Mohit Sharma

ABSTRACT Polyetherketone (PEK) is one of the least explored specialty thermoplastic polymers for its tribo-utility. It exhibits continuous operating temperature up to 280 °C and under short-term loads it can function up to 350 °C. In literature, hardly anything is reported on the adhesive wear performance of PEK and its composites. Three composites based on PEK containing short fibers of carbon/glass along with various solid lubricants were developed and characterized for thermal and mechanical properties. The tribo-properties were studied under varying loads and speeds by sliding a composites pin against a mild steel disc as a counter face. The studies were focused to examine the role of these ingredients on enhancing pressure × velocity limit (PVlimit), which is an indication of utility of a tribo-polymer in severe operating conditions. The performance assessment was done according to multiple parameters; such as magnitude of coefficient of friction (μ) and its fluctuations with time, PVlimit, compatibility with the counter-face, specific wear rate (K0), etc. Very low K0 (≈10−16 m3/Nm), very low μ (0.04–0.20) and very high PVlimit values (>95.2 MPa m/s) were reported for these composites. White graphite (hexa boron nitride—hBN) proved to be the most efficient solid lubricant. The wear mechanisms using scanning electron microscopy of worn surfaces of pins and discs were studied. It was interesting to observe that glass fibers in the composite showed extremely good performance instead of showing abrasion and high μ. A very different friction and wear mechanism was claimed to be responsible for this. A synergism between lubricating action of two lubricants and layer of molten glass on the disc was the main reason for the enhanced performance.

Carbon fabric (CF) reinforced polyethersulphone (PES) composites were fabricated using solution impregnation technique. Cold remote nitrogen–oxygen plasma (CRNOP) treatment to the CF was done to enhance the fiber–matrix adhesion. The developed composites ...

Powder-prepreg method was used to develop composites with untreated and cold remote nitrogen–oxygen (0.5%) plasma (CRNOP) treated carbon fabric (CF) (67–68 wt%) and poly-ether-ether-ketone (PEEK) followed by the evaluation of physical and mechanical properties. Tribo-evaluation in adhesive wear mode was done by sliding a composite pin against a mild steel disc under various loads. It was observed that surface treated fabric composites were excellent in mechanical (tensile, flexural and ILSS – interlaminar shear strength) and tribological properties. A low coefficient of friction (0.21–0.28) and wear rates (1–12 × 10−15 m3/Nm) were recorded for these composites. An enhanced fiber–matrix adhesion was found to play a key role for improvement in performance properties. Raman spectroscopic and SEM studies on worn composites were done and correlated with the wear performance.

A composite with continuous carbon fibers (CF) (80% by vol.) and high performance thermoplastic polyetherimide (PEI) matrix was developed and evaluated for various mechanical properties as a function of fiber orientation angle (0°, 30°, 45°, 60° and 90°). It was observed that ...

Abstract Polyethersulfone (PES) composites were developed with carbon fabric (CF). Cold remote nitrogen oxygen plasma (CRNOP) treatment was employed to the CF to incorporate functional groups and promote fiber– matrix adhesion. This study includes the effect of PES melt ...

This paper reports the experimental investigations on the effect of La3+ and Ta5+ substitution on the structural characteristics and dielectric and piezoelectric properties of lead calcium titanate (PCT) ceramic. The PCT samples with A-site and B-site substitution having the composition formula Pb0.76−x/2LaxCa0.24(Ti0.98Mn0.02)1−x/2O3 and Pb0.76Ca0.24Mn0.02Ti 0.98−5x/4TaxO3, x=0 and 0.02, respectively, were prepared using conventional solid-state reaction method. Phase formation and structural analysis were studied using X-ray diffraction and scanning electron microscopy, respectively. Dielectric constant (ε′) and loss tangent (tan δ) as a function of frequency were measured at room temperature as well as elevated temperature. Both ε′ and tan δ decreased with increase in frequency at room temperature. Curie temperature decreased with La and Ta doping in PCT ceramics due to a decrease in the tetragonality of PCT ceramics. Piezoelectric charge coefficients (d33, d31) increased with La3+ substitution due to reorientation of the grains and decreased with Ta5+ substitution because of the increase in porosity. Figure of merit dhgh increased and decreased with La and Ta substitution, respectively. A good ferroelectric behaviour is obtained for La substitution, while no hysteresis is obtained for Ta substitution.

Cold remote oxygen nitrogen plasma (CRNOP) treatment was used to enhance reactivity of carbon fabric (CF) towards PEEK. The composite with treated fibers exhibited significantly better mechanical properties due to enhanced fiber–matrix adhesion as evidenced from SEM studies. It was of interest to examine the effect of the treatment on erosive wear performance with variation in angle of impingement and under elevated temperatures. The treatment proved successful in imparting wear resistance to the composite as compared to that with untreated CF. Efforts were made to study correlation between mechanical properties and erosive wear behavior at high temperature. Micro-Raman spectroscopy (MRS) was used to analyze the effect CRNOP treatment on CF and also to study stresses introduced during the erosion of CF-PEEK composites at different angles of impingement. Fairly good correlation was observed in wear rate and strain produced on the surfaces of fibers. SEM was used to understand wear mechanisms.► Plasma treatment to carbon fabric proved beneficial for improvement in fiber–matrix adhesion and hence; mechanical and erosive wear properties of the composites. ► Micro Raman studies showed very good correlations in strain produced in the fibers due to treatment as well as erosion at various angles of impingements. ► With the increase in composite temperature both erosion wear resistance and tensile strength decreased.