Test data let WIDL model the stress response of ¼-in.-diameter × ¼-in.-thick buttons of Asahi Glass’s Aflas tetrafluoroethylene/ propylene (TFE/P) copolymer material without friction (top) and with a friction coefficient of 0.025 (bottom). The test is pure uniaxial compression only in a frictionless case; when friction is introduced to the FEA model, it is clear that stresses are triaxial.