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We describe models for the behavior of hot-pressed boron carbide that is subjected to extreme dynamic environments such as ballistic impact. We first identify the deformation and failure mechanisms that are observed in boron carbide under such conditions, and then review physics-based models for each of these mechanisms and the integration of these models into a single physics-based continuum model for the material. Atomistic modeling relates the composition and stoichiometry to the amorphization threshold, while mesoscale modeling relates the processing-induced defect distribution to the fracture threshold. The models demonstrate that the relative importance of amorphization and fracture are strongly dependent on the geometry and impact conditions, with the volume fraction of amorphized material being unlikely to be significant until very high velocities (~3 km/s) are reached for geometries such as ball impact on plates. These connections to the physics thus provide guidelines for the design of improved boron carbide materials for impact applications.

Epoxy resin, diglycidyl ether of bisphenol A (DGEBA) and triethylenetetramine (TETA), is known to be hygroscopic in nature, which eventually leads to mechanical performance degradation of the material. The long-standing debate on the nature of water-epoxy interaction has been investigated in this study with the help of terahertz spectroscopy, which is able to probe sub 100 cm− 1 wavenumbers in which hydrogen bonds of water are active as well as infrared spectroscopy, which is able to probe 600–1000 cm− 1 in which the libration motions of the water molecules are dominant. Based on observations, it can be demonstrated that both hydrogen-bonded water (with epoxy) and free interstitial water (hydrogen-bonded with itself) is present when the epoxy resin is exposed to normal or saline water. A schematic diagram is presented to demonstrate epoxy-water interactions.

We employ molecular dynamics simulations to investigate the evolution dynamics of {101¯2} twinning in single-crystal Ti under shock loading. The shock compression applied perpendicular to the c-axi...

Classical molecular dynamics simulations have been performed to investigate the microstructural evolution of single crystal titanium under equal channel angular extrusion process (ECAE). The ECAE l...

The concrete with polyester microfiber is being investigated for the behaviour of flexural strength under static loading. But their behaviour under dynamic loading is unclear and hence there is a n...

Epoxy resin (DGEBA/TETA) is commonly used as an adhesive material. When this material is subjected to low temperatures for an extended period of time, it undergoes changes in inter/intramolecular v...

The compressive behavior of the pristine cubic crystal form of tricalcium aluminate has been investigated in this study at the molecular level. Comparative evaluation of two different types of loading and boundary conditions – uniaxial and triaxial strain has been demonstrated in this manuscript. The simulated responses using molecular dynamics have been compared with the available experimental and DFT (Density Functional Theory) simulation results wherever applicable. The global behavior of the material has been explained through changes in the energy contributions of the bond length and angle deformations along with contributions from the non-bonded interactions. It is observed that even though energy due to bond length influences the global response of the material for both the uniaxial and triaxial compression, energy due to bond angle deformation and non-bonded contribution only influences the global response in the uniaxial case and not the triaxial case. A comprehensive study is also presented of the dynamics of different bond lengths, bond angles along with the evolution of puckered chain at different strain levels for the two different types of compressive loading to explain the changes in the lattice structure of material with application of load.

The polymerization of vinyl monomers with achiral carbon center forms polymers with different spatial arrangements resulting in products with a different set of mechanical and thermal properties. Therefore, control of the tacticity (stereochemistry) is of major importance for controlling the polymer properties. It is possible to manipulate the polymer stereoregularity through the application of appropriate synthetic protocols. However, the polymers obtained using these protocols are not perfect, and thereby, it is essential to know the amount of different stereoregular units in a polymer mass. Generally, extensive NMR techniques and vibrational spectroscopy are used in this regard. To investigate further, a detailed DFT has been employed in this manuscript for syndio and isotactic polypropylene. The DFT allows generation of the vibrational spectra in the far‐infrared (0–400 cm⁻¹) region, demonstrating the distinct nature of both types of polymers. The vibrational spectra for pure syndio and isotactic polypropylene as well as their conformer defects have been identified in this study. These studies of vibration spectra in the far‐infrared regime can be used to identify signatures of pure racemo and meso dyads along with the type of conformer defects present in pristine varieties. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1378–1385

The primary difference in between different forms of CaSO4 is in the presence of confined water molecules within the molecular structure. It has been demonstrated in this manuscript that the solvation of the metallic ions by the confined water molecules along with hydrogen bonding of the water molecule with anions in the material eventually results in improvement of the quasistatic uniaxial compressive mechanical performance of CaSO4.n H2O. The evolution of microstructure of the material is probed to explain the stress-strain response of the material in its unhydrated and hydrated state.

