ASCE-ASME journal of risk and uncertainty in engineering systems,, Aug 19, 2016
The safety predictions of composite armors require a probabilistic analysis to take into consider... more The safety predictions of composite armors require a probabilistic analysis to take into consideration scatters in the material properties and initial velocity. Damage initiation laws are used to account for matrix and fiber failure during high-velocity impact. A three-dimensional (3D) stochastic finite-element analysis of laminated composite plates under impact is performed to determine the probability of failure (Pf). The objective is to achieve the safest design of lightweight composite through the most efficient ply arrangement of S2 glass epoxy. Realistic damage initiation models are implemented. The Pf is obtained through the Gaussian process response surface method (GPRSM). The antisymmetric cross-ply arrangement is found to be the safest based on maximum stress and Yen and Hashin criteria simultaneously. Sensitivity analysis is performed to achieve the target reliability.
Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, Jun 8, 2023
An explosive attack on a vehicle can cause catastrophic damage, injury, and loss of life. Experim... more An explosive attack on a vehicle can cause catastrophic damage, injury, and loss of life. Experimentally evaluating the blast performance is very costly, hazardous, and environmentally polluting. The numerical investigation of blast behavior is a good alternative. However, this numerical study showed an effort toward improving metallic sandwich panels’ ability to withstand explosion loads of 1–3 kg of TNT at a distance of 100 mm. The blast mitigation of square and circular tube honeycomb cores was compared. The foam and circular tube stiffeners were used to optimize the honeycomb sandwiches’ blast mitigation characteristics. Radial face deflection, face center deflection, core crushing behavior, internal energy, and plastic dissipation energy parameters were used for the characterization of blast behavior. The obtained results indicate that the circular tube honeycomb has better blast mitigation characteristics than the square honeycomb, which improves with foam filling. The circular tube-strengthened square honeycomb provides the lightest stiffened sandwich panel with the smallest deformation and face deflections under all explosive loadings.
The probabilistic failure analysis of composite beams takes into consideration the effect of stat... more The probabilistic failure analysis of composite beams takes into consideration the effect of statistical scatter in its elastic and strength properties and velocity of impactor. Stochastic finite element analysis is used to study the response of ballistic impact. The limit state function is accordingly established, if the stresses in the lamina are such that the limit state function (g(x) ≤ 0). The Gaussian Response Surface method (GRSM) is able to reduce the time consumed and is ten times computationally efficient than MCS. Comparative probability of failure study is carried out using the GRSM. GRSM is used to predict the probability of failure (Pf) for different ply lay-up arrangements. The fiber failure of simply supported composite beams with symmetric cross ply lay-ups find maximum probability of failure than the other ply lay-ups namely anti- symmetric cross ply, symmetric angle ply and anti- symmetric angle ply. Sensitivity analysis showed shear strength (T13) is one of the most sensitive parameters to influence the probability of failure (Pf).
This paper presented an experimental and numerical investigation on the low velocity impact respo... more This paper presented an experimental and numerical investigation on the low velocity impact response of thermoplastic hybrid composites reinforced with Kevlar/basalt fabrics. Two hybrid and one Kevlar homogeneous composite laminates were manufactured with polypropylene as a resin. In the hybrid composites, one hybrid composite (H-1) was manufactured with alternate stacking of four layers of basalt and four layers of Kevlar and the second hybrid composite (H-2) was manufactured with four Kevlar layers on front face and four basalt layers on back face. Low velocity impact tests were performed using a drop-weight impact equipment at three different energies (25 J, 50 J and 75 J). Among the two hybrid composites H-1 hybrid composite exhibited 15.58–20.79% and 13.47–20.47% improvement in the peak force and energy absorption, respectively, than the H-2 hybrid composite. The peak force and energy absorption of Kevlar homogeneous composite was also improved by 10.07–14.37% and 5.38–11.29%, respectively, due to hybridization. A three dimensional (3D) dynamic finite element software, Abaqus/Explicit, was implemented to simulate the experimental results of low velocity impact tests. A user-defined material subroutine (VUMAT) based on Chang-Chang linear-orthotropic damage model was implemented into the finite element code. The predictions from numerical simulation were found to be in good agreement with the experimental results.
