Interfacial fracture testing in shape deposition manufacturing

Abstract: "Shape Deposition Manufacturing (SDM) is a manufacturing process in which three dimensional parts are built up layer by layer, realizing a computer-generated solid model. Because materials are deposited at high temperatures, residual stresses are induced throughout the process. Consequently, there can exist both warping of the part and a tendency to delaminate or fracture between layers, especially between those of dissimilar materials. Thus, in the design of SDM parts, it is important to know the critical energy release rate and mode of crack extension governing interfacial fracture for particular material combinations. Interfacial toughness tests using three layer composite beam specimens under four point bending are examined. Such a test on a two layer specimen has been considered in the literature. A steady-state energy release rate (independent of crack length) is deduced analytically for both the two and three layer specimens. Finite element models verify the analytical predictions and are used to extract the mode of crack extension. Experimental results are obtained for two bimaterial interfaces."