A numerical and experimental study of fracture in RP stereolithography patterns and ceramic shells for investment casting

A numerical and experimental study of fracture on epoxy web rapid prototyping (RP) stereolithography (SL) patterns during the burnout process of investment casting process is presented. Considered are the glass transition temperature of the epoxy resin, the buckling temperature of the web link and the fracture temperature of the ceramic shell. Our assumption is that ceramic fracture do not occur at higher ceramic shell rupture temperature and that craze fracture could occur when the epoxy expansion causes buckling of web for a temperature lower than the temperature of epoxy glass transition. This premises are validated by an acceptable correlation we obtained between numerical simulation and experimental observations. It is found that the web link buckling and epoxy fracture are strongly related to the cross-sectional zones of the web structure. The avoidance of shell fracture by buckling and craze fracture of the epoxy-webbed pattern in early stages of the burnout process is discussed.