This study investigates the quality of self-piercing riveted joints between vibration-damping aluminum (Al) and other dissimilar materials, namely aluminum alloy (AL5052-H32), steel alloy (GA590DP), and carbon-reinforced plastic (CFRP). The effects of die types (flat, cone, and nipple) on the geometrical characteristics and mechanical performance of the joints are studied using a cross-section examination and tensile shear load testing. The failure modes of each joint are also presented, showing the nature of the forces leading to the joint failures. The results indicate that, for all configurations, adequate joining between vibration-damping Al with AL5052-H32 is expected with a maximum shear load up to 3.28 kN. A shear load up to 3.6 kN was measured for the joints with GA590DP panels with acceptable top and bottom seal characteristics. A vibration-damping Al panel can only be positioned at the bottom when riveting with CFRP due to the brittle nature of CFRP. A tensile shear load up to 2.26 kN was found, which is the lowest amongst the materials tested in this study.

Directional sound beam forming is an area of interest in practical acoustic applications where leaky-wave principles and techniques may provide efficient solutions. Here, we present a type of high-gain acoustic leaky antenna used for acoustic beamforming using an admittance-modulation metasurface which consists of periodic subwavelength grooves with sinusoidal depth profiles. The acoustic metasurface converts the surface waves into far-field radiating waves forming a high-gain surface wave antenna. We numerically and experimentally demonstrate far-field propagation angles of −30°, 0°, and 30° at 19 300, 22 000, and 23 900 Hz, respectively, and show that the radiation angle and beamwidth can be independently controlled by modulating the sinusoidal profile. Also, we use a Laser Doppler Vibrometer to directly measure the surface wave damping along a circular sinusoidally modulated admittance surface (SMAS).

In this study, we present improved fusion-bonding strength results between carbon fiber-reinforced polyetheretherketone (CFR-PEEK) and zinc-coated steel through the introduction of pre-inscribed laser surface patterns. Optimized laser welding parameters, including laser power, focal position, pitch, number of passes, and clamping pressure, are presented along with parameters for producing the rectangular laser patterns. It was found that for the optimized parameters, the tensile shear strength of the welded samples is improved by as much as 100% when pre-inscribed laser patterns are present. Detailed SEM images of the fractured fusion welded joint samples after the tensile shear test are presented for analysis. The tight bonding between the polymer matrix and the zinc-coated steel inside the formed grooves is found to be the main reason behind the increased tensile shear strength. A comparison of the tensile shear loads for various joining methods is also presented and discussed.

Carbon plugging of active catalytic sites significantly degrades the performance of the hydrocarbon reformers. In this study, we show that small amount of Ir alloyed to Ni/CeO2 nanoparticle exhibit promising improvements to the carbon tolerance properties. XRD analysis indicates that the synthesized nanoparticles are comprised of independent NiO and CeO2 particulates and that the added Ir atoms tend to stay on the surface consistent with the theoretical calculation results of the proposed Ir-Ni alloy. The Ir rich samples show higher methane cracking rate and better carbon removal characteristics. Also, the CO selectivity result shows that adding Ir can prolong the lifetime of the Ni active sites despite a slight drop in the initial partial oxidization reforming rate. Our findings highlight the enhancement effects of Ir on the Ni-based metal carbon tolerance properties and bring us one step closer to finding a solution for the carbon plugging problem.