Parabolic profile of cracks is well known in fracture mechanics, which typically develops in metallic systems. The profile of Interfacial delamination cracks in polymer foam cored sandwich composite structure is being investigated in this work using a procedure of embedded fiber Bragg grating sensor array with wavelength division multiplexing. The observed arbitrary nature of the crack profile in the mode I dominated loading condition, raises questions on the parabolic crack profile as well as on the assumption of numerous variables for numerical simulations of crack propagation problems especially for polymer foam-cored sandwich materials.

The behavior of pristine single crystal gypsum under tensile loading at a molecular level has been probed in this study based on simulations. Uniaxial stress type tensile loading situations demonstrate anisotropy in response. For both uniaxial and triaxial loading situations, the non-bonded part of the energy governs the response. The response behavior of the tensile stress strain curves in uniaxial and triaxial conditions have been correlated with changes in the molecular structure along with interlayer and intralayer separation distances and layer slippages.

Fatigue damage of the cement concrete pavements is progressive under vehicular loads and these pavements are designed based on cumulative fatigue damage principle where stress level and material characteristics are considered. From the literature, contradictory results on aggregate size with fracture parameters are reported. An attempt is made in this study, to understand the influence of nominal maximum aggregate size (NMAS) on flexural fatigue of concrete specimens without a notch. The main objective is to understand the effect of concrete mixtures made with two NMAS having similar strength range on stiffness change. The results indicated that the concrete made with NMAS of 10 mm had higher the fatigue life and thus loss in stiffness is less compared to the mix with NMAS of 20 mm. The damage model is used to predict the stiffness degradation and found that the model is excellent with a very low root mean square error.

Performance evaluation of cementitious mortar reinforced with natural fibers (jute) and synthetic (polypropylene) fibers is carried out in this article with respect to mechanical response a...

It is been widely experimentally reported that Si under static compression (typically in a Diamond Anvil Setup-DAC) undergoes different phase transitions. Even though numerous interatomic potentials are used for numerical studies of Si under different loading conditions, the efficacy of different available interatomic potentials in determining the phase transition behavior in a simulation environment similar to that of DAC has not been probed in literature which this manuscript addresses. Hydrostatic compression of Silicon using seven different interatomic potentials demonstrates that Tersoff(T0) performed better as compared to other potentials with regards to demonstration of phase transition. Using this Tersoff(T0) interatomic potential, molecular dynamics simulation of cubic diamond single crystal silicon has been carried out along different directions under uniaxial stress condition to determine anisotropy of the samples, if any. β -tin phase could be observed for the [0 0 1] direction loading whereas Imma along with β -tin phase could be observed for [0 1 1] and [1 1 1] direction loading. Amorphization is also observed for [0 1 1] direction. The results obtained in the study are based on rigorous X-ray diffraction analysis. No strain rate effects could be observed for the uniaxial loading conditions.

The surface morphology of fibers influence the global performance of fiber-reinforced cementitious composites. Commercially available polypropylene fibers may be coated with polyglycol este...

A molecular dynamic study of the structure-property relationship of tricalcium aluminate subjected to uniaxial tensile loading has been investigated in this study. The suitability of interface force potential, being used in this study, has been verified against experimental observations and first principle calculations. The study demonstrates that energy associated with the non-bonded terms (Van der Walls, Coulombic and long-range interactions) contributes to the major part of the total energy which increases steadily with strain. Nucleation of voids are also observed in the post-peak regime. Different bond lengths and angles of the puckered chain, which constitute the crystal structure of the ionic-covalent solid, are observed to increase (either uniformly or non-uniformly) with application of load in the prepeak regime. It can also be observed that even though coplanarity of the O and Al atoms in the puckered chain is separately maintained throughout the straining process; the angle between the two different planes in the puckered chain are observed to increase with strain. For the first time in literature, this study provides details of the deformation mechanism at a molecular level of this ionic-covalent solid when subjected to uniaxial tensile loading situations.

