High Strain-Rate Compressive Properties and Constitutive Modeling of Bulk Structural Adhesives

The present paper is concerned with constitutive modeling of two different bulk structural adhesives at strain rates from 10(-3) to 10(3)/s using a modified Ramberg-Osgood equation. Commercially available two-part methacrylate structural adhesive and epoxy structural adhesive were tested. The high strain-rate compressive stress-strain loops for the two bulk structural adhesives were determined with a conventional split Hopkinson pressure bar using a tapered striker bar. Static and intermediate rate compressive stress-strain curves were measured in an Instron (R) testing machine. The five parameters for the modified Ramberg-Osgood equation were determined by fitting to the experimental stress-strain data using a least-squares fit. The compressive stress-strain curves at three different strain rates predicted from the modified Ramberg-Osgood model were compared with the experimental results. It is shown that the compressive stress-strain curves up to the maximum stress can successfully be predicted by the modified Ramberg-Osgood equation. The limitations of the modified Ramberg-Osgood model were discussed.