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Acoustic emission (AE) data acquired during intermittent load hold tensile testing of epoxy impregnated Kevlar(Registeres TradeMark) 49 (K/Ep) composite strands were analyzed to monitor progressive damage during the approach to tensile failure. Insight into the progressive damage of K/Ep strands was gained by monitoring AE event rate and energy. Source location based on energy attenuation and arrival time data was used to discern between significant AE attributable to microstructural damage and spurious AE attributable to noise. One of the significant findings was the observation of increasing violation of the Kaiser effect (Felicity ratio < 1.0) with damage accumulation. The efficacy of three different intermittent load hold stress schedules that allowed the Felicity ratio to be determined analytically is discussed.

Kevlar and PBA(Poly 1,4-benzamide) reinforcements were prepared in 96% H2 SO4. Watermethanol mixtures were used as the extracting solvent. Other solvent combinations were tried, but with less sucess. The structure obtained by SEM (scanning electron micrograph) showed small cells size but a non-uniform structure. Composites were made from this reinforcements using as matrices a variety of epoxy resins and acrylates. The curing times varied according to the matrix used. Structure and penetration of the matrix into the reinforcements was studied by optical microscopy. Liquid Crystalline polymers; Kevlar; PBA; Amides.

Volume I of this report (1) presents the findings of a study conducted to develop a low-density polyurethane foam system that is deployable within 5 seconds, and (2) documents a study of foam/fabric cylinders as potential structural members. An especially fast-reacting foam formulation was devised, hardware for delivery and mixing of foam chemicals was designed and evaluated, various geometric shapes of constant volume that the foam could be formed into were invesigated, and the impact loading characteristics of the foam at various times soon after generation were studied. Fabrication of fabric foam cylinders was also studied. Volume II of this report documents a study of fabric-skinned, foam-filled cylindrical beams and an analytical/experimental study of their bending properties. Results of the studies show that a low- density polyurethane foam system that will deploy within 5 seconds is practical to generate and to form into geometrically shaped lightweight fabric bags. The foam exhibits good impact absorption properties very quickly after formation; these properties can be used to attenuate rapidly applied loads of low to intermediate velocities. Finally, the fabric/foam composite beams possess interesting structural qualities commensurate with the fabric and foam used in making them. The analytical and experimental results compare very well. The analysis identified several factors of the mechanics involved that must be included in calculations to predict the loading response of such composites. (Author)

Book Source: Digital Library of India Item 2015.199938 dc.contributor.author: Sanjay Kumar Majumdar dc.date.accessioned: 2015-07-08T13:56:45Z dc.date.available: 2015-07-08T13:56:45Z dc.date.digitalpublicationdate: 2005-08-31 dc.identifier.barcode: 1990010088867 dc.identifier.origpath: /rawdataupload/upload/0088/867 dc.identifier.copyno: 1 dc.identifier.uri: http://www.new.dli.ernet.in/handle/2015/199938 dc.description.scannerno: 12 dc.description.scanningcentre: IIIT, Allahabad dc.description.main: 1 dc.description.tagged: 0 dc.description.totalpages: 85 dc.format.mimetype: application/pdf dc.language.iso: English dc.publisher: Indian Institute Of Technology Kanpur dc.rights: Out_of_copyright dc.source.library: Indian Institute Of Technology Kanpur dc.subject.classification: Technology dc.subject.classification: Engineering. Technology In General dc.subject.classification: Mechanical Engineering In General. Nuclear Technology. Electrical Engineering. Machinery dc.title: Axial Fatigue Behaviour Of Kevlar Fabric Reinforced Epoxy Resin Composites

