The Experts below are selected from a list of 132 Experts worldwide ranked by ideXlab platform
Ks Fancey - One of the best experts on this subject based on the ideXlab platform.
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viscoelastically prestressed Polymeric Matrix Composites an investigation into fibre deformation and prestress mechanisms
Composites Part A-applied Science and Manufacturing, 2018Co-Authors: Wang B, Ks FanceyAbstract:© 2018 Elsevier Ltd A viscoelastically prestressed Polymeric Matrix Composite (VPPMC) is produced by subjecting Polymeric fibres to a creep load, which is removed before moulding the fibres into a Polymeric Matrix. The resulting fibre viscoelastic recovery creates compressive stresses within the cured Matrix. Although mechanical properties can be improved by up to 50%, the effect of fibre creep stress magnitude on VPPMC performance is unknown. In this paper, viscoelastic effects were investigated for 24 h creep stress values of 330–590 MPa. This involved recovery force measurement and wide-angle X-ray diffraction (WAXD) on nylon 6,6 fibres and Charpy impact testing of nylon fibre-polyester resin VPPMCs. Greatest performance was achieved with an intermediate value (460 MPa), suggesting an optimum creep stress condition. Moreover, with increasing creep stress, WAXD demonstrated a progressive reduction in regions with viscoelastic energy storage capability. By considering Polymeric three-phase microstructural and latch-based m echanical models, a viscoelastic fibre-generated prestress mechanism is proposed.
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Viscoelastically generated prestress from ultra-high molecular weight polyethylene fibres
Journal of Materials Science, 2013Co-Authors: Adnan Fazal, Ks FanceyAbstract:The viscoelastic characteristics of ultra-high molecular weight polyethylene (UHMWPE) fibres are investigated, in terms of creep-induced recovery strain and force output, to evaluate their potential for producing a novel form of prestressed Composite. Composite production involves subjecting fibres to tensile creep, the applied load being removed before moulding the fibres into a resin Matrix. After Matrix curing, the viscoelastically strained fibres impart compressive stresses to the surrounding Matrix, to produce a viscoelastically prestressed Polymeric Matrix Composite (VPPMC). Previous research has demonstrated that nylon fibre-based VPPMCs can improve mechanical properties without needing to increase mass or section dimensions. The viability of UHMWPE fibre-based VPPMCs is demonstrated through flexural stiffness tests. Compared with control (unstressed) counterparts, these VPPMCs typically show increases of 20–40 % in flexural modulus. Studies on the viscoelastic characteristics indicate that these fibres can release mechanical energy over a long-timescale and fibre core–skin interactions may have an important role.
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viscoelastically prestressed Polymeric Matrix Composites effects of test span and fibre volume fraction on charpy impact characteristics
Composites Part B-engineering, 2013Co-Authors: Adnan Fazal, Ks FanceyAbstract:Abstract A viscoelastically prestressed Polymeric Matrix Composite (VPPMC) is produced by subjecting Polymeric fibres to tensile creep, the applied load being removed before moulding the fibres into a resin Matrix. After Matrix curing, the viscoelastically strained fibres impart compressive stresses to the surrounding Matrix, thereby improving mechanical properties. This study investigated the mechanisms considered responsible for VPPMCs improving impact toughness by performing Charpy impact tests on unidirectional nylon 6,6 fibre–polyester resin samples over a range of span settings (24–60 mm) and fibre volume fractions (3.3–16.6%). Comparing VPPMC samples with control (unstressed) counterparts, the main findings were: (i) improved impact energy absorption (up to 40%) depends principally on shear stress-induced fibre–Matrix debonding (delamination) and (ii) energy absorption improves slightly with increasing fibre volume fraction, but the relationship is statistically weak. The findings are discussed in relation to improving the impact performance of practical structures.
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Viscoelastically prestressed Polymeric Matrix Composites ― Potential for useful life and impact protection
Composites Part B-engineering, 2010Co-Authors: Kevin S. Fancey, Ks FanceyAbstract:Abstract A viscoelastically prestressed Polymeric Matrix Composite (VPPMC) is produced by applying tension to Polymeric fibres, the tensile load being released prior to moulding the fibres into a Matrix. Following Matrix solidification, compressive stresses imparted by the viscoelastically strained fibres improve Composite tensile, flexural and impact properties. This study focuses on the potential for useful life and impact protection capability by performing Charpy impact tests on nylon 6,6 fibre–polyester resin samples subjected to accelerated ageing. Prior to testing, time–temperature superposition principles were used, the samples being aged by heating to 60 °C for periods representing a 10-fold increase over previous work. The results demonstrated no deterioration in impact performance over a duration equivalent to 40 °C for ∼20 years. Combining these data with previous work showed that VPPMC samples absorbed, on average, ∼30% more impact energy than control (unstressed) counterparts. Four mechanisms are highlighted, which should enable VPPMCs to contribute towards high velocity (blast fragment) impact protection and crashworthiness applications, especially for situations requiring low mass components with complex geometries.
