This study develops an analytical–numerical framework for predicting the dynamic response of fully clamped metallic foam-filled Y-shaped sandwich plates (FYSPs) subjected to idealized blast loading. Based on rigid-plastic idealizations, the structural response is divided into an initial core-compression stage and a subsequent global bending–stretching stage. By formulating the combined compressive resistance of the Y-shaped webs and metallic foam, expressions are derived for the average core compressive strain and the critical impulse associated with core densification. The approximate yield locus of the foam-filled Y-shaped cross-section is then incorporated into a finite-deflection rigid-plastic plate formulation, yielding upper- and lower-bound solutions and a simplified membrane-mode solution. Finite element analysis (FEA) is performed using ABAQUS/Explicit software. The results indicate that the two-stage decoupling assumption for the structural dynamic response is reasonable within the investigated parameter range. As large plastic deformation develops, the analytical predictions progressively approach the numerical results. Parametric analyses indicate that metallic foam strength and density and Y-shaped web thickness significantly affect the structural response, whereas the influence of web angle is comparatively limited. The proposed model provides an analytical basis for evaluating the impulsive response of fully clamped FYSPs.
To enhance the mechanical performance of polylactic acid (PLA) while maintaining its sustainability advantages, thermoplastic starch (TPS) was incorporated to fabricate PLA/TPS biocomposites under shear and extensional flow fields. Owing to the intrinsic immiscibility and polarity mismatch between PLA and TPS, the system typically exhibits weak interfacial interaction and inefficient stress transfer. This study systematically investigates the effects of flow fields on morphology evolution, interfacial characteristics, crystallization behavior and mechanical properties of PLA/TPS blends, with emphasis on the reinforcement mechanisms of extensional flow. The results show that extensional flow significantly refines the dispersed TPS phase, leading to improved dispersion uniformity and enhanced interfacial interaction, which promotes more efficient stress transfer. In addition, extensional flow facilitates increased crystallinity of the PLA matrix. Mechanical testing reveals that although the yield strength slightly decreases, the elongation at break is markedly improved, resulting in enhanced ductility and overall toughness. These improvements are attributed to the synergistic effects of morphology refinement, strengthened interfacial interaction and flow-induced crystallization. This work provides valuable insights into flow-induced reinforcement mechanisms for designing high-performance sustainable biocomposites.
The global transition toward a circular economy has positioned chitosan (CS) as a premier biopolymer for replacing petrochemical plastics; however, a significant knowledge gap persists between laboratory-scale innovation and industrial-scale viability. This review provides an integrated synthesis of recent advances in CS-based composites, specifically addressing the functionality-scalability paradox that hinders commercial adoption. We analyze the technical performance of CS modified through biopolymer blending (starch, cellulose, alginate, gelatin), chemical cross-linking, and the incorporation of bioactive fillers including metallic nanoparticles, carbon dots, and natural extracts. Critical insights reveal that while CS composites significantly extend the shelf life of produce, meat, and seafood by regulating internal atmospheres and inhibiting microbial growth, their industrial application is restricted by high moisture sensitivity and processing brittleness. Furthermore, we uniquely evaluate the regulatory landscape, highlighting that stringent migration limits for metallic nanoparticles (Ag, ZnO, TiO 2 ) necessitate a strategic shift toward bio-based reinforcements. Future research must move beyond iterative material testing by using AI-assisted material design to optimize synergies among components, by developing extrusion-ready thermoplastic CS graft copolymers, and by implementing closed-loop waste-to-wealth models that utilize agricultural residues as both the polymer source and bioactive filler. By bridging material science with regulatory frameworks and economic feasibility, this review outlines a definitive roadmap for the commercialization of the next generation of active and sustainable food packaging.
This study investigates the thermo-mechanical bending behavior of perfect and porous functionally graded material (FGM) sandwich plates with temperature-dependent material properties. Temperature-dependent material properties are assumed to vary continuously along the thickness direction of the plate. To evaluate the effects of porosity on thermo-mechanical bending, five different distribution models have been considered: even, uneven, logarithmically uneven, linearly uneven, and sinusoidally uneven. It is assumed that the outer faces of the FGM sandwich plate are porous, while the ceramic core remains non-porous. A power law distribution is employed to ensure a smooth and continuous variation of the thermal and mechanical properties through the thickness of the FGM layers. The temperature distribution across the plate thickness is determined using a one-dimensional heat conduction equation and incorporated into the thermo-mechanical bending analysis. The hyperbolic shear deformation theory (HYSDT) that incorporates a hyperbolic distribution of transverse shear stresses and satisfies the traction-free boundary conditions, is employed in this study. The governing equations for the thermo-mechanical bending analysis are formulated using Hamilton's variational principle. Further, Navier's solution technique is employed to obtain analytical expressions for evaluating the central deflection, normal stress, and shear stress responses of porous FGM sandwich plates. A detailed parametric study is performed to investigate the effects of porosity distribution, porosity coefficient, temperature-dependent material properties, power law index, temperature difference, side-to-thickness ratio, and aspect ratio on the bending response. The results highlight the significant influence of material gradation, porosity characteristics, and thermal effects on the thermo-mechanical bending response of porous FGM sandwich plates. Furthermore, the close agreement between the present results and those available in the literature demonstrates the accuracy of HYSDT based analytical formulation.
Polyimide (PI) has become a critical coating material in aerospace and high-end equipment due to its outstanding thermal stability, mechanical strength, and chemical inertness. However, conventional PI faces bottlenecks such as insufficient wear resistance under high-friction conditions and poor synergy between thermal and mechanical properties. This work prepared the Fe3O4@polydopamine (Fe3O4@PDA) core-shell nanoparticles with three different morphologies (nanosphere, nanowire and nanosheet) as the reinforcements in polyimide (PI) coating composites to improve their thermal, mechanical and tribological properties. The SEM, XRD and XPS results showed that the Fe3O4@PDA core-shell nanoparticles had significant changes in size, surface roughness, crystal form and surface chemistry compared to the pristine Fe3O4, which contributed to the enhanced properties of the PI coating composites. Enhanced physical entanglements (from increased roughness of the Fe3O4@PDA) and stronger chemical interactions (from functional groups of the PDA and PI) collectively alter the energy dissipation mechanisms of the PI/Fe3O4@PDA composites under thermal, tensile, and frictional stress. The use of any of the three distinct morphological types of Fe3O4@PDA as additives resulted in a reduction of over 80% in the wear rate of the PI composites relative to pure PI. The improvement in the wear resistance, as well as the thermal and mechanical properties of the PI/Fe3O4@PDA composites over the pure PI. The most typical PI/Fe3O4NSh@PDA-0.25 exhibited 15.86% increase in toughness and 14.73% improvement in elastic modulus, and pyrolysis temperature of the PI/Fe3O4NW@PDA-0.25 increased by 1.51%, compared to pure PI.
