A rivetless nut plate assembly (20), which is fully preassembled, which can be installed into an aperture (1 12) of a composite material workpiece (110), such as a carbon fiber structure, without risking delamination of the workpiece. The rivetless nut plate assembly (20) includes a nut (22), a holding bracket (24), a retainer (28), and a sleeve member (25, 25a, 25b, 25c). Additionally, a stem (26) is used to install the rivetless nut plate assembly (20). The sleeve member (25, 25a, 25b, 25c) is configured such that the nut plate assembly (20) can be installed in a composite material workpiece (110) without risking delamination. The sleeve member (25, 25a, 25b, 25c) may be formed of 45Cb-55Ti Titanium Columbium, as Titanium Colurnbium is a high strength and ductile material that resists corrosion in the presence of, for example, a carbon fiber composite structure (110). Monel, Titanium alloys, and other soft Nickel alloys are also good material selections for the sleeve (25, 25a, 25b, 25c), for similar reasons. Non-metallic materials with high tensile and shear strengths, such as Torlon or Parmax, would provide the desired corrosion protection and also offer a potential weight savings.