Cross-linked polyurethane/filler composites based on polyester, diphenylmethane diisocyante, glycols, and glycerin were synthesized and characterized. The mechanical and thermal properties of PU/filler composites were investigated through tensile, thermogravimetry experiments. Therefore, to understand the behaviour of fillers, such as graphite, talc, CaCO3 and polyamide fiber added to cross-linked polyurethane resins, several thermal and mechanical tests were conducted on samples, using these new materials. It is shown that cross-linked polyurethane composites have decreased tensile strength, improved hardness and thermal stability relative to bulk polyurethane. The results show that the polyurethane component ratios in crosslinked polymers, the types of filler, and the amount of powder added all affect the damping behaviours and degree of phase separation of unfilled and filled cross-linked polyurethanes. The addition of filler into polyurethane composites yields an increase in the Young's modulus and a. decrease in the elongation at break.