In this study, four different types of helical composite springs were made of structures includin... more In this study, four different types of helical composite springs were made of structures including unidirectional laminates (AU), rubber core unidirectional laminates (UR), unidirectional laminates with a braided outer layer (BU), and rubber core unidirectional laminates with a braided outer layer (BUR), respectively. It aims to investigate the effects of rubber core and braided outer layer on the mechanical properties of the aforementioned four helical springs. According to the experimental results, the helical composite spring with a rubber core can increase its failure load in compression by about 12%; while the spring with a braided outer layer can not only increase its failure load in compression by about 18%, but also improve the spring constant by approximately 16%. The helical spring with a BUR structure has the highest mechanical properties among those considered herein, its failure load in compression approximately equals 336.2 kgf, and the spring constant is almost 16.27 kgf/mm.
Adhesives are viscoelastic polymeric materials with ratedependent behaviour. A personal body armo... more Adhesives are viscoelastic polymeric materials with ratedependent behaviour. A personal body armour for higher threat perception consists of hard ceramic facing adhesively joined to a composite laminate backing. This work focuses on the mechanical testing of two types of adhesive materials, i.e., epoxy-based and polyurethane-based by bonding dissimilar materials to understand their role in protection against ballistic impact. Block shear tests were conducted for two types of adhesive at various thicknesses of adhesives layer. Epoxybased adhesive showed higher shear strength than polyurethanes-based adhesive. Optimal thickness for each adhesive under shear loading was also determined from these tests. Split Hopkinson pressure bar tests were conducted to understand the compressive behaviour of adhesives at higher strain rates in order to simulate the high-velocity projectile impacts.
Abstract High temperature blast and ballistic resistant light weight fibre reinforced plastic com... more Abstract High temperature blast and ballistic resistant light weight fibre reinforced plastic composites are very much in demand. Accordingly, the present investigation is focused on the quasi-static and high strain rate behaviour of Basalt/Polyetherimide (PEI) composite. Nine different types of composite samples were fabricated by compression moulding. The moulding pressure and temperatures were varied in the range of 15 - 25 bars and 325°C - 375°C, respectively. Quasi-static testing was done at the rate of 3 mm/min to establish the optimum moulding parameters. High strain rate compression tests in the strain rate range of 900/s - 3200/s were performed on the optimum moulded composite specimens. High strain rate testing revealed that 40 layered Basalt/PEI composite moulded at 25 bar pressure and 350°C can attain highest stress of 932MPa whereas, the same was found to attain 446 MPa under quasi-static loading conditons. Thus, establishing the rate depedency of Basalt/PEI composite. Damage studies revealed that Basalt/PEI undergoes brittle damage, typically resulting in shear plane angle of 42° - 45°. SEM micrographs revealed brittle fibre failure and matrix free fibre bundles, indicating the importance of process parameters optimiation.
An investigation of the effect of strain rate on the dynamic compressive behavior of glass/polyt... more An investigation of the effect of strain rate on the dynamic compressive behavior of glass/polytetrafluoroethylene (PTFE) composite is presented. Experimental studies were carried out on two dimensional (2D), satin weave (SW) and
three dimensional (3D) woven glass/PTFE composites using split Hopkinson
pressure bar (SHPB) apparatus. Commercial grades of glass/PTFE fabrics were
autoclaved to prepare the composite laminates and circular specimens were
cut out using a high-pressure water jet. High strain rate studies confirmed the
rate-dependent behavior of all the woven composite systems under consideration. The highest rates of loading were attained by 3D woven specimens for
identical incident energies. The highest peak stress attained by 3D woven specimens was 501 MPa, which was trailed by 2D woven specimens with 482 MPa
stress. The advantage of satin weave was not reflected in the small specimens
as the peak stress attained for identical loading was limited to 405 MPa. Similarly, the highest strain and toughness were recorded for 3D woven composites. However, the SW pattern unlocked a new possibility of controlling the
primary damage axis. Furthermore, an analytical method is presented based
on variable rate power law to predict the dynamic compressive stress of
glass/PTFE.
