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Hydrotherapy is a supervised exercise session conducted in a specially designed swimming pool to induce healing health conditions against arthritis, inflammation and other ailments. Hydropool is a pool intended for such aquatic therapy whereby the users are seated in special-chairs on top of a platform that will be slowly submerged into the pool. However, existing platform structure and hoisting mechanism of hydropools are mostly physically strenuous for disabled people. Besides that, the cost of the lifting systems is often high owing to the sophisticated hydraulic or pneumatic apparatus and materials used. Thus, it is essential to design and analyze a hydropool platform and lifting mechanism to overcome these limitations. This study presents the numerical analysis of a 1200 mm (width) by 1015 mm (length) platform structure, and a scissor mechanism to lift the platform from a 1750-mm deep pool. The structure comprises nine individual components including base, scissor links, supporting and connecting links, leadscrew, platform, fence, bolts and nuts. The design objective is to minimize mass at optimum load carrying capacity with a reasonable safety factor. A few design options are considered to achieve this objective. A virtual model of the selected design is created using SolidWorks®. Finite element analysis (FEA) on the model is conducted using the ANSYS® workbench in static structural mode to evaluate the von Mises stresses and total deformations of the platform when a maximum load of 2943 N is applied vertically on the structure. The structure is made of SS316, which has a yield strength at 0.2% offset of 205 MPa as per the ASTM A276/A276M standard. The FEA results showed that the maximum von Mises stress of 67.9 MPa is obtained at the scissor link component of the structure. The corresponding maximum total deformation is 1.33 mm. The safety factor is found to be equivalent to 33.1% of the yield strength of SS316 at the maximum applied load. These observations indicate that the platform structure and scissor-lifting mechanism are safe under the loading conditions used in the simulation.

Contemporary military and other law enforcement operations are technology-driven with weapons and ammunition that demand a flexible, damage- and moisture-resistant, and lightweight protective materials with superior energy absorbing capacity. Ballistic fabrics made from high performance synthetic fibers such as para-aramid and natural fibers including basalt, and composites utilizing these fabrics, are among the leading materials for armor systems. Basalt fibers, which are extracted from igneous volcanic rocks, are natural fibers with mechanical and thermo-physical properties that are generally comparable or superior to glass and other synthetic fibers at a lower cost. This gives basalt-based composites an edge over existing materials for potential application as anti-ballistic protective panels. The aim of the present study is to experimentally determine the V50 performance and penetration resistance of a unidirectional woven basalt fiber laminated epoxy system at three different combinations of ply orientations [0, 45 and 90 degrees at both CW and CCW directions] consisting of 48 layers of the woven fabric. The V50 performance test was conducted in accordance to the MIL-STD-662F standard using the Universal Test Gun model UZ-2002. The V50 ballistic velocity are computed based on a minimum of six shots including three complete penetrations and three partial penetrations. The optimum number of layers of the basalt fabric to sustain the reference penetration velocity of 367 m/s corresponding to threat level II of the NIJ Standard-0101.04 are calculated for the current test specimen for future development.

Woven fabric composites based on different technical fiber material and different design architecture continue to be an attractive structural component against ballistic impact. Numerous studies have been conducted to identify material properties and design architecture that plays a role in determining the ballistic performance. This paper presents a short review on influence features that are important in enhancing the ballistic performance. Each of the features is outlined in depth including citation from its original references. Apart from this, an attempt to showcase trend in recent research publications and activity involves 2D, 3D and hybrid woven fabric composites is also covered. The reference list will provide a database for elementary knowledge and motivation for prospective research in woven composites.

A conventional tube is considered in oblique position when its longitudinal is oblique. However, oblique attachments vary as the tube can be a straight or angulated tube. In the present study, impact responses of different oblique positioned tubes subject to axial loading were numerically studied. Next, the best oblique arrangements were proposed that have higher critical load angle and energy absorption capacity. Results show that specimen of Top-Bottom Angulated (TBA) from horizontal is the best choice for its lowest initial peak load and mean crush load. This data therefore has great potential for further enhance the new design of energy absorbers in oblique position.

This paper presents the ballistic impact study for the non-filled aluminum tank. The objective was to determine the ballistic limit for front tank wall and rear tank wall. The tank was impacted with fragment simulating projectile (FSP) with various velocities range from 239 m/s up to 556 m/s. The aluminum tank was 3 mm thick, 150 mm wide and 750 mm long. The ends of tank were closed with two Polymethyl methacrylate (PMMA) windows which fixed to the tank with four steel bars. The test was conducted at the Science and Technology Research Institute for Defense (STRIDE) Batu Arang, Selangor. The results showed that the ballistic limit for the front tank wall and rear tank wall was 257.7 m/s and 481 m/s, respectively.

