This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This paper presents an analysis of 3D amplitude and functional parameters for worn surfaces of co... more This paper presents an analysis of 3D amplitude and functional parameters for worn surfaces of composites with polyamide 6 as matrix and different glass bead concentrations (0%, 2.5%, 5%, 10%, 20%, 30% and 50%wt). The worn surfaces after dry sliding of a steel pin on a disk, for 10 km, at constant velocity (0.5 m/s, 1 m/s and 1.5 m/s) and under an average pressure of 1 MPa. There were done two tests under the same conditions. On each worn track, there were investigated three surfaces of 500 μm x 500 μm with a contact profilometer. The number of points on the scan line was 200 points and the step between lines was 5μm. The following amplitude parameters were measured and calculated for assessed surfaces: the arithmetic mean deviation, Sa, the root mean square deviation, Sq, the maximum height of surface prominence, Sp, the maximum surface depth, Sv, the maximum height, St, the skewness factor, Ssk and the kurtosis, Sku. The discussed functional parameters are the reduced peak height, Spk, the height of the core of the surface, Sk and the depth of the valley zone, Svk. The comparison of their values makes posible to evaluate if the worn surface could function in a new running or the replacement of the component is recommended. Considering that machine components have intermittent operation, these worn surfaces becoming initial surfaces for the following cycle of contact operation. Based on the average values of amplitude and functional parameters, it was found that a relatively good surface quality is preserved for concentrations of 10...30%wt glass beads, for v=0.5...1 m/s (Sa and Sq having similar trend); for lower concentrations and for 50% glass beads, the parameter values increase but without identifying a distinct relationship with the working regime, especially for 2.5 and 5% glass beads.
Journal of Engineering Sciences and Innovation, Mar 23, 2023
This paper presents a comparison of two models for an impact with a projectile 9 mm FMJ (full met... more This paper presents a comparison of two models for an impact with a projectile 9 mm FMJ (full metal jacket), having 373 m/s on stratified composites, at meso level. The models contain yarn with the geometry similar to the actual yarns of glass fibers, used in an experimental test. The yarns' orientation is a repeated (0°/90°). The model includs 8 layers of yarns. One model is done including only friction among yarns and between yarn and projectile and the second model introduces both friction and delamination properties (as in the coehesive zone model). The paper reports the differences between the two simulations with the same geometry of the models and the same constitutive material models for yarn and projectile materials, but one with conditioned bonds as in the cohesive zone models. Applying the cohesive zone model (CZM) with zero thickness makes the impact to have a more localized action, reduce bending of the broken yarns. The models are compared to an actual panel made of stratified layers of glass fibers with similar properties of the yarns and the simulation with cohesive zone model gives a closer aspect of the failure as compared to the actual one.
This paper presents an analysis based on experimental data for pointing out the behavior of rapes... more This paper presents an analysis based on experimental data for pointing out the behavior of rapeseed oil when it is additivated with a modifier of friction and wear, the nano hexagonal Boron nitride. All tests are done on a four-ball machine, in mild regime. Test parameters were sliding velocity (0.38 m/s, 0.53 m/s, 0.69 m/s, corresponding to the spindle rotational speed of the four-ball machine of 1000 rpm, 1400 rpm, 1800 rpm (±10 rpm),), force (100 N-300 N), test duration 1 h. There were calculated the average friction coefficient during the test and the average wear scar diameter (WSD) for each test. The same test parameters were done twice and the values in this paper are the average of these two tests. Wear was discussed for the same velocity range, in terms of WSD, but for comparing tests with different sliding velocity (implicitly, different sliding distances), there was used the wear rate of the wear scar diameter. The results on wear parameters, using additivated rapeseed oil, do not show spectacular results for the parameters tested in this study, but underline the "insensitivity" of the lubricants to the variation of the test regime (especially with respect to sliding speed), which is desirable for certain applications.