In a previous study (Asp et al., 1995) the experimentally observed low strains to transverse tensile failure of unidirectional (UD) polymer matrix composites were explained as an effect of triaxial (composite- like) stress state in the epoxy matrix. Assuming cavitation as an underlying mechanism for brittle cracking under triaxial stress states, a dilatation energy density based criterion was put forth (Asp et al., 1996) and was shown to predict well the transverse failure of epoxy based UD composites (Asp et al., 1996). The assumption of cavitation in the epoxy matrix has hitherto not been supported by a mechanism study. The current study attempts to provide a systematic clarification of the cavitation mechanism by molecular dynamic simulation. By imposing uniaxial, equi-biaxial and equi-triaxial tension on a simulation cell of a crosslinked epoxy, the degrees of cavitation at various stages of the stress- strain response are revealed. The results show that triaxiality of the stress states is a governing factor in cavitation of epoxies.

Twinning plays an important role on the microstructure evolution of HCP metals. In this work, we perform c-axis compression of single crystal Ti under uniaxial stress conditions using molecular dynamics simulations. The objective is to demonstrate activation and evolution of compression twins along with dislocations when Ti single crystals are loaded in uniaxial stress conditions using two commonly utilized interatomic potentials. We find that activation of only { 1 0 1 ¯ 1 } compression twins with the Kim potential is inconsistent with the Schmid criterion while activation of both { 1 0 1 ¯ 1 } and { 1 1 2 ¯ 2 } compression twins with the Hennig potential is consistent with the Schmid criterion. Twin variants activated do not contribute equally to the total twinned volume even with equal Schmid factor for both potentials and thereby demonstrating inability of the Schmid criterion to predict dominance and evolution of twin variants. The Kim potential shows large amount of dislocation density in comparison to the Hennig potential. The strain rate sensitivity on activation of compression twin systems is observed with the Hennig potential. The study can be utilized to further investigate the evolution of compression twins required to develop/improve twin volume fraction evolution laws for crystal plasticity finite element simulations.

We perform molecular dynamics simulations to study the evolution of tension twinning in single crystal Ti under uniaxial strain conditions. The objective is to understand the evolution trends of twin volume fraction as well as number of twins and express them in terms of the individual twin dynamics. The compressive strain applied along 〈 2 1 ¯ 1 ¯ 0 〉 and 〈 0 1 1 ¯ 0 〉 directions leads to the activation of { 1 0 1 ¯ 2 } twin variants. We find that the activation of twin variants follows the Schmid criterion. However, they do not activate at the same time even with equal Schmid factor indicating the stochastic nature of the twin variant activation. For the case where four variants activate (loading along 〈 2 1 ¯ 1 ¯ 0 〉 direction), high nucleation events occur compared to the case where only two variants activate (loading along 〈 0 1 1 ¯ 0 〉 direction). The activated variants in each case do not evolve with same rate even with equal Schmid factor and a clear dominance of twin variants is observed. For the case where only two variants activate, average twin growth rate and overall twin volume fraction are high compared to the case where four variants activate. A correlation between the number of activated variants and the overall twin volume fraction is observed. The size distribution of the nucleated twins follows the power law function. The expressions provided for overall number of twins and overall twin volume fraction can serve as a basis to develop the physics-based twin evolution laws to model twinning at higher length scales.

Identification of interfacial delamination in the glass fiber/polymer-foam-core sandwich composites is difficult if the delamination does not propagate to the side surface of the specimen. However, these damages may eventually lead to compromising the sandwich composite structural component. A cost-effective novel embedded fiber optic sensor is being proposed in this manuscript, which works on the principle of multimode interference, to perform distributed sensing of interfacial delamination within the sandwich composites while in service. Even though this easy to use methodology has been used to identify interfacial delamination, this methodology can also be used for different other types of interfacial/interlaminar distributed strain sensing of samples under mechanical as well as thermal loads.

Structural phase transformation in bulk single crystal Cu in different orientation under shock loading of different intensities has been investigated in this article. Atomistic simulations, such as, classical molecular dynamics using embedded atom method (EAM) interatomic potential and ab-initio based molecular dynamics simulations, have been carried out to demonstrate FCC-to-BCT phase transformation under shock loading of 〈100〉 oriented bulk single crystal copper. Simulated x-ray diffraction patterns have been utilized to confirm the structural phase transformation before shock-induced melting in Cu(100).

