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In this study, carbon fiber reinforced polymer matrix composites were produced to investigate the trigger effect on energy absorption performance. Production was carried out by vacuum infusion method. Three types of trigger geometry were opened on the composite crash boxes produced and also comparison sample without trigger was prepared. The quasi-static compression tests of these four different samples were carried out and the energy absorption performances of the samples were evaluated with the obtained data. In addition, the damages of the samples were examined, and it was revealed how they changed with the trigger. Accordingly, the sample described as S-2, (the triggered sample, which consists of four symmetrical slits downwards from its upper surface) exhibited the best performance in terms of absorbed energy. Additionally, the peak forces were reduced with the triggers opened and the maximum peak force decreases were seen in S-3(with hole type triggers) and S-4 (with horizontal slit type triggers) samples. [ABSTRACT FROM AUTHOR]

Auxetic structures, which is a term used to describe materials with a negative Poisson's ratio, show beneficial properties like a low density, a high energy absorption capacity and an increased indentation resistance. This enables applications in many fields, such as aerospace and sports industries. Given their potential, many studies have already been conducted. Previously, the geometry of a selected auxetic re-entrant structure was optimized to maximize its mass-specific energy absorption capacity for ideal usage in lightweight applications. Moreover, a homogeneous material was used, whereas the combination of multiple materials could drastically increase the performance of such structures. Hence, in this study the use of two different materials combined into a modified re-entrant structure is investigated via Finite Element simulation. The Poisson's ratio could thus be improved, which leads to a more pronounced and longer lasting auxetic effect. [ABSTRACT FROM AUTHOR]

We have performed systematic molecular dynamics simulations to study the deformation behavior of a single crystal structure and a core-shell Cu@Ni nanoporous (NP) structure under shock loading for a wide range of shock intensities. Our results suggest that the core-shell structure exhibits less volume compression than the single crystal NP structure by virtue of its enhanced mechanical strength and associated interfacial strain-hardening under shock loading. The core-shell NP structure also demonstrates an increased shock-energy absorption efficiency of around 10.5 % larger than the single crystal NP structure because of its additional Cu/Ni interface. The mechanisms of shock-induced deformation are observed to vary greatly with shock intensity. Pores are observed to collapse partially in both NP structures at very low shock intensity, u p ≤ 0.15 km/s. Complete collapsing of the pores through plastic deformation followed by direct crushing and formation of internal jetting and hot-spot have been observed at higher shock intensities. The evolution of microstructure and the underlying mechanisms operating at different shock intensity regimes have been investigated in this article. At a shock pressure of ∼ 6.05 GPa, i.e., u p = 0.75 km/s, the shock-induced deformed microstructure of both NP structures recovered through dynamic recrystallization. The postshock dynamic recrystallization has been observed to be mediated through rapid relaxation of shear stress followed by atomic rearrangements. [ABSTRACT FROM AUTHOR]

In this paper, using a sputtering technique, ZnO, and AZO, CZO, and CAZO films at room temperature (RT) were prepared and then they were annealed at 500 °C in an argon atmosphere. In as deposited films, CZO films have maximum value and for films annealed at 500 °C, CZO films have maximum value the optical density. It is found that the CAZO films have maximum value cavity obtained from the bearing area. Due to decreasing oxygen vacancies in the CAZO films, x–y fluctuations in these films have minimum value. The distributions of nanoparticles on the CAZO films annealed at 500 °C were more uniformity. The CZO films were more order. We observed that the edge absorption energy in the CAZO films annealed at 500 °C have maximum value. Average oscillator wavelength λo in the CAZO films annealed at 500 °C have minimum value of 0.09 μm. [ABSTRACT FROM AUTHOR]

Currently, the presence of spurious microwave radiation is increasing in the environment, which has caused concern due to possible health problems in living beings and electromagnetic interference in electronic systems. To control this problem, studies in the materials area are taking place, aiming to attenuate the spurious radiation and meet requirements of good performance in broadband, low cost and low weight. The present work aimed to study Cu and Ni nanometric films with thicknesses of 65 and 200 nm, deposited on polyethylene terephthalate substrate by magnetron sputtering. Scanning electron microscopy with a field emission gun (FEGSEM) showed that the films produced have different morphological textures, due to the parameters used in the sputtering process and also the free energy of metals. Impedance spectroscopy measurements showed that the films have low conductivity values, due to the metallic oxides formed on the film surfaces, confirmed by X-ray diffraction, and also to the presence of defects. Electromagnetic characterization (8.2 - 12.4 GHz) showed that the Cu and Ni thin films had low performance, except the Ni_200 nm film, which showed a total shielding efficiency of about 30% in broadband. This result is promising considering the nanometric thickness of the Ni film. [ABSTRACT FROM AUTHOR]