International conference KNOWLEDGE-BASED ORGANIZATION
This paper presents a model for impact bullet – panel of woven aramid fabrics in order to use it ... more This paper presents a model for impact bullet – panel of woven aramid fabrics in order to use it for an initial assessment of similar panels to protect against bullets in a range of 100…800 m/s. Based on these initial simulations, the designer could select the number of layers for actual tests. The factors that could be varied in these simulations could be the shape and dimensions of the projectiles, their mass and impact velocity. It is presented only the case of impacting a panel with .357 Magnum, with an incidence velocity of 420 m/s. The panel is composed of 8 layers of plain woven fabrics (200 mm x 200 mm), with weft and warp yarns, the yarn geometry being close to Teijin CT736 phenolic fabric, with 1680 DTEX and 410 g/m2. The simulation helps to identify the stages of panel failure and to evaluate qualitatively the similarity in panel failure with that of the actual panel, tested under the same conditions as the model.
IOP Conference Series: Materials Science and Engineering
This paper presents a discussion on simulating the impact projectile – target, for a velocity of ... more This paper presents a discussion on simulating the impact projectile – target, for a velocity of 375 m/s and a comparison to actual stratified panels. Model is run in Explicit Dynamics (Ansys), with material constitutive models as isotropic bilinear hardening, the failure criterion being the equivalent plastic strain at break. Dependence on elastic properties of temperature is not available in simulations that use explicitly dynamic systems. Only one value is used for a property. These temperature dependent values will be used by the solver. The first values defined as temperature-dependent data will be used in numerical solving. In the case of projectile impact-protection panel, the use of properties without temperature dependence is justified by recordings with thermal cameras, by the results of models presented in the literature and the characteristics of the materials used for the panels, some of which (such as aramid or glass fibber composites), having constant properties over ...
This paper presents results from numerical and experimental investigation on Charpy tests in orde... more This paper presents results from numerical and experimental investigation on Charpy tests in order to point out failure mechanisms and to evaluate new polymeric blends PP + PA6 + EPDM. Charpy tests were done for initial velocity of the impactor of 0.96 m/s and its mass of 3.219 kg and these data were also introduced in the finite element model. The proposed model takes into account the system of four balls, including support and the ring of fixing the three balls and it has a finer discretization of the impact area to highlight the mechanisms of failure and their development in time. The constitutive models for four materials (polypropylene with 1% Kritilen, two blends PP + PA6 + EPDM and a blend PA6 + EPDM) were derived from tensile tests. Running simulations for each constitutive model of material makes possible to differentiate the destruction mechanisms according to the material introduced in the simulation, including the initiation and the development of the crack(s), based on equivalent plastic strain at break (EPS) for each material. The validation of the model and the simulation results were done qualitatively, analyzing the shape of broken surfaces and comparing them to SEM images and quantitatively by comparing the impact duration, energy absorbed by the sample, the value of maximum force during impact. The duration of the destruction of the specimen is longer than the actual one, explainable by the fact that the material model does not take into account the influence of the material deformation speed in Charpy test, the model being designed with the help of tests done at 0.016 m/s (1000 mm/min) (maximum strain rate for the tensile tests). Experimental results are encouraging for recommending the blends 20% PP + 42% PA6 + 28% EPDM and 60% PA6 + 40% EPDM as materials for impact protection at low velocity (1 m/s). Simulation results are closer to the experimental ones for the more brittle tested materials (with less content of PA6 and EPDM) and more distanced for the more ductile materials (with higher content of PA6 and EPDM).
International conference KNOWLEDGE-BASED ORGANIZATION
This study investigates the impact behaviour of glass fiber epoxy composites with a focus on achi... more This study investigates the impact behaviour of glass fiber epoxy composites with a focus on achieving enhanced safety. A drop weight impact test machine was used to perform a series of impact tests on the composite samples. Two different impactors as dimensions and three velocities were used to investigate the impact behavior of glass fiber epoxy composites. The study’s goal is to investigate the impact response of these composites and their potential for usage in impact protection applications. The study findings show that glass fiber epoxy composites have outstanding impact resistance properties, as well as high levels of the ability to absorb energy and withstand the initiation of damage. The findings suggest that both the impactor (as shape and dimensions) and the velocity of impact have a notable influence impact on the damage mechanisms and energy absorption capacity of the composite materials. The failure mechanisms detected in the composites were mostly delamination and fib...
