Multi-objective optimization of critical load and weight of composite shaft with elastic core under torsional loading

The use of foam core in a cylindrical hollow shaft could potentially improve the strength and torsional load carrying capacity of the composite light weight shaft. A study of design variables optimization was carried out with dual objectives of obtaining maximum torsional critical torque and minimum weight under static torsional loading in a composite shell cylindrical shaft with foam core. The shell with ۶,۸,۱۰ and ۱۲ layers and core with polystyrene foam was studied and the optimization was done by MATLAB software coding. Design variables including stacking sequence, fiber material, volume fraction of fiber, fiber orientation angle and known thicknesses and calculating unknown thicknesses of the layers were investigated. The Tsai Hill fracture strength constraint was considered for composite layers in Matlab coding. The assumption included applying loads to the edges of the shell, and the property of the shell was orthotropic and the core was isotropic attached to the shell from its outer surface. Multi- objective algorithm genetic (GA) was utilized as the optimization method due to the large number of design variables. The optimization results of the MATLAB for ۶-layer shaft with polystyrene foam core was validated using the Abaqus finite element method. Also, the optimization outcome of the critical load on the ۶-layer shaft with polystyrene foam core was compared with ۶-layer hollow-shaft. The results showed that, the ۶-layer foam core shaft demonstrated better results than those ۸,۱۰,۱۲ -layer foam core shaft and ۶-layer hollow shaft. The torque value of ۶-layer polystyrene foam cored shaft of ۱۸,۵۰۰ Nm was found to be about double than the ۶-layer hollow shaft torque value of ۹۳۰۰ Nm. The corresponding optimum weight of the ۶-layer foam cored shaft was ۲.۴ kg, which was slightly higher than the hollow shaft weight of ۱.۹ kg. The results of this study suggests that using foam can be a substantial option for making core shaft which could bear significantly higher torsional loads than a similar hollow shaft.

Keywords:

Design variable optimization , Composite shaft , Buckling , Strenght , Mathlab Programming , Genetic Algorithm , Foam core