In this study, the bonding strength of CFRP/Al hybrid joints was investigated according to different aluminum surface treatments. Also, their accelerated degradation behavior was analyzed under a galvanic corrosion environment induced by the potential difference between carbon fiber and aluminum. Single Lap Shear (SLS) specimens were made in accordance with the ASTM D5868 standard, applying three surface treatment variables: sanding, anodizing, and resin pre-coating (RPC). The bonding reliability was evaluated by measuring the changes in shear strength before and after exposure to the corrosive environment. Furthermore, the microstructural changes at the adhesive interface were observed using Scanning Electron Microscopy (SEM) to interpret the degradation and failure mechanisms associated with each treatment. The results demonstrated that the anodizing process exhibited the superior performance in terms of shear strength retention after degradation. This suggests that anodizing is a highly effective surface treatment strategy for enhancing the environmental durability of CFRP/Al hybrid structures.
Polypropylene (PP) is a versatile thermoplastic polymer with excellent physical properties and economic feasibility, making it a material used in many industrial fields. During application, PP resin is typically blended with various additives, including heat stabilizers, antioxidants, and inorganic fillers, to enhance its physical properties, processability, and functionality. Recently, in an effort to use eco-friendly additives, PP composites using natural additives are being studied. PP composites containing natural wax are bee-friendly materials and have improved UV blocking properties, so research is underway to apply them to PP. However, when beeswax, a natural antioxidant, is added to PP, mechanical properties such as tensile strength and modulus decrease, and thus improvement is required. Therefore, a filler such as talc with high rigidity was used to supplement the properties. In this study, composites were manufactured by mixing beeswax, wood powder (WPC), and talc with PP in various compositions, and the changes in the physical properties of the PP composites according to their contents were investigated. In addition, the antioxidant effect was confirmed using FT-IR and oxidation induction time. The UV resistance of the beeswax composite was evaluated through a tensile test after UV exposure.
The B-stage and charge pattern of Sheet Molding Compounds (SMC) govern processability and the mechanical performance of molded parts. We evaluated epoxy (EP-SMC) and vinyl ester SMC (VE-SMC) using four quantitative methods: viscosity, differential scanning calorimetry (DSC), probe test, and drape (overhang) tests. Viscosity identified the B-stage onset but was limited for detailed tack characterization. DSC showed decreasing peak exothermic heat flow with pre-reaction time, yet remained resin-state specific. Probe test offered high sensitivity within a narrow B-stage window but exhibited large scatters. In contrast, the drape test provided low variability and clear discrimination of B-stage progression, enabling efficient quantification. In compression molding, molded-part properties were evaluated with four charge patterns (Full, Center, Middle, Bottom) and the degree of B-stage advancement. Zone-based measurements revealed clear differences in tensile strength as well as porosity, resin content (RC), and thickness distribution along the mold-flow direction. For center-charge specimens, increasing B-stage advancement reduced void content (8.94 +/- 0.46% to 2.68 +/- 1.04%) and increased RC (39.9 +/- 0.08% to 47.4 +/- 0.09%), confirming that precise B-stage control and charge pattern design are critical for molding design and quality control.
The effective properties of composites are strongly governed by the microstructural factors such as fiber and matrix properties, fiber volume fraction, and fiber arrangement. In this study, multi-scale homogenization is applied to unidirectional composites to predict effective properties using analytical models and RVE-based finite element analysis, and the predictive accuracy of each method is compared. Pearson correlation analysis is conducted to evaluate the sensitivity of constituent properties on the composite response, and local stress distributions are examined to identify the characteristics and limitations of each model. These findings provide a basis for selecting appropriate property prediction methods in composite structural design.