International conference KNOWLEDGE-BASED ORGANIZATION
This paper presents a model for impact bullet – panel of woven aramid fabrics in order to use it ... more This paper presents a model for impact bullet – panel of woven aramid fabrics in order to use it for an initial assessment of similar panels to protect against bullets in a range of 100…800 m/s. Based on these initial simulations, the designer could select the number of layers for actual tests. The factors that could be varied in these simulations could be the shape and dimensions of the projectiles, their mass and impact velocity. It is presented only the case of impacting a panel with .357 Magnum, with an incidence velocity of 420 m/s. The panel is composed of 8 layers of plain woven fabrics (200 mm x 200 mm), with weft and warp yarns, the yarn geometry being close to Teijin CT736 phenolic fabric, with 1680 DTEX and 410 g/m2. The simulation helps to identify the stages of panel failure and to evaluate qualitatively the similarity in panel failure with that of the actual panel, tested under the same conditions as the model.
This paper presents an isothermal model of Storz coupling used in fire hose coupling. The model h... more This paper presents an isothermal model of Storz coupling used in fire hose coupling. The model has the actual geometry of the coupling Fire and Rescue NSW for the nominal diameter of 65 mm (NEN 3374). The simulation was done for a load interval on the coupling (from F=2 kN for an actual value of water pressure, to extreme conditions with F=3 kN and 6 kN when the coupling fails under load). The stress and strain distributions point out the stress concentrators and the maximum values of von Mises stress in order to compare them to the material limit. The coupling is made of aluminum alloy EN AW6082 (AlSi1MgMn), treatment T6 (solution heat treated, quenched and artificially aged). Bottom surface of one half-coupling is fixed and the upper surface of the other half-coupling is loaded with a tensile force, uniformly distributed on surface. The constitutive model of the material is bilinear with Young modulus of 71000 MPa, Poisson ration 0.33, yield limit of 280 MPa, ultimate tensile str...
IOP Conference Series: Materials Science and Engineering
This paper presents a laboratory scale technology for manufacturing a composite with ballistic pr... more This paper presents a laboratory scale technology for manufacturing a composite with ballistic protection characteristics for a certain level of threat. The composite is made of quadriaxial fabrics, with four oriented substrates (0°/+45°/90°/-45°), which assumes from the start that the fabric will have a quasi-isotropic behavior. The selected resin to bind the layers is made of two-component resin Biresin® CR82, with hardener CH80-2 (supplied by Sika Group). This technology implies cutting, a laying-up process, a maintenance in press, under load, for at least 8 hours, a natural aging during 7 days, and a heat treatment, in two stages, taking into account the software of the used oven, of 3 hours each, at 60 °C. There were manufactured sets of 8-layer panels and 16-layer panels, checking to have a narrow tolerance of the thickness for the set of panels with the same number of layers. The process has repeatability, precision and robustness. The recipe for making panels and the laborat...
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This paper presents experimental results and a failure analysis of a composite for ballistic prot... more This paper presents experimental results and a failure analysis of a composite for ballistic protection. The stratified plate is manufactured at laboratory scale, after a technology designed by the authors. The plates were tested for level FB2, taking into account the standard SR EN 1522:2004 (Windows, doors, shutters and blinds. Bullet resistance. Requirements and classification) and SR EN 1523:2004 (Windows, doors, shutters and blinds. Bullet resistance. Test method) and the results point out that this plate could face more dangerous threats. In order to evaluate the behavior of the plate under the impact characterizing a higher level of threat, the authors uses a FE model and simulated the system bullet-plate for different impact velocities.