Protecting a soldier’s head from injury is critical to function and survivability. Traditionally, combat helmets have been utilized to provide protection against shrapnel and ballistic threats, which have reduced head injuries and fatalities. However, home-made bombs or improvised explosive devices (IEDs) have been increasingly used in theatre of operations since the Iraq and Afghanistan conflicts. Traumatic brain injury (TBI), particularly blast-induced TBI, which is typically not accompanied by external body injuries, is becoming increasingly prevalent among injured soldiers. The response of personal protective equipment, especially combat helmets, to blast events is relatively unknown. There is an urgent need to develop head protection systems with blast protection/ mitigation capabilities in addition to ballistic protection. Modern military operations, ammunitions, and technology driven war tactics require a lightweight headgear that integrates protection mechanisms (against ballistics, blasts, heat, and noise), sensors, night vision devices, and laser range finders into a single system. The current paper provides a comparative study on the design, materials, ballistic and blast performance of the combat helmets used by the U.S. Army based on a comprehensive and critical review of existing studies. Mechanisms of ballistic energy absorption, effects of helmet curvatures on ballistic performance, and performance measures of helmets are discussed. Properties of current helmet materials (including Kevlar® K29 and K129 fibers, and thermoset resins) and future candidate materials for helmets (such as nano-composites, thermoplastic polymers, and carbon fibers) are elaborated. Also, experimental and computational studies on blast-induced TBI are examined, and constitutive models developed for brain tissues are reviewed. Finally, the effectiveness of current combat helmets against TBI is analyzed along with possible avenues for future research.

This paper presents the moisture absorption and shock cushioning properties of flexible polyurethane foams (PU) filled with saw dust fibers at 10, 15 and 20wt%. The compositeswere fabricated using open molded method from a two-part liquid foamsystem consisting of part-A (Isocyanate) and part-B (Polyol).The diffusion rates from the moisture absorption test is calculated using Ficks second law equation. Thesample with 10 wt% filler shows the highest diffusion ratewhile the lowest rateis sample with15wt% filler. The shock cushioning properties was determined via drop test where an 11.48-kg weight is dropped, from a height of 610 cm on the composites. The average Gvalue that represents product fragility was found to be 55.45.

This paper presents the coupling of finite element method (FEM) with smoothed particle hydrodynamics (SPH) to simulate the impact in hydrodynamic ram (HRAM). The main objective was to determine the pressure history by specific particle, which was a new point of view in HRAM study. Commonly, pressure history was obtained by many particles which located at the same location but at different time. Fragment simulating projectile (FSP) with velocity of 972 m/s was employed to impact water-filled tank. For validation purpose, two parameters i.e. mode of failure and wall deformation were employed. Good agreement was observed. On top of pressure history result, pressure and location of the particle at various times were presented.

This paper presents the terminal ballistic of 3 mm thickness aluminium plate impacted by fragment simulating projectile (FSP). Up to days, not many researchers are keen into terminal ballistic. They are more focus towards ballistic limit. Therefore, there is a need to highlight terminal ballistic as such in this study. The experiment was conducted at the Science and Technology Research Institute for Defence (STRIDE) Batu Arang, Selangor. For recording purpose, digital high speed camera with the capability of 250,000 frames per second (max) and the highest resolution 1024x1024 was used. For the data acquisition and processing, Photron Fastcam Viewer (PFV) software was used. For numerical simulation purpose, commercial software code Hyperworks was employed. Results showed that there were four main failure stages, which were first contact between FSP and the plate, partial perforation, full perforation with FSP and plug still intact and lastly separation of FSP and plug. Good agreement was observed between e...

The ballistic impact of Twaron CT709® plain weave fabrics is studied using a three-dimensional fabric model. The model is developed by treating each individual yarn as a continuum, and the time-dependent yarn behavior is phenomenologically described using a three-dimensional linear viscoelastic constitutive relation. A user subroutine VUMAT for ABAQUS/Explicit is compiled to incorporate the constitutive behavior. By using the newly developed model, a parametric study is carried out to analyze the effects of various parameters on the impact behavior of the fabrics, which include impact velocity, inter-yarn friction, and the number of fabric layers. The simulation results obtained include bullet residual velocity, fabric deformation and damage pattern, kinetic energy of the system, fabric strain energy, and frictional dissipation energy. The residual velocities predicted by the current model correlate well with existing experimental data, and the parametric study leads to the determination of the optimal nu...