In order to face the grand challenge of characterizing soft and light armour material system shav... more In order to face the grand challenge of characterizing soft and light armour material system shaving polymers and shear thickening fluids under impacts at high strain rates lead to design and development of this particular SHPB set up. The developed set up is designed for a maximum firing pressure of 300 bar of nitrogen gas and it comprises automated gas filling and firing, striker bar velocity recording and data acquisition system. Pressure bars are made of titanium alloy due to its high yield strength and reasonably lower density which could protect plastic deformation, wave dispersion and reduces impedance mismatch with the intended soft specimens, unlike maraging steel bars. The maximum stresses on the critical parts of the setup are crosschecked with simulation results and compared with corresponding yield strengths. Velocitypressure calibration of the developed setup shows higher velocities can be achieved at any particular pressure, when it is compared with the existing publi...
As a major challenge, development of lightweight fibre reinforced polymer (FRP) composite body ar... more As a major challenge, development of lightweight fibre reinforced polymer (FRP) composite body armour, characterization of candidate matrix polymers at high strain rate impact is the focus in this research. Polypropylene (PP) and the nano-composites with 1-5% by weight of NC (nanoclay) platelets are the candidates considered. In the characterization phase, high strain rate impact and quasi-static loading tests were performed to figure out the limiting (failure) responses. Comparison between the material systems is, subsequently, made to nominate one matrix configuration. Enhancements of mechanical properties with increase in weight percentage of the nanoparticles are observed at both quasi-static and dynamic loadings. Observations of dispersed imposed failure modes, development of novel model for failure modulus and evaluation of peak strength values are also attempted.
Aluminum-Silicon carbide (Al-SiC) metal matrix composite (MMC) have gained importance as a new cl... more Aluminum-Silicon carbide (Al-SiC) metal matrix composite (MMC) have gained importance as a new class of material capable of serving the future generation brake material requirements. The presented study deals with the compressive high strain rate behavior of Al-SiC composite comprising 15% SiC by weight. The MMC specimens were fabricated by powder metallurgy route. Three different ball milling times were selected for the study purpose after optimizing all other processing parameters. Incorporation of SiC invariably enhanced the hardness, quasi-static and dynamic compressive strength of Al-SiC composite. Hardness was noted to enhance as a function of increasing ball milling time. However, the quasi-static and dynamic compression properties were recorded highest for the ball milling time of 240 minutes. The study confirms that minor addition of a suitable reinforcing material can significantly improve the properties of an MMC. Also, increasing the ball mill time may not necessarily enhance all the material properties.
Shear thickening is a non-Newtonian flow behavior characterized by the increase in apparent visco... more Shear thickening is a non-Newtonian flow behavior characterized by the increase in apparent viscosity with the increase in applied shear rate, particularly when the shear rate exceeds a critical value termed as the critical shear rate (CSR). Due to this remarkable property of shear-thickening fluids (STFs), they are extensively used in hip protection pads, protective gear for athletes, and more recently in body armor. The use of STFs in body armor has led to the development of the concept of liquid body armor. In this study, the effect of particle size is explored on the low and high strain rate behavior of nanosilica dispersions, so as to predict the efficacy of STF-aided personal protection systems (PPS), specifically for ballistic applications. The low strain rate study was conducted on cone and plate rhe-ometer, whereas the high strain rate characterization of STF was conducted on in-house fabricated split Hop-kinson pressure bar (SHPB) system. Spherical nanosilica particles of three different sizes (100, 300, and 500 nm) as well as fumed silica particles of four different specific surface areas (Aerosil A-90, A-130, A-150, and A-200), respectively, were used in this study. The test samples were prepared by dispersing nanosilica particles in polypropylene glycol (PPG) using ultrasonic homogenization method. The low strain rate studies aided in determining the CSR of the synthesized STF dispersions, whereas the high strain rate studies explored the impact-resisting ability of STFs in terms of the impact toughness and the peak stress attained during the impact loading of STF in SHPB testing.