IOP Conference Series: Materials Science and Engineering, 2019
This paper is a review about glass fiber fabrics used for impact protection. The authors comment ... more This paper is a review about glass fiber fabrics used for impact protection. The authors comment on types of fabrics, tests done for pointing out the impact resistance. Many of applications refer to ballistic protection but, as one may notice, experimental studies in open literature are disperse from the point of view of parameter ranges. Many articles on the subject do not have details on materials (fabrics and adhesives) used to manufacture the protection samples and on technology for obtaining the final system of protection. Few tests are done according to national, international or military standards because of difficulties in sample manufacturing at industrial scale or the costs related to sample producing. This review could be useful for the start of a research on ballistic panels based on or including glass fiber fabrics, for making the researchers familiar to their particular failure mechanisms.
This paper presents preliminary results and discussion on two aramid fabrics in order to establis... more This paper presents preliminary results and discussion on two aramid fabrics in order to establish their stab resistance when used as panels with different numbers of layers. Twaron fabrics SRM509 and CT736CMP, were arranged in 16 and 20 layers and in a combination of them (10 layers SRM509 and 10 layers CT736CMP). Samples of 130 mm x 130 mm were cut from the fabrics, weighed and measured for thickness. All tests were done for an impact energy of 24 J (the resulting impact velocity being 3 m/s). The blade had the geometry recommended in the standard Stab Resistance of Personal Body Armor NIJ Standard-0115.00 as P1. The conclusion of this analysis is that the better behavior to stab is obtained for panels that have higher gradients in time, for all four characteristics here discussed: force, displacement, absorbed energy and velocity. When using hybrid panels, the results could intermediate those of the components, this solution could be recommended for reasons as price, weight.
"This paper presents an analysis of an isothermal model for an impact simulation in order to... more "This paper presents an analysis of an isothermal model for an impact simulation in order to use the results for virtually optimizing the thickness of the panel for the same threat. The target has a stratified structure; the connection between layers is ""bonded"", with ""breakable"" detachment when there is exceeded a value for tensile stress and shear stress, introduced with the value of 90 MPa for tensile loading and 60 MPa for shear stress, these being characteristic values for the resin used for attaching the layers in the actual panel. Using Explicit Dynamics Ansys, it is possible to distinguish the stages of the impact process and how they depend on panel thickness. All bodies involved in impact are deformable, the bullet materials having a Johnson-Cook model and the layer being characterized. Even if the layer material model was simplified to a hardening isotropic bilinear model with data from the literature, the results were validated by the number of layers destroyed for the partially penetrated panels and by the size of the delamination on the back of the last layer. This simulation is useful for reducing the number of initial tests for evaluating the ballistic resistance."
This paper presents an analysis of data resulting from the same material constitutive model, base... more This paper presents an analysis of data resulting from the same material constitutive model, based on experimental data and model developed by Johnson and Cook. The same case of impacting a cylindrical body on a perfectly rigid target was run with four different mesh size (2 mm, 1 mm, 0.5 mm and 0.25 mm). Here, the comparing criterion was the maximum value of von Mises stress and the authors pointed out that the finest mesh here presented is closer to reality. Depending on the case application the engineers could adopt a finer or coarse mesh, but not so coarse to denaturate the reality of body deformation and failure. How to decide? Having performant computer resources (hardware and software) and running several mesh in order to notice the convergence of one parameter or, more reliable, a set of criteria that could include qualitative resemblance with actual bodies as concerning failure and deformation, experimental dat on strain, yield and failure of the involved materials, values ...