Thomas L Attard - One of the best experts on this subject based on the ideXlab platform.
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linking nanoscale chemical changes to bulk material properties in iepm polymer Composites subject to impact dynamics
ACS Applied Materials & Interfaces, 2019Co-Authors: Thomas L AttardAbstract:A synthesizable interfacial epoxy–polyurea-hybridized Matrix (IEPM), composed of chemical bonded nanostructures across an interface width ranging between 2 and 50 μm, is a candidate for dialing-in molecular vibrational properties and providing high-impact dynamics resistance to conventional fiber(x)-reinforced epoxy (F/E), engendering an x-hybrid Polymeric Matrix Composite system (x-IEPM-tc). Atomic force microscopy and scanning electron microscopy elucidate the interfacial nanoscale morphology and chemical structure via reaction kinetics of curing epoxy (as a function of time, tc) and fast-reacting (prepolymerized) polyurea. Nano-infrared spectroscopy (nano-IR) spectra, per non-negative Matrix factorization analysis, reveal that simultaneous presence of characteristic epoxy and polyurea vibrational modes, within a nanoscale region, along with unique IEPM characteristics and properties following thermomechanical analysis and dynamic mechanical analysis (DMA), indicate chemical bonding, enabling IEPM react...
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tornado borne debris impact performance of an innovative storm safe room system protected by a carbon fiber reinforced hybrid Polymeric Matrix Composite
Engineering Structures, 2014Co-Authors: Hongyu Zhou, Kittinan Dhiradhamvit, Thomas L AttardAbstract:Abstract A new tornado safe room design is proposed using a recently developed Carbon-fiber reinforced Hybrid Matrix Composite (CHMC), or “CarbonFlex,” to withstand tornado-borne debris impacts. Test results reveal that the new CarbonFlex wall panel has superior impact resistance in comparison to conventional residential construction and some alternative residential tornado-resistant wall panel constructions observed in the literature and identified in the current work. Two CarbonFlex design groups successfully passed the high-debris impact tests at a missile speed of 44.7 m/s (100 mph), corresponding to a ground wind speed tornado of 111.7 m/s (250 mph) while the two other CarbonFlex wall panel designs passed tests at missile speeds of 40.2 m/s (90 mph), corresponding to ground wind speed tornados of 89.4 m/s (200 mph). Additionally, a control group wall panel design that was manufactured using a conventional carbon fiber reinforced polymer (CFRP), or more precisely a carbon fiber reinforced epoxy, indisputably failed two debris missile high-impact tests. The material processing parameters of CarbonFlex, i.e., the Matrix thickness, h p , and an intermittent curing time, t c , show to be evidently influential on the impact resistance capability of the CarbonFlex panels where the resistance generally increases with smaller values of t c and with greater values of h p . The merits of using CarbonFlex over conventional building envelop components are quantified via vulnerability assessments of both conventional and the newly developed Composite wall panel system under tornado transported debris impacts.
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rehabilitation of notch damaged steel beams using a carbon fiber reinforced hybrid Polymeric Matrix Composite
Composite Structures, 2013Co-Authors: Hongyu Zhou, Thomas L Attard, Yanli Wang, Jyan WangAbstract:Abstract The retrofit of notch damaged steel beams is investigated via the experimental testing of nine wide-flange steel beam specimens and finite element simulation. Three notch configurations representing various damage levels were identified, and the beam specimens were retrofitted using carbon fiber reinforced polymer (CFRP) laminates and a recently developed Carbon-fiber Hybrid-Polymeric Matrix Composite (CHMC) that has been termed CarbonFlex, and that exhibits superior energy dissipation and ductility properties. The peak-load deflections of the CarbonFlex-retrofitted beams were calculated to be between 67.8% and 73.1% higher than their CFRP-retrofitted counterparts. The results are attributed to the substantially higher damage tolerance of CarbonFlex than conventional carbon-fiber reinforced polymer. Finite element models were developed to investigate the damage mechanism and loading carrying capacities of the beams, and the strain/ stress distributions near the notch tips. The numerical results match closely with the experimentally determined load–deflection curves and the strain fields obtained by the digital imaging correlations (DIC) technique. Both experimental and numerical results clearly indicate the effectiveness of CarbonFlex, as a candidate retrofitting material, for damaged steel structures. Lastly, the micro-mechanisms by which CarbonFlex could sufficiently sustain a significant amount of the peak strength at large deformations are discussed through scanning electron microscopy (SEM) and nano-indentation studies.
Jacob Aboudi - One of the best experts on this subject based on the ideXlab platform.
