A polymeric fastener includes a body having multiple sides adapted to accept a tool for applying torque to the body to axially rotate the body with respect to a body longitudinal axis. A flange integrally connected to the body extends perpendicular to the longitudinal axis. A wave-shaped washer integrally connected to the flange has multiple valleys interposed between multiple oppositely directed peaks. Multiple triangular shaped frangible connectors integrally join the flange to the wave-shaped washer. Each frangible connector is integrally connected at a first end to the flange, and is integrally connected at an opposite connecting tip to an individual one of the peaks. The connecting tip has a reduced thickness compared to the first end to induce fracture of each frangible connector at the connecting tip.