The dynamic mechanical properties and dynamic energy absorption capacity of marine sandy clay, which was stabilized by cement with partial substitution of alkali-activated metakaolin (AAMK) and discrete polypropylene fibers, were experimentally investigated at strain rates of 80-280 s-1. The AAMK, as partial replacement of cement, is eco-friendly and economical, and polypropylene fibers with corrosion resistance can withstand severe environmental conditions. Dynamic mechanical properties of 16 different mix ratios were experimentally examined via split Hopkinson compression pressure bar (SHPB) tests. Typical macroscopic post-impact fragment patterns I and II were observed in dynamic stress-strain curves and macroscopic fragmentations. The results confirmed an obvious enhancement in the dynamic compressive strength and energy absorption density due to the use of cement with partial substitution of AAMK and the addition of polypropylene fibers and sand. Based on scanning electron microscopy (SEM) tests and nuclear magnetic resonance (NMR) tests, cemented sandy clay specimens treated with 0.2% fiber contents or higher exhibited a denser network of soil particles with hydration products. The connection mechanism and typical interface between fiber-sand-hydrate-sandy clay particles were observed via SEM tests. Furthermore, an optimal mix ratio was proposed to satisfy the demands of high dynamic mechanical properties, energy absorption capacity, and economic and environmental constraints. The optimal mix ratio corresponded to 0.2% fiber content or higher and sand content of up to 16%. Additionally, it was observed that the dynamic compressive strength of samples with 0.1% fibers or less deteriorated. Based on absorption energy density and failure modes analysis, the fiber content should be higher than or equal to 0.2% to effectively reduce the degree of fragmentation and increase the size of fragments. [ABSTRACT FROM AUTHOR]

Liquid flow in nano-environment has been utilized as an advanced mechanism of energy absorption. While the process of liquid outflow from nanopores has been shown to have a significant effect on the system's energy absorption efficiencies, its mechanism remains poorly understood. Here, we have studied the liquid defiltration behavior of liquid nanofoam (LN) systems by controlling the infiltration depth. The LN samples, composed of a different non-wettable liquid phase and hydrophobic nanoporous silica with wide pore size distribution, have been compressed in two different loading modes under the quasi-static condition, i.e., the single-step compression and consecutive-step compression. Considerably different mechanical behaviors have been observed in these two loading modes, suggesting that the liquid outflow from nanopores is determined by the critical infiltration depth D*. The nanopore size effect on D* is further studied by a consecutive-step cyclic test. It has been shown that D* increases as the pore size gets smaller, which is related to gas solubility and diffusion rate in the nano-environment. The electrolyte concentration and temperature dependences of the critical infiltration depth have also been investigated. These findings provide a better understanding of the liquid outflow from nanopores and can be exploited to facilitate the design of next-generation reusable energy absorption systems. [ABSTRACT FROM AUTHOR]

Metallic nanoparticles with large photo-thermal conversion capabilities have significant implications for solar absorption coatings. In this work, we develop a calculation model to analyze crowding effects on energy absorption, including effects of nanoparticle radius, size distribution, interparticle spacing, and spatial distributions in a plane. There is an optimal nanoparticle radius that maximizes energy absorption, which is different for different media, for example, 45 nm for air and 30 nm for water. For regular distributions of nanoparticles in a plane, a hexagonal lattice with an interparticle distance of about 315 nm is optimal for solar-thermal conversion. We expect these results to be useful for designing solar absorption coatings with high photo-thermal conversion efficiencies. [ABSTRACT FROM AUTHOR]

Plastic film has been widely used as one of the most important materials in various agricultural fields, due mainly to the chemical stability, thinness, and light properties. At the same time, the mechanical properties of plastic film can be the main research direction of film structure design in recent years. In this study, the experiment and numerical simulation were carried out for the damage analysis of plastic film under the hail impact. Among them, the air cannon test device was used to analyze the failure form and damage law of plastic film under hail impact. A high-speed camera and laser speed meter were then utilized to record the deformation process and energy absorption of plastic film that impacted by the ice ball. The finite element method (FEM) was also selected to evaluate the structural parameters of plastic film using ABAQUS software. The error analysis was performed on the failure area and the energy absorption of the plastic film, in order to verify the effectiveness of the numerical simulation. There was the relatively small error of the experimental and numerical simulation, indicating the better performance of the simulation. The plastic film under ice ball impact was also analyzed as follows. Firstly, the different sizes of the ice ball were selected to evaluate the impact angles of the ice ball impact plastic film. Secondly, the simulation was carried out in the the single and secondary impact of the ice ball impact on the plastic film. Finally, the ice ball impact plastic film was simulated with the different thicknesses and ice impacting double-layer plastic film with different distances between layers. The failure form and energy absorption of the plastic film were achieved in the better performance after numerical simulation. The following results were obtained: 1) The plastic film with the 0.12 mm thickness efficiently resisted the impact of hail with a diameter of less than 10 mm. Once the hail size was more than 30 mm, the plastic film was damaged rapidly, due to the action of the tensile stress wave. In addition, there was the larger damaged area that caused by the ellipsoidal hockey ball impact plastic film than that by the spherical one. 2) The secondary impact of the ice ball on the plastic film caused the superposition of stress waves, leading to the accelerated destruction of the film. 3) The largest damaged area of the film was observed, when the ice ball impact angle was 60° at the ice ball impact angle of 0°, 30° and 60°. 4) The damaged area of the double-layer film greatly increased with the increase of the distance between the plastic films. The anti-hail impact effect of the double-layer plastic film was better than that of the single-layer plastic film with the same thickness, when the distance between the double-layer plastic films was controlled within 5 mm. Therefore, the numerical simulation can be used to analyze the damage of plastic film under the impact of the ice ball. The tensile strength of plastic film can also be improved the better ability of hail impact resistance. This finding can provide a strong reference for the structural design and damage analysis of thin films. [ABSTRACT FROM AUTHOR]

