Thin, biocompatible, high-strength, composite materials are disclosed that are suitable for use in a valve for regulating blood flow direction. In one aspect, the composite material maintains flexibility in high-cycle flexural applications, making it particularly applicable to high-flex implants such as a prosthetic heart valve leaflet. The composite material includes a porous polymer membrane and an elastomer, wherein the elastomer fills substantially all of the pores of the porous polymer membrane.
