Brewing sustainability and strength: biocomposite development through tea waste incorporation in polylactic acid

This study aims to enhance the mechanical properties of polylactic acid by incorporating black tea waste as an economical and sustainable additive capable of being recycled. The black tea waste, after the hot water color removal process, is milled to a fine and uniform powder size. The combination of these particles with polylactic acid is carried out using a twin-screw extruder. Specimens of pure polylactic acid and biocomposites containing 3 and 5 wt% black tea waste are manufactured using a hot press machine at a temperature of 200 °C. The filaments are also successfully extruded for three-dimensional printing purposes. Scanning electron microscopy images reveal that in the polylactic acid-3% tea biocomposite, the tea particles are appropriately dispersed within the polylactic acid matrix. The tensile test results indicate that biocomposite polylactic acid-3% tea has the highest mechanical properties, with a tensile strength of 67 MPa, demonstrating a 34% increase compared to polylactic acid. Furthermore, the biocomposite of polylactic acid-3% tea waste exhibits the best performance with a fracture energy of 2.5 kJ/m 2 in the impact test. Hence, polylactic acid-3% tea biocomposite can be recommended as a suitable sustainable substitute. Finally, numerical simulations are performed on biocomposites containing double keyhole notches. This analysis is conducted to observe the behavior of biocomposite models with double keyhole notch under mixed-mode loading. The critical fracture load of the models is calculated using the strain energy density criterion. It is observed that an increase in the notch inclination angle and notch radius leads to a decrease in the fracture load in the models

Semi-active viscous damper for seismic response control

- Semi-active devices offer significant promise for their ability to add supplemental damping and reduce seismic structural response in an easily controllable manner, and can be used in some modes to modify or reshape hysteretic structural response. However, many current semi-active devices are highly complex, limiting robustness, while those that can generate larger forces suffer from increased response lag time to do so. Thus, an ideal semi-active device would offer high forces, low complexity, and fast response. Semi-active viscous dampers could offer all these properties given the widespread high force use of viscous dampers in large vehicles and other applications. Such a simple, well-known device used semi-actively to reshape hysteresis could bring the real application of such devices far closer to a reality.To demonstrate the efficacy of the proposed devices, they are installed in a bi-linear elastic structure. Three earthquakes from the medium suite of the SAC project is used to compare two device control laws individually or in combination to sculpt structural hysteretic behavior.Performance is assessed by evaluating maximum displacement (Sd), total base-shear (Fb) and maximum acceleration (Sa) indicative of structural, foundation and content damage, respectively. Results show that, the reduction in terms of displacement, base-shear and acceleration demand is only available with the semi-active 2-4 control method.Overall, these results indicate the robustness of potentially very simple and robust semi-active viscous dampers to mitigate the risk of seismic damage to both the structure and foundation in a way that is economically suitable for either new designs or retrofit.