Rock bolting technique is an important reinforcement measure in the geotechnical engineering practice. New rock bolts have been continuously emerging through the development of rock supporting technology. Complex conditions, such as high crustal stress, extremely soft rock, and strong mining disturbance often occur in the deep mining, resulting in large deformation of the surrounding rock masses. Since the deformation of traditional rock bolts is generally below 200 mm, failure often occurs to the rock bolts because of insufficient deformability. To effectively control the large deformation of surrounding rock masses caused by complex conditions, it is necessary to develop large deformation rock bolts with high constant resistance, also called energy-absorbing bolts. This paper systematically reviews the development of large deformation rock bolts and the structure, energy absorption mechanism, anchorage performance, and mechanical properties of several typical large deformation rock bolts. The advantages and disadvantages of existing large deformation rock bolts are compared and the concept of constant resistance large deformation support is introduced. [ABSTRACT FROM AUTHOR]

In the present study, Energy Absorption Buildup Factor (EABF) and Exposure Buildup Factors (EBF) of the CR-39 and Trivex optical lenses are calculated by using the Geometric Progression (GP) fitting method based on ANSI/ANS-6.4.3 database. The study analyses comprehensively for different penetration depths within the energy range of 0.015 - 15 MeV up to 40 mfp. The buildup factors are calculated in the examined materials depending on the photon energy that arrives, the penetration depths, and the chemical composition of the material reach at maximum values in the energy region where inconsistent scattering interaction probabilities are intensive. The results show that the CR-39 optical lens had better radiation shielding performance. The suitability of the results is compared with the powerful software tools (EPICS2017 and Phy-X/PSD), which are preferred frequently in the literature to calculate radiation shielding parameters. It is found that the relative changes between the EPICS2017 and Phy-X/PSD software compared with the results of this study are about 8% and 9% for the CR-39 and Trivex optical lens, respectively. This indicates that the results from the study are in good agreement. [ABSTRACT FROM AUTHOR]

Metamaterials have been proposed for absorber application. The research on absorber design has been highly focused on the design of each unit that is periodically laid out in an array. In this study, we present the layout of a unit structure as a new tuning factor for absorber performance based on the analysis of split ring resonator (SRR) resonances. Gap orientation of each SRR is the only variable in this approach. Simulation results show that random gap orientation layout exhibits much higher energy absorption compared to the other designs with periodic gap orientations. This significant absorption enhancement is neither due to a particular gap orientation nor due to the dimension of each SRR. Instead, it is due to the combination of the different gap orientations, which generates a particular layout for high energy absorption. The major part of absorbed energy goes to dielectric loss in substrate. The layout with high energy absorption creates higher localized electric field intensity that permeates into the substrate. We also present a new design that is periodically laid out but have four specially oriented SRRs in each unit "super cell". The periodicity of this super cell is easier to design since it is much more economical to simulate than randomly oriented SRRs. The maximum absorption of the super cell design is 80%, which is much higher than the other designs with the single SRR orientation. The high energy absorption of the super cell design proves that orientation of SRRs within a unit cell, a "supercell" can be a very useful tuning factor. [ABSTRACT FROM AUTHOR]

The plateau stress and energy absorption of low density (≤300 kg/m3) polyurea (PU) foams and expanded polystyrene (EPS) were measured at deformation rates ranging from 0.004 s-1 to 5000 s-1. Low (≤10-1 s-1) strain rate testing was performed using an Instron load frame, intermediate (101–102 s-1) strain rates using a drop-weight impact tower, and high (≥ 103 s-1) strain rate conditions using a modified split-Hopkinson pressure bar. The plateau stress and energy absorption of low density PU foams exhibit a strong rate dependence across all deformation rates. This result has been previously unreported for low density polymer foams under low and intermediate strain rates. The strain rate sensitivity of PU foams was found to be strongly dependent on cell size for low strain rates and cell wall aperture size for intermediate and high strain rates. EPS type foam, however, remained nearly insensitive to strain rate. At low and intermediate strain rates, the plastic crushing in the EPS and the high plateau stress yield a much higher energy absorption capability than the viscoelastic dissipation in the PU foams. However, PU foams were found to display similar energy absorption properties as EPS based foams under high strain rates. Thus, controlling the strain rate sensitivity of PU foams through aperture diameter can lead to an increase in energy absorption properties at high strain rates, while simultaneously maintaining the peak stress below certain injury thresholds. Additionally, unlike EPS, which undergo plastic crushing after first impact, flexible polyurea foams will recover fully after each impact and thus will have multiple hit capabilities. This will allow these materials to have a wide range of applications, in advance body armors and protective headgears to use in low-cost protection systems for a wide range of military platforms, civilian, and space applications. [ABSTRACT FROM AUTHOR]