This paper presents an analysis of two cases, simulating the impact of a cylindical projectile on... more This paper presents an analysis of two cases, simulating the impact of a cylindical projectile on a perfectly rigid plate. One case is run without friction, the second one is run taking into account a friction coeficient between the plate and the projectile. The authors used for the projectile the same material constitutive model for both cases, based on experimental data and model developed by Johnson and Cook. Here, the comparing criteria were the maximum value of von Mises stress, the velocity and acceleration of the central point on the opposite face to the contact face of the projectile. Introducing friction, the simulation is more realistic. Taking into account friction, the projectile is less deformed and there was no edge breakage, at the same time moment.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This paper presents an analysis of 3D amplitude and functional parameters for worn surfaces of co... more This paper presents an analysis of 3D amplitude and functional parameters for worn surfaces of composites with polyamide 6 as matrix and different glass bead concentrations (0%, 2.5%, 5%, 10%, 20%, 30% and 50%wt). The worn surfaces after dry sliding of a steel pin on a disk, for 10 km, at constant velocity (0.5 m/s, 1 m/s and 1.5 m/s) and under an average pressure of 1 MPa. There were done two tests under the same conditions. On each worn track, there were investigated three surfaces of 500 μm x 500 μm with a contact profilometer. The number of points on the scan line was 200 points and the step between lines was 5μm. The following amplitude parameters were measured and calculated for assessed surfaces: the arithmetic mean deviation, Sa, the root mean square deviation, Sq, the maximum height of surface prominence, Sp, the maximum surface depth, Sv, the maximum height, St, the skewness factor, Ssk and the kurtosis, Sku. The discussed functional parameters are the reduced peak height, Spk, the height of the core of the surface, Sk and the depth of the valley zone, Svk. The comparison of their values makes posible to evaluate if the worn surface could function in a new running or the replacement of the component is recommended. Considering that machine components have intermittent operation, these worn surfaces becoming initial surfaces for the following cycle of contact operation. Based on the average values of amplitude and functional parameters, it was found that a relatively good surface quality is preserved for concentrations of 10...30%wt glass beads, for v=0.5...1 m/s (Sa and Sq having similar trend); for lower concentrations and for 50% glass beads, the parameter values increase but without identifying a distinct relationship with the working regime, especially for 2.5 and 5% glass beads.
Journal of Engineering Sciences and Innovation, Mar 23, 2023
This paper presents a comparison of two models for an impact with a projectile 9 mm FMJ (full met... more This paper presents a comparison of two models for an impact with a projectile 9 mm FMJ (full metal jacket), having 373 m/s on stratified composites, at meso level. The models contain yarn with the geometry similar to the actual yarns of glass fibers, used in an experimental test. The yarns' orientation is a repeated (0°/90°). The model includs 8 layers of yarns. One model is done including only friction among yarns and between yarn and projectile and the second model introduces both friction and delamination properties (as in the coehesive zone model). The paper reports the differences between the two simulations with the same geometry of the models and the same constitutive material models for yarn and projectile materials, but one with conditioned bonds as in the cohesive zone models. Applying the cohesive zone model (CZM) with zero thickness makes the impact to have a more localized action, reduce bending of the broken yarns. The models are compared to an actual panel made of stratified layers of glass fibers with similar properties of the yarns and the simulation with cohesive zone model gives a closer aspect of the failure as compared to the actual one.
This paper presents an analysis based on experimental data for pointing out the behavior of rapes... more This paper presents an analysis based on experimental data for pointing out the behavior of rapeseed oil when it is additivated with a modifier of friction and wear, the nano hexagonal Boron nitride. All tests are done on a four-ball machine, in mild regime. Test parameters were sliding velocity (0.38 m/s, 0.53 m/s, 0.69 m/s, corresponding to the spindle rotational speed of the four-ball machine of 1000 rpm, 1400 rpm, 1800 rpm (±10 rpm),), force (100 N-300 N), test duration 1 h. There were calculated the average friction coefficient during the test and the average wear scar diameter (WSD) for each test. The same test parameters were done twice and the values in this paper are the average of these two tests. Wear was discussed for the same velocity range, in terms of WSD, but for comparing tests with different sliding velocity (implicitly, different sliding distances), there was used the wear rate of the wear scar diameter. The results on wear parameters, using additivated rapeseed oil, do not show spectacular results for the parameters tested in this study, but underline the "insensitivity" of the lubricants to the variation of the test regime (especially with respect to sliding speed), which is desirable for certain applications.