In this study, BaMoO4 dielectric ceramics were fabricated using a solid-state reaction and tape casting process, and the effects of calcination and sintering temperatures on their microstructure and dielectric properties were systematically investigated. The calcination temperature of the BaMoO4 powder was varied from 500 degrees C to 700 degrees C. By controlling the calcination temperature of BaMoO4 powders in the range of 500-700 degrees C, an optimal powder with suppressed grain growth and without secondary phase formation was obtained at 600 degrees C. The green sheets were sintered in the range of 700 degrees C to 850 degrees C. The specimen sintered at 800 degrees C exhibited the most densely packed microstructure along with the highest sintering density of 4.92 g/cm(3). The temperature coefficient of capacitance (TCC) analysis revealed highly stable dielectric behavior over a wide temperature range from-50 degrees C to 150 degrees C. In addition, dielectric characterization as a function of frequency revealed that the specimen sintered at 800 degrees C exhibited relatively low dielectric loss and stable dielectric behavior. These results suggest that low-temperature sintered BaMoO4 ceramics fabricated by tape casting are promising candidates for dielectric component applications requiring stable frequency-dependent dielectric behavior.
This paper numerically reproduces wrinkling of a plain-weave CFRTP laminate under a bias-extension test performed in the commercial finite element analysis(FEA) software, ABAQUS/Explicit, with user-defined material subroutine (VUMAT), implementing a shear angle based nonlinear shear law. Two finite element models of a coupled model where bending stiffness is derived from membrane stiffness, and a decoupled model that separates membrane and bending responses were compared. While both models showed similar shear-angle distributions and predicted wrinkle initiation in the same shear-concentrated regions, their wrinkle growth differed markedly: the coupled model exhibited abrupt, unstable out-of-plane growth, whereas the decoupled model showed earlier and more gradual accumulation. The results emphasize that decoupling the intrinsically low bending stiffness of woven fabrics is essential for accurate wrinkle prediction.
This study evaluated surface flame-retardant coatings for basalt fiber/epoxy FRP composites under direct flame exposure. Three coatings (Type A: phosphorus-based, Type B: inorganic-based, and Type C: carbon-based) and an uncoated (BFRP) specimen were tested by monitoring internal temperature and ignition behavior, observing surface damage (optical microscopy), measuring residual tensile strength, and conducting cone calorimetry (peak HRR and THR). The neat specimen showed rapid temperature rise and early ignition, whereas Type A and Type B suppressed temperature increase and maintained a stable protective layer, leading to improved residual strength. Type B exhibited the best thermal-barrier stability under prolonged exposure and the greatest THR reduction, making it the most favorable option considering both fire performance and residual structural performance. Type C showed an initial thermal-barrier effect but suffered protective-layer degradation during prolonged exposure, resulting in higher internal temperature and reduced residual strength, indicating the need for further improvement for practical use.
A deep neural network(DNN) based methodology is proposed to predict the effective thermo-mechanical properties of plain-weave CFRP composites. Ten distinct effective properties are evaluated by selecting three primary geometric parameters as design variables to account for variations in textile architecture. Representative volume element(RVE) modeling was performed using TexGen software, with periodic boundary conditions(PBCs) applied via the EasyPBC plugin. Effective thermo-mechanical analyses were subsequently conducted using the commercial finite element analysis(FEA) software, ABAQUS. The entire data generation process was automated to construct a comprehensive database of 728 datasets. Model performance was evaluated using 164 validation samples, which account for 20% of the total dataset. The evaluation yielded a Mean Relative Error(MRE) of 0.79% and a coefficient of determination(R-2) of 0.9991, confirming the model's reliability as a surrogate. While FEA-based homogenization required approximately 63.1 s, the DNN model completed predictions in only 14 ms, confirming a significant leap in computational efficiency. These results verify that the proposed DNN model effectively predicts effective thermomechanical properties in response to variations in weaving parameters.
This study proposes a 2D Shell-based injection molding-structural coupled analysis for efficiently predicting the structural behavior of injection-molded short-fiber reinforced composite structures. To this end, local short-fiber orientation during the manufacturing process were derived based on injection molding analysis, and the corresponding behaviors were considered in the process of the structural analysis. Furthermore, by applying a layered 2D Shell model, the 3D distribution of the local short-fiber orientation was approximately mapped onto the layer-wise orientation data of 2D Shell elements, enabling the in-plane and through-thickness distributions of orthotropic material properties to be efficiently considered within a dimension-reduced analysis model. As numerical examples, injection molding-structural coupled analysis was performed for tensile and bending specimens. The accuracy and computational efficiency of the proposed analysis model were verified by comparing obtained results with those of 3D Solid-based injection molding-structural coupled analysis.
