A main-chain, polydomain, smectic liquid crystalline elastomer (LCE) was prepared by reacting the LC epoxy monomer, diglycidyl ether of 4,4‘-dihydroxy-α-methylstilbene, with the aliphatic diacid, sebacic acid. When deformed in uniaxial tension, a “polydomain-to-monodomain” transition took place leading to bulk, macroscopic orientation. With this process was associated a plateau in the nominal stress-versus-strain curve and a dramatic change in optical properties from opaque to translucent. Polarized optical microscopy showed that the transition took place by an elongation of the LC domains and a rotation of the local director orientations along the stress axis. The strain and orientation of the deformed samples were retained upon unloading, even after annealing above T g for extended periods. Upon heating, the oriented LCEs disordered at the same temperature as the undeformed polydomains and “remembered” their original polydomain microstructure and sample dimensions when subsequently cooled from the isotropic state.

No abstract

Composites are most promising materials of recent interest. Metal matrix composites (MMCs) possess significantly improved properties compared to unreinforced alloys. There has been an increasing interest in composites containing low density and low cost reinforcements. Among various dispersoids used, fly ash is one of the most inexpensive and low density reinforcement available in large quantities as solid waste by-product. In the present investigation, pure aluminium-5 to 15% (by weight) fly ash composites were made by stir casting route. Phase identification and structural characterization was carried out on fly ash by X-ray diffraction studies. Scanning electron microscopy and optical microscopy was used for microstructure analysis. There was a uniform distribution of fly ash particles in the matrix phase and also existing a good bonding between matrix and fly ash. The hardness of the composites increased whereas the density of the composites decreased with increasing the amount fly ash than the pure aluminium. Enhanced mechanical properties were observed with increasing amount of fly ash under compression.

Composites are most promising materials of recent interest. Metal matrix composites (MMCs) possess significantly improved properties compared to unreinforced alloys. There has been an increasing interest in composites containing low density and low cost reinforcements. Hence, composites with fly ash as reinforcement are likely to over come thecost barrier for wide spread applications in automotive and small engine applications. In the present investigation, AA 2024 alloy – 2 to 10 wt% fly ash composites were made by stir casting route. Phase identification and structural characterization was carried out on fly ash by X-ray diffraction studies. Scanning electron microscopy and optical microscopy was used for microstructure analysis. The hardness, compression and pitting corrosion tests were carried out on all these alloy and composites. The SEM studies reveal that there was a uniform distribution of fly ash particles in the matrix phase and also very good bonding is exist between the matrix and reinforcement. With increasing the amount of fly ash the density of the composites was decreased and the hardness was increased. The increase in compression strength was observed with increase in amount of fly ash. Fly ash particles lead to an enhanced pitting corrosion of the aluminium–fly ash (ALFA) composites in comparison with unreinforced matrix (AA 2024 alloy). The enhanced pitting corrosion of ALFA composites is associated with the introduction of nobler second phase of fly ash particles.

No abstract