Toughness is defined as the ability of a material to absorb energy and plastically deform without fracturing or rupturing. There are multiple methods used to test toughness. Plastics used in 3D printing filaments are commonly tested using the IZOD Notched Impact Test. The IZOD test uses a pivoting arm and hammer that is raised to a certain height and released to swing into the test sample. The amount of energy the material absorbs can be easily calculated based on the height the arm swings to after hitting the sample.