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The presented studies concern the effects of graphite flake (GF) on the properties of a specific and challenging type of composite, that is, phenolic-carbon fabric (PC) composites. This type of materials are commonly used in large scale, but the studies in this manuscript try to explain in detail the effects of graphite on the characteristics of composites. The results show that Young's modulus exhibits increasing trend however tensile strength and interlaminar shear strength show decrement on increasing the GF content in the PC-GF composites. Dynamic mechanical thermal analysis (DMTA) reveals that storage modulus (E') increases by ~42% and 139% upon addition of 10 and 40 wt% GF in the PC-GF composites, respectively. Loss modulus (E') of the composites shows a drastic improvement (~145%) upon addition of only 10 wt% GF. Moreover, various interfacial interaction parameters such as entanglement density (N), reinforcement efficiency factor (r), C factor (the effectiveness of fillers on the modulus of the composites), interphase adhesion factor (A), and 'b' factor (fiber volume correction factor) of the composites are also evaluated using the data obtained from DMTA and correlated with mechanical properties of the composites., INTRODUCTIONCarbon fiber reinforced composite materials are widely used because of their excellent physical, thermal and mechanical properties [1, 2]. Among polymers, phenolic resins are finding their increased applications due to [...]

Exfoliated graphite (EG) was synthesized from natural flake graphite by acid treatment followed by microwave irradiation. A maximum expanded volume of 560 mL/g was achieved for this exfoliation of graphite. EG/phenolic resin composite bipolar plates for polymer electrolyte membrane fuel cell were fabricated with a high loading of EG by compression molding. The composites possess low density, high electrical conductivity, high thermal stability, and high compressive strength. The composite bipolar plates were also characterized by X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and so on. The composite prepared with 50 wt% of EG has shown the desired properties for bipolar plate as per the US Department of Energy (DOE-2015) targets. As a result, the EG-resin composites can be used as bipolar plates for polymer electrolyte membrane fuel cell applications., INTRODUCTION Polymer electrolyte membrane (PEM) fuel cells are potentially most promising and efficient power sources for transport, stationary, and portable applications owing to their excellent properties such as high efficiency, [...]

Functionally graded polymer composites (FGPCs) were prepared by construction based layering method employing natural rubber (NR) as a matrix and carbon black (CB) in graded form. CB particles were graded along the rectangular geometry polymer matrix comprising the variation of particle volume fraction along thickness direction. These FGPCs were characterized through hysteresis measurements and compared with uniformly dispersed polymeric composites (UDPCs) maintaining the same average amount of filler. Dynamic mechanical properties of these FGPCs and UDPCs were also compared. Dynamic mechanical characterization revealed that FGPCs show much higher storage modulus than the corresponding UDPCs for any given combination of stacking sequence. Loss tangent of FGPCs was also observed to be lesser when compared to UDPCs leading to less hysteretic losses followed by lesser heat buildup in the composite. Hysteresis measurements accorded with the results of dynamic mechanical characterization. POLYM. ENG. SCI., 50:871-877, 2010. [C] 2009 Society of Plastics Engineers, INTRODUCTION Functionally graded materials (FGMs) are a category of relatively recent and promising materials that engineer gradual variations in material functionality throughout the structure. Recent advancements in materials fabrication processes [...]

The abrasive flow machining (AFM) is used to deburr, radius, polish and remove recast layer of components in a wide range of applications. Material is removed from the workpiece by a flowing semisolid mass across the surface to be finished. In this study a medium for AFM has been developed from the various viscoelastic carriers and has been contrasted through experimental investigation. The viscoelastic media are selected on the basis of existing media through the studies of thermogravimetric analysis and are characterized by mechanical as well as rheological, properties with the help of a universal testing machine and a rheometer. The performance of the medium is evaluated through the finishing criteria on a two-way AFM setup. The investigation reveals that the styrene butadiene rubber (SBR) medium gives a good improvement in surface finish. The surface improvement through SBR media is 88%. It is also found that the strain, temperature, shear rate, time of applied constant stress, cyclic loading, etc. have an impact on the mechanical and rheological properties of the newly developed medium, which are ultimately governed by the performance of the medium in the target applications. [DOI: 10.1115/1.3046135]

With the use of the Boltzmann superposition principle, a statistical theory of rubber elasticity, and phenomenological theory, the hysteresis loss at high strain (greater than 100%) of nonlinear viscoelastic materials has been quantified in terms of material parameters. The theory incorporates both experimental and analytical parameters. The experimental results for natural rubber (NR) and styrene-butadiene rubber (SBR) vulcanizates having variations of loading of carbon black, silica, clay, resin and curatives are in good accord with the theoretical predictions., INTRODUCTION Mathematical constitutive theories for nonlinear large elastic deformation of rubber on the basis of the strain energy density function have been developed (1-7). However, the quantitative evaluation of hysteresis [...]