International conference KNOWLEDGE-BASED ORGANIZATION
This paper presents a model for impact bullet – panel of woven aramid fabrics in order to use it ... more This paper presents a model for impact bullet – panel of woven aramid fabrics in order to use it for an initial assessment of similar panels to protect against bullets in a range of 100…800 m/s. Based on these initial simulations, the designer could select the number of layers for actual tests. The factors that could be varied in these simulations could be the shape and dimensions of the projectiles, their mass and impact velocity. It is presented only the case of impacting a panel with .357 Magnum, with an incidence velocity of 420 m/s. The panel is composed of 8 layers of plain woven fabrics (200 mm x 200 mm), with weft and warp yarns, the yarn geometry being close to Teijin CT736 phenolic fabric, with 1680 DTEX and 410 g/m2. The simulation helps to identify the stages of panel failure and to evaluate qualitatively the similarity in panel failure with that of the actual panel, tested under the same conditions as the model.
IOP Conference Series: Materials Science and Engineering
This paper presents a discussion on simulating the impact projectile – target, for a velocity of ... more This paper presents a discussion on simulating the impact projectile – target, for a velocity of 375 m/s and a comparison to actual stratified panels. Model is run in Explicit Dynamics (Ansys), with material constitutive models as isotropic bilinear hardening, the failure criterion being the equivalent plastic strain at break. Dependence on elastic properties of temperature is not available in simulations that use explicitly dynamic systems. Only one value is used for a property. These temperature dependent values will be used by the solver. The first values defined as temperature-dependent data will be used in numerical solving. In the case of projectile impact-protection panel, the use of properties without temperature dependence is justified by recordings with thermal cameras, by the results of models presented in the literature and the characteristics of the materials used for the panels, some of which (such as aramid or glass fibber composites), having constant properties over ...
This paper presents results from numerical and experimental investigation on Charpy tests in orde... more This paper presents results from numerical and experimental investigation on Charpy tests in order to point out failure mechanisms and to evaluate new polymeric blends PP + PA6 + EPDM. Charpy tests were done for initial velocity of the impactor of 0.96 m/s and its mass of 3.219 kg and these data were also introduced in the finite element model. The proposed model takes into account the system of four balls, including support and the ring of fixing the three balls and it has a finer discretization of the impact area to highlight the mechanisms of failure and their development in time. The constitutive models for four materials (polypropylene with 1% Kritilen, two blends PP + PA6 + EPDM and a blend PA6 + EPDM) were derived from tensile tests. Running simulations for each constitutive model of material makes possible to differentiate the destruction mechanisms according to the material introduced in the simulation, including the initiation and the development of the crack(s), based on equivalent plastic strain at break (EPS) for each material. The validation of the model and the simulation results were done qualitatively, analyzing the shape of broken surfaces and comparing them to SEM images and quantitatively by comparing the impact duration, energy absorbed by the sample, the value of maximum force during impact. The duration of the destruction of the specimen is longer than the actual one, explainable by the fact that the material model does not take into account the influence of the material deformation speed in Charpy test, the model being designed with the help of tests done at 0.016 m/s (1000 mm/min) (maximum strain rate for the tensile tests). Experimental results are encouraging for recommending the blends 20% PP + 42% PA6 + 28% EPDM and 60% PA6 + 40% EPDM as materials for impact protection at low velocity (1 m/s). Simulation results are closer to the experimental ones for the more brittle tested materials (with less content of PA6 and EPDM) and more distanced for the more ductile materials (with higher content of PA6 and EPDM).
International conference KNOWLEDGE-BASED ORGANIZATION
This study investigates the impact behaviour of glass fiber epoxy composites with a focus on achi... more This study investigates the impact behaviour of glass fiber epoxy composites with a focus on achieving enhanced safety. A drop weight impact test machine was used to perform a series of impact tests on the composite samples. Two different impactors as dimensions and three velocities were used to investigate the impact behavior of glass fiber epoxy composites. The study’s goal is to investigate the impact response of these composites and their potential for usage in impact protection applications. The study findings show that glass fiber epoxy composites have outstanding impact resistance properties, as well as high levels of the ability to absorb energy and withstand the initiation of damage. The findings suggest that both the impactor (as shape and dimensions) and the velocity of impact have a notable influence impact on the damage mechanisms and energy absorption capacity of the composite materials. The failure mechanisms detected in the composites were mostly delamination and fib...