In the present work, dynamic compression response of polypropylene (PP) based composites reinforc... more In the present work, dynamic compression response of polypropylene (PP) based composites reinforced with Kevlar/Basalt fabrics was investigated. Two homogeneous fabrics with Kevlar (K3D) and Basalt (B3D) yarns and one hybrid (H3D) fabric with a combination of Kevlar/Basalt yarns were produced. The architecture of the fabrics was three-dimensional angle-interlock (3D-A). Three different composite laminates were manufactured using vacuum-assisted compression molding technique. The high strain rate compression loading was applied using a Split-Hopkinson Pressure Bar (SHPB) setup at a strain rate regime of 3633e5235/s. The results indicated that the dynamic compression properties of thermoplastic 3D-A composites are strain rate sensitive. In all the composites, the peak stress, toughness and modulus were increased with strain rate. However, the strain at peak stress of Basalt reinforced composites (B3D, H3D) decreased approximately by 25%, while for K3D specimens it increased approximately by 15%. The K3D composites had a higher strain rate as compared to the B3D and H3D composites. In the case of K3D composite, except strain at peak stress, remaining dynamic properties were lower than the B3D composite , however, hybridization increased these properties. The failure mechanisms of 3D-A composites were characterized through macroscopic and scanning electron microscopy (SEM).
In this study, four different types of helical composite springs were made of structures includin... more In this study, four different types of helical composite springs were made of structures including unidirectional laminates (AU), rubber core unidirectional laminates (UR), unidirectional laminates with a braided outer layer (BU), and rubber core unidirectional laminates with a braided outer layer (BUR), respectively. It aims to investigate the effects of rubber core and braided outer layer on the mechanical properties of the aforementioned four helical springs. According to the experimental results, the helical composite spring with a rubber core can increase its failure load in compression by about 12%; while the spring with a braided outer layer can not only increase its failure load in compression by about 18%, but also improve the spring constant by approximately 16%. The helical spring with a BUR structure has the highest mechanical properties among those considered herein, its failure load in compression approximately equals 336.2 kgf, and the spring constant is almost 16.27 kgf/mm.
Adhesives are viscoelastic polymeric materials with ratedependent behaviour. A personal body armo... more Adhesives are viscoelastic polymeric materials with ratedependent behaviour. A personal body armour for higher threat perception consists of hard ceramic facing adhesively joined to a composite laminate backing. This work focuses on the mechanical testing of two types of adhesive materials, i.e., epoxy-based and polyurethane-based by bonding dissimilar materials to understand their role in protection against ballistic impact. Block shear tests were conducted for two types of adhesive at various thicknesses of adhesives layer. Epoxybased adhesive showed higher shear strength than polyurethanes-based adhesive. Optimal thickness for each adhesive under shear loading was also determined from these tests. Split Hopkinson pressure bar tests were conducted to understand the compressive behaviour of adhesives at higher strain rates in order to simulate the high-velocity projectile impacts.
Abstract High temperature blast and ballistic resistant light weight fibre reinforced plastic com... more Abstract High temperature blast and ballistic resistant light weight fibre reinforced plastic composites are very much in demand. Accordingly, the present investigation is focused on the quasi-static and high strain rate behaviour of Basalt/Polyetherimide (PEI) composite. Nine different types of composite samples were fabricated by compression moulding. The moulding pressure and temperatures were varied in the range of 15 - 25 bars and 325°C - 375°C, respectively. Quasi-static testing was done at the rate of 3 mm/min to establish the optimum moulding parameters. High strain rate compression tests in the strain rate range of 900/s - 3200/s were performed on the optimum moulded composite specimens. High strain rate testing revealed that 40 layered Basalt/PEI composite moulded at 25 bar pressure and 350°C can attain highest stress of 932MPa whereas, the same was found to attain 446 MPa under quasi-static loading conditons. Thus, establishing the rate depedency of Basalt/PEI composite. Damage studies revealed that Basalt/PEI undergoes brittle damage, typically resulting in shear plane angle of 42° - 45°. SEM micrographs revealed brittle fibre failure and matrix free fibre bundles, indicating the importance of process parameters optimiation.
