Shaker A. Meguid

1. Whiplash injuries continue to be one of the most prevalent consequences of rear-end vehicle collisions. Despite the enormous amount of research conducted to understand whiplash injury mechanisms...

Smart composite laminates (SCLs) integrated with piezoelectric materials enable sensing and actuation for adaptive structural applications. In previous studies, the authors developed a fully coupled nonlinear finite element framework incorporating geometric nonlinearity and temperature-dependent material properties. Specifically, our earlier work investigated baseline responses and conducted parametric studies on patch size, number, and placement under simplified conditions. The present work extends this framework to systematically examine the thermo-electro-mechanical behavior of SCLs with distributed piezoelectric patches under combined thermomechanical loading. Particular emphases are placed not only on evaluating the performance of different SCL configurations of continuous laminates and distributed patch arrays, but also across the three operating modes of the smart structure: self-sensing, open-loop and closed-loop control. Our findings reveal that thermal effects significantly influence both the structural response and sensor output, while distributed patches provide enhanced spatial sensing resolution and more effective localized actuation. Increasing patch number improves shape control performance, especially under non-uniform loading. These findings extend prior modeling efforts to more realistic operating conditions and provide a comprehensive framework for the design of adaptive composite structures.

In this paper, the transient thermomechanical response of bilayered GDZ/YSZ thermal barrier coating (TBC) and the role of interphase regions in this multilayer system are investigated. A coupled transient finite volume–finite element (FV–FE) framework is employed to model the thermomechanical response of both single-layer (GDZ, YSZ) and bilayered GDZ/YSZ coatings, accounting for thermal cycling, bond coat oxidation, and temperature-dependent material properties. The effects of coating configuration and material properties on the evolution of residual stresses are systematically examined. In addition, molecular dynamics (MD) simulations are utilized to characterize the thermomechanical properties of interphase regions, particularly at the GDZ/YSZ interface. The results reveal that larger direct stresses, [Formula: see text], develop in single-layer GDZ coatings compared to YSZ due to the greater thermal mismatch with the substrate. In both GDZ and bilayered GDZ/YSZ topcoats, the location of peak residual stresses shifts from the peak to the valley of the surface undulation during thermal cycling. Furthermore, the stresses within the GDZ layer of the bilayered system show limited variation with thermal cycling, indicating a shielding effect provided by the underlying YSZ layer. Insights from MD simulations suggest that the GDZ/YSZ interphase exhibits reduced stiffness and thermal conductivity relative to the bulk materials, which may contribute to local compliance and influence stress redistribution within the coating system.

Electropulsing induces intense Joule heating in metallic materials, particularly in the presence of defects that disturb electric current flow. In this study, a coupled electro-thermo-mechanical finite element model is developed to investigate the transient elastic response of a titanium plate containing an elliptical inhomogeneity subjected to high-density pulsed electric currents. The effect of the inhomogeneous geometry, electrical pulse characteristics, and inclusion material properties is systematically examined within an elastic framework. The results show that cavities and insulating inclusions cause pronounced current density concentration at the inhomogeneity tips, leading to localized Joule heating and severe thermal stresses that intensify with increasing aspect ratio. Solid inclusions, on the other hand, significantly mitigate peak temperature and stress levels compared to cavities due to enhanced heat conduction and mechanical support. Among the inclusion properties considered, our work shows that the electrical resistivity plays a dominant role in governing current redistribution, temperature rise, and stress evolution. These findings provide mechanistic insight into Joule heating-defect interactions under electropulsing and establish an elastic baseline response, which serves as a foundation for subsequent investigations incorporating elasto-plastic material behaviour.

The release of a blade, hereafter referred to as a blade-out event, in an aviation gas turbine engine (GTE) represents a serious safety hazard. Such an event can result in severe dynamic imbalance, engine failure, and potential fire hazards. Full-scale blade-out testing of GTEs is extremely costly, hazardous, and time-consuming. To address these challenges, we developed a novel, instrumented, scaled-down test rig to perform multiple blade-out tests using dynamic similarity principles based on Buckingham’s theorem. In this design, the rotating disk assembly comprises sixteen pre-twisted blades, each 50[ ]mm in length and attached via dovetail roots. Both the blades and disk are composed of Polyamide 12 and were fabricated using the powder bed fusion of polymers with laser beam (PBF-LB/P), a 3D additive manufacturing technique that employs high-power lasers to fuse fine powder materials into solid structures with complex geometries. The application of PBF-LB/P was crucial for achieving accurate, rapid, and cost-effective manufacturing of the blades, allowing numerous blade-out tests to be performed efficiently. This is particularly significant since blade-out tests typically cause extensive damage not only to the released blade but also to the trailing blades. The use of PBF-LB/P therefore enabled the execution of a large number of blade-out tests, the results of which were compared with finite element (FE) simulations of blade release in real GTEs. The findings demonstrate excellent agreement between the two approaches, confirming that the scaled-down rig can accurately capture the trajectories of released blades and their interactions with trailing blades.