the previous research on the energy absorption of foam metal materials with different structures, a composite blast-resistant energy-absorbing material with a flexible core layer was designed. The material is composed of three different fiber materials (carbon fiber, aramid fiber, and glass fiber) as the core layer and foamed iron–nickel metal as the front and rear panels. The energy absorption characteristics were tested using a self-built gas explosion tube network experimental platform, and the energy absorption effects of different combinations of blast-resistant materials were analyzed. The purpose of this paper is to evaluate the performance of blast-resistant materials designed with flexible fiber core layers. The experimental results show that the composite structure blast-resistant material with a flexible core layer has higher energy absorption performance. The work performed in this paper shows that the use of flexible core layer materials has great research potential and engineering research value for improving energy absorption performance, reducing the mass of blast-resistant materials, and reducing production costs. It also provides thoughts for the research of biomimetic energy-absorbing materials. Full article

Sugar palm bunch/SPB (Arenga longipes Mogea) waste is a lignocellulosic material derived from the harvest of sugar palm fruit (kolang-kaling). Therefore, this study aims to examine the anatomical, physical, chemical, and mechanical characteristics of SPB. The anatomical characterization results showed that SPB had two forms of fibrovascular bundles (FVBs), namely large and small. Based on morphology, SPB fibers had a length, diameter, average lumen diameter, and cell wall thickness of approximately 1346.42 ± 415.71 μm, 20.05 ± 3.81 μm, 11.82 ± 2.95 μm, and 4.12 ± 1.08 μm, respectively. FVB tissue of the sample had a fairly high density of 4–6 FVB per 4 mm² with a non-vascular area/total area ratio of 57.25%. The results showed that the sample contained 45.31 ± 3.20% cellulose, 23.21 ± 3.73% hemicellulose, 27.23 ± 4.23% lignin, and 1.39 ± 0.32% ash content. In addition, the extractive content that dissolved in hot water, cold water, ethanol-benzene, and 1% NaOH was 4.79 ± 0.84%, 7.12 ± 0.68%, 7.27 ± 2.38%, and 29.81 ± 3.78%, respectively. The GC–MS analysis results showed that A. longipes bunch contained several compounds, including carboxylic acid (tetradecanoic, octadecanoic), methoxy group (3-hydoxyphthalide), and palmitic acid. Meanwhile, the FTIR analysis showed the presence of OH groups with high intensity, which were identified as aromatic groups, as well as phenol groups recognized as lignin. Based on these results, characteristics of SPB were more suitable as raw materials for biomass energy, absorbent activated carbon, composite board, and surfactant. Full article

An experimental study is performed to determine the head mechanics of American football helmets equipped with novel fiber energy absorbing material (FEAM). FEAM-based padding materials have substrates of textile fabrics and foam made with nylon fibers using electro-static flocking process. Both linear and angular accelerations of the sport helmets are determined under impact loads using a custom-built linear impactor and instrumented head. The effectiveness of padding materials and vinyl nitrile (VN) foam for impact loads on six different head positions that simulate two helmeted sport athletes in real-time helmet-to-helmet strike/impact is investigated. A high-speed camera is used to record and track neck flexion angles and compare them with pad effectiveness to better understand the head kinematics of struck players at three different impact speeds (6 m/s, 8 m/s, and 10 m/s). At impact speed of 6 m/s and 8 m/s, the FEAM-based padding material of 60 denier fibers showed superior resistance for angular acceleration. Although novel pads of VN foam flocked with 60 denier fibers outperformed with lowest linear acceleration for most of the head positions at low impact speed of 6 m/s, VN foam with no fibers demonstrated excellent performance for linear acceleration at other two speeds. Full article

Hydrogen (H₂) sensors are critical to various applications such as the situation where H₂ is used as the clean energy for industry or the indicator for human disease diagnosis. Palladium (Pd) is widely used as the hydrogen sensing material in different types of sensors. Optical fiber H₂ sensors are particularly promising due to their compactness and spark-free operation. Here, we report a Fabry–Pérot (FP)-cavity-based H₂ sensor that is formed with a freestanding Pd membrane and integrated on a conventional single-mode optical fiber end. The freestanding Pd membrane acts both as the active hydrogen sensing material and as one of the reflective mirrors of the cavity. When the Pd film absorbs H₂ to form PdH_x, it will be stretched, resulting in a change of the cavity length and thus a shift of the interference spectrum. The H₂ concentration can be derived from the amplitude of the wavelength shift. Experimental results showed that H₂ sensors based on suspended Pd membranes can achieve a detection sensitivity of about 3.6 pm/ppm and a detection limit of about 3.3 ppm. This highly sensitive detection scheme is expected to find applications for sensing low-concentration H₂. Full article

