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the studies have been carried out on the damage initiation behavior of polymer matrix woven fabric composite plates subjected to a transverse central low velocity point impact load. Specifically, the effect of incident impact velo...
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the studies have been carried out on the damage initiation behavior of polymer matrix woven fabric composite plates subjected to a transverse central low velocity point impact load. Specifically, the effect of incident impact velocity and impactor mass for the same incident impact energy on the impact behavior has been investigated with a square plate of 150 mm X 150 mm X 6 mm. The material systems considered are: E-glass/epoxy and T300/5208 carbon/epoxy woven fabric composites. Inplane failure of the layers in the form of matrix cracking/ lamina splitting and delaminations were the primary objectives of the study. The studies have been carried out using an inhouse Finite Element Analysis code. The inplane failure functions and the interalminar failure functions have been predicted using quadratic failure creiteria. It is observed that the use of incident impact energy alone as a parameter to characterize the impact behavior is inadequate. Instead, the effect of both incident impact velocity and impactor mass should be considered separately.
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Experimental studies have been presented on the impact behaviour of plain were E-glass-epoxy laminates with different combinations of impactor mass and incident impact velocity with the same incident impact energy of 24.43 J. Four...
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Experimental studies have been presented on the impact behaviour of plain were E-glass-epoxy laminates with different combinations of impactor mass and incident impact velocity with the same incident impact energy of 24.43 J. Four combinations of impactor mass-incident impact velocity have been considered. Imapct tests have been carried out on an instrumented drop weight impact test apparatus. The unsupported area of the specimens during the impact loading was 127 mm X 127 mm with clamped boundary condition. Thickness of the plate was 5 mm. Post-impact-compression testing of impacted specimens has been carried out using Compression-After-Imapct test fixture as per NASA 1142 standard. It is observed that for the materials tested, damage tolerance is higherfor low mass and high velocity combination as compared to high mass and low velocity combination.
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Plate glasses of windows and doors of buildings are often destroyed by the bullets in the criminal cases using firearms. When a plate glass is impacted by a projectile, the Hertzian cone is produced behind the impact point of this...
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Plate glasses of windows and doors of buildings are often destroyed by the bullets in the criminal cases using firearms. When a plate glass is impacted by a projectile, the Hertzian cone is produced behind the impact point of this glass. It is known that the apex angle of the Hertzian cone crack in Pyrex glass caused by small steel ball impact varies in a systematic manner with the impact velocity. However, there are few reports especially on the results caused by the lead bullet impact. In order to obtain the basic data to estimate the impact velocities and the incident angles of the projectiles, an experiment about the morphology of the Hertzian cone was carried out. In the experiment, projectiles (11mm dia. steel balls and 0.38 inch (9mm) dia. lead bullets) were shot onto the float plate glasses (soda-lime glasses). A strong correlation was found between the ratio of the Hertzian cone diame ter to the plate glass thickness and the impact velocity. It was also found that the Hertzian cone caused by inclined impact became the size equivalent to the velocity component which is normal to the glass surface. Thus, the morphology of the Hertzian cone can be one of the indexes for estimating the impact velocities and the incident angles of the projectiles.
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摘要 :
Plate glasses of windows and doors of buildings are often destroyed by the bullets in the criminal cases using firearms. when a plate glass is impacted by a projectile, the Hertzian cone is produced behind the impact point of this...
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Plate glasses of windows and doors of buildings are often destroyed by the bullets in the criminal cases using firearms. when a plate glass is impacted by a projectile, the Hertzian cone is produced behind the impact point of this glass. It is known that the apex angle of the Hertzian cone crack in Pyrex glass caused by small steel ball impact varies in a systematic manner with the impact velocity. However, there are few reports especially on the results caused by the lead bullet impact. In order to obtain the basic data to estimate the impact velocities and the incident angles of the projectiles, an experiment about the morphology of the Hertzian cone was carried out.In the experiment, projectiles (11mm dia. steel balls and 0.38 inch (9mm) dia. lead bullets) were shot onto the float plate glasses (soda-lime glasses). A strong correlation was found between the ratio of the Hertzian cone diameter to the plate glass thickness and the impact velocity. It was also found that the Hertzian cone caused by inclined impact became the size equivalent to the velocity component which is normal to the glass surface. Thus, the morphology of the Hertzian cone can be one of the indexes for estimating the impact velocities and the incident angles of the projectiles.
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This paper analyses the improvements in falling weight impact resistance characteristics of the laminates when highly flexible Polycarbonate (PC) sheet is sandwiched between Glass Fiber Reinforced Polymer (GFRP) laminates. Towards...
