Iraqi journal of mechanical and material engineering

Sandwich Structure with pin core is widely used in foam core for crushing, debonding and interfacial delamination prevention; this structure has manufactured by drilling foam core frequently. On the other hand, a novel method for manufacturing a pin core sandwich structure has been the aim of this research. Machinable wax panel was used to achieve cavities in form of pin within the core by drilling the wax panel by CNC-drilling machine then casting of thermoset resin (unsaturated polyester resin) into a wax mold, after that melting of the wax mold to get pin core sandwich structure. Complex structure can't be designed by conventional method but by this method allows to design such complex structures: spheres, pyramids, ellipse…etc. According to Response Surface Methodology method, fifteen specimens were achieved and three variables were investigated to get optimization and prediction model. The results show that 300% improvement of stiffness performance index with 40% weight reduction comparative to reference sample with 4.46 GPa0.5 cm3 g-1 optimal value for the specimen ((High=11mm), (Diameter=9 mm) and (Pin-to-Pin distance=4.3 mm)). Strength performance index improvement is 126% and 50% weight reduction comparative to reference sample with 35.9 MPa2/3 cm3 g-1 optimal value for the specimen ((High=11mm), (Diameter=6.115 mm) and Pin-to-Pin distance=1.5 mm)). ANOVA analysis shows that the pin height (H) is effective parameter on stiffness property. On the other hand, the height and diameter of the pin are effective parameters on strength property.

In this study, the effect of changing geometry of the heat sinks on forced convection heat transfer and laminar fluid flow features in a rectangular channel has been studied experimentally and numerically of the circular fins and circular-cut fins heat sinks with straight continuous fins as reference comparison. For the experimental conditions, the Reynolds number value varied as 2418.56- 806.19 according to the variation of flow rate values. The wall heat flux was varied as 11.11, 31.11, 58.05, 83.05, 112.5, 155 kW/m2. COMSOL Multiphysics was used to solve the governing equations under laminar flow conditions with air as the working fluid. To verify the accuracy of the analytical model, the simulation's optimal design was constructed and experimentally validated. The results indicated that circular-cut fins enhanced heat dissipation. Nusselt numbers for CCFs with Reynolds numbers of 797.7 and 2393.1 are roughly 83.6 and 132.4 at a heat flux of 11.1, kW/m2.