International conference KNOWLEDGE-BASED ORGANIZATION
This paper presents a model for impact bullet – panel of woven aramid fabrics in order to use it ... more This paper presents a model for impact bullet – panel of woven aramid fabrics in order to use it for an initial assessment of similar panels to protect against bullets in a range of 100…800 m/s. Based on these initial simulations, the designer could select the number of layers for actual tests. The factors that could be varied in these simulations could be the shape and dimensions of the projectiles, their mass and impact velocity. It is presented only the case of impacting a panel with .357 Magnum, with an incidence velocity of 420 m/s. The panel is composed of 8 layers of plain woven fabrics (200 mm x 200 mm), with weft and warp yarns, the yarn geometry being close to Teijin CT736 phenolic fabric, with 1680 DTEX and 410 g/m2. The simulation helps to identify the stages of panel failure and to evaluate qualitatively the similarity in panel failure with that of the actual panel, tested under the same conditions as the model.
This paper presents an isothermal model of Storz coupling used in fire hose coupling. The model h... more This paper presents an isothermal model of Storz coupling used in fire hose coupling. The model has the actual geometry of the coupling Fire and Rescue NSW for the nominal diameter of 65 mm (NEN 3374). The simulation was done for a load interval on the coupling (from F=2 kN for an actual value of water pressure, to extreme conditions with F=3 kN and 6 kN when the coupling fails under load). The stress and strain distributions point out the stress concentrators and the maximum values of von Mises stress in order to compare them to the material limit. The coupling is made of aluminum alloy EN AW6082 (AlSi1MgMn), treatment T6 (solution heat treated, quenched and artificially aged). Bottom surface of one half-coupling is fixed and the upper surface of the other half-coupling is loaded with a tensile force, uniformly distributed on surface. The constitutive model of the material is bilinear with Young modulus of 71000 MPa, Poisson ration 0.33, yield limit of 280 MPa, ultimate tensile str...
IOP Conference Series: Materials Science and Engineering
This paper presents a laboratory scale technology for manufacturing a composite with ballistic pr... more This paper presents a laboratory scale technology for manufacturing a composite with ballistic protection characteristics for a certain level of threat. The composite is made of quadriaxial fabrics, with four oriented substrates (0°/+45°/90°/-45°), which assumes from the start that the fabric will have a quasi-isotropic behavior. The selected resin to bind the layers is made of two-component resin Biresin® CR82, with hardener CH80-2 (supplied by Sika Group). This technology implies cutting, a laying-up process, a maintenance in press, under load, for at least 8 hours, a natural aging during 7 days, and a heat treatment, in two stages, taking into account the software of the used oven, of 3 hours each, at 60 °C. There were manufactured sets of 8-layer panels and 16-layer panels, checking to have a narrow tolerance of the thickness for the set of panels with the same number of layers. The process has repeatability, precision and robustness. The recipe for making panels and the laborat...
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This paper presents experimental results and a failure analysis of a composite for ballistic prot... more This paper presents experimental results and a failure analysis of a composite for ballistic protection. The stratified plate is manufactured at laboratory scale, after a technology designed by the authors. The plates were tested for level FB2, taking into account the standard SR EN 1522:2004 (Windows, doors, shutters and blinds. Bullet resistance. Requirements and classification) and SR EN 1523:2004 (Windows, doors, shutters and blinds. Bullet resistance. Test method) and the results point out that this plate could face more dangerous threats. In order to evaluate the behavior of the plate under the impact characterizing a higher level of threat, the authors uses a FE model and simulated the system bullet-plate for different impact velocities.