Ballistic helmet is a standard infantry equipment that provides ballistic protection from fragmenting to the head, temples, ear and neck of the wearer. This paper presents the study of the design of a locally used ballistic helmet, i.e. Personnel Armor System for Ground Troop (PASGT) type helmet, from ergonomic perspectives and the identification of potential risk areas of injury based on the current ballistic helmet design. Two quantitative assessment techniques are employed in the investigation. First, a set of questionnaires were distributed to the current users of the PASGT helmet. The result showed that the 54.8% of respondents experienced pain on the parietal (top) area of their head, which is a potential risk area of head injury. Second, an experiment with 10-mm thick sponge layer added to the interior part of the helmet was conducted to test its effect on the contact pressure between the head of the wearer and the medium size PASGT helmet while jogging on a treadmill at 8 km/h for 180 seconds. Mean of peak contact pressure with and without wearing the sponge of 2.5 kPa and 2.6 kPa, respectively, are obtained from the practical test. The maximum of peak contact pressure is found to be 3.6 kPa with the sponge and 4.2 kPa without the sponge. The results obtained in this study indicate that there are areas of discomfort interior to the PASGT helmet in contact with the wearer and that the discomfort can be minimized by appending a sponge layer to the frontal of the helmet.

The constitutive behavior of a Twaron CT709® fabric/natural rubber (Twaron®/NR) composite is studied using the four-parameter Burgers model (composed of a Maxwell element and a Kelvin-Voigt element in series), a proposed five-parameter model (consisting of a Maxwell element and a generalized Maxwell [GM] element in series), and a newly developed para-rheological model (comprising a GM element and a stress network element in parallel). The new model makes use of the affine network-based molecular theory of rubber elasticity. The uniaxial stress-strain relation of the Twaron®/NR composite is experimentally determined at two constant strain rates of 0.00001 s − 1 and 0.01 s − 1 . The values of the parameters involved in the three viscoelasticity models are extracted from the experimental data. It is found that both the Burgers model and the five-parameter model significantly under-predict the stresses for large strain values at both the strain rates. In contrast, the constitutive response at each strain rate...

This paper presents the ballistic limit study for the water-filled aluminum tank. The objective was to determine the ballistic limit for the rear tank wall by using numerical method. Commercial software Altair Hyperworks 12.0 was employed for this study. The finite element coupled with smoothed particle hydrodynamics (SPH) was developed to model the perforation of fragment simulating projectile (FSP) towards water-filled tank. Verification of the results was done by comparing with the experiment results. The results showed that there were four main phase failures occurred, which were shock phase, drag phase, cavitation phase and exit phase. The ballistic limit for the rear wall was 479.27 m/s.

Recently there is an increased concern for the development of not only well-designed but also sustainable materials. Material sustainability is associated with the extraction of renewable resources and disposal procedures that would not injure our ecosystem. In this respect, indigenous agricultural wastes or by-products are suitable alternatives to lightweight and disposable green-materials at low cost. Agro-waste and biomass materials are plentiful in many parts of the world including Malaysia. Fibers obtained from agricultural by-products are often used as fillers or reinforcement in non-biodegradable polymer matrix. Polylactic acid (PLA), which is a compostable and biodegradable thermoplastic, is derived from renewable agro-sources such as potato, corn, or sugarcane. The mechanical and thermal properties of select biofibers-filled PLA composites are comparable to that of the composites made from conventional fibers. Research findings imply the feasibility of processing PLA with natural fibers such as kenaf using existing manufacturing technologies. Natural fiber filled biodegradable polymer composite materials have the advantage of simple and safe disposal over petroleum-based polymers besides generating new low-carbon economy for the plantation sector. However, research outcomes show that the fiber/matrix interface of PLA and natural fiber is weak due to incompatible surface properties of the two material types. In this article, issues pertaining to fiber/matrix interfacial adhesion, potential renewable sources of polymers and processing technologies of natural fiber (or –eco)-biocomposite materials are reviewed. The prospect of replacing traditional polymers obtained from non-renewable fossil resources with biopolymers to develop sustainable eco-biocomposite materials for shock cushioning application such as for packing and packaging materials is discussed in particular.