In this paper, we show that the full Hamiltonian for a molecule in an electromagnetic field can be separated into a molecular Hamiltonian and a field Hamiltonian, both with gauge-invariant expectation values. The expectation value of the molecular Hamiltonian gives physically meaningful results for the energy of a molecule in a time-dependent applied field. In contrast, the usual partitioning of the full Hamiltonian into molecular and field terms introduces an arbitrary gauge-dependent potential into the molecular Hamiltonian and leaves a gauge-dependent form of the Hamiltonian for the field. With the usual partitioning of the Hamiltonian, this same problem of gauge dependence arises even in the absence of an applied field, as we show explicitly by considering a gauge transformation from zero applied field and zero external potentials to zero applied field, but non-zero external vector and scalar potentials. We resolve this problem and also remove the gauge dependence from the Hamiltonian for a molecule in a non-zero applied field and from the field Hamiltonian, by repartitioning the full Hamiltonian. It is possible to remove the gauge dependence because the interaction of the molecular charges with the gauge potential cancels identically with a gauge-dependent term in the usual form of the field Hamiltonian. We treat the electromagnetic field classically and treat the molecule quantum mechanically, but nonrelativistically. Our derivation starts from the Lagrangian for a set of charged particles and an electromagnetic field, with the particle coordinates, the vector potential, the scalar potential, and their time derivatives treated as the variables in the Lagrangian. We construct the full Hamiltonian using a Lagrange multiplier method originally suggested by Dirac, partition this Hamiltonian into a molecular term Hm and a field term Hf, and show that both Hm and Hf have gauge-independent expectation values. Any gauge may be chosen for the calculations; but following our partitioning, the expectation values of the molecular Hamiltonian are identical to those obtained directly in the Coulomb gauge. As a corollary of this result, the power absorbed by a molecule from a time-dependent, applied electromagnetic field is equal to the time derivative of the non-adiabatic term in the molecular energy, in any gauge. [ABSTRACT FROM AUTHOR]

To investigate the influence of the fissure morphology on the dynamic mechanical properties of the rock and the crack propagation, a drop hammer impact test device was used to conduct impact failure tests on sandstones with different fissure numbers and fissure dips, simultaneously recorded the crack growth after each impact. The box fractal dimension is used to quantitatively analyze the dynamic change in the sandstone cracks and a fractal model of crack growth over time is established based on fractal theory. The results demonstrate that under impact test conditions of the same mass and different heights, the energy absorbed by sandstone accounts for about 26.7% of the gravitational potential energy. But at the same height and different mass, the energy absorbed by the sandstone accounts for about 68.6% of the total energy. As the fissure dip increases and the number of fissures increases, the dynamic peak stress and dynamic elastic modulus of the fractured sandstone gradually decrease. The fractal dimensions of crack evolution tend to increase with time as a whole and assume as a parabolic. Except for one fissure, 60° and 90° specimens, with the extension of time, the increase rate of fractal dimension is decreasing correspondingly. [ABSTRACT FROM AUTHOR]

Rayleigh surface acoustic wave (SAW) devices based on 128° YX LiNbO3 and ZnO/Si substrates with different resonant frequencies from ∼62 MHz to ∼275MHz were fabricated and characterized. Effects of SAW frequency and power on microfluidic performance (including streaming, pumping, and jetting) were investigated. SAW excitation frequency influenced the SAW attenuation length and hence the acoustic energy absorbed by the liquid. At higher frequencies (e.g., above 100 MHz), the SAW dissipated into liquid decays more rapidly with much shorter decay lengths. Increasing the radio frequency (RF) frequencies of the devices resulted in an increased power threshold for streaming, pumping, and especially jetting, which is attributed to an increased absorption rate of acoustic wave energy. ZnO SAW devices could achieve similar streaming, pumping, and jetting effects as well as frequency effect, although the SAW signals are relatively weaker. [ABSTRACT FROM AUTHOR]

The present study concentrates on development of conceptual proof for sisal reinforced polymer matrix composite for structural applications subjected to low velocity impact using a finite element (FE) approach. The proposed sisal-epoxy composite of various thicknesses of 3.2 mm, 4 mm and 4.8 mm is subjected to different impact velocities of 1 m/s, 2 m/s and 3 m/s ranging in the low velocity impact regime to study the energy absorbed and damage mitigation behaviour of the proposed composite. The consequence of velocity of impact and thickness of laminate on the sisal epoxy composite's impact behaviour is assessed statistically using Taguchi's experimental design. Outcome of the present study discloses that the energy absorption increases with increased impact velocity and laminate thickness. However, the statistical study shows that impact velocity is predominant factor affecting the impact response of sisal epoxy composite laminate compared to laminate thickness. The role of matrix and fiber in damage initiation is studied using Hashin criteria and it is found that matrix failure is predominant over the fiber failure. [ABSTRACT FROM AUTHOR]

In this paper, energy absorption of aluminum thin-walled combined geometry, including a cylinder and a hemisphere under axial and oblique loading, is investigated using numerical simulation. The aim of this research is optimizing the dimensions of the combined geometry in order to increase the energy absorption capacity and comparing it with an equal weight thin-walled simple cylinder. Numerical simulations were performed at 0, 7, 14, and 21 degree of loading using ABAQUS software. The results showed that with increasing the radius of curvature and decreasing the height of the combined geometry, energy absorption parameters increase, and in general the combined geometry has better performance than the simple cylinder especially in oblique loading. The SAE and CFE of the optimum combined geometry with dimensions of R = 25mm, h = 25mm, H = 181:92mm, and D = 50mm in the 0 and 7 degree of loading is similar and in the 14 and 21 degree of loading increased 300% and 200% respectively in comparison with an equal weight thin-walled simple cylinder. [ABSTRACT FROM AUTHOR]

