Bhabani K. Satapathy

Influence of Carbon Fabric on Fretting Wear Performance of Polyetherimide Composite

A carbon fabric composite of Polyetherimide (PEI) was fabricated and studied for fretting wear behavior along with neat PEI. The operating parameters were load, temperature, amplitude and frequency of fretting. It was observed that carbon fabric proved to be significantly beneficial for reducing friction and wear of PEI. The friction coefficient of PEI was quite high and independent of operating parameters. For the carbon fabric composites (CFC) it reduced from 0.3 to 0.18 with an increase in load. On the other hand it showed marginal increase (0.18 to 0.28) with increase in temperature from 25°C to 200°C. The wear rate of the composite, CFC showed little variation with increase in load and temperature. Amplitude and frequency also proved to be important influencing parameters. Microscopic studies proved useful for understanding wear mechanism.

FRICTION BRAKING PERFORMANCE OF NANOFILLED HYBRID FIBER REINFORCED PHENOLIC COMPOSITES: INFLUENCE OF NANOCLAY AND CARBON NANOTUBES

Graphite lubricated phenolic-based friction composites filled with nanoclay and Multiwalled carbon nanotubes (MWCNT) and reinforced with lapinus and Kevlar fibers have been successfully fabricated for evaluation of their physical, chemical, mechanical and tribological properties, respectively. The increase in nanoclay and MWCNT contents led to the increase in bulk physical properties such as void contents, ash contents, water absorption and compressibility. The impact, tensile and flexural strengths get affected deleteriously when complemented by lapinus and kevlar fibers in the composites. However, with the increase in nanoclay and MWCNT contents the μ-performance, friction fade resistance and friction recovery enhanced whereas, friction fluctuations, stability and variability coefficients have been observed to be dependent on the composition. The addition of nanoclay and MWCNT raises the disc temperature whereas wear resistance of the friction composites increases with the decreasing in nanoclay and MWC...

Effect of Carbon Nanotubes on Tribo‐Performance of Brake Friction Materials

Brake friction composites filled with multiwalled carbon nanotubes have been fabricated and evaluated for their tribo‐performance. The tribological behavior of the frictional composites has been evaluated on a krauss testing machine as per the ECE regulations. The friction performance (μP), frictions fade (μF) and friction recovery (μR) gets enhanced with the addition of carbon nanotubes. The wear performance and brake pad thickness loss of the composites decreased with the increase in carbon nanotubes.

Thermo-mechanical characterization of nano filled and fiber reinforced brake friction materials

Brake friction materials filled with multiwalled carbon nanotubes (MWCNT) and nanoclay have been fabricated and characterize for thermo-mechanical properties. Thermo gravimetric analysis (TGA) show that the stability of the friction composites increased with increase in MWCNT and nanoclay contents. Dynamic mechanical analysis (DMA) of the composite have been carried out to characterize the storage modulus (E′), loss modulus (E″) and damping factor (Tan δ) as a function of temperature. The storage and loss modulus show a maxima at lower content of MWCNT and nanoclay.

Dynamic mechanical response and fade–recovery performance of friction composites: effect of flyash and resin combination

Flyash-filled and glass fibre-reinforced phenolic composites have been fabricated by compression molding. The composites were characterized for their mechanical, thermo-mechanical, tribological and morphological attributes. Temperature dependence of mechanical properties has been investigated using dynamic mechanical analyzer. Tribological properties of the composites were evaluated by chase friction tester conforming to SAE J661a standard. An inverse relation between the storage modulus and wear has emerged, indicating wear to be mainly controlled by the fibre/filler matrix interfacial characteristics. Tribo-analysis reveals improvement in the friction fluctuations, whereas wear resistance deteriorates with increase in the ratio of flyash to resin content. Temperature-dependent reduction and revival of friction coefficient revealed the improvement in the average friction–recovery performance although the friction–fade response was found to be mostly unaffected due to compositional variation. SEM analysis is carried out to study the topography of the contact patches/friction film and associated wear mechanism of the phenolic-based composites, which has further revealed more of the secondary plateaus for composites containing more of the phenolic content. Disc rubbing intensity, as obvious from the energy-dispersive X-ray analysis (Fe content), becomes less prominent with increase in the ratio of flyash to resin content.

Investigations on friction-fade and friction-recovery performance of phenolic composites based on fly ash–graphite combinations for braking applications

Friction composite materials based on combinatorial variations of fly ash and graphite were fabricated and evaluated on Krauss friction tester under inertia-braking mode following the ECE R-90 regulation. The frictional responses, such as friction fade at elevated temperatures and friction recovery on cooling, of the composites have demonstrated three regimes of friction evolution irrespective of the composition and the test runs. The composite with the highest fly ash content (i.e. 65 wt.%) and without graphite, shows the highest frictional performance, comparable frictional fluctuation, permissible fading but the highest wear with the highest rise in disc temperature. The composite with 60 wt.% fly ash in combination with 5 wt.% graphite showed higher frictional performance, permissible fading, lower wear volume and relatively lesser rise in disc temperature. However, the other composites having <60 wt.% fly ash and >5 wt.% graphite contents show unacceptable frictional level and friction-fade characteristics. Recovery performances of all composites remained above 100%. The study comprehensively established that composite material with ≥60 wt.% fly ash content in combination with ≤5 wt.% graphite content is functionally ideal to meet the desired performance requirements. Analysis of frictional data revealed the predominance of fade coefficient, whereas material coefficient remained minimally influential. Wear data analysis indicates that the inherent material factor predominates the wear performance followed by temperature-induced effects. Among the fade and recovery influences, the recovery coefficient has been observed to be predominant over the fade coefficient in the determination of the wear behaviour. Worn surface morphology revealed the role of topographical attributes in controlling the friction and wear performances.

