Search

Dynamic and quasi-static in-plane compression failure process of a 2D-SiC/SiC composite were explored in this paper. Specular Reflection Method (SRM) was introduced to capture the real-time high-resolution images of the SiC/SiC composite in tests. The fracture surfaces of the subject composite under dynamic and quasi-static loading show different angles with loading direction. Dynamic fracture surface results showed a larger angle with the loading direction, with fiber breakage without debonding. However, in the quasi-static tests fracture surface showed a small angle with the loading direction, with fiber debonding and fiber bundle buckling. Scanning electron microscope (SEM) characterization of fragments obtained after experiments were used to characterize the deformation mechanisms of the 2D-SiC/SiC composite. Although both shear deformation and delamination were found under quasi-static and dynamic loading, shear deformation dominated the failure process of specimens during dynamic compression. Two microscopic fracture modes were concluded from the failure process of quasi-static and dynamic loadings. The strength of the fiber-matrix interface significantly influenced the fracture modes. Finally, an effort was made to simulate the dynamic failure process of SiC/SiC composite using the topological structure of a full-size specimen.

The mechanical behavior of un-strengthened aluminosilicate (ALS) glass is studied experimentally by using modified Split Hopkinson pressure bar and electronic universal testing machine. The compression tests on glass specimens are performed at strain-rates in the range of 10− 4 to 102 s−1. The compression tests data revealed that ALS glass is strain-rate sensitive vis-a-vis the compressive strength of the glass. In dynamic compression tests, failure process of glass is investigated using a high-speed camera and the failure process in ALS glass is explicated with the associated stress-time history. The initiation of crack, development, and glass debris are discussed to explain the failure process of glass specimens. Test results showed that the axial splitting lead to final rupture of the glass. From both static and dynamic compression tests, the compressive strength, failure strain and energy absorption results for ALS glass specimens are also compared.

Explosively Formed Projectile (EFP) is a self-forging shape charged structure having very high penetration ability compared to conventional kinetic energy projectile. The penetration capability of an EFP is strongly dependent on various design parameters. The present research is an effort to study the effect of liner thickness, explosive type and length to diameter ratio of charge (L/D) on the formation of EFP and its effectiveness is studied in terms of penetration subjected to ballistic impact and penetration of Rolled Homogeneous Armor (RHA) target. The study is carried out by performing a number of simulations by using explicit finite element (FE) hydrocode ANSYS/Autodyn. Under the explosive loading the liner collapses severally without breakage and forms a high-speed projectile. In all the simulations, the explosive is modeled using Euler processor to best predict the large material flow and venting of explosive gases whereas the liner and casing are numerically discretized using Lagrange processor. The interaction of explosive gases with casing and liner is modeled through Euler-Lagrange coupling technique available in ANSYS/Autodyn. It was originated that for same EFP design only by varying the liner thickness from 6 to 4 mm gives an increased velocity of the developed high-speed projectile without losing structural integrity. The developed high-speed projectile velocity is further enhanced by using more powerful charge types having a higher velocity of detonation (VOD). Three different charge types are analyzed for EFP performance and it was found that HMX based charge gives a significant increase in projectile velocity and henceforth penetration in RHA target. Finally, by increasing the length-diameter ratio of EFP system from 0.75–1.1 either the high-speed projectile or the long stretchy projectile can be formed. The field tests were conducted for selected EFP configurations for validation of calculated results. It was found through simulations that by decreasing the thickness of liner the 40 % increase in EFP velocity and 31 % increase in penetration depth in RHA can be achieved. In addition to this using HMX based charges for length-charge diameter ratio of 1.0, the 21 % increase in EFP velocity and 35 % increase in penetration depth in RHA was estimated. This research provides EFP designers to get an optimum high-speed projectile by incorporating different geometrical parameters.

