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Background: In vitro assessment is mandatory for artificial heart valve development. This study aims to investigate the effects of pulse duplicator features on valve responsiveness, conduct a sensitivity analysis across valve prosthesis types, and contribute on the development of versatile pulse duplicator systems able to perform reliable prosthetic aortic valve assessment under physiologic hemodynamic conditions. Methods: A reference pulse duplicator was established based on literature. Further optimization process led to new designs that underwent a parametric study, also involving different aortic valve prostheses. These designs were evaluated on criteria such as mean pressure differential and pulse pressure (assessed from high‐fidelity pressure measurements), valve opening and closing behavior, flow, and regurgitation. Finally, the resulting optimized setup was tested under five different hemodynamic settings simulating a range of physiologic and pathologic conditions. Results: The results show that both, pulse duplicator design and valve type significantly influence aortic and ventricular pressure, flow, and valve kinematic response. The optimal design comprised key features such as a compliance chamber and restrictor for diastolic pressure maintenance and narrow pulse pressure. Additionally, an atrial reservoir was included to prevent atrial–aortic interference, and a bioprosthetic valve was used in mitral position to avoid delayed valve closing effects. Conclusion: This study showed that individual pulse duplicator features can have a significant effect on valve's responsiveness. The optimized versatile pulse duplicator replicated physiologic and pathologic aortic valve hemodynamic conditions, serving as a reliable characterization tool for assessing and optimizing aortic valve performance. [ABSTRACT FROM AUTHOR]

In liquid composite molding (LCM) processes such as resin transfer molding (RTM), particle distribution can be problematic as the particle fillers can be filtered by the reinforcement fibers during the resin infusion process. In this paper, the filtration of alumina and silica nanoparticles in the production of aramid fiber epoxy composites is characterized. The laminates are produced by in-plane RTM and the effects of selected process variables on the laminate particle distribution are investigated. The objective is to evaluate the assumption that nanoparticles due to their small physical size inherently do not filter in resin infusion processes. The nanosilica particles are found to effectively not filter, while the nanoalumina particles are much more sensitive to filtration as they formed microscale agglomerates as small as a few microns in size prior to injection. The filtration behavior follows a simple theoretical model for micro-scale particle filtration, already existing in the literature. For the filtration sensitive particles, it was found that the filtration is influenced by the preform fiber volume content. Other common process variables such as resin viscosity, particle concentration in the injected resin, and saturated resin flow time (resin overflow volume) are found to be filtration independent and do not change the filtration behavior. POLYM. ENG. SCI., 59:22-34, 2019., INTRODUCTION In liquid composite molding (LCM) processes, a resin matrix is injected into a fibrous reinforcement. Particle fillers are often added to the matrix to enhance or provide additional properties [...]

Shape memory alloys (SMA) allow for the realization of smart actuators capable of achieving large stresses and large strains but highly demanding in terms of power input. This work presents a solution integrating shape memory polymers (SMP) in a novel type of selectively compliant actuator to reduce the power input of SMAs. The thermally induced variation in stiffness of the SMP is used to achieve large deformations by temporarily increasing the compliance of the actuator and to lock the actuator in a deformed state by restoring the initial stiffness. The behavior of the actuator is simulated taking into account the viscoelastic behavior of the SMP and validated through a comparison with experimental results. The latter show that the proposed actuator can achieve a maximum contraction of 3.0% and hold a contraction of about 1.6% multiple times without constantly powering the SMA. Finally, a reconfigurable sandwich panel is considered as possible application. A distributed actuator network is implemented in the face sheets of the panel and a digital image correlation system is used to prove the capability of the proposed structure of undergoing large deformations, holding a deformed shape without consuming energy, and recovering its initial shape. A further development of this panel might find application as support structure for morphing aerodynamic surfaces or reconfigurable antennas. [ABSTRACT FROM AUTHOR]