In this paper, the contribution and constitutive modelling of the intercostal muscles (ICM) in a computational thorax FE model is studied. This helps in improving our knowledge to predict the number and locations of the fractured ribs during automotive accidents. ICM demonstrates a number of complex features including nonlinearity, viscoelasticity, and anisotropy. These muscles consist of an external and an internal layer, each of them having its own fiber orientation.
Tensile tests were performed on ICM samples harvested from one cadaver. Each specimen consisted of a 15 mm-long rectangle of ICM connected to the adjacent superior and inferior sections of the ribs. The load and applied displacement were measured. An optical system (ARAMIS) was used to measure the strain field on the external layer. Preconditioning, ramp and hold (relaxation), and quasi-static failure tests were performed.
The hyperelastic material parameters were estimated through an optimization process based on the experimental force–displacement curves of the quasi-static tensile tests. The results of the parameters optimization revealed that the ICM exhibited a high degree of anisotropy. The identification of the viscoelastic parameters was accomplished from the ramp and hold (relaxation) tests using Prony series.