The accurate numerical simulation of projectile penetration process is a complex challenge. Experimental investigation of these time-dependent non-linear events is expensive and time-consuming. In this paper, 3-D numerical simulations are carried out to estimate the penetration performance of designed penetrators against the double and triple brick-wall, plain concrete wall and light armor targets at impact velocities of 120 to 300 m/s, undergoing normal and oblique impacts. In all simulations, both the projectile and targets are modeled using Lagrange solver facility, available in ANSYS/Autodyn. During penetration process, targets experience severe grid deformation in the region local to the penetrator. Highly distorted elements are removed from the calculation using erosion strain algorithm. The simulation results suggest that at maximum velocity flat-nose (FN) projectile successfully perforate all the targets with significant residual velocity, for both normal and maximum oblique impact scenarios. For impact velocity of 120 m/s, the FN projectile perforated the armor and concrete targets but was not able to penetrate and cross through these targets. However, both brick-wall targets were perforated at normal and maximum oblique angle with sufficient residual velocity. The validation of the calculated results and numerical setup were made with experiments against double and triple brick-wall targets for impacting velocity of 170 m/s. Good agreement between the experimental and estimated projectile residual velocity has been achieved. In contrast to FN projectile, the ogive-nose penetrator calculated results has shown ricocheting behavior on impacting the light armor target at minimum velocity and maximum obliquity. The FN projectile has shown better perforation and penetration performance against light armor and domestic targets. The projectile minimum velocity is also estimated numerically to fully penetrate three different types of targets. These results would be beneficial for the designers and operators to get the desired performance against domestic and light armor targets with sureness. Keywords: Numerical simulation, Oblique impact, Perforation, Penetration, Brick-wall

In this work, the mechanical and failure behavior of injection molded aviation standard optical grade polycarbonate (PC) was investigated through uniaxial tensile testing. The effect of different injection molding process parameters including injection velocity, packing pressure, cooling time, mold temperature, and melt temperature were determined to observe their effect on yield and postyield behavior of PC. Out of these examined parameters, the mold and melt temperature show significant effect on mechanical behavior of studied polymer. The yield and flow stresses in polymer increase with the increase in mold and melt temperature during injection molding. However, other process parameters i.e., packing pressure, injection velocity, and cooling time showed little effect on mechanical performance of the polymer. The molded specimens were annealed at different temperatures and residence time to evaluate its effect on mechanical behavior and fracture morphology. The yield stress increases gradually with the increase in annealing temperature and time. The annealing treatment also changed the failure mode of PC specimens from ductile to brittle. In addition to process parameters, the effect of increased loading rate was also undertaken which shows substantial effect on mechanical and failure behavior of PC. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44474.

Explosively Formed Projectiles (EFPs) are used to attack armored vehicles, on the other hands the armored vehicles use Explosive Reactive Armor (ERA) to enhance their protection. Using LS-DYNA software, this paper studies the problem of interaction of EFP with single sandwich ERA. The effect of various ERA configurations like the thickness of metal flyer plates/explosive and the inclination angle of ERA is analyzed against an EFP. The study concludes that the effect of light ERA i.e. with flyers upto 5mm is limited and the residual EFP still has enough energy to penetrate significant thickness of steel target, however when the ERA configuration is changed to heavier steel plates, most of the EFP is consumed during interaction with the ERA and only a small portion reaches the steel target, which does not have sufficient energy to penetrate the target. The simulation results were validated by testing the EFP against ERA.

Soft body impact tests were conducted using an artificial bird of 0.2 kg with a striking velocity of 150 m·s−1 on three different configurations of metallic wing leading edge (LE) structures. The objective of these experiments is to address the preliminary design of LE wing structures to soft body impact loads. The explicit finite element software PAM-CRASH was selected to simulate these experiments using smoothed particle hydrodynamics (SPH) techniques for modelling the bird. The impact tests were also performed for a velocity of 70–180 m·s−1 on instrumented aluminium and steel flat plates to attain the bird material parameters. The artificial bird material parameters for a hydrodynamic material model (Murnaghan equation of state) and elastic-plastic solids with damage and failure were optimised using iSIGHT and PAM-CRASH coupling technique in conjunction with tests on flat plates. The experimental and numerical correlations of the flat plates suggested that at high velocity the hydrodynamic material mod...

Projectile penetration of reinforced concrete structures has enormous significance because in plain concrete only the compressive strength offers resistance to penetration and projectile residual velocity. It is of great interest to observe how the amount of reinforcement can greatly influence the penetration process and projectile residual velocity. In this paper, numerical simulations on projectile penetration of medium strength reinforced concrete were performed using commercial hydrocode AUTODYN‐3D. A combined Lagrange, meshless and beam solver method was used for this kind of problem. For validation of our numerical scheme, simulation results were first compared with residual velocity and damage given by Hanchak et al. Based on this numerical scheme, the influence of reinforcement on projectile residual velocity was investigated. The analysis shows that the residual velocity of projectile decreases with the increase in reinforcement and, on the other hand, ballistic limit increases. Finally, ...