This paper presents the details of experimental set-up to determine the ballistic limit for the aluminium tank for two cases, empty and water-filled tank. The experiment was carried out at Science and Technology Research Institute for Defense (STRIDE) Batu Arang. The aluminum tank was 3 mm thick, 150 mm wide and 750 mm long. At the end of the tank were closed with two Polymethyl methacrylate (PMMA) windows. Silicone was used to seal the contact between the end of the tank and PMMA. Four steel bars used to fix the windows to the tank. Fragment simulating projectile (FSP) was used to the impact the aluminium tank. The velocity varied from 239 m/s to 972 m/s. Among results obtained were ballistic limit for the front and rear of the tank, correlation between impact velocity versus residual velocity, damage area, wall deflection, velocity drop and terminal ballistic for empty and water-filled tank.

This paper presents the footage from a hi-speed camera used in the experiment on both cases of a non-filled and water-filled aluminium tank. The objective was to determine the failure stages that will be used as a reference in the simulation works later on. The tank was impacted by fragment simulating projectiles (FSP) at 260 m/s for the non-filled tank and 972 m/s for the water-filled tank. The aluminium tank was 3 mm thick, 150 mm wide and 750 mm long. The ends of the tank were closed with two Polymethyl methacrylate (PMMA) windows. The gas gun was used to launch the projectile and a digital chronograph was used to capture the velocity of the FSP that impacted the tank. For recording purposes, a digital high speed camera with the capability of 250,000 frames per second (max) and the highest resolution of 1024 x 1024 was used. For the data acquisition and processing, Photron Fastcam Viewer (PFV) software was used. The test was conducted at the Science and Technology Research Institute for Defence (STRIDE), Batu Arang, Selangor, Malaysia. The results showed four main failure stages for the non-filled tank, these being, first contact between FSP and the tank, partial perforation, full perforation with FSP and plug still intact and lastly separation of FSP and plug. Meanwhile for the water-filled tank, there were seven main failure stages, which were first contact between FSP and the tank, partial perforation, full perforation, drag phase, cavity phase, bounce wave event and the collapse of the cavity.

Natural rubber latex (NRL) is commonly used in the manufacture of thin-film product, especially dipped goods. It has interesting physical properties such as high elasticity, high tensile strength and water vapour barrier properties that make it very suitable to be used as coating element. The present paper studies the effect of prevulcanised NRL coated unidirectional fabric on the ballistic performance of fabric systems. There are 4-ply of NRL coated fabrics arranged alternately at the back side of the 18-, 25-, and 28-layer of fabric systems. The energy absorption for the combination of neat and NRL coated fabric system seems to improve ballistic performance by reducing the depth of indentation on the clay backing material. This may due to the higher frictional forces between the neat and NRL coated plies which reduce the mobility of the bullet before it reaches the coated plies in the fabric system. Post-mortem deformation identified to support the energy absorption characteristics of the fabric systems are broken fibers, fiber delamination and ballistic punch effect.

The sound absorption characteristics of wooden and porous materials including fibrous media and porous foams vary with the nature of their surface porosity. The low frequency absorption, which is of interest in noise control engineering, of these material types is generally enhanced by introducing an air gap of a certain width or a flexible support at the rear face of the material posterior to the impinging sound waves. This study investigates the effect of air gap with and without hind support on the low frequency absorption of a kenaf/epoxy composite, a Meranti wood, a low-density rigid foam and a high-density rigid foam. The sound absorption coefficient of these materials are determined using the two-microphone impedance tube transfer-function method according to ISO 10534-2 standard in the frequency range between 20 Hz and 1600 Hz. In this study, 5-mm, 10-mm, 50-mm and 100-mm wide air gaps are introduced at the posterior of the specimens to measure the influence of the quarter-wavelength absorption on sound absorption coefficient. Backing panels made from polyethylene are used to study the effect of hind support on sound absorption coefficient at different frequencies. The dBFA Suite 4.8.1 program is used to acquire and process the acoustic signals and the SCS8100 software package is employed for the computation of sound absorption coefficient. The sound absorption coefficient and characteristics of each material within the range of frequency tested are discussed based on the width of air gap (i.e., the quarter-wavelength effect) in tandem with the presence or absence of the hind support. It is found that the low frequency absorption of the high-density foam with the hind support improved the absorption by 50% as the air gap is increased from 0 to 100 mm. The opposite effect is observed for the other materials tested whereby the sound absorption coefficient is reduced by 30 to 40% with the hind support.Copyright © 2012 by ASME

