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.