Abstract Experimental and numerical investigations are carried out to determine the low velocity ... more Abstract Experimental and numerical investigations are carried out to determine the low velocity impact (LVI) response of three different polypropylene (PP) composites. Three dimensional (3D) angle-interlock fabrics with Kevlar, basalt and a hybrid combination of both are produced. 3D composites are manufactured with these three fabrics using vacuum-assisted compression molding process with PP resin. LVI tests are conducted using a drop-weight impact equipment at the energy level of 240 J. The LVI response of the three 3D-PP composites is compared in terms of peak force, energy absorption and damage modes. The experimental results indicate that the basalt 3D composites showed 6.62–13.73% higher peak force and H3D composites absorbed 7.67-48.49% more energy than the remaining composites. Results indicate that there is a considerable enhancement in the energy absorbing capability of hybrid composites as compared to Kevlar/PP and basalt/PP composites. Numerical simulations are carried out using the commercial finite element (FE) code ABAQUS/Explicit. A user-defined material subroutine (VUMAT) based on Chang-Chang linear orthotropic damage model, is implemented into the FE code. Good agreement between experimental and numerical simulations is achieved in terms of impact response characteristics.
The low velocity impact (LVI) result of laminated targets is an imperative study to evaluate its ... more The low velocity impact (LVI) result of laminated targets is an imperative study to evaluate its failure for applications to inconsequential structures. The work has extensive applications to off shore and naval industry. Safety and reliability assessment as per the international standards is one of the basic objectives of the study. LVI on composite plates is performed taking the material parameters and loading condition as random variables. Graphite fiber reinforced laminated plates are vulnerable to damage due to impact by foreign objects and in plane loading. In order to evaluate the safe load carrying capacity and the reliability under impact, dynamic analysis of composite plate subjected to LVI is carried out. Probabilistic finite element method (PFEM) is performed to determine the stochastic response. During impact, the in-plane damage modes such as matrix cracking, fiber failure and shear cracking are modeled using a failure criterion. The out of plane de-lamination is modeled using cohesive surfaces. The randomness associated with the system properties due to the inherent scatter in the geometric and material properties and input loads are modeled in a stochastic fashion. Random parameters represent various characteristics appearing in the performance function. The stochastic response and reliability forecast of the system is determined by Gaussian processes response surface method (GPRSM) and validity of method for the present problem is establish using Monte Carlo simulation (MCS) procedure. The safety level qualification is achieved in terms of reliability level targeted.
Journal of Sandwich Structures and Materials, Sep 19, 2022
In this study, dynamic explicit analysis was performed to examine the air-blast performance of va... more In this study, dynamic explicit analysis was performed to examine the air-blast performance of various hybrid sandwich designs in terms of face plate deflections and energy dissipation capacity under the conventional weapons effects program (CONWEP) air-blast loads ranging from 3 kg to 8 kg trinitrotoluene for stand-off distance ranges from 150 mm to 200 mm. The blast resistance of honeycomb sandwich configurations was evaluated using steel honeycomb with different core topologies, crushable Al foam-filled steel honeycomb, and steel or steel with 3D Kevlar/polypropylene laminate employing fiber metal laminate (FML) front face. For an accurate prediction of the deformation mechanism of all steel parts, the Johnson-Cook (J-C) model was used. The composite failure criteria of Hashin, Puck, and Matzenmiller were implemented to accurately examine the fiber and matrix damage behavior. The novel hybrid design of the honeycomb sandwich structure’s blast resistance is improved by the employment of foam-filled honeycomb, an FML front face, and a circular honeycomb core. In comparison to other sandwich configurations, a novel designed hybrid sandwich construction composed of foam filled circular honeycomb with FML front facing and steel back facing (FCH-1KP0.5) achieved the highest blast resistance due to its lowest face deflection with the smallest plastic dissipation energy.