In this paper, energy absorbing characteristics of aluminum/polypropylene/steel sandwich cups are investigated. To this end, sandwich panels were fabricated using hot pressing technique. Then the panels were deep drawn using a circular punch to produce three-layer cups. Subsequently, the cups were axially compressed (crushed) under quasi-static deformation in order to investigate their energy absorption capacity. Finally, the effects of thickness of polypropylene layer as well as circular cutout triggers on energy absorption of the sandwiched cups were evaluated. The results show that changing the thickness of polypropylene layer from 1 to 2mm could successfully increase the energy absorption by about 24%. Furthermore, adding geometrical triggers like circular cutouts with radius of 2.5mm could reduce the absorbed energy from 346J in the sample without trigger to about 335J in the sample with trigger (3.2% reduction). The trigger could also reduce the peak force near 14% (from about 29kN to about 26kN) that can be considered as a positive point of triggers to mitigate damage in the samples. [ABSTRACT FROM AUTHOR]

• Laser-induced heat treatment improved the PCE of PSCs. • PCE of 13.03% was obtained at a defocusing distance of 5 mm and scan speed of 1 m/s. • Temperature of 115 °C was predicted for the optimized laser operation by COMSOL. We fabricated perovskite solar cells (PSCs) using laser-induced heat treatment. Perovskite films were prepared on substrates using the two-step solution deposition method. Subsequently, a pulsed laser source was illuminated to the perovskite film to stimulate the growth of perovskite crystals, which enhanced the power conversion efficiency (PCE) of the PSCs. The laser operation parameters, such as the defocusing distance and scan speed, were investigated to control the grain size of the perovskite. Based on optimized laser operation parameters, the best and average PCEs of 13.03% and 12.45 ± 0.28%, respectively, were achieved, which are higher than those obtained with conventional thermal heating (the best and average PCEs of 11.43% and 10.98 ± 0.25%, respectively). A perovskite layer temperature of 115 °C was predicted by simulating the energy absorption of the perovskite film under optimized laser operation conditions using COMSOL software. [ABSTRACT FROM AUTHOR]

We present first-principles calculations for nonlinear photoionization of diamond induced by the intense femtosecond laser field. A real-time and real-space time-dependent density functional theory with the adiabatic local-density approximation is applied to describe the laser-material interactions in the Kohn-Sham formalism with the self-interaction correction. For a certain laser wavelength, the intensity dependence of energy absorption on multiphoton and/or tunnel ionization mechanisms is investigated, where laser intensity regions vary from 1012 W/cm2 to 1016 W/cm2. In addition, the effect of laser wavelength on energy absorption at certain ionization mechanism is discussed when the Keldysh parameter is fixed. Theoretical results show that: (1) at the fixed laser wavelength, the relationship between the energy absorption and laser intensity shows a good fit of E = cMIN (N is the number of photons absorbed to free from the valence band) when multiphoton ionization dominates; (2) while when tunnel ionization becomes significant, the relationship coincides with the expression of E = cTIn (n < N). [ABSTRACT FROM AUTHOR]

Spectroscopic ellipsometry is applied to investigate the effect of Cu/Zn disorder in a Cu 2 ZnSnSe 4 crystal on the optical transitions. We observe that the degree of order has an impact not only on the first optical transition E 0 at the gamma point, which is the commonly discussed direct band gap in kesterites. It also varies the further optical transition E 1 away from the gamma point. While E 0 shows an increasing trend with higher degree of order, the transition E 1 shows an opposite behavior, indicating a fundamental impact of disorder on the shape of the electronic bands of kesterite material. • SE was used to investigate the effect of different degrees of Cu-Zn order in Cu 2 ZnSnSe 4 crystal on the optical transitions. • Cu/Zn ordering not only effects the fundamental band gap E 0 , it also effects the further optical transition E 1. • While E 0 is increasing with increasing Cu/Zn ordering level in Cu 2 ZnSnSe 4 crystal, E 1 shows an opposite behavior. • Relative energy differences between ordered and disordered state in this study are in good agreement with previous reports. [ABSTRACT FROM AUTHOR]

Highlights • A type of self-locking multi-cell structure assembled by open sections is proposed. • Quasi-static and dynamic axial crushing tests are performed for aluminum sections. • Numerical analyses are carried out to simulate the static and dynamic tests. • The influence of various factors on the performance of multi-cell sections is studied. • Theoretical expressions are derived and give good predictions for the crush resistance. Abstract A new type of self-locking multi-cell structure fabricated by assembling four C-shaped open sections is proposed in this paper. Quasi-static and dynamic experimental tests are performed to investigate the axial crush resistance and energy absorption characteristics of this type of structures. The experiment results show that the SEA of the assembled multi-cell sections is 35–40% and 40–50% higher than that of the constituent C-shaped elements for quasi-static and dynamic loading, respectively. Numerical analyses are carried out to simulate the experiment and perform the parametric study on the influences of geometric parameters, boundary condition and load speed on the crush resistance of structures. The behavior and performance of single C-shaped open sections are also studied, and the interaction effects originated from the self-locking features are investigated quantitatively. In addition, theoretical expressions are derived to predict the crush resistance of the assembled self-locking multi-cell sections. Comparisons show that the theoretical expressions can predict the static and dynamic mean crushing forces of the self-locking multi-cell structures with errors below 5% in most cases. [ABSTRACT FROM AUTHOR]

