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Simultaneous interpenetrating networks (IPNs) comprising of polymethylsilsesquioxane (PMSQ) and phenolic resole (PF) systems at various PMSQ to PF ratios (0–75% w/w PF) which formed the matrix resin for 60% w/w short silica fibre reinforced composites (SR-PMSQ-PF) are subjected to a controlled heating regime in argon atmosphere at 1500 °C to investigate the microstructure and phase evolution based on IPN composition. This study aims at giving an insight into thermal, mechanical and chemical stability of silicone-phenolic IPN composites, particularly for high temperature thermal protection applications as in aerospace. The morphology and microstructure of the pyrolysed composites are well characterized using Raman and FTIR spectroscopy, XRD and SEM-EDS and based on this a mechanism for microstructure evolution is proposed. It is inferred that the pyrolysis of SR-PMSQ-PF composites results exclusively in the formation of cristobalite silica. In addition to that, the formation of SiC is also facilitated particularly in nano dimension with increase in phenolic content, by carbothermal reduction of silica derived from PMSQ and silica fibre predominantly through solid-vapour phase reaction along the (111) crystalline plane. The systematic evaluation of microstructure and morphology of pyrolysed SR-PMSQ-PF IPN composites is useful to define specific thermal protection applications for these composites.

The epoxy resins are widely used in nuclear and aerospace industries. The certain properties of epoxy resins as well as the resistance to radiation can be improved by the incorporation of different fillers. This study examines the effect of electron beam irradiation on the thermal and mechanical properties of the epoxy composites filled with aluminum nanoparticles at percentage of 0.35 wt%. The epoxy composites were exposed to the irradiation doses of 30, 100 and 300 kGy using electron beam generated by the linear electron accelerator ELU-4. The effects of the doses on thermal and mechanical properties of the aluminum based epoxy composites were investigated by the methods of thermal gravimetric analysis, tensile test, and dynamic mechanical analysis. The results revealed that the studied epoxy composites showed good radiation resistance. The thermal and mechanical properties of the aluminum based epoxy composites increased with increasing the irradiation dose up to 100 kGy and decreased with further increasing the dose.

Workplace noise is hazardous to worker safety and health. Noise can not only cause hearing impairment but also act as a causal factor for stress and raise the systolic blood pressure.There are many methods available and being used in industries at present to reduce acoustic emissions from various equipment. The process of reducing sound emissions from equipment is called acoustic quieting. The method of using piezoelectric material to reduce transmitted sound from equipment rather than damping structural vibration can be applied where it is difficult to damp structural vibrations completely. If piezoelectric materials are attached to vibrating machine parts,withthe supply of suitable voltages, they counter-vibrate which helps in damping structural vibration. Previous studies conducted using simulations with the help of ANSYS software showed noise reductions of up to20 decibels. This paper presentsan effective technique for tuning the frequencies of vibrations of the piezoelectric material with the source vibrations for the reduction of noise. It can help in cancelling the original vibrations which ultimately lead to the reduction in transmitted noise levels. Experiments reveal that a reduction of 9 decibels innoise level is possible by using a filtercontrol circuit.