This study applied nanocellulose, a natural polymer, as an additive to compensate for the low wettability and mechanical strength of silicone hydrogel contact lenses and to impart additional functions such as ultraviolet blocking and antibacterial activity. For lens fabrication, nanocellulose was added at varying concentrations ranging from 0.03 wt% to 0.10 wt% to a silicone hydrogel formulation primarily composed of HEMA, NVP, DMA, and TRIS, and the optical properties, physical characteristics, and biological safety of the fabricated lenses were comprehensively evaluated. As a result, UV-B transmittance continuously decreased with increasing nanocellulose content from 76.22% in the control group to 36.21% at 0.10 wt%, confirming the expression of UV-blocking performance without an additional blocking agent. The water content increased from 42.2% in the control group to a maximum of 48.0%, while the refractive index remained within 1.4260-1.4265, indicating a trend of increased hydrophilicity without compromising optical transparency. Surface analysis of the fabricated lenses showed that the contact angle markedly decreased from 105 degrees in the control group to 84 degrees, and AFM and SEM analyses confirmed that a fine network structure formed by nanocellulose particles contributed to changes in surface roughness and improved hydrophilicity. In mechanical strength evaluation, tensile strength increased by more than approximately threefold, from 0.12 kgf/mm(2) to 0.38 kgf/mm(2), due to the physical crosslinking effect of the nanoparticles. In the safety evaluation, pH, potassium permanganate reduction, and UV absorbance all fell within the regulatory limits set by the Ministry of Food and Drug Safety, demonstrating chemical safety with respect to extractables. In addition, antibacterial tests showed that lenses containing nanocellulose exhibited excellent inhibitory effects against Escherichia coli and Staphylococcus aureus. In conclusion, nanocellulose is considered a multifunctional additive capable of simultaneously improving wettability, durability, and antibacterial performance without impairing the fundamental properties of silicone hydrogel lenses.
With the rise of new industrial paradigms such as AI and autonomous driving, semiconductors have become essential components across various platforms, from data centers to personal devices. As demands for high performance, high integration and lightweight packaging grow, challenges such as warpage arise due to large-area structures and heterogeneous materials. Although simulation-based warpage prediction methods have been developed, fully reflecting high-resolution circuit patterns in finite element model leads to excessive mesh counts, increasing computational cost and reducing numerical stability. To overcome these issues, in this research, proposal of the modeling approach that specifies Cu pattern orientation and density in each region of high-resolution circuit images. These analyzed results are used to construct an equivalent model with effective anisotropic thermo-mechanical properties. This method enables efficient thermo-mechanical analysis while preserving key circuit characteristics, allowing accurate warpage prediction in semiconductor packages.
To address water scarcity issues caused by climate change and overcome environmental pollution from conventional plastic mulch films, this study experimentally analyzed the chemical composition and water absorption and retention properties of hemp and kenaf hurds, sustainable non-wood resources. Component analysis revealed that kenaf hurds, with their low hydrophobic lignin content, exhibited over twice the water absorption rate compared to hemp hurds and demonstrated superior hydrophilicity. In water retention tests, both materials recorded optimal water-retaining performance at a particle size of 5 mm, where drying rates were slowest. Notably, in actual soil application, kenaf hurds stably maintained approximately 70% soil moisture for 65 hours, whereas 3 mm hemp hurds reached a critical point after 55 hours, causing soil moisture to sharply decrease to the 20% range. This demonstrates that the porous structure of the material and the physical shielding effect due to particle size interact synergistically to influence soil moisture retention capacity.
This numerical study evaluated the effect of glass-fiber (GF) content in PA66/GF composites (PA66, GF15, GF25, GF35, and GF50) on hotspot stress, deflection, and fatigue life of a mini-chain under reverse-driving conditions. A static finite element model with remote displacement and frictional contact (mu = 0.3), combined with a stress-life assessment based on literature S-N curves (Basquin fit with Goodman correction, R = 0), revealed a tradeoff: increasing GF reduced deflection but increased hotspot stress and maximum contact pressure (interpreted conservatively as a wear-propensity indicator). GF50 exhibited the lowest life (potentially <106 cycles), whereas GF25 provided the most balanced performance while meeting the 10(6) cycle durability criterion, with GF15 regarded as a conservative option showing lower stress/contact responses.