The effect of natural rubber (NR) coating on the quasi-static tensile properties of unidirectional Dyneema® SK-76 single yarn is experimentally studied. Single Dyneema® SK-76 yarns are uniformly coated with pre-vulcanized natural rubber latex. Quasi-static tensile tests are performed on plain (uncoated) and NR-coated samples at the strain rates of 0.006 s−1, 0.06 s−1 and 0.6 s−1. The force and strain at peak, and the tenacity of the plain and NR-coated yarns are obtained for each strain rate. The results show that the peak force in the plain samples increases with strain rate to a maximum of 163 N. The tenacity (breaking force per denier) of the uncoated yarns also, in correspondence, increases with strain rate. In contrast, the tenacity of the NR-coated samples remained constant at but a lower value than that of the plain samples. It is observed that peak force sustained by the NR-coated yarns is insensitive to strain rate and up to 560% higher than that supported by the plain yarns. The peak strain of both the plain and NR-coated samples varies with strain rate in a comparable fashion. However, the peak strain values of the NR-coated yarn are greater by an average of 20% than of the plain yarn. The experimental data thus reveal that NR coating has a constructive effect on the peak force and peak strain of the yarn but decreases its tenacity to a constant value. Micrographs of the fractured samples obtained from Field Emission Scanning Electron Microscope are studied to explore the role of NR in the failure mechanism of the coated yarn.Copyright © 2012 by ASME

The internal combustion engines that are widely used as power sources nowadays emits hazardous emissions that can cause negative consequences on the environment and society such as pollution and climate change. Transportation industries are starting to rely on the renewable energy as the alternative energy sources for the future. Fuel cells are a promising alternative power source for vehicles because of their high specific energy, efficiency, and reliability. Hydrogen proton exchange membrane (PEM) fuel cells produce zero carbon emissions. The electrochemical processes that generate power exhaust only water vapor and heat. Fuel cell research for aircraft is relatively new. Therefore, there is a need for a thorough study on the development of the fuel cell powered aircraft. A five meter wingspan unmanned aerial vehicle technology demonstrator, called Kenyalang-l, was recently developed at Universiti Teknologi MARA. A Horizon H-1000 PEM fuel with a maximum power of 1 kW was used as the primary power plant for its DC brushless motor propulsion system. The system was tested in ground-based static tests. The objective of the research that is reported in this paper is to obtain the performance characteristic of the fuel cell propulsion system. The data collected from these tests includes the output voltage, output current, power, thrust, and rotational speed of the system. Results and analysis of this data were used to characterize the effectiveness of the fuel cell propulsion system. The results obtained indicate that the thrust of the propeller is directly proportional to output power generated by the fuel cell.

This paper presents the high velocity impact case study of projectile-wall collision by employing smoothed particle hydrodynamics (SPH). SPH is a method, which is based on the particles that have their own properties and governing equations. SPH has the capability to simulate high velocity impact, excessive deformation and breakage. Among parameters explored in this study are stages of failure, perforation limit and effects of variations of yield strength and velocity impacts. The velocity ranges were from 100 m/s up to 2000 m/s, and it was observed that when the velocity reached 500 m/s the target was perforated by the projectile. The effects of the yield stress towards deformation behavior and von misses stresses for both target and projectile were also investigated and presented in this paper.

The first part of this paper presents a comparative study on the design, protection mechanisms and performance evaluation of three modern ballistic helmets namely, Personnel Armor System Ground Troops (PASGT), Advanced Combat Helmet (ACH), and Enhanced Combat Helmet (ECH), based on a review of current advances and findings of related investigations In the second part of this paper, the deformation, impact resistance and shock absorption properties of a ballistic helmet similar to the PASGT helmet are determined experimentally via a stiffness test, resistance to penetration test, and shock absorption test. This paper discusses the results obtained from the experiment s and compares them with the performance of the other types of helmets with respect to their designs, comfort levels and protection mechanisms The result of the shock absorption test shows that the helmet absorbed 78% of a nominal impact energy of 49 J. The 8-mm thick helmet resisted full penetration at an applied impact force of 132.3 N with an average penetration depth of 4.52 mm. These results indicate that the ballistic helmet being investigated provide a good impact protection but not superior to that of the ACH-type helmet.

The stress relaxation behavior of a Twaron CT709® fabric/natural rubber composite under a uniaxial constant strain is studied using three viscoelasticity models with different levels of complexity and a newly developed para-rheological model. The three viscoelasticity models employed are a one-term generalized Maxwell model (comprising one Maxwell element and an additional spring in parallel), a two-term generalized Maxwell model (including two Maxwell elements and an additional spring in parallel), and a four-parameter Burgers model. The values of the parameters involved in each model are extracted from the experimental data obtained in this study. The stress relaxation tests reveal that the stress starts to decay exponentially for a short duration and then continues to decrease linearly with time. It is found that the initial relaxation response of the composite is predicted fairly well by all of the four models, while the long-time stress relaxation behavior is more accurately predicted by the para-rheological model. The accuracy of each model in describing the stress relaxation behavior of the composite is quantitatively compared.