Book Source: Digital Library of India Item 2015.198300 dc.contributor.author: Ravikumar. D dc.date.accessioned: 2015-07-08T12:41:17Z dc.date.available: 2015-07-08T12:41:17Z dc.date.digitalpublicationdate: 2005-08-27 dc.identifier.barcode: 5990010100121 dc.identifier.origpath: /rawdataupload/upload/0100/121 dc.identifier.copyno: 1 dc.identifier.uri: http://www.new.dli.ernet.in/handle/2015/198300 dc.description.scannerno: 14 dc.description.scanningcentre: IIIT, Allahabad dc.description.main: 1 dc.description.tagged: 0 dc.description.totalpages: 108 dc.format.mimetype: application/pdf dc.language.iso: English dc.publisher: Indian Institute Of Technology Kanpur dc.rights: Out_of_copyright dc.source.library: Indian Institute Of Technology Kanpur dc.subject.classification: Technology dc.subject.classification: Engineering. Technology In General dc.subject.classification: Mecanical Engineering dc.title: Damage Identification In Kevlar/epoxy Composites Through Cluster Analysis Of Acoustic Emission Data

An Extruded Sheet Tooling Compound (ESTC) was developed for use in quickly building low cost molds for fabricating composites. The ESTC is a very highly mineral-filled resin system formed into a 6 mm thick sheet. The sheet is laid on the pattern, vacuum (bag) is applied to remove air from the pattern surface, and the assembly is heat cured. The formed ESTC is then backed and/or framed and ready for use. The cured ESTC exhibits low coefficient of thermal expansion and maintains strength at temperatures of 180 to 200 C. Tools were made and used successfully for: Compression molding of high strength epoxy sheet molding compound, stamping of aluminum, resin transfer molding of polyester, and liquid resin molding of polyester. Several variations of ESTC can be made for specific requirements. Higher thermal conductivity can be achieved by using an aluminum particle filler. Room temperature gel is possible to allow use of foam patterns.

The current research aims to develop epoxy-based S-Glass/Kevlar fiber reinforced hybrid composites filled with graphite powder. Hybrid composite are fabricated by hand layup method and mechanical characterization is carried out as per the ASTM standards. It is observed that 10% of graphite powder filled epoxy is effectively reduced the weight of the composites in comparison with non filled hybrid composites. On filler addition, the impact strength of the composite shows maximum at 5% of filler and tends to decrease further. The tensile capacity of the composites are increased by 23% and 13.6% and the flexural strength increased by 4.5% and 4.12% when 5% and 10% of filler added to composites, respectively compared to S-glass/Kevlar/epoxy composites. The present research aims to process and characterize the hybrid composites based on S-glass based hybrid fiber with Kevlar fiber and epoxy resin for thermal and mechanical properties incorporation of solid graphite powder. Many polymer based composites have glass transition temperature in the range of 100–240 °C, so that they are said to possess good thermal stability. This paper presents an effort undertaken to understand the effect of glassy fiber addition to composite systems on thermal conductivity of composites. The densified composites show improvement in fracture toughness and tensile strength at the cost of toughness.

Book Source: Digital Library of India Item 2015.192235 dc.contributor.author: Sanjay Kumar Majumdar dc.date.accessioned: 2015-07-08T01:20:46Z dc.date.available: 2015-07-08T01:20:46Z dc.date.digitalpublicationdate: 2005-08-31 dc.identifier.barcode: 1990010090677 dc.identifier.origpath: /rawdataupload/upload/0090/677 dc.identifier.copyno: 1 dc.identifier.uri: http://www.new.dli.ernet.in/handle/2015/192235 dc.description.scannerno: 12 dc.description.scanningcentre: IIIT, Allahabad dc.description.main: 1 dc.description.tagged: 0 dc.description.totalpages: 85 dc.format.mimetype: application/pdf dc.language.iso: English dc.publisher: Indian Institute Of Technology Kanpur dc.rights: Out_of_copyright dc.source.library: Indian Institute Of Technology Kanpur dc.subject.classification: Technology dc.subject.classification: Engineering. Technology In General dc.subject.classification: Mechanical Engineering In General. Nuclear Technology. Electrical Engineering. Machinery dc.title: Axial Fatigue Behaviour Of Kevlar Fabric Reinforced Epoxy Resin Composites