The increasing demand for lightweight electromagnetic interference (EMI) shielding materials has made single-walled carbon nanotubes (SWCNTs) attractive candidates due to their intrinsically high electrical conductivity. In this study, we investigate the effect of acid doping on the EMI shielding (EMI SH) performance of SWCNT films. The films were fabricated via a simple vacuum filtration process and doped using camphor sulfonic acid (CaSA) and chlorosulfonic acid (CSA). A systematic investigation of CaSA concentration revealed only minimal changes in the overall EMI shielding effectiveness. In contrast, increasing the maceration time during CSA post-treatment resulted in a modest enhancement in shielding effectiveness (approximate to 2-3 dB). However, prolonged maceration led to noticeable structural degradation of the SWCNT films. These results indicate that acid doping primarily influences the shielding behavior rather than significantly improving the total shielding effectiveness, highlighting the importance of optimizing acid strength and processing conditions for SWCNT-based EMI shielding materials.
In this study, the impact resistance properties and strain behavior under static compressive load according to the mold temperature (80, 100, 120, 140, and 160oC) of the PPS/GF 65 wt.% composites applied to the housing part of an electric vehicle film capacitor were quantitatively evaluated using 3D digital image correlation analysis (DIC). The Izod impact strength increased by approximately 30% at 160oC compared to 80oC, and the drop-weight impact energy absorption improved by approximately 70% in the range of 80-160oC. The static compression test on each component was conducted by injection molding the component under mold temperature conditions of 120, 130, and 140oC. As a result, the 140oC mold condition showed the highest stiffness, toughness, and energy resistance, with an average maximum load of 28.4 kN and a principal strain of 4.5%. The DIC strain field revealed that strain concentration occurred at the lower left corner of the part during the loading phase prior to fracture initiation. Lower mold temperatures resulted in increased strain deviation and crack propagation variability due to non-uniform heat transfer along the thickness gradient. Accordingly, 140 degrees C was identified as the optimal processing condition for uniform glass fiber orientation, maximizing unit impact resistance and energy absorption.
Interlaminar shear stress in laminated composites is a critical factor governing the initiation of delamination and overall structural integrity, and the short-beam shear test is widely used to evaluate this behavior. However, due to the complex contact-shear interactions that arise near the indenter and support regions, classical beam theory and finite element analysis-based approaches suffer from limitations in terms of computational cost and modeling efficiency. To address these issues, this study proposes a Hybrid Physics-Informed Neural Network (Hybrid PINN) framework for predicting interlaminar shear stress by incorporating anisotropic Hertzian contact theory. The proposed model embeds the governing equations of an orthotropic elastic solid under plane stress conditions into the loss function and imposes the load-dependent contact pressure distribution as a physical constraint. In addition, reference data obtained from finite element analysis are used to guide the early stage of training, thereby improving convergence stability and prediction accuracy. Validation under short-beam shear test conditions demonstrates that the Hybrid PINN successfully reproduces interlaminar shear stress distributions that are qualitatively consistent with FEA results, while the maximum interlaminar shear stress is predicted within 1% error. These findings indicate that the proposed approach provides an efficient alternative for predicting interlaminar shear stress in laminated composites.
