The feasibility of incorporating fly ash cenospheres in die cast magnesium alloy has been demonstrated. The effects of fly ash cenosphere additions on the microstructure and some of the salient physical and mechanical properties of magnesium alloy (AZ91D) metal matrix composites were investigated. The control AZ91D alloy and associated composites, containing 5, 10, and 15 wt.% of fly ash cenospheres (added), were synthesized using a die casting technique. A microstructural comparison showed that microstructural refinement – occurred due to the fly ash additions and became more pronounced with an increase in the percentage of the fly ash added. The metal matrix areas nearer to the fly ash particles exhibited a greater degree of refinement than was observed in the areas further away from these particles. Both filled and unfilled fly ash cenospheres, and porosity were observed in the composite microstructures. The composite specimen densities decreased and the coefficient of thermal expansion did not change significantly as the volume percent of fly ash was increased within the range investigated. The hardness values of the composite specimens exhibited an increase in proportion to the increase in percentage of added fly ash. The tensile strength of the composites also increased as the concentration of fly ash cenospheres was increased. In contrast, the Young’s modulus of these composite samples, as measured by non-destructive pulse-echo method, decreased as the percentage of fly ash in the composite was increased. SEM micrographs of the tensile fracture surfaces showed broken cenospheres on the fracture surface and evidence of ‘pull outs’, where fly ash particles were previously embedded in the matrix. Compression testing results showed that the presence of 5 wt.% cenospheres decreased the compressive strength and compressive yield strength of the composite relative to that of the AZ91D matrix alloy. Surprisingly, a significant change in compression strength was not observed for the composites with 10 and 15 wt.% cenospheres in comparison to the AZ91D matrix alloy. In contrast to the tensile tests, no cenosphere remnants were observed on the compressive test fracture surface of the composites. This observation suggests that the fracture of the composite was initiated within the AZ91D matrix by normal void nucleation and growth, followed by crack propagation through the matrix, avoiding any of the cenospheres, leading to composite fracture of the matrix.

Microstructure and mechanical behavior of die casting AZ91D-Fly ash cenosphere composites

The present study proposes a bolted/co-cured hybrid joining method, and experimentally investigates the joint strength The bolted/co-cured hybrid joints combine co-cured adhesive joints and bolted joints without damaging reinforcing fibers The method allows for low scatter strength in static and fatigue loading for easily manufactured co-cured joints Testing of the static tensile lap-shear and fatigue strengths is performed using aluminum alloy A5052-F and knit fabric glass epoxy composites The results show that the hybrid joints have 184 times higher maximum shear strength and a quarter of the standard deviation compared with conventional co-cured joints Furthermore, less stress concentration and undamaged glass fibers in the hybrid joints contribute to a much higher fatigue strength than that of the bolted joint

Improving performance of GFRP/aluminum single lap joints using bolted/co-cured hybrid method

Materials in machine tool structures

Influence of firing temperature and mineralogical composition on bending strength and porosity of ceramic tile bodies

Prediction of the torsional strength of the hybrid aluminum/composite drive shaft

Design and manufacture of an automotive hybrid aluminum/composite drive shaft

Reduction of residual stresses in thick-walled composite cylinders by smart cure cycle with cooling and reheating

The propeller shaft comprises a transmission shaft 10 consisting of a hollow metal tube 11 with excellent torque transmissibility and a composite material prepregs 12 having higher specific stiffness than a metal material and stacked to the inner surface of the metal tube, and metal yokes 40 mounted on both ends of the transmission shaft and assembled with other devices. The composite material prepregs is co-cure bonded while applying an axial compressive preload to the transmission shaft and creating a vacuum in a space between a vacuum bag inserted in the transmission shaft and the composite material prepregs of the transmission shaft. Teeth 43 or embossments 44, and adhesive-retaining grooves 45 are formed on inner surfaces of the metal yokes, so the transmission shaft is desirably compression-fitted into the metal yokes. Accordingly, the propeller shaft has advantages of securing improved impact, abrasion, and water resistance.

Jong Woon Kim

Papers

Design and manufacture of an automotive hybrid aluminum/composite drive shaft

Reduction of residual stresses in thick-walled composite cylinders by smart cure cycle with cooling and reheating

Hybrid propeller shaft made of metal and composite material and method of manufacturing the same

Measurement of residual stresses in thick composite cylinders by the radial-cut-cylinder-bending method

Novel applications of composite structures to robots, machine tools and automobiles