Methods are provided to make a prosthetic valve having a thin, biocompatible, high-strength, composite material. In one aspect, the composite material maintains flexibility in high-cycle flexural applications, making it particularly applicable to high-flex implants such as a heart valve leaflet. The composite material includes a porous expanded fluoropolymer membrane and an elastomer, wherein the elastomer is present in the pores of the porous expanded fluoropolymer.