This research investigates the effects of weave styles and crimp gradients (CGs) on the damage-tolerance levels and energy-absorption capacities of woven fabric-reinforced polymer (WFRP) composites. A comparative study was conducted to determine the specific failure mechanisms including fiber/matrix cohesive failures, matrix cracking, fiber breakage, and fiber buckling resulting from static and dynamic loading events. The tests Included flexure, short beam shear, drop impact, flexure-after-impact, ballistic impact, and split Hopkinson compression bar (SHCB) and were performed on 20-ply Kevlar/epoxy WFRP laminates. Laminates of three different Kevlar fabric weave styles were fabricated using plain, 2x2 twill, and 4H satin weaves. A fourth fabricated laminate used a mixture of weave styles forming a hybrid CG construction. The experimental results demonstrated (1) that weave style selections and CGs can positively influence the spatial and temporal distributions of stress resulting from severe loading events and (2) that the fiber/matrix cohesive zone stresses that often lead to delaminations can be reduced. Accordingly, the dependence of mechanical performance on weave styles, crimp contents, and CGs can be exploited to increase the damage-tolerance levels and energy-absorption capacities in WFRP composites.

The stab resistance of shear thickening fluid (STF)-Kevlar and STF-Nylon fabric composites are investigated and found to exhibit significant improvements over neat fabric targets of equivalent areal density. Specifically, dramatic improvements in puncture resistance (spike threat) are observed under high and low speed loading conditions, while slight increases in cut protection are also observed. These results, combined with improvements in ballistic properties reported in earlier studies (Lee et al., 2002, Lee et al. 2003), indicate that these novel materials could be used to fabricate flexible body armors which provide improved protection against both stab and ballistic threats.

The stab resistance of shear thickening fluid (STF)-Kevlar and STF-Nylon fabric composites are investigated and found to exhibit significant improvements over neat fabric targets of equivalent areal density. Specifically, dramatic improvements in puncture resistance (spike threat) are observed under high and low speed loading conditions, while slight increases in cut protection are also observed. These results, combined with improvements in ballistic properties reported in earlier studies (Lee et al., 2002, Lee et al. 2003), indicate that these novel materials could be used to fabricate flexible body armors which provide improved protection against both stab and ballistic threats.

Book Source: Digital Library of India Item 2015.193972 dc.contributor.author: D.s.rajan dc.date.accessioned: 2015-07-08T03:41:20Z dc.date.available: 2015-07-08T03:41:20Z dc.date.digitalpublicationdate: 2005-08-20 dc.identifier.barcode: 1990010086787 dc.identifier.origpath: /rawdataupload/upload/0086/787 dc.identifier.copyno: 1 dc.identifier.uri: http://www.new.dli.ernet.in/handle/2015/193972 dc.description.scannerno: 14 dc.description.scanningcentre: IIIT, Allahabad dc.description.main: 1 dc.description.tagged: 0 dc.description.totalpages: 126 dc.format.mimetype: application/pdf dc.language.iso: English dc.publisher: Indian Institute Of Technology Kanpur dc.rights: Out_of_copyright dc.source.library: Indian Institute Of Technology Kanpur dc.subject.classification: Technology dc.subject.classification: Engineering. Technology In General dc.subject.classification: Mechanical Engineering In General. Nuclear Technology. Electrical Engineering. Machinery dc.title: Investigation Of Damege In Kevlar -epoxy Composites Using Acoustic Emission Technique

In a molecular composite, a ductile matrix is reinforced with a stiff, strong, rigid-rod polymer molecule. One of the approaches used to make a rigid-rod molecular composite involves the physical mixing by coprecipitation of single-phase solutions of a rigid-rod and a flexible-coil polymer in a common solvent. We and others have reported previously on the preparation of three-dimensional fibrous materials using the phase separation of polymer solutions at low temperature and sublimation or extraction of the solvent. It is conceivable that a molecular composite would give a superior 3D fibrous material by combining the strength of the rigid-rod macromolecules with the better processibility of the random-coil polymer. This preprint describes our attempts to test this hypothesis. Molecular composites from Kevlar and diaminophenylindane polyimide were fabricated by quenching sulfuric acid solutions. The structure and properties of the resulting three-dimensional fibrous structures were then determined.

