Top PDF Performance of Pre-Stressed Sandwich Composites Subjected to Shock Wave Loading

Performance of Pre-Stressed Sandwich Composites Subjected to Shock Wave Loading

Performance of Pre-Stressed Sandwich Composites Subjected to Shock Wave Loading

In the present study, the shock wave loading, generated by the shock tube, has an incident peak pressure of approximately 1 MPa and a wave velocity of approximately 1030 m/s. The in-plane compression loading was applied on the specimen and held at a constant level until the specimen is subjected to the transverse shock wave loading. Three levels of static compression loading were chosen: 0 kN, 15 kN, 25kN. For each compression loading, at least two samples were tested. When the shock wave was released, the computer and high-speed photography system were triggered to record the pressure data and deformation images.
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Shock Wave Behavior of Particulate Composites

Shock Wave Behavior of Particulate Composites

The study of heterogeneous and anisotropic materials and non normal impact geometries neces- sitated the development out of plane velocity measurements. These measurements were subject to the same bandwidth limitations as those faced by normal velocity interferometers. Just as VISAR provided a solution for normal motion, one of several designs implemented to desensitize transverse displacement interferometers for use with slow recording equipment is the Variable Sensitivity Dis- placement Interferometer (VSDI) developed at Brown University [35]. VSDI is a diffraction assisted displacement interferometer capable of resolving both normal and transverse motion of a grating affixed to the rear surface of a target plate in gas gun experiments. Its primary use is to determine the structure and magnitude of a shear wave pulse traveling through a solid material undergoing combined pressure and shear loading. This experimental arrangement, known as Pressure Shear Plate Impact (PSPI) generates combined loading in a thin foil of a material of interest sandwiched between two high shock impedance anvils. The surface normal of the composite stack is then inclined relative to the direction of impact. A keyed gas gun is then used to propel a similarly inclined flyer plate, which generates normal and transverse motion in the target plate due to the impact direction being inclined relative to the impact surfaces.
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Use of Genetic Algorithms for Optimal Design of Sandwich Panels Subjected to Underwater Shock Loading

Use of Genetic Algorithms for Optimal Design of Sandwich Panels Subjected to Underwater Shock Loading

In the present study, the optimal design of sandwich panels subjected to underwater shock loading is treated. The effect of cavitation on the structure is also considered. Cavitation is mentioned to a phenomenon which occurs in water, caused by the reflection of a shock wave at a free surface. For large structures, such as the design of a hull or superstructure, the optimization is divided into smaller, tractable, subproblems using predefined local loads to constrain the optimization [5]. The mass of the sandwich plates with orthotropic facesheets and core is minimized, considering deflection and certain failure loads as constraints. The design process requires the specification of the stacking sequence, which is defined by the orientation and material type of each ply layer, creating a discrete optimization problem.
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Containment Ultimate Pressure Capacity with Consideration of Aircraft Impact

Containment Ultimate Pressure Capacity with Consideration of Aircraft Impact

The impact of a large commercial aircraft is multi-hazard loading: except direct mechanical loading on the impacted structures the aircraft impact also induces significant vibratory loading on the target building and extensive post-crash fires. The second two phenomena could lead to internal accident and elevated pressure and temperature loads in the hermetic volume. Therefore, the most widely adopted current approach for handling the aircraft impact load is by implementing the so called “double shell” concept, where an external shield structure provide protection from external hazards while an internal containment structure serves as ultimate barrier for radiological release in case of internal accidents.
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Influence of sweeping detonation-wave loading on shock hardening and damage evolution during spallation loading in tantalum

Influence of sweeping detonation-wave loading on shock hardening and damage evolution during spallation loading in tantalum

Finally, the experiment that showed pronounced spall, specimen III, developed a tensile stress (spall strength of ∼ 5.4 GPa for a 10.6 GPa applied peak shock stress) below that quantified in previous studies of spallation in tantalum at equivalent peak shock stresses [16–20]. Previous 1D loading experiments have documented spall strengths of 5.2 GPa for a 6 GPa shock amplitude, a 7.3 GPa spall strength for a peak shock stress of 9.5 GPa [19, 20], a spall strength of 6.2 GPa after shock compression to 19 GPa. [21], and a spall strength of 8.1 GPa Under quasi- isentropic loading to 60 GPa [18]. The lower apparent spall strength observed during sweeping-wave loading is postulated to reflect a change in the damage evolution in Ta from essentially pure void nucleation and growth to a higher contribution of shear-damage processes consistent with the increased imposed shear stresses commencesurate with the increased shear stresses, shock hardening, and increased twin formation propensity as a function of shock obliquity [11]. A higher propensity for twin formation with increasing obliquity coupled with the previous correlation of twins with void nucleation, may provide a plausible mechanism towards lowering spall strength. Further study is required to address the physical processes responsible for this decrease in spall strength.
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Dynamic behavior of zirconium alloy E110 under submicrosecond shock-wave loading

