There are 2 repositories under umat topic.
Basics to implement user-defined materials (usrmat, umat) in LS-Dyna with Fortran
UMAT4COMSOL: An Abaqus user material (UMAT) subroutine wrapper for COMSOL
UMAT subroutines (for FEA code Abaqus) to model progressive damage/failure in FRP composites
This is a nonlinear elastic constitutive model(Duncan-CHANG EB) UMAT widely used in the field of geotechnical engineering. It can be used in abaqus6.14-5 to calculate the dam settlement deformation.
User Material Model Implementation (UMAT) based on Finite Viscoelasticity Theory for Hydrogels in Abaqus
UMAT for ABAQUS using 3D Hashin Based Orthotropic Damage Model
A modern Fortran library for tensor calculus
A Tsai-Wu based 2D Damage Model UMAT for ABAQUS (discontinued)
Fortran code for the transformation into the logarithmic strain space
A Hashin 2D Damage Model UMAT for ABAQUS (discontinued)
UMAT for ABAQUS using Mazars Concrete Damage Model with Fracture Energy Regularization
Comparison of Abaqus Library, UMAT, and Analytical Solution for Neo-Hookean Hyperelastic Material Under Large Deformations