Advanced Structural and Functional Materials for Protection, 2008

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Authors: M.V. Hosur, Jessie B. Mayo Jr., E. Wetzel, S. Jeelani
Abstract: Kevlar has demonstrated the ability to protect well against ballistic threats but has low resistance to puncture. Correctional Kevlar has shown good resistance to puncture. However, the fabric is expensive, difficult to manufacture because of its tight weave construction, and has limited protection against ballistic threats. In an effort to produce materials that are less bulky, more flexible, and resistant to puncture, thermoplastic-Kevlar (TP-Kevlar) composites have been examined. Kevlar fabric was impregnated with thermoplastic film using a hot press to produce the composites. Static and dynamic puncture resistant properties of the TP-Kevlar composites were investigated using a National Institute of Justice (NIJ Standard 0115.00) Stab Tower. The TP-films used in this study were polyethylene, Surlyn, and co extruded-Surlyn, which is a co extrusion of Surlyn and polyethylene. Response of the polyethylene (PE)-Kevlar composites, Surlyn-Kevlar composites, and co extruded (COEX)-Kevlar composites to spike and knife threats under static and dynamic conditions were compared with that of neat Kevlar. The infusion of thermoplastic films into the Kevlar fabric was shown to dramatically increase puncture resistance during quasi-static and dynamic testing with spikes. The TP-film type also made a difference when examining the resistance on a comparative basis of the TP-Kevlar targets. The TP-Kevlar composite targets showed more resistance to quasi-static spike testing than quasi-static knife testing. Weapon comparisons revealed that the TP-Kevlar composite targets had more resistance to dynamic knife testing than dynamic spike testing.
Authors: Sioh Ek Leng
Abstract: Ceramic composite armour in general utilises a front layer of dense ceramic, typically backed by a second layer of metal. Thereby creating a sharp interface that is the weakest link within the material system and would result in cracking of the ceramic prematurely and hence not able to provide the requisite protection. One promising possibility has been found is the use of functionally gradient materials as armour materials. In such materials, the high hardness of ceramics is combined with the ductility of metals. Laboratory scale experiments were being performed to exhibit the potential of this material in terms of physical and mechanical properties. A comparison was made with the current ceramic armour system and it was found that the new material system had better ballistic properties.
Authors: B. Suresha, T. Jayaraju, P.R. Sadananda Rao, Mohammed Ismail, Kunigal N. Shivakumar
Abstract: Fiber reinforced polymer composites are generally known to possess high strength and attractive wear resistance in dry sliding conditions. The behaviour of such composites performing in abrasive wear situations needs a proper understanding. Hence, in the present work of the three-body abrasive wear behaviour of two dimensional stitched carbon fabric, E-glass woven fabric and three dimensional E-glass woven fabric reinforced vinyl ester composites was investigated. Three-body abrasive wear tests were conducted using rubber wheel abrasion tester (RWAT) under different abrading distances at two loads, wherein the wear volume loss were found to increase and that of specific wear rate decrease. The results indicate that the type of fabric in vinyl ester have a significant influence on wear under varied abrading distance/loads. Further, it was found that carbon fabric reinforced vinyl ester composite exhibited lower wear rate compared to E-glass woven fabric reinforced vinyl ester composites. The worn surface features, as examined through scanning electron microscope (SEM), show higher levels of broken glass fiber in two dimensional glass woven fabric reinforced vinyl ester composite compared to carbon fabric and three dimensional glass fabric reinforced vinyl ester composites.
Authors: Madusudhanan R. Parlapalli, Kwok C. Soh, Dong Wei Shu
Abstract: In the present paper, effects of through-the-thickness stitching of delaminated glass/epoxy composite laminates with two different types of aramid threads, Kevlar® and Twaron® threads, on the buckling loads are studied. The buckling loads are predicted based on the Southwell, Vertical displacement and Membrane strain plot methods from the experimental data. Flexural modulus of the stitched and unstitched glass/epoxy composite laminates, knot tensile strength of Kevlar® and Twaron® stitching threads are obtained experimentally. From the Southwell, Vertical displacement and Membrane strain plot methods it is observed that stitching either by Kevlar® or Twaron® threads is effective in improving the buckling strength of glass/epoxy composite laminates when the delamination length is greater than 0.5L, L is the length of the laminate.