Highlights • Transient deformation of sandwiched plate. • Strain-rate effects on adhesives. • Time-Resolved Catadioptric Stereo Digital Image Correlation. • Energy absorption. • Inverse methodology to determine material properties. Abstract Adhesive joint technology is gaining acceptance since it leads to weight reduction, provides uniform stress distribution across the joints, allows the bonding of similar and dissimilar materials, and contributes to shock and vibration damping. The literature on adhesive joints subjected to static loads is extensive. However, the response of adhesive joints to high loading rates such as blast or ballistic loading has not been studied extensively. In this study, fully bonded plates composed of aluminum plates (381 mm in diameter and 1.59 mm thick) and commercial epoxy adhesive were tested under shock wave loading. Full displacement field over the test plates was obtained by digital image correlation techniques, and full-field strains of the plates were computed by classical plate theory for large deflections. An axisymmetric Finite Element Method model was used to gain more insight on the response of fully bonded plates to shock-wave loading. The material properties of the epoxy film subjected to high loading rates were estimated through an algorithm developed for an FEM-based parametric study. Finally, the influence of the adhesive thickness and Young's modulus on the behavior of the bonded adhesive under shock-wave loading were investigated using an FEM model. [ABSTRACT FROM AUTHOR]

A front cover of journal "Polymer Composites" is presented along with information regarding editorial members and table of content including ways to increase Tensile Strength of materials, Energy-Absorption Performance of materials, and Effects of GNP Addition on Optical Properties on thin films.

To improve the energy‐absorbing capacity of composite corrugated plate, the axial impact responses under axial quasi‐static crush loading is numerically studied and compared. Both the intra‐ply damage and delamination interface damage are considered. To accurately capture the progressive damage propagation, the failure material is modeled with a stiffness degradation method combined with the exponential damage evolution laws. To improve the crush performance, a novel corrugated‐shape ditch plug initiator (CDP) is proposed. The effects of extensive parameters including the ditch width and the inner geometry are carried out. Results show that well agreements between the numerical model and experimental results are identified on failure modes and energy‐absorption characteristics. The corrugated plate with CDP can increase the specific energy absorption by 20.3% than non‐plug initiator. The total of energy absorption is the decreasing function with respect to the width of ditch. The crushing performance can be improved due to the change in the inner geometry parameters. POLYM. COMPOS., 40:1708–1717, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Abstract Composites are considered as effective materials in absorbing the energy of blast and impact, and have been often used in complex loading environments. A numerical model is developed to analyze the response and damage of S-2 glass/SC-15 epoxy composite laminate subjected to combined loadings with blast and fragments. A composite progressive failure model is used to investigate the damage and the failure of the material. The proposed numerical model is validated by its comparison with the experimental data obtained from the literature. Three different types of loading combinations: (1) ammunition fragments impact loading, (2) bare blast loading, and (3) the combinations of blast and fragments loading, correspond to the scenarios of the near-field and the far-field explosions. Moreover, the response and the damage evaluation of the composite are analyzed here. It is concluded that the damage modes of the laminate are correlated to the type of the loading. Furthermore, the synergetic effects for the composite laminate subjected to the combined blast loading and the fragments impact are verified and evaluated. By comparing the energy absorption and the damage zone in the laminate, the synergetic effect is attributed to the conjunction of damage and the continuous pressure of the detonation products. [ABSTRACT FROM AUTHOR]

Highlights • Field tests were conducted on large scale CFDST columns subjected to close-in explosion. • Numerical models were developed and verified against experimental results. • Damage mechanisms of CFDST columns under close-in blast loading were investigated. • Energy absorption mechanisms of CFDST columns under close-in explosion were analyzed. • Effects of explosive charge setups and axial loads were assessed and discussed. Abstract The dynamic behaviour of concrete-filled double-skin steel tube (CFDST) columns under close-in blast loading was investigated using experimental and numerical approaches in the present study. Field test results on three large scale CFDST column specimens subjected to different blast loading conditions were presented. High-fidelity physics-based numerical models were developed utilizing the Arbitrary-Lagrangian-Eulerian (ALE) formulation coupled with Fluid-Structure Interaction (FSI) algorithm available in the nonlinear dynamic analysis program LS-DYNA. The numerical models were verified with the experiment results and were then used to investigate the dynamic response, damage mechanism and energy absorption capacity of CFDST columns subjected to close-in explosions. The results indicated that the typical failure pattern of CFDST columns under close-in blast loading is dominated by localized denting of the cross-section directly facing the explosion with minor global deformation of the column. The concrete core suffers severe damage while the steel tubes remain almost undamaged except in a limited region in the vicinity of the detonation. The energy absorbed by each part of the CFDST columns demonstrates that the severe plastic damage of concrete core plays a significant role in the energy absorption mechanism of CFDST columns under blast loading from close-in explosion. The primary function of the steel tubes is to provide confinement to the concrete core therefore prevent concrete spall damage. In addition, the influence of explosive charge setups and level of axial loads on the structural response and damage was assessed and discussed. [ABSTRACT FROM AUTHOR]

