Structural defects such as resin pocket area are inevitably created between surface and core of composite structures during the production of wind turbine blades using vacuum infusion process. In this article, four-point bending tests were performed on tapered sandwich composites to investigate the effect of resin pocket area on the mechanical strength, crack growth path, and failure mode. Specimens were in similar shape to wind turbine blade profiles, and a shear-dominant load was applied to the resin pocket area during the experiments. The extended finite-element method was applied in order to predict crack growth path and failure mode. The average static strength of the specimens including the small size of resin pocket area had almost no change in compare with the specimen with no resin pocket area. Moreover, the medium size of resin pocket area decreased the strength for 3.5% while the large size one enhanced it for 1.75%. Thus, it can be deduced that the defect area does not have a significant effect on the flexural strength of the sandwich composite tapered specimens, but it can arrest the crack. Therefore, the crack propagates in the opposite direction at the interface of the face and core. Although the resin pocket area arrests the crack, it was observed that the size of resin pocket area directly affects the crack growth and its path. The smaller resin pocket area leads to slower crack growth, and early collapse occurs for the larger size of defect area. So, the size of resin pocket area has considerable importance during manufacturing of such structures. Finally, numerical results have shown good agreement with experimental ones.
This research aims to investigate the effect of adding copper oxide nanoparticles to the oil Gr‐6004 base fluid and its concentration changes from 0.1% to 0.4% on the surface roughness of gudgeon pin and the thermal conductivity of the nanofluids during the superfinishing process. The main novelty of this investigation is analyzing the impact of utilizing CuO/oil Gr‐6004 nanofluid on thermal conductivity of oil and surface quality of gudgeon pin during superfinishing process. Based on the results, adding nanoparticles to the oil Gr‐6004 has significantly reduced the surface roughness. In addition, by increasing the concentration of nanoparticles to 0.4%, the surface roughness has decreased by 57% compared to oil Gr‐6004. Also, by adding nanoparticles, the thermal conductivity of the nanofluids has increased to 19.5%. In addition, dispersing CuO nanoparticles into base fluid reduces oil temperature by 17.44%.
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