Bin Yang

Gearboxes, as essential components of mechanical transmission systems, are extensively used in aerospace, automotive, and marine engineering. However, they are susceptible to shock and vibration under external impacts and complex operating conditions, necessitating effective energy dissipation solutions. Shear thickening fluid (STF), a non-Newtonian fluid characterized by remarkable impact resistance and energy dissipation capacity, was employed in this study to develop a novel shock absorber incorporating countersink damping holes. This design utilizes both the intrinsic energy dissipation of STF and the additional frictional dissipation induced by the countersink structure. The energy absorption mechanism of the STF-based shock absorber was investigated through compressive and impact tests. The absorber was integrated into a gearbox impact isolation system, and its maximum isolation efficiency reaches 86% under shock resistance tests, demonstrating the STF-based shock absorber’s high impact mitigation capability. This work proposes a structural enhancement for STF-based shock absorbers used in the gearbox system and validates their practical applicability in dynamic mechanical protection systems.

In aerospace applications, composite grids have been widely utilized to enhance the strength of large thin-shell components. Recently, a growing focus has been on the research of 3D printing continuous fiber-reinforced thermoplastic composites. The 3D printing method offers various advantages over traditional molding processes, including a simpler process, higher material utilization, and lower manufacturing costs. However, the use of 3D printing for manufacturing continuous fiber-reinforced composite structures presents challenges, such as a high occurrence of defects within the structure and insufficient mechanical properties. These limitations hinder its widespread application. To address these issues, this study proposes a method for treating 3D-printed composite grid structures using induction heating. Initially, the induction heating mechanism of 3D-printed composite grids was analyzed by studying the impedance at the junction, including direct contact resistance and dielectric hysteresis loss. Subsequently, the impact of induction heating treatment on internal defects was explored by observing micro morphologies. The results show that the combination of induction heating and vacuum pressure effectively reduces porosities within the 3D-printed carbon fiber composite grids. Additionally, 3D-printed composite grid-stiffened PLA structures were fabricated with induction heating, and the bending and impact tests were conducted to evaluate their mechanical properties. The results indicate that using a grid-unit size of 4 mm leads to significant increases in bending strength and modulus of the grid-stiffened structure, with improvements of 137.6% and 217.8%, respectively, compared to the neat PLA panel. This demonstrates the exceptional mechanical enhancement efficiency of the 3D-printed lightweight composite grids.

Shear thickening fluid (STF) is a dense colloidal suspension of nanoparticles in a carrier fluid in which the viscosity increases dramatically with a rise in shear rate. Due to the excellent energy absorption and energy dissipation of STF, there is a desire to employ STFs in a variety of impact applications. In this study, a comprehensive review on STFs’ applications is presented. First, several common shear thickening mechanisms are discussed in this paper. The applications of different STF impregnated fabric composites and the STF’s contributions on improving the impact, ballistic and stab resistance performance have also been presented. Moreover, recent developments of STF’s applications, including dampers and shock absorbers, are included in this review. In addition, some novel applications (acoustic structure, STF-TENG and electrospun nonwoven mats) based on STF are summarized, to suggest the challenges of future research and propose some more deterministic research directions, e.g., potential trends for applications of STF.

This study presents a finite-element (FE) model considering intralaminar damage and interlaminar delamination to predict the biaxial compression behavior of carbon fiber–reinforced composites (CFRCs) with low-velocity impact damage. First, the FE model was validated by a uniaxial compression experiment. The FE predictions in terms of compression after impact (CAI) strength and failure patterns were consistent with the experimental results. Then the validated FE model was used to predict the biaxial compression behavior of the CFRCs. It was found that the residual strength of the CFRCs was dependent on the buckling mode of the laminate due to the coupling effect of the longitudinal and transverse compressive loadings. Correspondingly, the CAI strength under biaxial compression was lower than that under longitudinal or transverse compressive loading.

This work develops nature‐inspired tough helicoidal composites with aligned short carbon fibers by 3D printing. The alignment of short carbon fibers (SCF) in the composite is achieved by shear flow during 3D printing process. First, unidirectional composites with aligned SCFs are prepared with various fiber contents ranging from 2 wt% to 10 wt%. It is found that the shear strength of the unidirectional composites with the SCFs perpendicular to the shear loading is the highest at a fiber content of 10 wt%, 46% higher than that of the pristine nylon. Then, helicoidal composites with four helical angles (i.e., 0°, 30°, 45° and 90°) are prepared using 3D printing. The impact testing results show that the impact toughness highly depends on the build orientation. The impact toughness of the composites with on‐edge build orientation is significantly greater than those with flat build orientation. The greatest impact toughness of the helicoidal composites is achieved at a helical angle of 45° with a value of 31.9±4.4 kJ m⁻², which is mainly attributed to misaligned fiber plane‐induced crack deflection, forcing cracks to advance in multiple planes under impact.