ASCE-ASME journal of risk and uncertainty in engineering systems,, Aug 19, 2016
The safety predictions of composite armors require a probabilistic analysis to take into consider... more The safety predictions of composite armors require a probabilistic analysis to take into consideration scatters in the material properties and initial velocity. Damage initiation laws are used to account for matrix and fiber failure during high-velocity impact. A three-dimensional (3D) stochastic finite-element analysis of laminated composite plates under impact is performed to determine the probability of failure (Pf). The objective is to achieve the safest design of lightweight composite through the most efficient ply arrangement of S2 glass epoxy. Realistic damage initiation models are implemented. The Pf is obtained through the Gaussian process response surface method (GPRSM). The antisymmetric cross-ply arrangement is found to be the safest based on maximum stress and Yen and Hashin criteria simultaneously. Sensitivity analysis is performed to achieve the target reliability.
Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, Jun 8, 2023
An explosive attack on a vehicle can cause catastrophic damage, injury, and loss of life. Experim... more An explosive attack on a vehicle can cause catastrophic damage, injury, and loss of life. Experimentally evaluating the blast performance is very costly, hazardous, and environmentally polluting. The numerical investigation of blast behavior is a good alternative. However, this numerical study showed an effort toward improving metallic sandwich panels’ ability to withstand explosion loads of 1–3 kg of TNT at a distance of 100 mm. The blast mitigation of square and circular tube honeycomb cores was compared. The foam and circular tube stiffeners were used to optimize the honeycomb sandwiches’ blast mitigation characteristics. Radial face deflection, face center deflection, core crushing behavior, internal energy, and plastic dissipation energy parameters were used for the characterization of blast behavior. The obtained results indicate that the circular tube honeycomb has better blast mitigation characteristics than the square honeycomb, which improves with foam filling. The circular tube-strengthened square honeycomb provides the lightest stiffened sandwich panel with the smallest deformation and face deflections under all explosive loadings.
The probabilistic failure analysis of composite beams takes into consideration the effect of stat... more The probabilistic failure analysis of composite beams takes into consideration the effect of statistical scatter in its elastic and strength properties and velocity of impactor. Stochastic finite element analysis is used to study the response of ballistic impact. The limit state function is accordingly established, if the stresses in the lamina are such that the limit state function (g(x) ≤ 0). The Gaussian Response Surface method (GRSM) is able to reduce the time consumed and is ten times computationally efficient than MCS. Comparative probability of failure study is carried out using the GRSM. GRSM is used to predict the probability of failure (Pf) for different ply lay-up arrangements. The fiber failure of simply supported composite beams with symmetric cross ply lay-ups find maximum probability of failure than the other ply lay-ups namely anti- symmetric cross ply, symmetric angle ply and anti- symmetric angle ply. Sensitivity analysis showed shear strength (T13) is one of the most sensitive parameters to influence the probability of failure (Pf).
This paper presented an experimental and numerical investigation on the low velocity impact respo... more This paper presented an experimental and numerical investigation on the low velocity impact response of thermoplastic hybrid composites reinforced with Kevlar/basalt fabrics. Two hybrid and one Kevlar homogeneous composite laminates were manufactured with polypropylene as a resin. In the hybrid composites, one hybrid composite (H-1) was manufactured with alternate stacking of four layers of basalt and four layers of Kevlar and the second hybrid composite (H-2) was manufactured with four Kevlar layers on front face and four basalt layers on back face. Low velocity impact tests were performed using a drop-weight impact equipment at three different energies (25 J, 50 J and 75 J). Among the two hybrid composites H-1 hybrid composite exhibited 15.58–20.79% and 13.47–20.47% improvement in the peak force and energy absorption, respectively, than the H-2 hybrid composite. The peak force and energy absorption of Kevlar homogeneous composite was also improved by 10.07–14.37% and 5.38–11.29%, respectively, due to hybridization. A three dimensional (3D) dynamic finite element software, Abaqus/Explicit, was implemented to simulate the experimental results of low velocity impact tests. A user-defined material subroutine (VUMAT) based on Chang-Chang linear-orthotropic damage model was implemented into the finite element code. The predictions from numerical simulation were found to be in good agreement with the experimental results.