Abstract Hybrid square tubes wrapping fiber reinforced polymer (FRP) around metallic tubes are excellent structures for both collision energy absorption and lightweight. This paper deals with axial crushing theory of hybrid square tubes wrapped with antisymmetric angle-ply. The energy dissipation mechanism of hybrid square tubes is analyzed based on deformation of metallic square tubes. Considering the effects of stacking sequences of FRP on the crashworthiness and energy absorption, theoretical expressions of the membrane force and fully plastic bending moments per unit length of hybrid squares tube are derived. Then, the expression of mean crushing force of hybrid square tubes wrapped with antisymmetric angle-ply is established. Theoretical predictions compare well with the results of three groups of experiments and forty simulation models. The theoretical calculation presented in this paper can predict the behavior of hybrid square tubes during the conceptual design. Highlights • The energy dissipation mechanism of hybrid square tubes wrapped with antisymmetric angle-ply is analyzed. • Membrane force and bending moments are derived considering the effect of stacking sequences of FRP on energy absorption. • The mean crushing force of hybrid square tubes is obtained and validated by experiments and simulations. • The theoretical analysis provides a method to predict the behavior of hybrid square tubes during the conceptual design. [ABSTRACT FROM AUTHOR]

Abstract Thin-walled energy absorbers are one of the common structures that are used in vehicle body for increasing the crashworthiness and consequently decreasing injuries. Investigated new type of thin-walled aluminum matrix and a thin-walled steel punch energy absorber structure has been investigated in this paper. Energy is absorbed as the matrix expansion followed by simultaneous matrix and punch folding. Present study proposes a sandwich panel based on expanding-folding absorber units to evaluate their crush mechanism. Parametric study has been done using finite element code LS-DYNA while experimental tests have been implemented to validate the FE model. The panels have been tested under three axial quasi-static loading conditions including a rigid half-cylinder and a rigid plate. Parametric study considers the punch angle, matrix thickness and punch thickness. The optimum structure based on energy absorption has then been used as a structural member in the sandwich panel until a panel with high specific energy absorption be introduced. Also it have been seen that all the curves for the expansion section can be estimated using polynomial second order functions, with a high accuracy. Graphical abstract fx1 Highlights • To absorb the kinetic impact energy effectively, the sandwich panels show structural need for high interconnection. • Increasing the thickness of thin-walled mandrel shows a direct effect in increasing the maximum and average forces. • Increasing the thickness of thin-walled matrix and increasing the angle of thin-walled mandrel increase the slope of the curve in expansion area. • The output diagrams for the expansion section can be estimated using specific polynomial second order functions. [ABSTRACT FROM AUTHOR]

Abstract In order to develop an efficient energy absorption structure for protecting equipment against impact and blast shock, this research proposes a fourfold-tube system (FT) consisting of four tubes. Its performance was analyzed experimentally (quasi-static test) and numerical simulation with FE (finite element) models. The deformation mode of the FT system was described in detail by simulation and experiment. With the collapse of the outer tube, the upper inner tubes were pushed towards both sides of the lower inner tube, then three inner tubes are side-by-side in the outer tube and all the tubes were collapsed simultaneously, therefore the stress transmits to the protected structure to be distributed more evenly. As a consequence, the protection capability of the nested tube system is improved by enhancing energy absorption capacity and the robustness of deformation mode. The performance of FT system was compared with that of the triple-tube system (TT) and single-tube system (ST), both the experimental result and simulation results show that the FT system can provide the most stable deformed mode and the highest energy absorption efficiency. For mild-steel nested tube systems, the energy absorbed by the FT system is larger than that of the TT system by 30%, so the defense ability of the FT system is better than the TT system. The deformation mode of the FT system under dynamic load tested experimentally, the results prove that the nested system can works as expected at high strain rates. Finally, the FT system was tested with two type of dynamic loading conditions, impact and blast shock. The results demonstrate that the FT system can provide the most efficient impact force reduction and blast mitigation in protecting the structures from damage under impact and shock wave from the explosion. Highlights • An energy absorber based on fourfold-tube nested circular tube system was present. • The FT system can provide an efficient impact force reduction and blast mitigation. • The system has an excellent performance on robustness. [ABSTRACT FROM AUTHOR]