Book Source: Digital Library of India Item 2015.228849 dc.contributor.author: Lt. D. Ravi Kumar dc.date.accessioned: 2015-07-10T15:51:45Z dc.date.available: 2015-07-10T15:51:45Z dc.date.digitalpublicationdate: 0000-00-00 dc.identifier.barcode: 5990010117756 dc.identifier.origpath: /rawdataupload/upload/0117/758 dc.identifier.copyno: 1 dc.identifier.uri: http://www.new.dli.ernet.in/handle/2015/228849 dc.description.scanningcentre: IIIT, Allahabad dc.description.main: 1 dc.description.tagged: 0 dc.description.totalpages: 108 dc.format.mimetype: application/pdf dc.language.iso: English dc.publisher: Iit Kanpur dc.rights: Out_of_copyright dc.source.library: I I T Kanpur dc.subject.classification: Technology dc.subject.classification: Engineering. Technology In General dc.subject.classification: Mechanical Engineering In General. Nuclear Technology. Electrical Engineering. Machinery dc.title: Damage Identification In Kevlar-epoxy Composites Through Cluster Analysis Of Acoustic Emission Data

Surface modification of Kevlar(R) fibers with titanate coupling agents for improved adhesion of the fiber and resin in Kevlar(R)/phenolic composites has been attempted to explore the possibility of enhancement in adhesion and bulk properties of composites for friction materials. Titanate coupling agents were used and flexural properties of the Kevlar(R)-fiber reinforced composites determined. A study of different amounts of the coupling agents at the fiber-matrix interface suggested that 2% by weight of fiber was the optimum amount, in terms of improvement in flexural properties. The composite samples with the coupling agents, showed an increase in flexural strength, over the untreated samples with the maximum increase being approx. 18% over the control. Water absorption studies were conducted on Kevlar(R)/phenolic composites treated with organotitanates to determine the effectiveness of these coupling agents in improving resistance to moisture attack. The treated Kevlar(R)/phenolic composite samples exhibited greater resistance to moisture- ingress over the untreated samples. The control samples showed a decrease of 17% in flexural strength. The largest decrease in strength was 14% for the treated samples containing coupling agent tetrakis(2-ethylhexyl)titanate (TYZOR TOT). Recovery in strength on reconditioning, was also greater for treated samples over control. A recovery in strength of ca. 94% was seen for some treated samples. Coupling agents, Composites, Kevlar, Interfaces, Mechanical properties.

Fiber-reinforced polymer matrix composite materials display quite complex deformation and failure behavior under ballistic/blast impact loading conditions. This complexity is generally attributed to a number of factors such as (a) hierarchical/multi-length scale architecture of the material microstructure; (b) nonlinear, rate-dependent and often pressure-sensitive mechanical response; and (c) the interplay of various intrinsic phenomena and processes such as fiber twisting, interfiber friction/sliding, etc. Material models currently employed in the computational engineering analyses of ballistic/blast impact protective structures made of this type of material do not generally include many of the aforementioned aspects of the material dynamic behavior. Consequently, discrepancies are often observed between computational predictions and their experimental counterparts. To address this problem, the results of an extensive set of molecular-level computational analyses regarding the role of various microstructural/morphological defects on the Kevlar fiber mechanical properties are used to upgrade one of the existing continuum-level material models for fiber-reinforced composites. The results obtained show that the response of the material is significantly affected as a result of the incorporation of microstructural effects both under quasi-static simple mechanical testing condition and under dynamic ballistic-impact conditions.