Influence of Modified Phenolic Resins on the Fade and Recovery Properties of the Friction Materials: Supportive Evidence Multiple Criteria Decision-making Method (MCDM)

Multiple criteria decision-making method (MCDM), called balancing and ranking method, is employed for the ranking of five non asbestos fiber reinforced organic friction materials (FMs). This variant of MCDM uses three steps to derive a transitive overall final order of a finite set of options. First, an outranking matrix is derived in which pairwise comparison indicates the frequency with which one option is superior to all other options based on each criterion. Second, the outranking matrix is triangularized to obtain an implicit pre ordering or provisional order of options. Third, the provisional order of options is subjected to various screening and balancing operations that require sequential application of a balancing principle to the advantage and disadvantage table. Five FMs based on five different phenolic resins are evaluated on Krauss friction tester according to ECE R-90 regulation (Economic Commission for European regulation). Resins used for friction composites are; (i) straight phenolic resin, (ii) alkyl benzene modified resin, (iii) cashew nut shell liquid modified resin, (iv) NBR modified resin, and (v) linseed oil modified resin. The various performance criteria selected for the analysis are: performance-μ,% recovery in μ,% Fade in μ, wear, and temperature rise in the rotor disc. After optimization of various performance parameters of five FMs it was observed that the alkyl benzene modified phenolic resin composite performed well and linseed oil modified phenolic resin based composite was poor. The order obtained after evaluating this method complies with the results presented theoretically.

Filler-immobilization assisted designing of hydroxyapatite and silica/ hydroxyapatite filled acrylate based dental restorative composites: Comparative evaluation of quasi-static and dynamic mechanical properties

The comparative effect of filler combinations on the quasi-static and thermo-mechanical properties of light cured acrylate based restorative composites is addressed in the study. Two series of acrylate based restorative composites filled with hydroxyapatite (Hap) and silica/Hap combination were prepared. FTIR spectroscopy showed the filler-assisted functional interference with the chemical structure of the resin, whereas SEM–EDX revealed the state of micro-dispersion/distribution morphology of the filled composites. The silica/Hap combination filled (micro-hybrid) composites with 30 wt.-% filler showed highest compressive strength (CS) and composites with 20 wt.-% filler showed highest diametral tensile strength (DTS) as well as flexural strength (FS). Dynamic mechanical properties revealed reinforcement effectiveness correlated to extent of filler immobilization effects estimated from Kerner equation. Our study conceptually establishes the possibility of manipulating the mechanical and thermo-mechanical strength requirements, by catering to the extent of filler induced bulk hardening contributions, as characterized by immobilized volume fraction of the polymer chains. It was imperatively deduced that at very high amount of overall filler content (e.g. > 50 wt.-%) the reinforcement effectiveness is filler-controlled whereas the same extent of effectiveness may be obtained by manipulating the filler induced immobilization effects (e.g. < 20 wt. - %).

Wear Performance Forecasting of Chopped Fiber–Reinforced Polymer Composites: A New Approach Using Dimensional Analysis

ABSTRACT Solid particle erosion of polymer matrix composites is a complex process in which wear occurs from the target surface by impingement of rigid sand particles in an air medium. The rate of material removal (RMR), also referred to as the erosion rate, mainly depends on target material parameters and the erosion conditions such as impact angle, impact velocity, and erodent size. A new semi-empirical model for prediction of the erosion rate of polymer matrix composites has been developed using a dimensional analysis technique based on Buckinghams π theorem. The predictive model analytically rests upon parameters related to chopped glass fiber composites, erodent (target material properties), and operating variables that mainly affect the erosion process of chopped glass fiber–vinyl ester resin composites. The forecasting ability of the predictive model has been assessed and verified by experimental investigations for chopped glass fiber–reinforced vinyl ester resin (VGF) composites. Validation of the theoretical erosion rates obtained from the predictive model showed that they were in good agreement with the experimentally determined erosion rates, where the average error range was estimated to be ∼10 to ∼20%.

Temperature dependence of friction and wear performance and thermomechanical response of flyash-filled brake composites

Flyash-filled glass fibre reinforced composites have been fabricated and evaluated for drag braking performance on a chase friction testing machine following SAE J 661a standard. The friction build-up and decay phenomena in the drag braking mode as a function of drum temperature have consistently been found to be in the composites with ∼5−7.5 wt% of glass fibres, whereas the absolute friction effectiveness remained higher in the composites with maximum flyash/maximum glass fibre contents. Temperature-dependent friction performance remained broadly composition specific and qualitative correlations of performance to compositional attributes have been found to be complex. Topographical variations and their possible roles in controlling the tribological performance have been characterized by worn surface morphology. Scanning electron microscopy–energy dispersive X-ray combined analysis have revealed that at higher amount of glass fibre content in combination with flyash, the composite exhibited enhanced noise and judder propensity apart from higher Fe-content deposition on friction film. The energy dissipation ability modes as revealed from dynamic mechanical analysis showed not only a correspondence between the damping ability of the composites and compositional variations but also qualitatively established a correlation between wear and storage moduli.