Additive Manufacturing of Locally Weakened Parts to Obtain a Designed Fracture

Today, the additive manufacturing (AM) approach has led to profound changes in part and process design, enabling previously impossible material properties. With the freedom to create the material as components are built layer by layer, AM has permitted precise spatial control of the material properties in manufactured parts. In this work, an original approach is proposed to locally control component and process design and create intentionally weakened regions with designed fracture, which paves the way to tuneable mechanical properties. Tensile tests of specimens with embedded weakened area of various geometries are used to verify the feasibility of a-priori-designed fracture modes and to characterise the variation in material behaviour. The results show that an ad hoc design of the artificially weakened areas is effective for predictable breakage, with load and strain being the precursor for active control of the mechanical behaviour. The attainability of a quantitative relationship between the defect and the mechanical response is exemplified by the fact that, e.g. for a flat geometry, the maximum stress and strain are reduced by half when the thickness of the weak region is doubled.