An investigation of the effect of strain rate on the dynamic compressive behavior of glass/polyt... more An investigation of the effect of strain rate on the dynamic compressive behavior of glass/polytetrafluoroethylene (PTFE) composite is presented. Experimental studies were carried out on two dimensional (2D), satin weave (SW) and
three dimensional (3D) woven glass/PTFE composites using split Hopkinson
pressure bar (SHPB) apparatus. Commercial grades of glass/PTFE fabrics were
autoclaved to prepare the composite laminates and circular specimens were
cut out using a high-pressure water jet. High strain rate studies confirmed the
rate-dependent behavior of all the woven composite systems under consideration. The highest rates of loading were attained by 3D woven specimens for
identical incident energies. The highest peak stress attained by 3D woven specimens was 501 MPa, which was trailed by 2D woven specimens with 482 MPa
stress. The advantage of satin weave was not reflected in the small specimens
as the peak stress attained for identical loading was limited to 405 MPa. Similarly, the highest strain and toughness were recorded for 3D woven composites. However, the SW pattern unlocked a new possibility of controlling the
primary damage axis. Furthermore, an analytical method is presented based
on variable rate power law to predict the dynamic compressive stress of
glass/PTFE.
In order to face the grand challenge of characterizing soft and light armour material system shav... more In order to face the grand challenge of characterizing soft and light armour material system shaving polymers and shear thickening fluids under impacts at high strain rates lead to design and development of this particular SHPB set up. The developed set up is designed for a maximum firing pressure of 300 bar of nitrogen gas and it comprises automated gas filling and firing, striker bar velocity recording and data acquisition system. Pressure bars are made of titanium alloy due to its high yield strength and reasonably lower density which could protect plastic deformation, wave dispersion and reduces impedance mismatch with the intended soft specimens, unlike maraging steel bars. The maximum stresses on the critical parts of the setup are crosschecked with simulation results and compared with corresponding yield strengths. Velocitypressure calibration of the developed setup shows higher velocities can be achieved at any particular pressure, when it is compared with the existing publi...
As a major challenge, development of lightweight fibre reinforced polymer (FRP) composite body ar... more As a major challenge, development of lightweight fibre reinforced polymer (FRP) composite body armour, characterization of candidate matrix polymers at high strain rate impact is the focus in this research. Polypropylene (PP) and the nano-composites with 1-5% by weight of NC (nanoclay) platelets are the candidates considered. In the characterization phase, high strain rate impact and quasi-static loading tests were performed to figure out the limiting (failure) responses. Comparison between the material systems is, subsequently, made to nominate one matrix configuration. Enhancements of mechanical properties with increase in weight percentage of the nanoparticles are observed at both quasi-static and dynamic loadings. Observations of dispersed imposed failure modes, development of novel model for failure modulus and evaluation of peak strength values are also attempted.
Aluminum-Silicon carbide (Al-SiC) metal matrix composite (MMC) have gained importance as a new cl... more Aluminum-Silicon carbide (Al-SiC) metal matrix composite (MMC) have gained importance as a new class of material capable of serving the future generation brake material requirements. The presented study deals with the compressive high strain rate behavior of Al-SiC composite comprising 15% SiC by weight. The MMC specimens were fabricated by powder metallurgy route. Three different ball milling times were selected for the study purpose after optimizing all other processing parameters. Incorporation of SiC invariably enhanced the hardness, quasi-static and dynamic compressive strength of Al-SiC composite. Hardness was noted to enhance as a function of increasing ball milling time. However, the quasi-static and dynamic compression properties were recorded highest for the ball milling time of 240 minutes. The study confirms that minor addition of a suitable reinforcing material can significantly improve the properties of an MMC. Also, increasing the ball mill time may not necessarily enhance all the material properties.
