Debonding and substrate reuse in structural bonded joints are of great interest for sustainability and circular economy. In this study, numerical modelling of reversible vitrimer adhesive multi-material bonded joints was performed and validated against experimental results, with a final focus on optimizing design parameters for maximum bonding strength and debonding. Multi-material single-lap bonded joints were prepared using aluminum alloy (Al6061), stainless steel (SS304), and glass fiber-reinforced plastic (GFRP) composite substrates using a reversible vitrimer as an adhesive. Debonding of single lap joints was examined by immersion in a mixed solvent of dimethylformamide (DMF) and ethylene glycol (EG). The finite element method using the cohesive zone model accurately predicted the failure load of all similar and dissimilar bonded joints is accurately predicted by finite element method using cohesive zone model (CZM). Design parameters, overlap length of 40 mm, and adhesive thickness of 0.35 mm were found to be optimum for a higher bonding strength of 11 MPa. The failure of similar and dissimilar joints occurred at the adhesive interface; however, the GFRP-GFRP joints underwent a mixed mode of failure, which implies a strong bond between the GFRP substrate and adhesive. A successful demonstration of the debonding of bonded joints through immersion in a mixed solvent within 2 h occurs at 150 ℃, which enables the reuse of substrates for other structural applications, contributing to a circular economy.
Additive manufacturing enables fabrication of porous piezoelectric ceramics with spatially controlled microstructure, allowing tailoring of their functional properties. In piezoelectric bimorphs, thickness-wise grading of porosity provides an additional design variable for performance enhancement. Porous piezoelectric layers are modeled as two-phase composites with material properties depending on porosity. An applied theory of a functionally graded bimorph with quadratic electric potential distribution is developed. Two optimization problems are solved using a genetic algorithm for PZT‑4 ceramics: maximization of the first natural frequency and maximization of quasi-static deflection. Three classes of porosity distribution functions are considered: linear, quadratic, and piecewise linear. In all cases, piecewise linear functions outperform linear and quadratic distributions. The obtained results demonstrate that simple non-smooth porosity profiles can provide better electromechanical performance than smooth distributions. For the first natural frequency, the optimal piecewise linear distribution increases the frequency from 6992 Hz (homogeneous case) to 7663 Hz (≈10
An analytical approach is presented to evaluate the time-varying meshing stiffness (TVMS) of silicon carbide (SiC) nanoparticle-reinforced aluminum composite helical gears. The method combines a layer-wise discretization scheme with the potential energy formulation. The effective elastic parameters of each layer are determined using the Halpin-Tsai model, enabling the influence of microstructural characteristics to be incorporated into the stiffness calculation. The proposed approach provides accurate predictions of meshing stiffness and captures the effects of reinforcement distribution. The results show that the spatial distribution and content of SiC nanoparticles significantly influence stiffness behavior. The study establishes a link between material design and gear dynamic characteristics and offers a practical solution for the analysis and design of composite gear systems.
This study examines the propagation of horizontally polarized shear (SH) waves in a fiber-reinforced composite (FRC) structure consisting of two conventional membranes separated by a mechanical spring layer and attached to an FRC half-space. A mathematical model is formulated to derive the dispersion relation, and numerical analysis is performed to evaluate the effects of membrane stiffness, anisotropic shear properties, mass density, and spring constant on wave behavior. The results are compared with single-membrane and unreinforced configurations to understand the influence of reinforcement and interfacial design. The model is validated with existing results from the literature, showing good agreement. It is observed that the dual membrane configuration significantly improves wave stability, reducing phase velocity variations by up to 45 times for membrane’s elastic constant and 6 times for membrane’s density, compared to the single membrane structure. These findings demonstrate the significance of multi-layered interfaces in modifying wave characteristics and offer practical insights for designing advanced composite structures for applications in waveguiding, vibration control, and ultrasonic sensing.
The rising demand for sustainable engineering materials has led to the need to develop environmentally friendly polymer composites from agricultural wastes. This in-depth research investigated the tribological characteristics of polyester hybrid composites reinforced with bagasse fiber and pinewood dust through an integrated experimental and computational framework. Hybrid composites were prepared using the hand-lay-up method, and the bagasse fiber loading was fixed at 5 wt.
