The nonlinear and time dependent stress-strain response of non-crimp fabric (NCF) [±45] s laminates in tension is studied. Testing methodology is suggested to separate and quantify the effect on the inelastic response of damage development, nonlinear viscoelastic effects and viscoplasticity. Material model based on Schapery’s work on viscoelasticity and Zapas viscoplastic functional with added damage terms is used. Simulation is performed and validated with constant stress rate tensile tests, identifying the nonlinear viscoelasticity and viscoplasticity as the major sources of the nonlinear response.