We have carried out multimillion atom non-equilibrium molecular dynamics simulations for investigating the effect of crystallographic orientation over the evolution of deformation pathway of single crystal copper under shock compression. Based on symmetry, three different crystallographic directions, 〈 1 0 0 〉 , 〈 1 1 0 〉 and 〈 1 1 1 〉 are selected and taken as shock directions. Shock Hugoniot points has been calculated and compared among these different directions up to ∼ 450 GPa of shock pressure i.e. piston velocity of 3.0 km/s. Orientational anisotropy has been observed for the bulk Cu single crystals shock loaded along these three different directions. Even though this feature may not show up explicitly in experimental investigations which typically measures shock-velocity and density Hugoniot curve, it is apparent from large scale atomistic simulations which measures the temperature Hugoniot curve quite accurately. Differences are observed in the von-Mises strain and stress plot distributions for shock loading of different intensities along the three directions. Large directional dependency is also evident in the evolution mechanism of deformation. Temperature profiles at different piston velocities for the shock front and the shock equilibrated regions shows significantly different and interesting patterns along the three orientations. Maxwell-Boltzmann distribution is observed in the atomic velocities (thereby the temperature profiles also) for both the shock front region as well as the shock equilibrated region for shock loading along all the three directions.

Epoxy resin is used as binder material for various composites which are used in aerospace, naval and space vessels. Epoxy resin has excellent adhesion properties but it is well known that they are brittle in nature and show poor resistance to crack initiation and crack propagation [1]. To address this issue different nanofillers are added to observe the changes in the mechanical strength of epoxy before and after exposure to UV for an extended period of time.

Epoxy resin (DEGBA/TETA), used as a major ingredient for manufacture of composite and sandwich composites may be subjected to different extreme environment situations such as that of cold weather conditions. In this study, samples were exposed to cold weather conditions and FTIR was done to probe changes in the molecular structure of the material which might provide an answer for the brittleness observed in the material

Shock-induced plasticity in FCC crystals has been demonstrated in many experimental and numerical simulation studies. Even though some theories have been proposed with regard to dislocation nucleation, the phenomenon occurring in the elastically shock-compressed region and the elastic-plastic transition region, which might be the origin region for dislocation nucleation, is largely unexplored. In this work, we present a molecular dynamics simulation of the shock compression of a Cu single crystal along the < 110 & rang; direction specifically focusing on the mechanisms observed in the elastically compressed and the elastic-plastic transition regions. A distribution of planes of high and low atomic volume is observed in the elastically compressed region near the shock front, but the distribution becomes random as the elastic-plastic transition regime is approached. Density variations are also observed. It is observed that the formation of the defects initiates through local atomic shuffling/rearrangement. Shear stress distribution shows values greater than those required for homogeneous nucleation, and Shockley partials are observed at a certain region behind the shock front. Potential energy variations are also observed in these regions, explaining the mechanisms leading to dislocation nucleation. The present findings shed new insight into the mechanism of dislocation nucleation in shock-induced single-crystal FCC metals.

Epoxy resin (DGEBA/TETA) is an adhesive material which is used for manufacture of several composite structures for use in aerospace, naval vessels as well as automobiles and various infrastructure applications. Whenever these structures are subjected to various kind of extreme environment situations typically one of the most common modes of failure is primarily due to delamination of the laminates which is typically due to changes in properties of the epoxy resin matrix. Terahertz spectroscopy is being used in this study to probe the degradation mechanism in epoxy resin subjected to saline water, Cold temperature as well as UV light.

Reactive interatomic potentials for water have been developed by researchers based on their ability of bond breaking and formation, which have numerous advantages and applications in different fields. The question that is being addressed in this work is whether these reactive interatomic potentials properly account for the intermolecular dynamics of water that includes both hydrogen bonding as well as librational motions. It should be noted that breaking and reformation of hydrogen bonds occur prior to covalent bond breaking of water molecules (which requires a significant amount of energy), which has numerous applications in absorption as well as solvation problems. Based on correlations with experimental observations, it has been demonstrated that the current forms of the reactive potentials perform poorly in comparison to other well-established empirical interatomic potential models of water, such as TIP4P/2005f, with regard to the intermolecular dynamics of water. Translational and rotational diffusivities, power spectra, and hydrogen-bond lifetime analyses are carried out and compared to available experimental data as well as those obtained from TIP4P/2005f models to arrive at such conclusions.