Dynamic behavior of zirconium alloy E110 under submicrosecond shock-wave loading

Investigation into processes of elastic-viscous-plastic deformation of metals and alloys under shock-wave loading [1] allows us to measure velocity-temperature relationships how these materials resist to deformation and fracture. In shock waves, a wide range of strain rates of solid bodies can be covered and thus we can accumulate experimental data that can serve as the basis for construction of defining relationships needed to predict materials behavior under high-intensity shock loads [2]. The structure of shock waves in solid bodies depends on processes of their elastic-viscous-plastic deformation, possible phase transformations, as well as on kinetics of fracture incipience and development [3–5]. In recent years, shock-wave methods were used for [6–9] systematic investigations into the velocity-temperature relationships for yield stresses and fracture of pure metals with face- centered and body-centered cubic structures. These data are practically absent for metals with hexagonal close- packed structure.
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Strength and fracture of uranium, plutonium and several their alloys under shock wave loading

Strength and fracture of uranium, plutonium and several their alloys under shock wave loading

In work [10] the samples of uranium 0.1 mm in thick- ness were loaded by copper projectiles 0.05 mm thick in the range of shock wave compression from 1.6 to 10.5 GPa. The values of 4.4 and 2.9 GPa were obtained for the spall strength of high-purity and unpurified rolling uranium. In work [11] the samples of an alloy of uranium with titanium 6 mm in thickness were loaded by projectiles 2 mm thick speeded up to velocities of 130–500 m/s. Increasing the spall strengths of an alloy from 2.3 to 4.1 GPa was noted with the growth of shock wave loading intensity. In work [12] spall fracture of uranium and an alloy of uranium with titanium was studied in a temperature range of 20– 860 ◦ C. The samples 2 mm in thickness were loaded by copper projectiles 1 mm thick speeded up to a velocity of 300 m/s. The velocity of the free surface of samples was measured using a laser interferometer. Increasing the spall strengths of uranium was noted in the temperature range corresponding to the existence of the β-phase of uranium.
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Impact performance of specimens subjected to fatigue loading – experimental investigation

Impact performance of specimens subjected to fatigue loading – experimental investigation

Abstract. The impact performance of reinforced concrete specimens subjected to fatigue loading has not been quantified properly yet. This topic is significant in the field of vehicle impact or similar applications. The paper aims to fill this gap by presenting the on-going experimental program. The paper presents outcomes of the experiments focused on the performance of RC beams subjected to drop-weight impact loading. The behaviour of the beams which were prior to the impact testing subjected to cyclic loading was compared to the behaviour of the beams which were not subjected to cyclic loading.
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Shock Wave Propagation in Composites and Electro Thermomechanical Coupling of Ferroelectric Materials

Shock Wave Propagation in Composites and Electro Thermomechanical Coupling of Ferroelectric Materials

The assumption of elastic homogeneity in the composite restricts the heterogeneous nature to shock waves. This removes the scattering of elastic waves in the system. This process can be reintroduced by changing the moduli of the layers, and corre- spondingly adding more Riemann problems. The scattering of elastic waves will add structure in the particle velocity profiles at the free end of the target, due to internal reflections in the last layer. The assumption of same modulus for the two branches of stress strain curve ensures only one type of elastic wave in the system. While this simplifies the analysis, the piecewise linear curve can deviate from the actual Hugoniot beyond a certain strain. The analysis can be extended to allow different modulus for different branches by introducing more Riemann problems. The shocked region is compressed and has higher modulus. This ensures that the analysis remains valid for much larger strain values. This also allows the shock speed to be greater than the elastic wave speed corresponding to the lower modulus branch. This is also referred to as an overshocked condition. Similarly, other quan- tities such as density and yield stress can be chosen differently for different layers by introducing even more Riemann problems.
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Research of brick dynamic strength when subjected to shock loading by method of computer modelling

Research of brick dynamic strength when subjected to shock loading by method of computer modelling

In Tomsk State University of Architecture and Building, the symbolic behavioural model was generated, taking into consideration the shock-wave loading of one-piece structure environments, including concrete, reinforced concrete, and fiber reinforced concrete, to make the strength design of the structural engineering elements to the explosion and to the impact loading.

