Experimental and numerical study for determining the mechanical properties of automobile weatherstrip seals

Abstract

Structural parts made of hyperelastic materials such as rubber mounts in automotive powertrains and weatherstrip seals are widely used in automotive and other engineering applications. In this study, compression load deflection (CLD) behavior of a highly non-linear type of joint, automotive weatherstrip seal made of Ethylene Propylene Diene Monomer (EPDM) sponge rubber is examined using finite element modeling techniques. The finite element modeling (FEM) results are then compared with the compression load deflection data obtained experimentally. The compression load deflection data for various punch velocities can be used to model the weatherstrip seal as a nonlinear spring-dashpot system with varying stiffness and damping coefficient proportional to the amount of compression. The weatherstrip seals should be modeled accurately in order to predict the dynamic performance of the automobiles under various load conditions. First part of the study includes modeling of the seal using various hyperelastic material models which are available in ANSYS. The strain energy functions' coefficients required for the various material models are calculated using both linear and nonlinear least square fit procedures implemented in ANSYS for fitting the tension, shear and compression test data. After the coefficients are calculated, the compression test is performed in ANSYS using various hyperelastic material models. Second part of the study includes the compression experiment of weatherstrip seal with a robotic indenter specifically designed for measuring hyperelastic materials. The measured CLD data is then compared with the FEM results. The accuracy of using only simple tension test data to acquire the coefficients for strain energy functions is investigated and suitable strain energy functions to model compression of weatherstrip seal are determined. Additionally, Mullins Effect (stress softening) for this application is investigated using the compression experiments data.