Abstract Experimental and numerical investigations are carried out to determine the low velocity ... more Abstract Experimental and numerical investigations are carried out to determine the low velocity impact (LVI) response of three different polypropylene (PP) composites. Three dimensional (3D) angle-interlock fabrics with Kevlar, basalt and a hybrid combination of both are produced. 3D composites are manufactured with these three fabrics using vacuum-assisted compression molding process with PP resin. LVI tests are conducted using a drop-weight impact equipment at the energy level of 240 J. The LVI response of the three 3D-PP composites is compared in terms of peak force, energy absorption and damage modes. The experimental results indicate that the basalt 3D composites showed 6.62–13.73% higher peak force and H3D composites absorbed 7.67-48.49% more energy than the remaining composites. Results indicate that there is a considerable enhancement in the energy absorbing capability of hybrid composites as compared to Kevlar/PP and basalt/PP composites. Numerical simulations are carried out using the commercial finite element (FE) code ABAQUS/Explicit. A user-defined material subroutine (VUMAT) based on Chang-Chang linear orthotropic damage model, is implemented into the FE code. Good agreement between experimental and numerical simulations is achieved in terms of impact response characteristics.
The low velocity impact (LVI) result of laminated targets is an imperative study to evaluate its ... more The low velocity impact (LVI) result of laminated targets is an imperative study to evaluate its failure for applications to inconsequential structures. The work has extensive applications to off shore and naval industry. Safety and reliability assessment as per the international standards is one of the basic objectives of the study. LVI on composite plates is performed taking the material parameters and loading condition as random variables. Graphite fiber reinforced laminated plates are vulnerable to damage due to impact by foreign objects and in plane loading. In order to evaluate the safe load carrying capacity and the reliability under impact, dynamic analysis of composite plate subjected to LVI is carried out. Probabilistic finite element method (PFEM) is performed to determine the stochastic response. During impact, the in-plane damage modes such as matrix cracking, fiber failure and shear cracking are modeled using a failure criterion. The out of plane de-lamination is modeled using cohesive surfaces. The randomness associated with the system properties due to the inherent scatter in the geometric and material properties and input loads are modeled in a stochastic fashion. Random parameters represent various characteristics appearing in the performance function. The stochastic response and reliability forecast of the system is determined by Gaussian processes response surface method (GPRSM) and validity of method for the present problem is establish using Monte Carlo simulation (MCS) procedure. The safety level qualification is achieved in terms of reliability level targeted.
Journal of Sandwich Structures and Materials, Sep 19, 2022
In this study, dynamic explicit analysis was performed to examine the air-blast performance of va... more In this study, dynamic explicit analysis was performed to examine the air-blast performance of various hybrid sandwich designs in terms of face plate deflections and energy dissipation capacity under the conventional weapons effects program (CONWEP) air-blast loads ranging from 3 kg to 8 kg trinitrotoluene for stand-off distance ranges from 150 mm to 200 mm. The blast resistance of honeycomb sandwich configurations was evaluated using steel honeycomb with different core topologies, crushable Al foam-filled steel honeycomb, and steel or steel with 3D Kevlar/polypropylene laminate employing fiber metal laminate (FML) front face. For an accurate prediction of the deformation mechanism of all steel parts, the Johnson-Cook (J-C) model was used. The composite failure criteria of Hashin, Puck, and Matzenmiller were implemented to accurately examine the fiber and matrix damage behavior. The novel hybrid design of the honeycomb sandwich structure’s blast resistance is improved by the employment of foam-filled honeycomb, an FML front face, and a circular honeycomb core. In comparison to other sandwich configurations, a novel designed hybrid sandwich construction composed of foam filled circular honeycomb with FML front facing and steel back facing (FCH-1KP0.5) achieved the highest blast resistance due to its lowest face deflection with the smallest plastic dissipation energy.
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