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Micromechanical prediction of the two-way shape memory effect in shape memory alloy Composites
International Journal of Solids and Structures, 2009Co-Authors: Yuval Freed, Jacob AboudiAbstract:AbstractThe two-way shape memory effect in monolithic shape memory alloys has been widely investigated both theoretically and experimentally. In the present study, this effect is analyzed for shape memory alloy Composites by employing a micromechanical model. To this end, the responses of Polymeric Matrix and metal Matrix unidirectional Composites with embedded shape memory alloy fibers are determined. For the Polymeric Matrix Composite, the effect of axial, transverse and shear loadings as well as the fiber volume fraction on the resulting two-way shape memory behavior are studied. The local distributions of stresses among the shape memory alloy fiber and epoxy Matrix in the low- and high-temperature shapes of the Composite are also investigated. Two training procedures that generate the two-way shape memory effect in the metal Matrix Composite are offered. The present analysis shows that the two-way shape memory effect in the chosen type of metal Matrix Composite is not as useful as in the Polymeric Matrix one. Finally, for a Polymeric Matrix Composite that is subjected to a transverse normal loading, the effect of imperfect bonding between the shape memory alloy fibers and the neighboring Matrix is investigated
Yuval Freed - One of the best experts on this subject based on the ideXlab platform.
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Micromechanical prediction of the two-way shape memory effect in shape memory alloy Composites
International Journal of Solids and Structures, 2009Co-Authors: Yuval Freed, Jacob AboudiAbstract:AbstractThe two-way shape memory effect in monolithic shape memory alloys has been widely investigated both theoretically and experimentally. In the present study, this effect is analyzed for shape memory alloy Composites by employing a micromechanical model. To this end, the responses of Polymeric Matrix and metal Matrix unidirectional Composites with embedded shape memory alloy fibers are determined. For the Polymeric Matrix Composite, the effect of axial, transverse and shear loadings as well as the fiber volume fraction on the resulting two-way shape memory behavior are studied. The local distributions of stresses among the shape memory alloy fiber and epoxy Matrix in the low- and high-temperature shapes of the Composite are also investigated. Two training procedures that generate the two-way shape memory effect in the metal Matrix Composite are offered. The present analysis shows that the two-way shape memory effect in the chosen type of metal Matrix Composite is not as useful as in the Polymeric Matrix one. Finally, for a Polymeric Matrix Composite that is subjected to a transverse normal loading, the effect of imperfect bonding between the shape memory alloy fibers and the neighboring Matrix is investigated
Adnan Fazal - One of the best experts on this subject based on the ideXlab platform.
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Viscoelastically generated prestress from ultra-high molecular weight polyethylene fibres
Journal of Materials Science, 2013Co-Authors: Adnan Fazal, Ks FanceyAbstract:The viscoelastic characteristics of ultra-high molecular weight polyethylene (UHMWPE) fibres are investigated, in terms of creep-induced recovery strain and force output, to evaluate their potential for producing a novel form of prestressed Composite. Composite production involves subjecting fibres to tensile creep, the applied load being removed before moulding the fibres into a resin Matrix. After Matrix curing, the viscoelastically strained fibres impart compressive stresses to the surrounding Matrix, to produce a viscoelastically prestressed Polymeric Matrix Composite (VPPMC). Previous research has demonstrated that nylon fibre-based VPPMCs can improve mechanical properties without needing to increase mass or section dimensions. The viability of UHMWPE fibre-based VPPMCs is demonstrated through flexural stiffness tests. Compared with control (unstressed) counterparts, these VPPMCs typically show increases of 20–40 % in flexural modulus. Studies on the viscoelastic characteristics indicate that these fibres can release mechanical energy over a long-timescale and fibre core–skin interactions may have an important role.
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viscoelastically prestressed Polymeric Matrix Composites effects of test span and fibre volume fraction on charpy impact characteristics
Composites Part B-engineering, 2013Co-Authors: Adnan Fazal, Ks FanceyAbstract:Abstract A viscoelastically prestressed Polymeric Matrix Composite (VPPMC) is produced by subjecting Polymeric fibres to tensile creep, the applied load being removed before moulding the fibres into a resin Matrix. After Matrix curing, the viscoelastically strained fibres impart compressive stresses to the surrounding Matrix, thereby improving mechanical properties. This study investigated the mechanisms considered responsible for VPPMCs improving impact toughness by performing Charpy impact tests on unidirectional nylon 6,6 fibre–polyester resin samples over a range of span settings (24–60 mm) and fibre volume fractions (3.3–16.6%). Comparing VPPMC samples with control (unstressed) counterparts, the main findings were: (i) improved impact energy absorption (up to 40%) depends principally on shear stress-induced fibre–Matrix debonding (delamination) and (ii) energy absorption improves slightly with increasing fibre volume fraction, but the relationship is statistically weak. The findings are discussed in relation to improving the impact performance of practical structures.