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Performance of carbon nanofiber-cement composites subjected to accelerated decalcification

Performance of carbon nanofiber-cement composites subjected to accelerated decalcification

Given the growing interests and economic incentives for extending the safe storage period of nuclear wastes beyond 100 years, it is critical to ensure that the structural integrity of the storage systems can be maintained for long periods of time. Fiber reinforced cement composites provide an excellent alternative for amelioration, protection, and deterioration prevention of the containment structure based on a demonstrated resistance to corrosion, control of crack propagation and exceptional strength to weight ratios [1]. Lately, with the recent advances in nanotechnology, the use of carbon nanofibers (CNFs) in cement composites has received increasing attention due to the promising potential for the development of superior structural and multifunctional materials [2]. CNFs possess a number of unique properties, such as high specific strength, chemical resistance, and electrical and thermal conductivity, making them excellent candidates for nanoscale reinforcement in cement composites [3, 4]. While most studies to date have been conducted to examine the direct structural, mechanical, and electrical properties provided by the CNFs [5-7], the long-term chemical and structural stability of these materials in response to severe conditions such as decalcifying environments and the potential impact of the CNF dispersion on the chemo-mechanical behavior of CNF-cement composites has received little attention.
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Polymer Laminated Composites Reinforced With Bi-Woven Glass Fibers: Subjected To Tensile And Compression Loading

Polymer Laminated Composites Reinforced With Bi-Woven Glass Fibers: Subjected To Tensile And Compression Loading

Experimental evaluation of mechanical properties like tensile, compressive, impact & flexural strength of Bi-woven glass fibre reinforced polymer laminates as per ASTM standards has been successfully completed. The tensile properties have been studied and the breaking load has been measured. The inclusion of Bi-woven glass fibre mat reinforced polymeric composite significantly enhanced the ultimate tensile strength, yield strength and peak load of the composite. The tensile test is performed and the stress bearing capacity of GFRP composites under tension has been constantly increased from layer 1 to layer 4 i.e. from 38.26 MPa to 74.55 MPa and decreased for layer 5 up to 68.59 MPa as the reinforcement weight percent is increased over epoxy and composite strength is decreased with more than 4 layers of reinforcement. The compression test is performed and the stress bearing capacity of GFRP composites under compression has been constantly increased from layer 1 to layer 4 i.e. from 42.68 MPa to 84.27 MPa and decreased for layer 5 up to 79.94 MPa as the reinforcement weight percent is increased over epoxy.
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Peridynamic modeling of composite laminates under explosive loading

Peridynamic modeling of composite laminates under explosive loading

The applicability of this approach is demonstrated by simulating the damage evolution in a 13-ply composite laminate under shock-type loading. The PD predictions are compared against an experimental study performed by LeBlanc [4]. A Conical Shock Tube (CST) was used to replicate underwater shock phenomena. The geometry and mechanical properties of the composite plate are the same as those reported by LeBlanc. The CST experimental setup is shown in Fig. 4. Shock wave propagates from the breech, at which the charge is located, and strikes the test plate. The test plate, shown in Fig 5, is clamped along the boundary region using bolts.
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On localised vibrations in incompressible pre stressed transversely isotropic elastic solids

On localised vibrations in incompressible pre stressed transversely isotropic elastic solids

This paper is concerned with 2D localised vibration in incompressible pre-stressed fibre-reinforced elastic solids and the closely related problem of surface wave propaga- tion in such materials. An appropriate constitutive model is derived and its stability discussed within the context of the strong ellipticity condition. Surface wave propaga- tion in an associated half-space is considered, with the particular cases of propagation along a principal direction of primary deformation and that of almost inextensible fibres also investigated. The problems of free and forced edge vibration of a semi- infinite strip are analysed, revealing a link between the natural edge frequencies and the associated Rayleigh surface wave speed.
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Seismic Performance of a Pre stressed Tied Arch bridge Fitted With Dampers

Seismic Performance of a Pre stressed Tied Arch bridge Fitted With Dampers

M40 grade concrete is designated to be used for construction of the bridge along with Fe500 grade steel bars. The concrete is modelled using solid elements and the rebars, hangers and pre stressing cables are modelled as beam elements. The hangers used are Macalloy tension rods M76 of 72 mm nominal diameter. A brief material description is given in Table-2.

