The Computational Materials Science of Concrete Laboratory at the National Institute of Standards and Technology have developed a number of finite element / finite difference programs applied to composite material models.
Dr. Edward Garboczi has written programs for computing the material properties of digital images (composite materials) in 2D/3D. The Fortran 77 programs are self-contained, very efficient and well-annotated. They may be downloaded from NIST ftp site.
This directory also contains postscript and pdf versions of the user manual which is in the form of a monograph "Finite element and finite difference programs for computing the linear electric and elastic properties of digital images of random materials". The manual may be viewed online.
See also Dr. Garboczi's web page which provides access to an electronic monograph "Modelling and measuring the structure and properties of cement-based materials" by E.J.Garboczi, D.P.Bentz, K.A.Snyder, N.S.Martys, P.E.Stutzman, C.F.Ferraris. This monograph includes the FDFEMANUAL mentioned above, and in addition includes CEMHYD3D, a 3D cement hydration and microstructure development modelling package.
The programs developed by Dr. Garboczi and others are similar in design to those in the OOF package but are not limited to 2 dimensions.