Bipul Barua

Ultrasound Assisted Hybrid Carbon Epoxy Composites Containing Carbon Nanotubes

A simple approach has been reported toward the development of hybrid nano/microfiber composite structures with improved mechanical properties. Ultrasound assisted atomization process has been utilized for depositing carbon nanotubes (CNTs) on the surface of carbon fiber (CF) cloth using dilute solutions of CNTs in N, N-dimethylformamide (DMF). Dilute solutions with three different CNT concentrations such as 1 × 10−4 g/ml, 5 × 10−4 g/ml, and 10 × 10−4 g/ml were fed into an ultrasonic atomizer probe using a positive displacement syringe pump and sprayed directly on CF cloth rested on a hot plate inside a deposition chamber. Several layers of hybrid CF cloths containing CNTs were used to fabricate composite laminates using a vacuum assisted resin transfer molding (VARTM). Although the dispersion of CNTs in DMF was found very well for all three concentrations, the distribution of CNTs on CFs was only found homogeneous for 1 × 10−4 g/ml solution. It was found that the hybrid composite containing 0.3 wt. % CNTs loading fabricated using 1 × 10−4 g/ml solution showed about 25% improvement in flexural strength, although moderate improvement in flexure modulus was achieved for all three concentrations. The improved strength is believed to be due to homogeneous distribution of CNTs, which resulted in increased surface roughness and mechanical interlocking between fibers and matrix.

Investigation of Mechanical Properties of Nanoclay Incorporated Room Temperature Vulcanized (RTV) Silicone Foams

Room temperature vulcanized (RTV) silicone foams (SFs) have unique thermal and chemical properties due to the presence of inorganic Si-O backbones with organic methyl side groups. However, their low mechanical strength and low tear resistance are major drawbacks for many applications. We have incorporated Nanoclay as reinforcing filler to improve mechanical properties of silicone foams. A three step blending process was used to disperse Nanoclay in silicone elastomers. Initially, Nanoclay in the concentration range of 0.5%–1% by weight were mixed to silicone polymer using a mechanical mixer at 1200 rpm for 10 min followed by a tip sonication at 20% amplitude for 1 hr. Finally, a high speed mechanical mixer was used at 2000 rpm for 2 hours. Two different types of Nanoclays with different sizes were investigated. Both compression and tear properties were found to improve with addition of 0.5 wt% Nanoclay. It was found that the smaller Nanoclay particle size showed the best compressive property while the Nanoclay with larger particle size improved tear strength the greatest.Copyright

Scenario-Based Learning Environment to Support Peer-Learning

It is well documented that students learn more effectively when they are actively involved in the learning process, and interacting with peers. Interactive scenario-based education is a novel concept expected to stimulate active learning and provide a peer-learning experience. In this paper we present Create your Scenario Interactively (CSI) module, which is an interactive storybook-like learning tool composed of interactive storyline, 2D/3D visualization, simulation, and state-of-the-art interaction technology. The CSI method allows peer-interactions and prepares students to solve open-ended problems.The CSI module has been developed for metal casting and implemented in manufacturing engineering courses at the University of Oklahoma and Tuskegee University. In this paper, we discuss the impact of the CSI on students’ learning in manufacturing engineering education. Our preliminary results suggest that a majority of the students feels that the CSI module is very effective in keeping them engaged. We also analyze the effect of peer-learning to develop critical thinking and solve design problems. The details of the CSI module, implementation details, and assessment results are discussed in the paper.Copyright

Manufacturing and Flexure Properties Characterization of Hybrid Nano-/Micro-Fiber Reinforced Epoxy Composites

We report an approach for the deposition of carbon nanotubes (CNTs) on carbon fabrics (CFs) en route for the development of hybrid nano-/micro-fiber composite structures. Ultrasonic atomization process was utilized for the direct deposition of CNTs on the surface of carbon fiber fabric. A dilute solution of CNTs was prepared by dispersing very small amount of multi walled CNTs (MWNT) in N,N-Dimethylformamide (DMF) using a low frequency ultrasonic water bath. The dispersed solution was then fed into the ultrasonic atomizer probe using a syringe pump and sprayed directly on the carbon fiber fabric rested on a hot plate. The dispersion of MWNTs in DMF solvent was characterized using UV spectroscopy and the distribution of CNTs on CF was characterized using scanning electron microscopy (SEM). Vacuum assisted resin transfer molding (VRTM) was used to manufacture composite laminates using several layers of CNTs hybrid CF fabrics. We prepared hybrid composite laminates containing 0.03-wt% of CNTs. Dispersion of CNTs in DMF and distribution of CNTs on CFs was found to be very good which we believed to be resulted in about 15% improvement in flexure strength and about 12% improvement in strain to failure compared to neat composites. Such improvements in composite properties with only 0.03% CNTs are very promising in hybrid composite structures.Copyright

Interactive Scenario-Based Teaching of Metal Casting Processes

It is well documented that students learn more effectively when they are actively involved in the learning process. Interactive scenario-based education is a novel concept expected to stimulate active learning and provide an engaging learning experience. Recently we have developed a Create your Scenario Interactively (CSI) module to teach metal casting and have implemented it in manufacturing engineering courses at the University of Oklahoma. In this paper, we discuss the impact of the CSI on students’ learning in manufacturing engineering education. The pedagogical effectiveness of the CSI instruction has been evaluated in several areas such as students’ engaging and active learning through pre-test and post-test format and survey questionnaires. Our preliminary results suggest that a majority of the students feels that the CSI module is very effective in keeping them engaged. Results also indicate that the CSI instructions help improve their understanding of the metal casting process. The details of the CSI module, implementation details, and assessment results are discussed.Copyright

Tensile Stress Relaxation of Thermosetting Polyurethane Solid and Foam

Stress relaxation behavior of thermosetting polyurethane (PU) solid and foam were investigated in tensile mode using a dynamic mechanical analyzer (DMA). PU solid samples were manufactured in a closed mold under compression to avoid any foam formation, whilst the foam samples were manufactured inside a woven using a silicone mold. Effects of cure and the post-cure temperature were also investigated on the stress relaxation behavior. Samples in the form of rectangular cross-section were subjected to a predetermined amount tensile strain and the tensile force was recorded as a function of time. Relaxation modulus was determined for different temperatures up to near the glass transition temperature. It was found that the viscous part becomes dominant with increasing test temperature. The experimental data was precisely modeled using a generalized Maxwell’s model and the characteristic relaxation time was identified with the corresponding relaxation process. Although the stress relaxation behavior of PU solid and PU foams were found similar at room temperature, the relaxation behavior of the foam was found to be influenced by the cell morphology at higher temperature.Copyright