The creep behavior of a Twaron CT709® fabric/natural rubber composite under a uniaxial constant stress is studied using three viscoelasticity models with different levels of complexity and a newly developed para-rheological model. The three models employed are a one-term generalized Maxwell (GMn = 1 ) model (consisting of one Maxwell element and an additional spring in parallel), a two-term generalized Maxwell (GMn = 2 ) model (including two parallel Maxwell elements and an additional spring in parallel), and a four-parameter Burgers model. The values of the parameters involved in each model are extracted from the experimental data obtained in this study. The creep tests reveal that the axial strain starts to increase exponentially during the primary stage and then continues to equilibrate linearly with time. The results show that the initial creep response of the composite is predicted fairly well by the GMn = 2 model, while the secondary creep is more accurately described by the GMn = 1 model. An implicit solution, together with a characteristic retardation time spectrum, obtained using the para-rheological model is found to provide more accurate predictions of the composite creep response than the three viscoelasticity models at both the primary and secondary stages.Copyright © 2010 by ASME

Modern military operations, technology-driven war tactics, and current on-street weapons and ammunition necessitate the development of advanced ballistic protection body armor systems that are damage-resistant, flexible, lightweight, and of great energy absorbing capacity. A number of studies related to new concepts and designs of body armor materials (including those derived from or inspired by nature) have been conducted in the past two decades to meet the new demands. Ballistic fabrics, ceramics, and laminated composites are among the leading materials used in modern body armor designs, and nano-particle and natural fiber filled composites are candidate materials for new-generation body armor systems. Properties and ballistic resistance mechanisms of such materials have been extensively investigated. Based on a comprehensive and critical review of the advances and findings resulting from these investigations, a comparative study on design, protection mechanisms, and performance evaluation of various types of anti-ballistic body armor is presented in this paper. Body armor systems made from different materials and exhibiting distinct ballistic energy absorption mechanisms are discussed, and key factors that influence the ballistic performance and energy absorbing mechanisms of the body armor systems are identified.

Ballistic fabrics are made from high performance polymeric fibers such as Kevlar® , Twaron® and Spectra® . These fibers often behave viscoelastically in high strain rate deformations. The Kelvin-Voigt and Maxwell rheological models have been used to characterize such viscoelastic responses at different strain rates. However, these two-parameter models have been found to be inadequate and inaccurate in some applications. As a result, three-parameter rheological models have been utilized to develop constitutive relations for viscoelastic polymeric fabrics. In this study, a generalized Maxwell (GM) model and a generalized Kelvin-Voigt (GKV) model are proposed to describe the viscoelastic behavior of a ballistic fabric, Twaron® CT716, at the strain rates of 1 s−1 and 495 s−1 . The GM model consists of a Maxwell element (including a viscous dashpot and a spring in series) and a second spring in parallel to the Maxwell element, while the GKV model is an assembly of a Kelvin-Voigt (KV) element (containing a viscous dashpot and a spring in parallel) and a second spring in series with the KV element. The predictions by the GM and GKV models are compared with existing experimental data, which shows that the two sets of results are in fairly good agreement. In particular, the comparison reveals that the GKV model gives more accurate results at the low strain rate, whereas the GM model performs better at the high strain rate while still providing accurate predictions for the low strain rate responses.Copyright © 2008 by ASME

Modern military operations, technology-driven war tactics, and current on-street weapons and ammunition necessitate the development of advanced ballistic protection body armor systems that are damage-resistant, flexible, lightweight and have superior energy absorbing capacity. A number of studies related to new concepts and designs of body armor materials have been conducted in the past two decades to meet the new demands. Ballistic fabrics, ceramics, nanocomposites, and hybrid material systems are among the leading candidates for modern armor design. Properties and ballistic resistance mechanisms of such materials have been extensively investigated. Based on a comprehensive and critical review of the advances and findings resulting from these investigations, a comparative study on design, characterization and performance evaluation of various types of anti-ballistic body armor made from different material systems and exhibiting distinct ballistic energy absorption mechanisms is presented in this paper by identifying and discussing key factors that influence the ballistic performance and energy absorbing mechanisms.