Authors: Da Zhi Jiang, Fu Biao Yang, Su Li Xing, Jia Yu Xiao
Abstract: Traditional sandwich structure consists of two face sheets and a core. With an internal sheet inserted into the core, a two-core sandwich structure is then formed. Two-core sandwich structures with composite laminated face sheets and a thin internal sheet subjected to low velocity impact are studied in this paper. Local displacement of the core under the point of impact is investigated. Simulated results show that the local displacement of the core along the direction of the impact has been decreased significantly by introducing the internal sheet into a traditional single sandwich structure and by reducing the space between the internal sheet and the impacted face sheet. Shear deformation in the cores of a two-core sandwich structure is also investigated and attention is focused on shear strains on interfaces between face/internal sheets and the cores. Results further show that strain levels in selected elements at the interested interfaces depend upon locations of the selected elements and arrangements of the internal sheet.
Authors: Lian Yong Xu, Hong Yang Jing, Jun Wei, Hui Zou
Abstract: In this paper, the local approach based on the Weibull stress criterion was used to investigate the interfacial fracture behavior between LX88A coating and Q345 steel. LX88A coating was deposited by high velocity electric arc spraying technology (HVAS). The finite element method (FEM) was used to analyze the stress-strain fields of the coating specimen which consisted of three different specimen geometrics or modes of loading. It was found that the Weibull stress for all specimen geometries was almost identical under the same fracture probability when the interfacial fracture initiation occurred for different specimen geometries. It showed that the geometry dependence on the interface brittle fracture toughness data can be reduced through application of the local approach, and the local approach can be used to describe the interfacial fracture behavior.
Authors: Satreerat K. Hodak, T. Seppänen, Sukkaneste Tungasmita
Abstract: The ternary nitride (Zr,Ti)N thin films were grown on silicon substrates by ion-assisted dual d.c. reactive magnetron sputtering technique. The substrates were exposed to ion bombardment with varying kinetic energy in the range of 3-103 eV under N/Ar ratio of 1:3. The (Zr0.6Ti0.4)N was formed at all growth conditions. X-ray diffraction measurement indicates the presence of (Zr,Ti)N solid solution with (111) and (200) preferred orientations. The (200) orientation is only present when the films are grown at ion bombardment energies higher than 33 eV. Optimum conditions for film growth produced hardness in the range of 27-29 GPa.
Authors: Vijay Kumar Srivastava, Saurabh Srivastava, Ratnamala Chatterjee
Abstract: The initials results on growth and structural properties of Ni-Mn-Al full Heusler alloy thin films on silicon substrates deposited by RF magnetron sputtering is reported in this paper. Good crystallinity in the film is obtained by optimizing the sputtering parameters. The as-deposited film was post-annealed in vacuum in the temperature range between 150 °C, 250 °C and 450 °C for 60 min. It is observed that as deposited film shows nanocrystalline in nature. The film annealed at 450 °C shows L21 structure. The magnetic properties of the NiMnAl films at room temperature are measured by vibrating sample magnetometer [VSM]. It is found that the annealed samples shows clear saturating loop whereas the as prepared film is paramagnetic in nature.
Authors: Bryan Lim, Pei Jun Hong
Abstract: Concrete when subjected to a blast loading from a close-in detonation will experience spalling due to formation of tension waves on the opposite face of the concrete panel. The spalled concrete may be ejected at high velocity causing undesirable effects to occupants. Tests using 1/2kg TNT blocks were conducted on 100mm thick concrete panels to study the effects of spalling and whether the spalled materials can be arrested using a sprayed-on polymeric coating. From the tests, it was observed that without the sprayed-on polymeric coating, extensive spalling occurred. However, with just a 3-4mm thick layer of sprayed-on polymer, the spalled materials were arrested and contained. Numerical models of the reinforced concrete slab were created using Autodyn 2D and the results of the simulation were compared to observations from the tests. There was good correlation between the test results and the simulation results as the size of the crater, both front and back, on the concrete slab were rather similar.
Authors: Agung Purniawan, E. Hamzah, M.R.M. Toff
Abstract: Diamond is the hardest material and has high chemical resistant which is one form of carbon. In the present work a study was carried out on polycrystalline diamond coated Si3N4 substrate. The diamond was deposited by Microwave Plasma Assisted Chemical Vapor Deposition (MPACVD) under varying deposition parameters namely CH4 diluted in H2, microwave power and chamber pressure. SEM and AFM are used to investigate the surface morphology and surface roughness. Nucleation phenomena and crystal width were also studied using AFM. Based on SEM investigation it was found that the chamber pressure and %CH4 have more significant effects on nucleation and facet of polycrystalline diamond, In addition microwave power has an effect on the diamond facet that changed from cubic to cauliflower structure. Surface roughness results show that increasing the %CH4 has decreased surface roughness 334.83 to 269.99 nm at 1 to 3% CH4, respectively. Increasing microwave power leads to increase in diamond nucleation and coalescence which lead to less surface roughness. Increasing gas pressure may eliminate Si contamination however it reduces diamond nucleation.

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