IOP Conference Series: Materials Science and Engineering, 2019
This paper is a review about glass fiber fabrics used for impact protection. The authors comment ... more This paper is a review about glass fiber fabrics used for impact protection. The authors comment on types of fabrics, tests done for pointing out the impact resistance. Many of applications refer to ballistic protection but, as one may notice, experimental studies in open literature are disperse from the point of view of parameter ranges. Many articles on the subject do not have details on materials (fabrics and adhesives) used to manufacture the protection samples and on technology for obtaining the final system of protection. Few tests are done according to national, international or military standards because of difficulties in sample manufacturing at industrial scale or the costs related to sample producing. This review could be useful for the start of a research on ballistic panels based on or including glass fiber fabrics, for making the researchers familiar to their particular failure mechanisms.
This paper presents preliminary results and discussion on two aramid fabrics in order to establis... more This paper presents preliminary results and discussion on two aramid fabrics in order to establish their stab resistance when used as panels with different numbers of layers. Twaron fabrics SRM509 and CT736CMP, were arranged in 16 and 20 layers and in a combination of them (10 layers SRM509 and 10 layers CT736CMP). Samples of 130 mm x 130 mm were cut from the fabrics, weighed and measured for thickness. All tests were done for an impact energy of 24 J (the resulting impact velocity being 3 m/s). The blade had the geometry recommended in the standard Stab Resistance of Personal Body Armor NIJ Standard-0115.00 as P1. The conclusion of this analysis is that the better behavior to stab is obtained for panels that have higher gradients in time, for all four characteristics here discussed: force, displacement, absorbed energy and velocity. When using hybrid panels, the results could intermediate those of the components, this solution could be recommended for reasons as price, weight.
"This paper presents an analysis of an isothermal model for an impact simulation in order to... more "This paper presents an analysis of an isothermal model for an impact simulation in order to use the results for virtually optimizing the thickness of the panel for the same threat. The target has a stratified structure; the connection between layers is ""bonded"", with ""breakable"" detachment when there is exceeded a value for tensile stress and shear stress, introduced with the value of 90 MPa for tensile loading and 60 MPa for shear stress, these being characteristic values for the resin used for attaching the layers in the actual panel. Using Explicit Dynamics Ansys, it is possible to distinguish the stages of the impact process and how they depend on panel thickness. All bodies involved in impact are deformable, the bullet materials having a Johnson-Cook model and the layer being characterized. Even if the layer material model was simplified to a hardening isotropic bilinear model with data from the literature, the results were validated by the number of layers destroyed for the partially penetrated panels and by the size of the delamination on the back of the last layer. This simulation is useful for reducing the number of initial tests for evaluating the ballistic resistance."
This paper presents an analysis of data resulting from the same material constitutive model, base... more This paper presents an analysis of data resulting from the same material constitutive model, based on experimental data and model developed by Johnson and Cook. The same case of impacting a cylindrical body on a perfectly rigid target was run with four different mesh size (2 mm, 1 mm, 0.5 mm and 0.25 mm). Here, the comparing criterion was the maximum value of von Mises stress and the authors pointed out that the finest mesh here presented is closer to reality. Depending on the case application the engineers could adopt a finer or coarse mesh, but not so coarse to denaturate the reality of body deformation and failure. How to decide? Having performant computer resources (hardware and software) and running several mesh in order to notice the convergence of one parameter or, more reliable, a set of criteria that could include qualitative resemblance with actual bodies as concerning failure and deformation, experimental dat on strain, yield and failure of the involved materials, values ...
This paper presents an analysis of two cases, simulating the impact of a cylindical projectile on... more This paper presents an analysis of two cases, simulating the impact of a cylindical projectile on a perfectly rigid plate. One case is run without friction, the second one is run taking into account a friction coeficient between the plate and the projectile. The authors used for the projectile the same material constitutive model for both cases, based on experimental data and model developed by Johnson and Cook. Here, the comparing criteria were the maximum value of von Mises stress, the velocity and acceleration of the central point on the opposite face to the contact face of the projectile. Introducing friction, the simulation is more realistic. Taking into account friction, the projectile is less deformed and there was no edge breakage, at the same time moment.
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Papers by George Ojoc