Kazi Imran - Academia.edu (original) (raw)

Papers by Kazi Imran

CONFERENCE: 2017 World of Coal Ash-(www.worldofcoalash.org) ABSTRACT The U.S. has been producing ... more CONFERENCE: 2017 World of Coal Ash-(www.worldofcoalash.org) ABSTRACT The U.S. has been producing over 90 million metric tons of coal ash per year from coal burning steam power plants; and about 50% of it was used in concrete, soil stabilization, land and mine fills, etc. Most of the ashes used were already characterized and classified. The excess ash and other unclassified ash were stored in ponds. The current estimate of pond ash within the state of North Carolina alone is in excess of 100 million metric tons and the estimate all over the world will exceed billions of tons. EPA studies in 2006 and 2008 have shown that coal ash leaches inorganics such as arsenic, antimony, selenium and thallium into ground water. Concentrations of inorganics can exceed the EPA's municipal drinking water limit. This paper presents an alternative safe use of pond/coal ash in building and infrastructure composite products.

A three roll mill processing technique was used to disperse graphene nanoplatelets in epon 828 ep... more A three roll mill processing technique was used to disperse graphene nanoplatelets in epon 828 epoxy system. As a first step of this research, processing graphene/epoxy nanocomposites was explored with different weight percent of graphene. After establishing a repeatable process to achieve good electrical properties, the materials were tested for thermal conductivity and mechanical properties. The as received graphene nanoplatelets had average diameter of 25 microns, thickness 6-10 nanometers and epon 828 epoxy system were selected. Conventional mechanical mixing, sonication and three roll mill dispersion techniques were investigated. Based on this study three roll dispersion was found to be repeatable, consistent and scalable. Through the thickness (T-T-T) or volume electrical conductivity increased by nine log cycle, thermal conductivity doubled and fracture toughness increased by one-third over the base with 1.0 wt.% dispersion of graphene to epon 828. However, tensile and flexure properties changed little.

A primary limitation of fiber-reinforced polymer composites in aircraft applications is susceptib... more A primary limitation of fiber-reinforced polymer composites in aircraft applications is susceptibility to lightning because of poor electrical, thermal and electromagnetic properties. The current methods to mitigate the lightning strike in aircraft have added weight and reduced the performance. Previous graphene-modified epon 828 epoxy matrix study showed that three-roll dispersion is effective, repeatable and potentially scalable to disperse graphene in to epoxy to increase the electrical conductivity. Percolation threshold of graphene was found to be about 1.0 wt.% that enhanced electrical conductivity of epon 828 epoxy matrix from 4.3 Â 10 À15 to 2.6 Â 10 À6 S/m, thermal conductivity doubled and fracture toughness increased by one-third. In the present study, the same graphene/epon 828 is reinforced by carbon fabric by hand lay-up followed by compression molding. The resulting composite laminate was tested for electrical, thermal and mechanical properties and results of this nanocomposite laminates were compared with base composite laminate.

One of disadvantages of polymer composites is poor electrical and thermal conductivity. As a firs... more One of disadvantages of polymer composites is poor electrical and thermal conductivity. As a first step in this direction, graphene-modified polypropylene polymer is being developed to improve its electrical and thermal conductivity. Two techniques were investigated: surface coating and extrusion. In the case of coating technique, the percolation threshold was found to be 0.5 wt % of graphene and electrical conductivity of polypropylene increased around 13 log cycles. Coating technique breaks the agglomerations due to magnetic stirring followed by sonication and gives homogeneous graphene-coated polypropylene pellets. When polymer melts under compression molding, the graphene platelets network formed on the surface of polypropylene pellets as well as through-the-thickness of the molded disk, which provide continuous network of graphene. However, in extrusion technique, graphene segregated and did not disperse properly in polypropylene. V

A three-roll mill processing technique was used to disperse graphene nanoplatelets into epon 828 ... more A three-roll mill processing technique was used to disperse graphene nanoplatelets into epon 828 epoxy system. As a first step of this research, processing of graphene/epoxy nanocomposites was explored with different weight percentages of graphene. After establishing an optimal and repeatable process to achieve good electrical properties, the materials were tested for thermal conductivity and mechanical properties. The xGnP-25 graphene nanoplatelet supplied by XG Science Inc. was used; the graphene average diameter was 25 lm and thickness was 6–10 nm. Mechanical mixing, sonication and three-roll mill dispersion techniques were investigated to disperse graphene in epon 828 epoxy. The study showed that the three-roll dispersion is effective, repeatable and potentially scalable to disperse graphene into epoxy to increase the electrical conductivity. The weight percentage of graphene used ranged from 0.5 to 5.0. Percolation threshold of graphene was found to be 1.0 wt%. Through-the-thickness or volume electrical conductivity increased by nine log cycles, thermal conductivity doubled and fracture toughness increased by one-third for 1.0 wt% addition of graphene to epon 828. However, the mechanical properties remained almost unchanged.

