scholarly journals Fabrication and Evaluation of Low Density Glass-Epoxy Composites for Microwave Absorption Applications

2017 ◽  
Vol 67 (6) ◽  
pp. 682
Author(s):  
Srikanth Ivaturi ◽  
P S.N.S.R. Srikar ◽  
K. Anusha ◽  
S. K. Majee ◽  
Himanshu Bhusan Baske ◽  
...  
Keyword(s):  
Carbon Fibers ◽  
Loss Tangent ◽  
Microwave Energy ◽  
Electromagnetic Properties ◽  
Low Density ◽  
Low Velocity ◽  
Interfacial Polarisation ◽  
X Band ◽  
Novel Method ◽  
Laminar Shear

<p class="p1">In the present work, fabrication and evaluation of low density glass – epoxy (LDGE) composites suitable for absorbing minimum 80 per cent of incident microwave energy in 8 GHz to 12 GHz (X-band) is reported. LDGE composites having different densities were fabricated using a novel method of partially replacing conventional S-glass fabric with low density glass (LDG) layers as the reinforcement materials. Flexural strength, inter laminar shear strength and impact strength of the prepared LDGE composites were evaluated and compared with conventional High density glass-epoxy (HDGE) composites to understand the changes in these properties due to replacement of S-glass fabrics with LDG layers. To convert LDGE structures to radar absorbing structures controlled quantities of milled carbon fibers were impregnated as these conducting milled carbon fibers can act as dielectric lossy materials which could absorb the incident microwave energy by interfacial polarisation. Electromagnetic properties namely loss tangent and reflection loss of carbon fiber impregnated LDGE composites were evaluated in 8 GHz -12 GHz frequency region and compared with HDGE composites. It was observed that both LDGE and HDGE composites have shown loss tangent values more than 1.1 and minimum 80 per cent absorption of incident microwave energy. Thus the results indicates that, LDGE composites can show EM properties on par with HDGE composites. Furthermore these LDGE composite could successfully withstand the low velocity impacts (4.5 m/s) with 50 J incident energy. Due to their ability to show good mechanical properties and light weight, LDGE composites can be used as a replacement for conventional HDGE composites to realise radar absorbing structures.</p>

Distribution of milled carbon fibers as a function of their length on S-glass fabric and its effect on the electromagnetic properties of S-glass epoxy composites

2018 ◽  
Vol 53 (20) ◽  
pp. 2891-2899 ◽  
Author(s):  
Srikanth Ivaturi ◽  
Himanshu Baske ◽  
Partha Ghosal
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Carbon Fibers ◽  
Optical Microscope ◽  
Microwave Energy ◽  
Epoxy Composites ◽  
Electromagnetic Properties ◽  
Interconnected Network ◽  
Large Clusters ◽  
Scanning Electron

Milled carbon fibers added S-glass epoxy composites were fabricated using milled carbon fibers as fillers. Milled carbon fibers having five different lengths namely 7, 20, 60, 200 and 400 µm were used to fabricate five different S-glass epoxy composites. Optical microscope and scanning electron microscope studies of S-glass epoxy composites indicated that milled carbon fibers having 400 µm length settled at weave openings as large clusters besides spreading on the tow surfaces at the interfilament undulations. Milled carbon fibers having 200 µm length were found to form smaller clusters at weave openings with an array of interconnected network in the resin-rich grid zones on the tow surfaces at the interfilament undulations. Milled carbon fibers having 60 µm and further lower lengths were found to get arrested at the interfilament undulations with random orientations without interconnectivity. Electromagnetic properties namely permittivity, loss tangent, and reflection loss of the fabricated composites measured in the range of 8 GHz to 18 GHz indicated that controlled agglomeration of the milled carbon fibers with interconnectivity is required for observing increase in the electromagnetic properties. This study indicated that S-glass epoxy composites added with milled carbon fibers having 400 µm length can show better conductivity due to increased interconnectivity but cannot effectively absorb incident microwave energy due to their inability to confine within the resin-rich grid zones as well as increased reflections from the large clusters that are formed at weave openings.