Ultraconfined interlayer water within the tobermorite molecular structure is responsible for changes in the uniaxial tensile and compressive response of the family of tobermorites: 9, 11 and 14 A. These confined interlayer water molecules are engaged in solvation of cations and anions within the tobermorite structure, which has been demonstrated through the intermolecular vibrational spectra and hydrogen bond lifetime of the water molecules. This study demonstrates that instead of ionization of water molecules (as proposed in an earlier study), breaking of hydrogen bonds of water is more plausible leading to solvation of ions within the molecular structure of tobermorite. A schematic of the coordinate covalent bonds between the water molecules and the cations and anions of the tobermorite structure has been proposed in this study.

Microstructural changes in concrete, mortar, and cementitious composite material were investigated to determine the efficacy of these materials subjected to shock loading. An experimental m...

Hydrated cement produces the strength and stiffness of concrete, a widely utilized infrastructural material. Estimation of elastic constants of hydrated cement, a heterogeneous material con...

Thermal conductivity of cement paste is significantly influenced by the presence of macro-pores within it. These pores (pores with size greater than 6 μm, measured using microCT) which may be filled with air and/or water significantly alters the thermal conductivity of the resulting material. A combination of experiments, molecular dynamic investigations of major constituents of the cement paste, multiscale homogenization techniques, and inclusion of thermal conductivity of the pores containing either air or water has been utilized in this study to reveal the influence of pores in the calculation of thermal conductivity of the composite material.

Portlandite is an important naturally available mineral and also an important component of hydrated cement. The mineral is subjected to uniaxial, equi-biaxial, equi-triaxial compressive loading at molecular level. Changes in the stress-strain plots for different types of compressive loading have been presented in this manuscript along with explanations from deformations of the molecular structure. Changes in bond order and partial atomic charges have also been calculated and related to the stress-strain curves observed for different compressive loading situations. It should be noted that this change in partial atomic charges have not been highlighted for the reactive potentials in any previous publications.

We perform molecular dynamics simulations to simulate the c-axis compression of single crystal Ti at high strain rates under uniaxial strain conditions. Since it is well known that molecular dynamics simulations heavily rely upon the type of potential used, a comprehensive study is presented in which four different commonly utilized potentials for Ti (Ackland, Mishin, Kim and Hennig) are evaluated against their abilities to demonstrate different variants of compression twins, dislocation structures and structural phase transformation. We find that { 1 0 1 ¯ 1 } and { 1 1 2 ¯ 2 } twins activate for Ackland and Mishin potentials, while only { 1 0 1 ¯ 1 } twins activate for Kim potential. No compression twin systems activate for Hennig potential. The c-vector analysis of unknown structure generated with Ackland, Mishin and Kim potentials shows that the unknown structure has { 1 0 1 ¯ 1 } twin-like orientations and the structure factor analysis gives a signature of pressure-induced ω phase for the twin-like oriented unknown structure. No signature of twin-like oriented unknown structure and ω phase is observed for Hennig potential. The large amount of dislocation density is observed for Ackland potential followed by Mishin, Kim and Hennig potentials. The presence of compression twins and high dislocation density for Ackland, Mishin and Kim potentials suggest that the c-axis deformation is accommodated by twins and slip together, while only slip accommodates the c-axis deformation for Hennig potential. Based on these observations and as well as on the formulation of the above mentioned potentials, Kim potential is being recommended for use under c-axis uniaxial compressive strain loading situations.

An experimental investigation on sandwich composite materials composed of glass-fiber face sheet and polyvinyl-chloride foam core has been carried out. The research demonstrates improvement in mixed-mode delamination fracture toughness values of samples under mixed-mode bending condition. The improvement is recorded with addition of a certain percentage by weight of multiwalled carbon nanotubes in comparison to conventional samples. An easy and cost-effective methodology of multiwalled carbon nanotube insertion through sonication of epoxy resin followed by mixing with hardener and vacuum resin infusion technology for manufacturing of sandwich composites has been utilized in this study. The study also identifies the optimum weight percentage of multiwalled carbon nanotube addition in the resin system for maximum performance gain in mixed-mode fracture toughness. The results of observations in this study have been supported by field emission scanning electron microscope studies as well as high-resolution transmission electron microscope analysis.