The effect of nanoclay on the degradation of low velocity impact responses of carbon fiber reinfo... more The effect of nanoclay on the degradation of low velocity impact responses of carbon fiber reinforced polymer (CFRP) composites manufactured by the vacuum assisted resin transfer molding (VARTM) process is experimentally investigated with and without exposure to seawater for marine applications. Nanoclay was dispersed into the matrix by using magnetic stirring. Samples (100 mm by 100 mm) exposed to seawater for 0, 6, and 12 months in laboratory conditions were impacted at 20, 30, and 40 J energy levels using a Dynatup8210. The damage sustained by the samples was evaluated by a thermo-graphic imaging technique. Comparisons between conventional and nanophased CFRP composites both in conditioned and unconditioned cases were made in terms of peak force, absorbed energy, deflection, delamination area, and specific delamination energy. Water absorption was observed to be reduced due to nanoclay infusion. After 12 months of exposure to seawater 2% nanophased samples absorbed 0.39% moisture whereas control samples absorbed 0.67% moisture. Impact strength, toughness, and energy absorption decreased with increasing conditioning time by weakening the bond between the fiber and matrix and softening the matrix materials. However, reduction in properties is significantly extenuated by the incorporation of nanoclay in the matrix. Specific delamination energy (SDE) is observed to be higher in the nanophased CFRP compared to that of the conventional one at different aging periods indicating enhanced fracture toughness in the nanophased composites. The larger and stronger inter-facial area produced by the nanoclay inclusion has been found to facilitate more energy absorption in the nanophased sample compared to the conventional one. Furthermore, nanoclay reduced the development of delamination by arresting the crack propagation path or by toughening the matrix. It is concluded that the excellent barrier capacity, higher surface area, and high aspect ratio of nanoclay are responsible for the superior performance of CFRP composites, which in turn, enhances the durability of composites.

Composites used for marine applications are subjected to various environmental effects, such as m... more Composites used for marine applications are subjected to various environmental effects,
such as moisture, temperature, UV radiation, and seawater. In this study, effect of
seawater on the degradation of mechanical properties of conventional and nanophased
carbon=epoxy composites was investigated. Epoxy resin was modified using 1 wt. %,
2 wt. %, and 3 wt. % nanoclay. Carbon=epoxy composites were fabricated by vacuum
assisted resin transfer molding process and compared with neat samples with and without
exposure to seawater. Nanoclay was dispersed into matrix by using magnetic stirring.
Mechanical characterization performed through three point bending tests showed that
2 wt. % nanoclay loading was optimum. Flexural strength and modulus were increased
by 25% and 12.51%, respectively, compared to neat system for samples not exposed to
seawater. Flexure samples exposed to the seawater for 30-, 60-, and 180-day periods
revealed that samples with nanoclay retained better mechanical properties compared to
neat samples. After 30-day exposure to seawater, there was no significant reduction in
the strength and modulus. However, flexural strength was reduced by 10.24%, 7.08%,
5.28%, and 7.13% for neat, 1 wt. %, 2 wt. %, and 3 wt. % nanoclay-infused samples,
respectively, after the samples were exposed to seawater for 180-day. At the same time
flexural modulus was reduced by 12.61%, 7.16%, 4.59%, and 6.11%, respectively. From
scanning electron microscopy (SEM) studies, it was found that failure occurred due to
delimitation and initiated from the compression side. Nanophased composites exhibited
better bonding between fiber and matrix. SEM micrographs also revealed that both
unconditioned and conditioned nanophased epoxy, which produce relatively rougher
fracture surfaces compared to neat samples. Optical microscopy study revealed no significant
physical change in outer surfaces of the samples conditioned up to a 90-day period.

The effect of seawater on thermal behavior of conventional and nanophased carbon/epoxy composites... more The effect of seawater on thermal behavior of conventional and nanophased carbon/epoxy
composites was investigated in this study. Composites were fabricated with 1 wt.%, 2 wt.%, and
3 wt.% nanoclay by vacuum assisted resin transfer molding (VARTM) process and compared
with neat samples with and without exposure to seawater. Thermal characterization was
performed by the dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA).
Samples exposed to the seawater for 30- and 60-day periods revealed that samples with nanoclay
retained better thermal properties compared to the neat samples. Storage modulus was reduced
by 6.28%, 6.76%, 6.15%, and 7.05% for neat, 1 wt.%, 2 wt.%, and 3 wt.% nanoclay infused
samples, respectively, after the samples were exposed to seawater for 60 days . From TGA
results, it was observed that the thermal stability is not related to nanoclay content and
conditoning. Optical microscope (OM) and scanning electron microscope (SEM) studies
revealed no significant change in surface morphology in the 30-day conditioning samples.