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Research of dynamic properties of alloys of AMg6BM and AMg6M in shock-wave experiment on a gas gun

Research of dynamic properties of alloys of AMg6BM and AMg6M in shock-wave experiment on a gas gun

The studies of dynamic properties of alloys AMg6B and AMg6M we are made in two series of experiments (Tables 1 and 2). The presence of spall destruction was fixed according to appearance so called “spall” signals on amplitude-time dependences of free surface velocity W (t) that speak about relaxation of stress waves under destruction in the samples [3]. The amplitude of shock- wave impact was varied in the range of 1.1 to 14.2 GPa (the range of collision velocity was from 0.15 to 2 km/s), deformation rate was from 0.2 to 3.6 · 10 5 s − 1 . Figures 2 and 3 show the profiles of free surface velocity W (t) obtained in experiments with samples of AMg6BM and AMg6M, respectively.
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Buckling and vibration of initially stressed composite sandwich plates

Buckling and vibration of initially stressed composite sandwich plates

Autoresonant Systems and Phase Control of Nonlinear Vibration 5 Babitsky, V., Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University, UK.. ENERGY METHODS Ses[r]

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BEHAVIOR OF SANDWICH COMPOSITES UNDER FLEXURAL AND FATIGUE LOADING: EFFECT OF VARIATION OF CORE DENSITY

BEHAVIOR OF SANDWICH COMPOSITES UNDER FLEXURAL AND FATIGUE LOADING: EFFECT OF VARIATION OF CORE DENSITY

the areas of interest has been examined is the fatigue behavior of polymer sandwich composites. During the regular service of sandwich composites are subjected to dynamic loads that may cause some induced stresse in the structures [4]. Therefore their fatigue behavior is significant in reliability and ensuring safety of these sandwich structures. The flexural fatigue strength of sandwich structure depends on the strengths of outer skins, foam and interfacial bond strength between the skin and the light weight core. The failure of any one of these would cause failure of the sandwich structures [5, 6]. In several literatures it is reported that the fatigue strength of the sandwich panel is influenced by the facesheet strength and thickness since the face sheet delamination is an important flaw leading to failure. Whereas, during the flexural fatigue test the sandwich specimens radius of curvature increases with the increase in foam thickness [7], it is thus clear from the above reviews and references, the fatigue testing of sandwich composites are characterized by two important factors, foremost the core-skin debonding and the other is the effect of core density. This paper makes an attempt to study the core- skin compatibility at higher cyclic loading in conjunction with the variation of core density observed between low to higher test frequencies. Review literature reveals that there is a scope for sandwich structures by varying the core density for predicting the fatigue strength of the sandwich structures. Hence the present paper discusses the flexural behavior of three different PUF core materials and tested at varied frequency is presented adding a note on their failure mechanism is reported.
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Fracture Analysis Of FRP Composites Subjected To Static and Dynamic Loading

Fracture Analysis Of FRP Composites Subjected To Static and Dynamic Loading

Further, Reddy.P.R [9] has studied the fracture behavior of ceramic matrix composites using singular and higher order elements. The following conclusions are drawn: as the notch depth is increasing, corresponding fracture load, fracture toughness and work of fracture values are decreasing for a particular orientation of fibers The inverse is true when the results of another orientation composite were studied. It was also observed from the load displacement curve that fibers offer resistance to crack propagation. But all fibers do not participate in strengthening the composite because of poor bonding.
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Behaviour of the peach under underwater shock wave loading

Behaviour of the peach under underwater shock wave loading

processed food. In some previous research see e.g. (Itoh, 2008), shock wave treatment of some foods containing water, such as apple, Japanese radish, and pineapple, leads to so ening the food by main tai- ning their original shape. Without cutting the grate foods, juice was easily obtained by squeezing by hand. Also, the permeability of Japanese radish for seasoning was improved. In the case of making dry foods, such as coff ee beans and green tea leaves, un- derwater shock treatment can make easier the pow- dering of these samples. It is obvious that eff ective use of this technology is conditioned by the research of this kind of loading. The research is mostly based on the numerical simulation of the shock wave ef- fect. In order to perform such study some model of the peach mechanical behaviour is needed. This problem is solved in the presented paper.
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