Effect of graphite incorporation on the compressive strength and wear properties of polyurethane composites

Polyurethane-based composites (PUCs) are promising materials for stretch-forming dies used in aircraft skin components; however, their limited load-bearing capacity and insufficient wear resistance under severe conditions remain major challenges. In this work, graphite powder (GP) was incorporated into a polyurethane matrix to enhance its compressive and tribological performance. PUCs with different GP contents were fabricated by room temperature casting. Static compression tests, dynamic compression experiments using a split Hopkinson pressure bar, and wear tests under various normal loads were systematically performed. The results demonstrate that both elastic modulus and compressive strength first increase and then decrease with increasing GP content. When the GP content reached 5%, the composite exhibited the highest static compressive strength of 141.41 MPa, representing a significant improvement compared with the GP-free composite. Under dynamic loading, the composite containing 5% GP achieved the maximum dynamic compressive stress, which was 635.99 MPa at an impact pressure of 0.2 MPa. Moreover, composites with higher GP content exhibited markedly enhanced wear resistance under elevated normal loads. Scanning electron microscopy observations confirmed that GP promoted the formation of a stable lubricating transfer film, leading to a transition from severe adhesive wear to mild wear behavior.