Abstract Thin-walled structures are widely used in energy absorbing devices attributed to their light weight and excellent energy absorption efficiency. In this paper, an innovative sandwich sinusoidal lateral corrugated tubes (SSLCTs) was proposed. It consists of the outer circular tubes (OCTs), the inner circular tubes (ICTs) and a new type of lateral corrugated tubes (LCTs) with a sinusoidal cross-section in the middle. Systematic crashworthiness study for SSLCTs is carried out with multi-objective optimization design. The results show that the wall thickness of ICTs plays an important role in the specific energy absorption, while the wall thickness of OCTs plays a major role in initial peak force. The multi-objective optimizations of SSLCTs with N = 6 and N = 10 were performed. The optimization results show that the Pareto frontier coverage is wider for SSLCTs with N = 6 than N = 10. But these two different SSLCTs get almost identical optimal solutions. Finally, the interaction effects were also studied and it was found that the highest initial peak force was reduced by 22.39%, and the specific energy absorption was increased by 16.75% compared to the separate compression of individual tube. Highlights • An innovative sandwich sinusoidal lateral corrugated tubes (SSLCTs) was proposed. • The highest initial peak force was reduced by 22.39% compared to the separate compression of individual tubes. • The specific energy absorption was increased by 16.75% compared to the separate compression of individual tubes. [ABSTRACT FROM AUTHOR]

Abstract The present paper introduces two types of inner cellularization geometry in the thin-walled cylinders derived from previous studies on this area of subject. Novel geometries were proposed in this research. These configurations were the result of modifications to the previous works. Moreover, these absorbers were proposed to increase the specific energy absorption, reduce the peak energy, and improve crushing. The maximum Specific Energy Absorption (SEA), minimum Initial Peak Crushing Force (IPCF) under quasi-static axial compression test at the rate of 10 mm/min, and thickness and height parameters of the thin-walled cylinder and length of the inner square's sides were considered the design variables to achieve the optimal state. In the present work, two DOEs (design of experiment) were performed in Design-Expert in accordance with the given surfaces for both geometries of the thin-walled cylinder's inner cores. Subsequently, for further investigation, the experimental results were compared with those obtained from the finite element simulation in Abaqus, revealing the desirable accuracy of the results. Finally, by applying the equations derived from the proposed model to each of the responses and geometries, their optimal states were obtained using both the desirability approach in Design-Expert and the MOPSO method in MATLAB. Thickness had the highest impact on both configurations. Moreover, the optimal thickness for both configurations was 1.4 mm in the selected range. As regards the multi-objective function, the best inner square edge lengths for the C2R and S2R configurations were the central and upper limits, respectively. Finally, the cylinder heights for the C2R and S2R geometries were 174 and 153 mm, respectively. Highlights • The present paper introduces two types of inner cellularization geometry in the thin-walled cylinders derived from previous studies on this area of subject. In the present investigation, the quasi-static compressive experimental and numerical simulation test cylindrical absorbers is discussed. • The thin-walled cylindrical energy absorbers are considered with combined hybrid geometries and novel internal cells. • The response surface method (RSM), which is one of the design of experiments (DOE) techniques has been used to examine the effect of the parameters on energy absorption. • The equations derived from the proposed model for each of the responses and each geometry. • Optimal states were also obtained using both the desirability approach in Design Expert software and MOPSO method in MATLAB software. [ABSTRACT FROM AUTHOR]

Abstract The Moon is the nearest celestial body to the Earth and the starting point of the space exploration for the human being. The impact energy absorption and landing stability of lunar landers are extremely critical for lunar exploration. However, traditional landers cannot adapt to complex landing conditions and response to any unforeseen accidents during the landing process. Although some researchers have proposed the idea for the lander with MRF dampers, there are relatively few detailed structural designs and practical landing research studies. In this paper, we propose a detailed new type of lander with magnetorheological fluid dampers implemented as the primary struts, which can absorb the impact energy from landing. Its damping force is controlled by semi-active controlled currents based on the derived hydrodynamics of magnetorheological fluid dampers and can adjust to practical landing conditions. The simulation models of landers with the aluminum honeycomb and semi-active control are constructed in MSC Adams separately to compare their landing performances. Their simulation results show that this new type of lander can effectively reduce the largest acceleration by 26.18% under the largest acceleration response condition and the largest compression by 11.77% under the largest compression of primary struts condition. Its performance for more inclined and both smoother and rougher landing surfaces is better than that of traditional passive landers. It is believed that the proposed new type of lander is capable of landing on more complex and unexplored terrains for future lunar explorations. Highlights • A new type of lunar lander using magnetorheological fluid is proposed. • The damping forces of the new lander can be controlled by the currents. • The new lander has better landing performances under critical conditions. • The new lander is suitable for the more complex environment. [ABSTRACT FROM AUTHOR]

Because of the low rigidity of thin-walled parts, the cutting vibration is commonly encountered and has a vital influence on machined surface quality. Theoretical simulation of surface topography is one of the main methods to evaluate and control surface quality in practice. In this paper, a simulation model of surface topography is developed based on cutting edge motion model that incorporates the dynamics of thin-walled parts milling system. The theoretical model used to describe the trajectory of cutting edge takes tool vibration and workpiece vibration into account. Then, the influence of system vibration on surface topography is investigated. Particularly, a new method is proposed in this paper to predict the texture interval, texture distribution, and residual height for different milling areas by identifying the dynamic characteristics of thin-walled parts. In addition, the validity of surface topography model is conducted by experiment. The results show that the simulated topography is consistent with the experimental topography, and the model is proved to be able to predict roughness accurately. [ABSTRACT FROM AUTHOR]