Solid Model Creation for Materially Graded Objects

Materially graded objects are objects composed of different constituent materials and could exhibit continuously varying composition and/or microstructure [1][2]. Such continuous changes results in gradation in their properties and distinguish them from objects made of conventional composites. They are also known as heterogeneous objects, functionally graded/gradient materials (FGM) and multi-material objects/structures [1]. In this paper, we use the terms "materially graded objects" and "heterogeneous objects" interchangeably. Recently, heterogeneous objects have found use in several engineering applications. The fabrication process that has shown potential to manufacture heterogeneous objects is called Solid Freeform Fabrication (SFF), also known as Layered Manufacturing (LM) [3][4]. SFF is a material deposition process in which the material deposition can be controlled to vary the material composition throughout an object, thus fabricating a materially graded object. All SFF technologies are computer-based and require the CAD model ofthe object to be manufactured. However, current CAD systems are capable of representing only the geometry/topology information. Therefore, heterogeneous objects are fabricated using SFF by manually feeding the material information along with the geometry data. This is a cumbersome process and leads to the under-utilization ofthe SFF process. An assessment of existing representations for SFF is presented in [5] highlighting the need for CAD models which represent material information along with the geometry data of the object.Mechanical Engineerin