A novel hybrid procedure for the characterization of rubber-like membranes

This paper presents a new hybrid procedure for identifying mechanical properties of rubber-like materials. The procedure can be also extended to either natural and synthetic bio-membranes. Here, a very sensitive Projection Moiré (PM) system is utilized to monitor the surface shape changes of a thin circular latex membrane under inflation. Sample geometry and loading pressure values are then given as inputs to a finite element model. Optimization routines finally correlate finite element predictions on membrane behaviour with the experimental data. In particular, the difference  between the displacement field found experimentally and the displacement field computed numerically is minimized by an optimization algorithm which finally finds the values of the unknown material properties. The  function has been minimized with the optimization routines available in a commercial finite element package. The latex membrane under investigation has been modelled as a two-parameter Mooney-Rivlin (MR) hyper-elastic material. Target values for the MR constants of the latex specimen tested have been determined by fitting experimental data gathered with equibiaxial test. Results indicate that the procedure presented in this paper can determine accurately the material properties of the elastomeric material under investigation. In fact, the average residual error between the displacements measured by PM and those computed at the end of the optimization identification process was less than 1% while the % error on the MR constants was less than 3%.