We perform molecular dynamics simulations to investigate the microstructural evolution and role of twinning on ω -phase transformation in single crystal Ti for loading perpendicular to the c-axis under uniaxial strain conditions. We find that both tension twinning and ω -phase evolve simultaneously and compete with each other. The number of activated tension twin variants not only affects the overall twin volume fraction but also the ω -phase volume fraction. For the case where four twin variants activate, the overall twin volume fraction is lowest and ω -phase volume fraction is highest in comparison to the case where only two twin variants activate. Significant amount of unconsumed parent HCP structure occurs for the case where four twin variants activate in comparison to the case where only two twin variants activate. This suggests that the number of activated twin variants and the spatial distribution of twins belonging to these variants play an important role on the amount of unconsumed parent HCP structure. The presence of high dislocation density for the case where four twin variants activate in comparison to the case where only two variants activate indicates that the number of activated twin variants also affects the overall dislocation density. The foregoing observations can be useful to develop a dynamic material strength model which can account for the coupled evolution of plasticity and phase transformation.

An experimental investigation on sandwich composite materials composed of glass-fiber face sheet and polyvinyl-chloride foam core has been carried out which demonstrates improvement in interface fracture toughness values of samples with addition of a certain percentage by weight of multi-walled carbon nanotubes (MWCNT) in comparison to conventional samples. An easy and cost-effective methodology of MWCNT insertion through sonication of epoxy resin followed by mixing with hardener and thereby using vacuum resin infusion technology for manufacturing of sandwich composites has been prescribed in this study. The study also identifies the optimum weight percentage of MWCNT addition in the resin system for maximum performance gain in interfacial fracture toughness. The results of observations in this study has been supported by high-resolution transmission electron microscope (HRTEM) analysis as well as field emission scanning electron microscope (FESEM) studies.

DFT calculations (typically done at 0 K), Helmholtz free energy and Gibbs free energy calculations (for high temperature) within the quasi-harmonic approximation have been done in this manuscript to probe a metastable phase of Cu observed at high temperature and high pressure. The high electronic thermal conductivity observed for this new metastable phase of Cu may be beneficial for high temperature engineering applications in electronic and spacecraft device designs.

Plain concrete used in pavements undergoes fatigue damage with repeated traffic and thermal loading. Numerous studies were conducted previously to evaluate the effect of various parameters on the fracture behavior of concrete. Nominal maximum aggregate size which is one of the parameters investigated in the past, to evaluate the fracture characteristics was focused to influence the fracture energy of concrete significantly. This could be due to a larger crack path and greater crack growth resistance offered by the larger aggregates in the fracture process zone. Hence, it is worthwhile to investigate the effect of nominal maximum aggregate size (NMAS) of aggregate on the fatigue life of concrete. This factor, if influential, might be a feasible approach for field application to control the fatigue performance of concrete. In the present study, the effect of nominal maximum aggregate size was evaluated under different stress levels (80, 85, and 90%) and different frequencies of loading (2, 5, and 10 Hz). For this purpose, flexural fatigue test was conducted on concrete beam specimens. The specimens were prepared with a blend of fine aggregate and coarse aggregate with two different nominal maximum aggregate sizes (10 mm and 20 mm, designated as S10 and S20 respectively). A total of 100 specimens of 100 mm × 100 mm × 500 mm size were used in the experimental investigation. The results show that the fatigue life of samples with S10 mixture is significantly higher compared to S20 mixture for 80% stress level but are almost similar for 90% stress level irrespective of the loading frequency. The fatigue results are in better agreement with three-parameter Weibull distribution compared to other distributions such as lognormal as confirmed by the goodness of fit test Anderson-Darling statistic. The value of β, the Weibull distribution characteristic shape parameter, obtained as less than 1.0 in this study, indicates the risk of early life failures for the considered stress levels. The survival probability plots and p-value statistics suggest that stress level influences the fatigue life estimation for both S10 and S20 samples but not the loading frequency. Based on the present study, it can be concluded that smaller nominal maximum aggregate size is more beneficial for the fatigue performance of concrete.

Intense shock wave through water requires study of the phase transformation in water which results in change in sound speed and density of the medium. This information is required along with Us–up relationship to determine the impulse transmission of the structure using a continuum model. A combination of molecular dynamic simulations along with continuum formulations based on Rankine–Hugoniot jump conditions is used in this study. The continuum model is suitably modified to account for core compression which is a prevalent mode of energy dissipation in sandwich composite structures.