Lime–cement concrete (LCC) is a type of lime-based concrete in which lime and cement are utilized as the main binding agents. This type of concrete has been extensively used to construct support layers for shallow footings and road backfills in some warm regions. So far, there has been no systematic research conducted to investigate the mechanical characteristics of polyamide fiber-reinforced LCC. To address this gap, LCC specimens were prepared with 0%, 0.5%, 1%, and 2% of polyamide fibers (a synthetic textile made of petroleum-based plastic polymers). Specimens were then cured for 3, 7, and 28 days at room and oven temperatures. Then, the effects of the fibers’ contents, curing conditions, and curing periods on the mechanical characteristics of LCC, such as secant modulus, deformability index, bulk modulus, shear modulus, stiffness ratio, strain energy, failure strain, strength ratio, and failure patterns, was investigated. The results of the unconfined compressive strength (UCS) tests showed that specimens with 1% fiber had the highest UCS values. The curing condition and curing period had significant effects on the strength of the LCC specimens, and oven-cured specimens developed higher UCS values. The aforementioned mechanical properties of the LCC specimens and the ability of the material to absorb energy significantly improved when the curing period under the oven-curing condition was increased, as well as through the application of fibers in the mix design. Based on the test results, a simple mathematical model was also established to forecast the mechanical properties of fiber-reinforced LCC. It is concluded that the use of polyamide fibers in the mix design of LCC can both improve mechanical properties and perhaps address the environmental issues associated with waste polyamide fibers. Full article

We report the fabrication of an erbium-doped fiber-based saturable absorber (SA) of niobium aluminium carbide (Nb₂AlC) nanomaterial that can generate a dissipative soliton mode-locked pulse. Stable mode-locked pulses operating at 1530 nm with repetition rates of 1 MHz and pulse widths of 6.375 ps were produced using polyvinyl alcohol (PVA) and the Nb2AlC nanomaterial. A peak pulse energy of 7.43 nJ was measured at 175.87 mW pump power. In addition to providing some useful design suggestions for manufacturing SAs based on MAX phase materials, this work shows the MAX phase materials’ immense potential for making ultra-short laser pulses. Full article

Triply periodic minimum surface (TPMS)-based lattice structures have gained interest for their outstanding capacity to absorb energy, their high load-bearing capacity, and their high surface-to-volume ratio. This study considered three TPMS cell topologies, including Diamond, Gyroid, and Primitive. The FDM process was used to print the lattice structures with two materials: pure polylactic acid (PLA) and carbon fiber-reinforced PLA (PLA + CF). The influence of carbon fiber (CF) incorporation, unit cell type (topologies) and size, and relative density (RD) on mechanical properties and failure patterns were explored comprehensively under uniaxial compression testing. The results demonstrate a change in the compressive modulus (0.09 to 0.47 GPa), compressive strength (2.98 to 13.89 MPa), and specific energy absorption (SEA) (0.14 MJ/m³/g to 0.58 MJ/m³/g) due to the influence of CF incorporation, cell type and size, and RD. Results indicate that the Diamond structure outperformed both Primitive and Gyroid structures in terms of compressive modulus and strength, and SEA. All the CF-based TPMS structures showed a higher compressive modulus. Compressive strength and energy absorption capacity were both slightly enhanced in most PLA + CF-based Diamond structures. On the contrary, Gyroid and Primitive structures showed better performance for pure PLA-based structures in terms of compression strength and specific absorption energy. Full article

As destructive power of firearms raises over the years, ballistic armors are in continuous need of enhancement. For soft armors, this improvement is invariably related to the increase of stacked layers of high-strength fiber fabrics, which potentially restrains wearer mobility. A different solution was created in the early 2000s, when a research work proposed a new treatment of the ballistic panels with non-Newtonian colloidal shear thickening fluid (STF), in view of weight decreasing with strength reinforcement and cost-effective production. Since then, databases reveal a surge in publications generally pointing to acceptable features under ballistic impact by exploring different conditions of the materials adopted. As a result, several works have not been covered in recent reviews for a wider discussion of their methodologies and results, which could be a barrier to a deeper understanding of the behavior of STF-impregnated fabrics. Therefore, the present work aims to overview the unexplored state-of-art on the effectiveness of STF addition to high-strength fabrics for ballistic applications to compile achievements regarding the ballistic strength of this novel material through different parameters. From the screened papers, SiO${}_2$, Polyethylene glycol (PEG) 200 and 400, and Aramid are extensively being incorporated into the STF/Fabric composites. Besides, parameters such as initial and residual velocity, energy absorbed, ballistic limit, and back face signature are common metrics for a comprehensive analysis of the ballistic performance of the material. The overview also points to a promising application of natural fiber fabrics and auxetic fabrics with STF fluids, as well as the demand for the adoption of new materials and more homogeneous ballistic test parameters. Finally, the work emphasizes that the ballistic application for STF-impregnated fabric based on NIJ standards is feasible for several conditions. Full article