Composite specimens with resin contents of 33.5%, 35.4%, and 35.9%, respectively, were manufactured by controlling the type of subsidiary material used in the bagging process for a composite material having the same composition.The effect of controlling the resin content on the microstructure and mechanical properties of composite specimens was investigated. The flow of resin and air during the cure process was inferred and explained by connecting it with the microstructure. Specifically, the behavior of the resin determined the thickness, density, and void of the composite laminate, which acted as a factor causing the difference in mechanical properties of the composite materials. As the resin content increased, there was no significant difference in tensile strength, but Young's modulus decreased. In the case of the compression test, there was a difference in mechanical properties due to the combined effect of the reinforcement and the resin. The maximum compressive strength value was shown in the process with low void content, and Young's modulus tended to decrease as the resin content increased. In the bagging process, the subsidiary material controlled the flow of resin and air, and caused a difference in microstructure, affecting the change of mechanical properties.
The field of application of Glass Fiber Reinforced Polymer expands as well as the size of the component where composite material is applied. Due to the size limitation of the prepreg used, it is difficult to apply 1ply to large parts. Many studies have been reported on the bolt joint that assembles parts and parts for the joint area, butt and overlap design for joining dissimilar materials, and mechanical properties. Although the mechanical properties of the joint areas are important, studies on the microstructure are also needed. In this study, the microstructure was observed by controlling the type of subsidiary materials in the bagging process by applying prepregs of the same composition. It was found that the air and resin flow inside the prepreg acted differently depending on the type of subsidiary material. The flow of resin during curing was inferred from the influence of subsidiary materials and explained by connecting it with the microstructure. The behavior of the resin determined thickness, resin, and void contents of the composite. This flow affects voids in the joint area, causing differences in microstructure and mechanical properties. There was no significant difference in the tensile strength of the laminate specimens manufactured according to the process, but the minimum strength was found in the specimens containing many void contents. The joint specimen showed a decrease in strength as the void content increased. It was discussed that this reduced the adhesive force of the specimen due to the effect of the void generated in the joint area.
It is necessary to develop a low‐loss dielectric material based on the low‐temperature co‐fired ceramic (LTCC) process, which is essential for expanding 5G service. LTCC is designed by mixing SiO2 and glass to secure low dielectric constant. The density, porosity, and average diameter of pores of the sintered specimen are analyzed and evaluated to confirm the change in sintering behavior according to the mixing composition ratio of SiO2 and glass and the heating rate. When the ratio of the mixed filler is 35 vol%, the density is the highest at 2.30 g cm−3, the porosity is the lowest at 4.59%, and the diameter of the pores is also the smallest at about 5.80 μm. Therefore, it is selected as the optimal mixing ratio. When the heating rate is used as a variable, the density is high in 1, 3, and 5 °C min−1, and the porosity and pore diameter are small. However, it is confirmed that as the heating rate increases, the density gradually decreases, while the porosity as well as pore diameter increases. As a result of analyzing the sample under the optimal conditions, the dielectric constant 3.64 and loss 0.01 are shown in 30 GHz.
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