Hms Iqbal

Processing and Characterization of Space-Durable High-Performance Polymeric Nanocomposite

In this investigation, efforts were given to develop carbon-nanofiber-reinforced polybenzimidazol nanocomposite for space application. Processing of polybenzimidazol was carried out by using polybenzimidazol in powder and solution forms. Thermomechanical properties of compression-molded polybenzimidazol, unfilled polybenzimidazol films, and nanofiber-reinforced polybenzimidazol films were investigated using thermogravimetric analysis, dynamic mechanical analysis, and tensile testing. Thermogravimetric analysis revealed that both compression-molded polybenzimidazol and polybenzimidazol films show high thermal stability. Dynamic mechanical analysis studies depicted that both compression-molded polybenzimidazol and polybenzimidazol neat films exhibited a high storage modulus, even at a temperature of 250°C. Polybenzimidazol nanocomposite films were cast with different loadings of carbon nanofibers from 0.5 to 2 wt % in polymer solution. Addition of carbon nanofibers improved the thermal stability and storage modulus of polybenzimidazol film. Mechanical testing showed that both compression-molded polybenzimidazol and polybenzimidazol films resulted in the highest ultimate tensile strength in comparison to any unfilled polymer. Investigation under scanning electron microscopy confirmed uniform dispersion of carbon nanofibers in polymer solution. Analysis of fractured surfaces revealed that neat polybenzimidazol film exhibited ductile failure and dispersion of carbon nanofibers into the polybenzimidazol, resulting in transformation from ductile to brittle failure.

Thermo-mechanical Characteristics of Space Durable Nano Adhesive Joint of High Performance Polymer

In recent times, considerable efforts are given through out the world for the development of composite materials lighter in weight as well as with superior thermomechanical properties. These materials can withstand a temperature in excess of +300°C for longer time or much higher temperatures for short time. Due to excellent thermal, physical and mechanical properties, polybenzimidazol (PBI) is considered to be one of the leading candidates for aerospace and space applications. Polymers and composite materials are often fabricated by adhesive bonding to form structural components. Therefore, in this investigation; PBI, carbon fiber reinforced and glass fibers reinforced polyphenylene sulfide (PPS) composites are fabricated by employing recently developed ultrahigh temperature resistant epoxy adhesive, DURALCO 4703 (service temperature -250 0 C to +350 0 C). Prior to fabrication, the polymer surfaces are modified by atmospheric pressure plasma in order to increase their surface energy leading to improving adhesion. Lap shear tensile test is carried out to evaluate the adhesion characteristics of the polymers. Three to four times increase in the lap shear strength is observed for PPS-CF and PPS-GF composite joints after plasma treatment when compared with untreated composite joints. Carbon nanofibers (CNFs) are added to enhance the mechanical and physical properties of adhesive. Addition of 1% CNFs to epoxy adhesive has increased the thermal stability of the adhesive up to 15% when compared to basic adhesive. Lap shear strength of nano-adhesive using PPS-GF composite is increased up to 20%. No real increase in lap shear strength of nano-adhesive is observed with PPS-CF composite. Optical microscopic analysis of untreated and plasma treated is carried out to analyze the surface. After plasma treatment, enlarged peaks are observed on the surface which helps in improving the adhesion. Finally, the fractured surfaces of the joints are examined by scanning electron microscope.