Tuesday  |  Virtual Track 1  |  09:48 AM–10:00 AM

#12115, Shear Damage Model Identification for Off-axis IBII Composites Specimen Loaded and Unloaded at High Strain Rates

The rate dependent properties of orthotropic materials such as Carbon Reinforced Fibre Composites (GFRP) composites are important to simulate events like bird-strike or general third body impact. The current test technique for obtaining high-strain-rate material properties is the split Hopkinson pressure bar (SHPB). This technique relies on several assumptions including that the sample must be in a state of quasi-static equilibrium and that the sample undergoes uniform 1D deformation. These assumptions limit the ability of the SHPB technique to accurately extract a single stiffness component let alone identify multiple orthotropic stiffness components in a single test.

Recently, the Image-Based Inertial Impact (IBII) test has emerged as an alternative technique that does not rely on the assumptions of quasi-static equilibrium or 1D deformation. In fact, the use of image-based measurements allows for deformation that is intentionally inhomogeneous providing a large database of points for material property identification. Thus far applications of the IBII test have shown that it is possible to extract the transverse and shear moduli for a carbon fibre in-plane and through-thickness [1,2].

However, as is well known for such composites, the shear behaviour exhibits a non-linear response generally attributed to either diffuse damage (matrix micro-cracks) and/or matrix plasticity. In quasi-static, this behaviour is generally characterized by cyclic loadings/unloadings for which modulus decrease is evaluated from the different unloading slopes, and plasticity identified through the permanent strain at zero stress. However, at high strain rates, such cyclic loadings have so far eluded experimentalist, the best achievable being interrupted loadings. The IBII test provides this unique opportunity to perform one loading/unloading cycle at rates on the order of 1000 /s. This paper will present the inverse identification of a shear damage model based on IBII test data (full-fields kinematic measurements at 5 MHz with a Shimadzu HPV-X camera and inverse identification with the Virtual Fields Method). Coupling of damage with a plasticity model is also investigated.

References
[1] https://doi.org/10.1007/s40870-020-00258-4
[2] https://doi.org/10.1007/s40870-020-00271-7

Fabrice Pierron   University of Southampton
Sam Parry   University of Southampton
Lloyd Fletcher   University of Southampton