In the aerospace industry, Out-of-Autoclave (OoA) processes are increasingly adopted to enhance manufacturing efficiency for large-scale structures, with Automated Fiber Placement (AFP) and Automated Tape Laying (ATL) technologies serving as core methods for precise dry preform layup. However, the incorporation of the veil exerts complex effects on the final mechanical properties; while it offers the positive benefit of enhancing interlaminar toughness by suppressing crack propagation, it simultaneously acts as a physical barrier that impedes resin flow and hinders direct bonding between the carbon fibers and the resin. This study investigates the effects of Polyamide (PA) binder veil insertion on the Interlaminar Shear Strength (ILSS) and micro-interfacial characteristics of carbon fiber composites, focusing on variations in consolidation pressure and veil layers. The results showed that all veil-inserted specimens exhibited a significant decrease in ILSS compared to non-veil specimens, regardless of pressure conditions. This degradation occurs because the veil acts as a physical barrier hindering resin impregnation and increasing interlaminar thickness, thereby weakening interfacial bonding. By identifying the mechanisms of mechanical degradation caused by binder veils in AFP/ATL-based processes, this study emphasizes the need for optimized process designs that balance manufacturing efficiency and mechanical integrity.
This study investigates the mechanical behavior and interfacial reliability of CFRP/PVC foam core sandwich composites manufactured using an adhesive-free co-curing process. Building upon previous work that verified interfacial bonding integrity through ultrasonic non-destructive evaluation and ASTM C297 flatwise tensile tests, additional experimental and numerical investigations were conducted to further assess the structural feasibility of eliminating the adhesive layer. Finite element analysis based on the ASTM C297 configuration was performed to validate the interfacial modeling approach, showing excellent agreement with experimental tensile results, with prediction errors within 2% for the UD specimens. To evaluate structural performance under more realistic loading conditions, three-point bending tests were carried out in accordance with ASTM C393, and the results revealed that, regardless of the presence of an adhesive film, flexural failure was predominantly governed by face-sheet and/or core failure for most configurations, while Mode-II-related interfacial shear effects did not dominate the overall failure response. Interfacial delamination was observed only in specific UD configurations under relatively high flexural load levels, which was attributed to localized stress concentrations arising from fiber orientation rather than insufficient interfacial bonding strength. A simplified quantitative assessment based on classical sandwich beam theory further demonstrated that the estimated face-sheet bending stresses approached 86-103% of the CFRP strength, whereas the estimated interfacial shear stresses remained only about 11-13% of the interfacial shear strength obtained from flatwise tensile tests. These findings confirm that, for sandwich structures with CFRP face sheets thinner than 1 mm, the flexural response is governed primarily by the mechanical limits of the face sheets and core rather than by Mode-II interfacial fracture, and overall demonstrate that adhesive-free co-cured sandwich composites with woven CFRP face sheets can achieve sufficient interfacial reliability and structural performance for lightweight load-bearing applications without the use of an adhesive film.
This paper analyzed the anatomical and chemical characteristics of non-woody plant resources such as flax, hemp, and ramie, and reviewed the latest research trends in their applications as tissue engineering and orthopedic medical materials. Non-woody resources offer advantages such as short growth cycles and the potential for low-carbon model implementation. The high-strength bast fibers and porous pith constituting the stems of nonlignified plant resources are utilized for their mechanical structural properties and as scaffolds for cell growth. Notably, composite materials based on non-lignified bast fibers can achieve elastic moduli similar to human cortical bone, thereby resolving the stress shielding phenomenon associated with metallic implants. Furthermore, the core components of non-lignified plant resources-cellulose, hemicellulose, and lignin-possess excellent biocompatibility, antioxidant, and antibacterial properties. This has confirmed their utility across diverse biomedical engineering fields, and dental barrier membranes.
In this study, coconut shell-based activated carbon was employed to fabricate monoliths for gas storage, designed as a key material for adsorbed natural gas (ANG) systems to replace conventional liquefied natural gas (LNG) technology. The monoliths were prepared by mixing granular activated carbon with an acrylic binder, carboxymethyl cellulose (CMC), and distilled water, followed by pressing the mixture in a 2.5 cm diameter mold at 10 MPa for 2 min. The molded bodies were dried at room temperature for 24 h and subsequently in an oven at 80oC. The surface morphology, internal structure, and elemental composition of the monoliths were characterized using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The specific surface area, pore structure, and pore size distribution were analyzed by Brunauer-Emmett-Teller (BET) measurements. The density of the monoliths was determined using Acrchimedes' principle, and their mechanical stability was evaluated by compressive strength testing. These results demonstrate the potential of coconut shell-based activated carbon monoliths as efficient storage media for ANG systems.
