Combinatorial Search to Optimize Vent Locations in the Presence of Disturbances in Liquid Composite Molding Processes

In liquid composite molding processes, the resin is injected into a mold cavity containing preplaced reinforcement fabrics through openings known as gates, and the air leaves the mold through openings called as vents. Under nominal conditions, the last points to fill are chosen as vent locations. However, due to imperfect preform placement, gaps and channels may form along the edges and at curvatures in a mold, offering a path with less resistance for resin flow. The faster advance of resin through these gaps and channels, a common disturbance known as racetracking, will cause the last filled regions to vary, which complicates the vent selection process. We introduce a methodology that uses set and probability theories to forecast racetracking conditions in a mold and have developed a combinatorial search algorithm to locate corresponding optimal vent locations. The accuracy, efficiency and usefulness of the approach is illustrated with three case studies.     

Electrical and compositional properties of TaSi2 films

Tantalum silicide (TaSi₂) thin films were sputter deposited on p- and n-type silicon substrates using ultrapure TaSi₂ targets. The TaSi₂/Si samples were annealed in nitrogen or forming gas or oxygen containing steam at temperatures in the range of 400–900°C. The sheet resistances of TaSi₂/Si were measured by four-point probe before and after anneal. The structure of these films was investigated using x-ray diffraction (XRD) methods. It has been found that the sheet resistance decreases with the increase in annealing temperature and also with the increase in film thickness. X-ray diffraction patterns show changes in the morphological structure of the films. Oxidation characteristics of the film have been investigated in the temperature range of 400–900°C in oxygen containing steam ambient. The oxidation time ranged from 0.5 to 1.5 h. No oxide formation of the tantalum silicide films was observed in this investigation. This has been attributed to the high purity of TaSi₂ sputter targets used in the preparation of the films.