We employ molecular dynamics simulations to simulate the c-axis compression of single crystal Ti at high strain rate under uniaxial strain conditions. The Schmid factor calculations have been performed to understand the activation of compression twin systems and the c-vector calculations have been performed to identify the activated compression twin systems and their variants. The signature of pressure-induced ω-phase is obtained by performing the structure factor calculations. The orientation relationship between α and ω phases obtained matches with that reported in experiments.

We have carried out a series of multi-million atoms non-equilibrium molecular dynamics simulations to investigate the effect of crystal orientation over the shock induced plasticity and phase transformation in single crystal copper. Crystallographic orientation of [100], [110] and [111] has been studied for various intensity of shock ranging from 1.0 km/s to 3.0 km/s. During shock wave propagation along and , a FCC-to-BCC phase transformation has been observed to occur behind the shock front at higher intensity of shock. Nucleated body centered phase is identified through common neighbor analysis, polyhedral matching template method, radial distribution function and also from the energetic of the particles.

Face–core delamination is one of the major problems of using sandwich composite structures composed of a thin composite face sheets of Eglass/epoxy along with a low density PVC foam core. An innovative cost-effective methodology of inserting pre-manufactured shear keys in foam-core grooves has been proposed in this manuscript which increases the delamination resistance capacity of initially delaminated sandwich composite column subjected to in-plane compressive loading. Manufacturing of the sandwich composite panels with shear keys along with detailed experimental and numerical investigations have been performed in this manuscript to demonstrate the potential of the proposed simple methodology which can be utilized for face–core delamination sensitive design and analysis of sandwich composite structures and/or components. Numerical simulation considering cohesive damage at the face/core interface is shown to accurately simulate behavior as observed in experimental investigation. A numerical parametric study has also been carried out to determine the effect of change in stiffness of the face sheets and the shear keys on the in-plane and out-of-plane global response of sandwich composite panels.

Researchers have developed several measures to improve shear resistance capacity of sandwich structures composed of thin composite face sheets of Eglass/epoxy and low density PVC foam core, but these methodologies are either costly or result in damage to the sandwich composites before being placed for production. A novel, innovative cost-effective methodology of introducing fiberglass shear keys attached to face skins to improve the stiffness and strength of the sandwich composite panel is being proposed in this manuscript. Manufacturing of the sandwich composite panels along with experimental and numerical investigations have been performed in this manuscript to demonstrate the potential of the proposed simple methodology which can be utilized for shear-sensitive design and analysis of sandwich composite structures and/or components. A parametric study has also been carried out to determine the effect of change in shape, size, spacing and material of the shear keys on the sandwich composite panel global response.

Even though there are numerous experiments and molecular dynamic simulations of Cu under shock loading, there appears to be no literature on the evolution of different types of dislocation mechanisms and their mutual interactions during the process of shock loading, which this article addresses through molecular dynamic simulations using the Mishin EAM potential for Cu. Three different directions , , and that have been considered in this article are subjected to shock compression with piston velocities ranging between 0.3–3 km s−1. The evolution of Hirth locks, Lomer–Cottrell locks, cross-slips, jogs, and dislocation-originated stacking-fault tetrahedra are demonstrated in this article for different direction shock loading of single-crystal Cu.

Sandwich composite panels are being primarily utilized in many engineering sectors such as civil, infrastructure, mechanical, aerospace, marine, space, and nuclear industry primarily because of their high strength and stiffness to low weight ratio. This article considers primarily sandwich composite construction that is typically utilized in the marine industry. This article discusses the application areas of sandwich composite panels in the marine industry, material utilized as component materials for the sandwich composite construction, the manufacturing methodologies, the novel methodologies that are applied to sandwich composite construction, and different experimental procedures utilized for sandwich composite structures. Keywords: sandwich composite; vacuum resin infusion; stitching; Z-pinning; shear keys; fracture energy mode tests; mixed mode tests

Novel analytical models have been proposed in this study which extends current available fluid-structure interaction (FSI) theories for explosion induced shock loading on monolithic and laminated composite plates to sandwich composite panels, featuring core compression. The proposed models have been asymptotically validated against other FSI existing theories in low pressure range. A qualitative comparative analysis of the proposed models has been made with other existing FSI theories from the viewpoint of energy conservation. Core compression as predicted by the proposed models can be utilized for more economical, robust design of blast resistant sandwich composite structures.