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It has been demonstrated that effective medium approximation and mean field homogenization technique is a useful computational tool to predict the effective thermal and structural properties of alumina‐nickel (Al2O3‐Ni) composites. Nickel particle size and volume fraction, thermal interface resistance and porosity are found significant factors that affect thermal conductivity, elastoplastic behavior, elastic modulus and thermal expansion coefficient of Al2O3‐Ni composite. To complement the computational design, Al2O3‐Ni composite samples with designed range of volume fractions and nickel particle size are developed using spark plasma sintering process and properties are measured for model verification.

Polysulphone (PSU) composites with carbon nanotubes (PSU-CNT) and graphene nanoplatelets (PSU-GNP) were developed through the solution casting process, using various weight load percentages of 1, 3, 5, and 10 wt% of CNT and GNP nanofillers. The microstructural and thermal properties of the PSU-based composites were compared. The microstructural characterisation of both composites (PSU-CNTs and PSU-GNPs) showed a strong matrix–filler interfacial interaction and uniform dispersion of CNTs and GNPs in the PSU matrix. The analysis demonstrated that both the thermal conductivity and effusivity improved with the increase in the weight percentage (wt%) of CNTs and GNPs because of the percolation effect. The polysulphone-based composite containing 10 wt% CNTs showed a remarkably high thermal conductivity value of 1.13 (W/m·K), which is 163% times higher than pure PSU. While the glass transition temperature (Tg) was shifted to a higher temperature, the thermal expansion was reduced in all the PSU-CNT and PSU-GNP composites. Interestingly, the CNTs allowed homogeneous distribution and a reasonably good interfacial network of interaction with the PSU matrix, leading to better microstructural characteristics and thermal properties than those of the PSU-GNP composites. The findings highlight the importance of controlling the nature, distribution, and content of fillers within the polymeric matrix.

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Friction stir welding is a recently developed technique for joining low-melting metals and polymers. In the present work, friction stir welded joints of high-density polyethylene (HDPE) sheets were produced using a newly designed tool with a concave shoulder and a grooved conical pin. The joints were produced with and without the additions of ceramic particulates including silicon carbide (SiC), alumina, graphite, and silica. The effect of strain rate on the tensile properties of base material and plain welded joints was examined. In addition to tensile properties of composite joints, hardness profiles across the weld nugget were analyzed. It was observed that the increasing strain rate improved both the tensile strength and the ductility of the plain welded joints. The tool was able to yield a joint efficiency of around 84% in the plain welded samples. Although, in terms of joint efficiency, the composite joints were less efficient than the plain welded HDPE, SiC additions were found to yield better material properties relative to other reinforcements. Finally, it was concluded that an SiC–HDPE composite joint can be of practical importance in high strain rate applications, provided the optimum tool design and stir welding parameters are available.