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Polyurea (PUR) has been widely used as a protective coating in recent years. In order to complete the understanding of the relationship between PUR microstructure and its energy absorption capabilities, the mechanical and dynamic performance of PURs containing various macrodiol structural units were compared using material characterization techniques and molecular dynamic simulation. The results showed that the PUR polycarbonate diols formed as energy absorbing materials showed high tensile strength, high toughness, and excellent loss factor distribution based on the comparison of stress–strain tensile curves, glass transition temperatures, phase images, and dynamic storage loss modulus. External energy from simple shear deformation was absorbed to convert non-bond energy, in particular, based on fractional free volume, interaction energy, and total energy and hydrogen bond number change from the molecular dynamic simulation. Hydrogen bonds formed between soft segments and hard segments in the PURs have been proven to play a significant role in determining their mechanical and dynamic performance. The mechanical and dynamic properties of PURs characterized and tested using experimental techniques were quantified effectively using molecular dynamic simulation. This is believed to be an innovative theoretical guidance for the structural design of PURs at the molecular level for the optimization of energy absorption capabilities. [ABSTRACT FROM AUTHOR]

Lightweight lattice structure is of great significance in the fields of aerospace thermal protection and energy absorption. In this study, compressive properties and energy‐absorbing characteristics of additively manufactured body‐centered cubic (BCC) lattice structures of a high‐temperature titanium matrix composite (TMC) are investigated systematically. It is found that compressive strength increases monotonically as either lattice strut diameter or temperature increases. With lattice strut diameter increasing from 1.0 to 1.5 and 2.0 mm, strength increases from 78 to 94 and 108 MPa at room temperature (RT) and from 71 to 104 and 123 MPa at 650 °C. Unexpectedly, specific energy absorption (SEA) capability increases as strut diameter decreases, although also increases as temperature increases. BCC lattice structure with a strut diameter of 1.0 mm presents the highest SEA being up to 13.7 MJ m−3 at RT and 142 MJ m−3 at 650 °C. And sphericizing the lattice nodes is found incapable of enhancing strength and SEA. Besides, numerical simulation is used to demonstrate the compressive stress and strain fields, in order to explain the fracture modes and SEA capability of individual BCC lattice structures. This study provides deep insights into the mechanical properties and energy absorption behavior of additively manufactured lattice structures of TMCs. [ABSTRACT FROM AUTHOR]

The energy-absorption mechanism of nanofluidic systems is being investigated under dynamic cases, represented by the split Hopkinson pressure bar experiment. However, the cost of this cannot be ignored. Therefore, numerical simulation is playing an increasingly important role in optimizing the split Hopkinson pressure bar experimental technology and analyzing its accuracy. In this paper, a three-dimensional finite element simulation model of the split Hopkinson pressure bar experimental devices was proposed to analyze the energy-absorption capabilities of nanofluidic-system-filled tubes. The reliability of this methodology was discussed in terms of model construction, model validation and potential application, indicating the simulation methodology is applicable to further investigation and can provide a reference for engineering practice. The simulation results showed that the infiltration pressure and the mass ratio of solid to liquid determine the post-buckling compression stress and the effective compression stroke, respectively. [ABSTRACT FROM AUTHOR]

• The Fused Deposition Modeling (FDM) method was used to manufacture the specimens. • The energy absorption capabilities of sandwich structures with different core topologies and various numbers of inner cells were investigated. • The influences of the thermal aging durations on the energy absorption performances of sandwich structures were studied. • Quasi-static three-point bending tests were conducted and mechanical properties of sandwich structures were evaluated. • The energy absorption performance of sandwich structures generally decreased with increasing thermal aging duration. In recent years, the Fused Deposition Modeling (FDM) method has been employed in the production of small-scale structural elements with moderate loads, such as small-unmanned aerial vehicles, sports equipment, dental implant molds, and similar applications. In these cases, the FDM technique can utilize polymers like Polyamide (PA), Polylactic Acid (PLA), and Acrylonitrile Butadiene Styrene (ABS) to manufacture structural components. Lightweight sandwich structures are utilized as structural elements in various industries due to their unique characteristics, high stiffness-to-weight ratio, and energy absorption capabilities. Although the number of studies on the mechanical properties of sandwich structures manufactured with FDM has increased in recent years, experimental data on the mechanical characteristics of sandwich structures manufactured with FDM under different thermal aging durations are still insufficient. Driven by this motivation, the energy absorption capabilities of sandwich structures with different four core geometries (i.e., circular, hexagonal, square, and triangular) were experimentally investigated under different thermal aging durations. The sandwich structures were manufactured from PLA material by the FDM method. Four different thermal aging durations, 0, 15, 30 and 45 days, were considered for environmental conditions. Quasi-static three-point bending experiments were conducted to assess the energy absorption capability of lightweight sandwich structures featuring diverse core topologies. The bending test results demonstrate that the core topology significantly affects the energy absorption abilities of sandwich structures. Moreover, fractographic analysis using scanning electron microscopy (SEM) was conducted to gain deeper insights into the impact of thermal aging on aged specimens. In addition, it was concluded that the energy absorption performances of all sandwich structures with different core structure topologies were adversely affected by increasing the thermal aging time. [Display omitted] [ABSTRACT FROM AUTHOR]