Shear thickening is a non-Newtonian flow behavior characterized by the increase in apparent visco... more Shear thickening is a non-Newtonian flow behavior characterized by the increase in apparent viscosity with the increase in applied shear rate, particularly when the shear rate exceeds a critical value termed as the critical shear rate (CSR). Due to this remarkable property of shear-thickening fluids (STFs), they are extensively used in hip protection pads, protective gear for athletes, and more recently in body armor. The use of STFs in body armor has led to the development of the concept of liquid body armor. In this study, the effect of particle size is explored on the low and high strain rate behavior of nanosilica dispersions, so as to predict the efficacy of STF-aided personal protection systems (PPS), specifically for ballistic applications. The low strain rate study was conducted on cone and plate rhe-ometer, whereas the high strain rate characterization of STF was conducted on in-house fabricated split Hop-kinson pressure bar (SHPB) system. Spherical nanosilica particles of three different sizes (100, 300, and 500 nm) as well as fumed silica particles of four different specific surface areas (Aerosil A-90, A-130, A-150, and A-200), respectively, were used in this study. The test samples were prepared by dispersing nanosilica particles in polypropylene glycol (PPG) using ultrasonic homogenization method. The low strain rate studies aided in determining the CSR of the synthesized STF dispersions, whereas the high strain rate studies explored the impact-resisting ability of STFs in terms of the impact toughness and the peak stress attained during the impact loading of STF in SHPB testing.
In the present work, dynamic compression response of polypropylene (PP) based composites reinforc... more In the present work, dynamic compression response of polypropylene (PP) based composites reinforced with Kevlar/Basalt fabrics was investigated. Two homogeneous fabrics with Kevlar (K3D) and Basalt (B3D) yarns and one hybrid (H3D) fabric with a combination of Kevlar/Basalt yarns were produced. The architecture of the fabrics was three-dimensional angle-interlock (3D-A). Three different composite laminates were manufactured using vacuum-assisted compression molding technique. The high strain rate compression loading was applied using a Split-Hopkinson Pressure Bar (SHPB) setup at a strain rate regime of 3633e5235/s. The results indicated that the dynamic compression properties of thermoplastic 3D-A composites are strain rate sensitive. In all the composites, the peak stress, toughness and modulus were increased with strain rate. However, the strain at peak stress of Basalt reinforced composites (B3D, H3D) decreased approximately by 25%, while for K3D specimens it increased approximately by 15%. The K3D composites had a higher strain rate as compared to the B3D and H3D composites. In the case of K3D composite, except strain at peak stress, remaining dynamic properties were lower than the B3D composite , however, hybridization increased these properties. The failure mechanisms of 3D-A composites were characterized through macroscopic and scanning electron microscopy (SEM).
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Papers by Hemant Chouhan
three dimensional (3D) woven glass/PTFE composites using split Hopkinson
pressure bar (SHPB) apparatus. Commercial grades of glass/PTFE fabrics were
autoclaved to prepare the composite laminates and circular specimens were
cut out using a high-pressure water jet. High strain rate studies confirmed the
rate-dependent behavior of all the woven composite systems under consideration. The highest rates of loading were attained by 3D woven specimens for
identical incident energies. The highest peak stress attained by 3D woven specimens was 501 MPa, which was trailed by 2D woven specimens with 482 MPa
stress. The advantage of satin weave was not reflected in the small specimens
as the peak stress attained for identical loading was limited to 405 MPa. Similarly, the highest strain and toughness were recorded for 3D woven composites. However, the SW pattern unlocked a new possibility of controlling the
primary damage axis. Furthermore, an analytical method is presented based
on variable rate power law to predict the dynamic compressive stress of
glass/PTFE.
three dimensional (3D) woven glass/PTFE composites using split Hopkinson
pressure bar (SHPB) apparatus. Commercial grades of glass/PTFE fabrics were
autoclaved to prepare the composite laminates and circular specimens were
cut out using a high-pressure water jet. High strain rate studies confirmed the
rate-dependent behavior of all the woven composite systems under consideration. The highest rates of loading were attained by 3D woven specimens for
identical incident energies. The highest peak stress attained by 3D woven specimens was 501 MPa, which was trailed by 2D woven specimens with 482 MPa
stress. The advantage of satin weave was not reflected in the small specimens
as the peak stress attained for identical loading was limited to 405 MPa. Similarly, the highest strain and toughness were recorded for 3D woven composites. However, the SW pattern unlocked a new possibility of controlling the
primary damage axis. Furthermore, an analytical method is presented based
on variable rate power law to predict the dynamic compressive stress of
glass/PTFE.