Low-density and high-modulus carbon fibers from polyacrylonitrile with honeycomb structure

Carbon ◽  
2015 ◽  
Vol 95 ◽  
pp. 710-714 ◽  
Author(s):  
Prabhakar V. Gulgunje ◽  
Bradley A. Newcomb ◽  
Kishor Gupta ◽  
Han Gi Chae ◽  
Thomas K. Tsotsis ◽  
...  
Keyword(s):  
Carbon Fibers ◽  
Honeycomb Structure ◽  
Low Density ◽  
High Modulus

scholarly journals Validity of a Novel Method for Estimation of Low-Density Lipoprotein Cholesterol Levels in Diabetic Patients

2016 ◽  
Vol 23 (12) ◽  
pp. 1355-1364 ◽  
Author(s):  
Hideto Chaen ◽  
Shigesumi Kinchiku ◽  
Masaaki Miyata ◽  
Shoko Kajiya ◽  
Hitoshi Uenomachi ◽  
...  
Keyword(s):  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Lipoprotein Cholesterol ◽  
Diabetic Patients ◽  
Low Density ◽  
Low Density Lipoprotein Cholesterol ◽  
Cholesterol Levels ◽  
Novel Method

Plume-modified mantle flow in the northern Basin and Range and southern Cascadia back-arc region since ca. 12 Ma

Geology ◽  
2019 ◽  
Vol 47 (8) ◽  
pp. 695-699 ◽  
Author(s):  
Victor E. Camp
Keyword(s):  
United States ◽  
Seismic Velocity ◽  
Flow Line ◽  
Basin And Range ◽  
Mantle Flow ◽  
Low Density ◽  
Low Velocity ◽  
Northern Basin ◽  
High Lava Plains ◽  
Back Arc

AbstractBimodal volcanism and rhyolite migration along the High Lava Plains in central Oregon (United States) lie above a broader feature defined by low seismic velocity in the upper mantle that emanates from the Yellowstone hotspot (northwest United States) and extends westward across the northern Basin and Range. It was emplaced by a westward current, driven in part by rapid buoyancy-driven flow across the east-west cratonic boundary of North America. Geothermometry studies and geochemical considerations suggest that the low-velocity feature may be composed of moderately hot, low-density mantle derived from the Yellowstone plume but diluted by thermomechanical erosion and entrainment of colder mantle lithosphere. Finger-like conduits of plume-modified mantle beneath Quaternary eruption sites delineate flow-line channels that have developed across the broader mantle structure since 2 Ma. These channels have allowed low-density mantle to accumulate against the Cascades arc, thus providing a heated mantle source for mafic magmatism in the Newberry (Oregon) and Medicine Lake (California) volcanic fields.

Pre-Programmed Failure Behavior Using Biology-Inspired Structures

2007 ◽  
Author(s):  
Brian Bay ◽  
Mike Bailey
Keyword(s):  
Failure Modes ◽  
Variable Density ◽  
Failure Behavior ◽  
Filler Materials ◽  
Low Density ◽  
Low Velocity ◽  
Working Stress ◽  
Component Strength ◽  
Box Beams ◽  
Increasing Demand

Core (filler) materials are key components of the sandwich panel and box-beams that are used in the design of lightweight structures. They perform a variety of elastic-range functions such as transferring and supporting working stresses and energy and collapse management. There is an increasing demand, however, for post-yield performance characteristics such as buckling control, impact toughness, and maintenance of component strength after damage. Low density is also an important consideration, as overall component mass is critical in most applications. These cellular solids need to perform well under normal working stress conditions, yet still resist damage from simple and unavoidable low velocity impacts. A new design approach is suggested by biological systems that have evolved for toughness and damage tolerance (bones, trees, plants, corals, etc.). These systems share the relatively low density cellular arrangements of common synthetic core materials, but also exhibit variable density gradients within the core. (Figures 1 and 2) This paper describes engineering design methods that are inspired by such biology. The result is that a design’s failure modes can be more effectively “designed-in”, controlling locations and amounts of failure.

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