This chapter discusses new material models or changes to existing material models. It provides an overview of the following enhancements:

• “Enhancements to parallel rheological framework,” Section 6.1

• “Eulerian elements with anisotropic materials,” Section 6.2

• “Enhancements to creep models,” Section 6.3

• “User-defined frequency domain viscoelastic behavior,” Section 6.4

• “New hybrid formulations for user-defined material behavior,” Section 6.5

• “Different stiffness in tension versus compression for traction-separation elasticity,” Section 6.6

• “Element deletion controlled by state variables,” Section 6.7