The control fin is a key component in a guided missile's propulsion system, stabilizing the missile's attitude and maintaining its flight trajectory under high-speed conditions. Such components demand high mechanical strength and thermal stability. However, traditional control fin designs have primarily focused on external geometry, overlooking opportunities to enhance performance through internal structural design.To address this limitation, this study proposes a design approach that integrates lattice structures within the control fin using metal additive manufacturing. A body-centered cubic (BCC) lattice was selected, with strut diameter and unit cell aspect ratio defined as the primary design variables. Finite element analysis in Abaqus was used to evaluate structural behavior, analyzing stress and displacement distributions based on variations in these lattice parameters. Manufacturability and lightweight characteristics were also assessed. Results indicate that increasing the strut diameter improves structural stability, with stress predominantly concentrated near lattice joints. Building on these findings, a non-uniform lattice design, derived from the uniform lattice analysis, was applied, demonstrating improved stress distribution and overall structural performance. This approach shows that lattice-based internal structures, enabled by metal additive manufacturing, can significantly enhance the structural performance of guided missile control fins while achieving substantial weight reduction.
Silicon nitride/cobalt tungsten boride (SiN/CoWB) passivation layer improves mass transport rate at copper thin film layers of semiconductor wafers after chemical mechanical polishing process. This study evaluates mass transport at the interface between copper and passivation layers by stress relaxation method, followed by deduction of interface diffusivity via a kinetic model. For comparison, SiN/CoWB, SiN, silicon carbon nitride (SiCN) and silicon carbide (SiC) passivation layers are introduced. A thin layer of SiN/CoWB demonstrates an outstanding performance as diffusion retarding material, especially at high temperature. The order of stress relaxation in terms of passivation layers is SiN/CoWB < SiN < SiCN < SiC, implying the order of mass transport at the interface. Using the kinetic model, the diffusivities and activation energies regarding passivation layers are calculated and reveal a good agreement with experimental results.
Polyacrylamide (PAM) was used for matrix material to fabricate composite hydrogels reinforced with natural cellulose nanocrystal (CNC). Invoking in situ free-radical polymerization with different concentration of cellulose nanocrystal, polyacrylamide hydrogels were fabricated. The chemical structure, compression strength, morphology and dielectric properties of the composite hydrogels were investigated. The CNC played a role as a reinforcing filler and a multifunctional cross-linker in the hydrogel. The elastic modulus and dielectric property of the composite hydrogels increased as increasing the CNC concentration. The electrical actuation test of the PAM/CNC hydrogel shows its possibility for soft electro-active materials for active lens.
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