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This paper analyses the improvements in falling weight impact resistance characteristics of the laminates when highly flexible Polycarbonate (PC) sheet is sandwiched between Glass Fiber Reinforced Polymer (GFRP) laminates. Towards this, low-velocity impact (LVI) tests at different impact energies were conducted on various thicknesses of GFRP and hybrid laminates. For each given incident impact energy, the load--time data were extracted and the transient absorbed energy, as well as displacement, are computed by numerical integration. The impact energy obtained from this data is computed for all the laminates. Experimental investigation reveals that the hybrid laminate shows a significant increase in the maximum impact energy that can be absorbed before complete perforation as compared to bare GFRP laminate. Other impact resistance characteristics such as initial stiffness and peak load as a function of incident impact energy have been analyzed and the influence of PC insertion in the laminate (hybrid) on these parameters are experimentally investigated.
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The purpose of the paper is to investigate the discharge characteristics of plasma generated by a projectile high-velocity impact solar array with 2A12 aluminum substrate structures at the incidence angles of 30 degrees, 45 degree...
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The purpose of the paper is to investigate the discharge characteristics of plasma generated by a projectile high-velocity impact solar array with 2A12 aluminum substrate structures at the incidence angles of 30 degrees, 45 degrees and 60 degrees, respectively. Three sets of experiments were performed to impact solar array by taking advantage of discharge measurement system established and two-stage light gas gun loading system. Experimental results showed that the second discharge phenomenon did happen in the solar array at the given experimental conditions, and the discharge current peak and time interval between the primary discharge and the second discharge are the biggest at the projectile incidence angle of 45 degrees in the conditions of the near impact velocity and the different projectile incidence angles.
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An effort has been made to study the effects of variable incident impact energy and laminate thickness (obtained by varying the number of fabric layers at constant moulding pressure and also by varying the pressure for a fixed num...
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An effort has been made to study the effects of variable incident impact energy and laminate thickness (obtained by varying the number of fabric layers at constant moulding pressure and also by varying the pressure for a fixed number of fabric layers),on the low velocity impact damage tolerance of GFRP composite laminates (woven E-glass fabric in a room temperature cure epoxy system LY556/HY951).Repeated drop tests were conducted using an in-house built drop weight impact tester.Number of drops to failure (Nf),was considered as the impact damage tolerance index.Correlations between Nf and composite material parameters (fiber weight fraction -Wf,laminate thickness - t,number of fabric layers - L) and a test parameter (incident impact energy E) were found out and the bounding limits for these were defined.Critical values of impact energy (Ec) and laminate thickness (tc) were defined (for the particular resin - hardener system chosen for the study) which can quite possibly be used as designer's guidelines.A new ratio,(t/Wf},was introduced for the study of composite systems where both fiber weight fraction and laminate thickness get affected upon alteration of a process parameter (the pressure - P as in this case).
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This study predicts the residual strength of composite structures with impact damage by using the characteristic length of the composite with the hole corresponding to the impact damage area. Since C shaped structure differs from ...
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This study predicts the residual strength of composite structures with impact damage by using the characteristic length of the composite with the hole corresponding to the impact damage area. Since C shaped structure differs from that of the specimen, the shape factor was obtained from the concentration factor of the plate specimen and that of the structure by finite element analysis. The factor was applied to the prediction model for the residual strength of the CFRP composite plate specimen. Comparison between the experimental result and prediction result shows that the prediction method using the characteristic length can be applied to the prediction of the residual strength of CFRP composites after impact.
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In the case of wind-driven rain, as the angle of rain incidence increases, greater force components act parallel to the surface and lower force components act perpendicular to the surface. Therefore, raindrop impact angle could in...
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In the case of wind-driven rain, as the angle of rain incidence increases, greater force components act parallel to the surface and lower force components act perpendicular to the surface. Therefore, raindrop impact angle could influence the detachment process in the existence of substantial lateral jet development. This could be particularly significant for a cohesionless sand surface that has a weaker resistance to the dislodgement by a raindrop impact than a soil surface. Experiments of simulated wind-driven rain were conducted to evaluate sand detachment rates under increased lateral jetting induced by wind velocities of 6.4, 10.0, and 12.0 in s(-1) at nozzle operating pressures of 75, 100, and 150 KPa and incident on windward and leeward slopes of 4 and 9 degrees. With these set-ups, it was possible to have varying angles of incidence and to determine the effect of the compressive stress and shear stress, evaluated by the horizontal and vertical kinetic energy fluxes (E-tx and E-tz, respectively), on the detachment rates from the sand surface. At the same vectorwise sum of E-tz and E-tx, the results showed that there was, for similar values of E-tz and E-tx in windward slopes, more sand detachment rate; however, for dissimilar values of E-tz and E-tx in leeward slopes where E-tx was significantly higher than E-tz there was less sand detachment rate. Consequently, with certain values of the compressive stress and shear stress, the sand detachment rates under wind-driven rains peaked; and E-tz was the limiting component since the rates significantly decreased as E-tz particularly decreased in spite of very large values of E-tx. (C) 2007 Elsevier B.V. All rights reserved.
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