The quest for innovative and superior materials is a challenge in the realm of materials science and engineering. Traditional materials often fall short in meeting the demands of modern industries, especially in the military. Technological developments in the military domain are still progressing, one of which involves a new material for combat vehicle applications: a laminated composite. In this research, a composite consisting of AA7075 sheet metal and kevlar with epoxy resin and TiC nanopowder were prepared. A test was conducted to assess its performance in absorbing ballistic energy from projectiles. Solid Thickening Fluid (STF) was created by mixing TiC nanopowder with PEG-400 through 2 hours of stirring. The laminate composite structure was prepared using the hand layup method, followed by a drying process at room temperature. The addition of kevlar layers yielded promising results in the ballistic and impact tests, as the diameter of the perforation decreased progressively with each additional kevlar layer. The IK sample impact test value improved by 35.7% compared to the unimpregnated one. The production process of this material also consumes minimal energy, which suggest a potential for environmental sustainability.

The Logistical and Tactical Targets Branch (LTTB) of the Ballistic Vulnerability Lethality Division (BVLD) has a requirement to conduct vulnerability analyses for the Command and Control Vehicle (C2V). Analysts in LTTB recognized the need for a single penetration algorithm for evaluating the aluminum-Kevlar composites serving as C2V armor materials. Existing penetration equations were not developed to address composites. The Systems Analysis Branch (SAB) designed and executed an experimental program to provide support for the development of a penetration algorithm for armor-piercing (AP) projectiles against aluminum-Kevlar composites. The Simulation Technology Division (STD) assisted SAB in the program design and developed an algorithm for predicting residual velocity behind aluminum-Kevlar composites. This report documents the experimental program, results, and modeling efforts.

Book Source: Digital Library of India Item 2015.196575 dc.contributor.author: Bharat Bhushan dc.date.accessioned: 2015-07-08T09:07:11Z dc.date.available: 2015-07-08T09:07:11Z dc.date.digitalpublicationdate: 0000-00-00 dc.identifier.barcode: 5990010096518 dc.identifier.origpath: /rawdataupload/upload/0096/518 dc.identifier.copyno: 1 dc.identifier.uri: http://www.new.dli.ernet.in/handle/2015/196575 dc.description.scannerno: 1 dc.description.scanningcentre: IIIT, Allahabad dc.description.main: 1 dc.description.tagged: 0 dc.description.totalpages: 92 dc.format.mimetype: application/pdf dc.language.iso: English dc.publisher: Iit-kanpur dc.rights: Out_of_copyright dc.source.library: I I T Kanpur dc.subject.classification: Technology dc.subject.classification: Engineering. Technology In General dc.subject.classification: Mechanical Engineering In General. Nuclear Technology. Electrical Engineering. Machinery dc.title: Flexual Fatigue Behaviour Of Kevlar Fabric Reinforced Eproxy Resign Composites

Fiber-reinforced polymer matrix composite materials display quite complex deformation and failure behavior under ballistic/blast impact loading conditions. This complexity is generally attributed to a number of factors such as (a) hierarchical/multi-length scale architecture of the material microstructure; (b) nonlinear, rate-dependent and often pressure-sensitive mechanical response; and (c) the interplay of various intrinsic phenomena and processes such as fiber twisting, interfiber friction/sliding, etc. Material models currently employed in the computational engineering analyses of ballistic/blast impact protective structures made of this type of material do not generally include many of the aforementioned aspects of the material dynamic behavior. Consequently, discrepancies are often observed between computational predictions and their experimental counterparts. To address this problem, the results of an extensive set of molecular-level computational analyses regarding the role of various microstructural/morphological defects on the Kevlar fiber mechanical properties are used to upgrade one of the existing continuum-level material models for fiber-reinforced composites. The results obtained show that the response of the material is significantly affected as a result of the incorporation of microstructural effects both under quasi-static simple mechanical testing condition and under dynamic ballistic-impact conditions.