A Constitutive Model for Polyurethane Foams with Strain-Rate and Temperature Effects

This paper describes the testing and constitutive model development of polyurethane foams for characterization of their material dynamic properties. These properties are needed not only for understanding their behavior, but also for supplying essential input data to foam models, which help provide design directions through simulations of foam selection for cushioning occupant head impacts against the vehicle door and upper interior.

Polyurethane foams of varying densities were tested statically and dynamically under uniaxial compressive impact loading at constant velocities of various rates and different temperatures. The test results were utilized for developing a constitutive model of polyurethane foams by taking the density, strain rate and temperature effects into consideration.

Uniaxial constitutive models are developed in two ways. One approach is by interpolating the test data, and other is by deriving an analytical expression that describes the dynamic behavior of polyurethane foams based on test results. The development of an analytical constitutive model is presented in details. The model predicts results that are in better agreement with compression test data than previously reported methods.