Study On The Dynamic Mechanical Properties Of Brittle Materials By High-speed DIC

The brittle materials are easy to be destroyed under small deformation. For examplethe Al₂O₃ceramic is a typical brittle material and has been widely used in various domains,especially as armor in military. The dynamic mechanical properties under high strain rate aremuch interested. Due to the micro porous structure and the micro cracks during the sinteringand machining process, its mechanical behaviors are highly affected. For the purpose of thewide application of brittle materials, it’s significantly important to study its dynamicmechanical behaviors.The Digital Image Correlation （DIC） is a typical optical full-field measurementtechnique. It can provide the obvious and quantitative analysis. By using this technique, thewhole deformation process such as the heterogeneous deformation fields and the crackpropagation can be measured. In this paper, the dynamic mechanical behaviors of variousbrittle materials were experimentally investigated by using the SHPB device combined withhigh-speed DIC method. The deformation fields of various geometries specimen made ofAl₂O₃ceramic, PMMA, gel and PTFE were measured during the dynamic deformation andfracture process, and then the dynamic mechanical behaviors were studied.Brazilian test and flat Brazilian disc （FBD） test under dynamic loading by SHPB wereused to measure the dynamic tensile damage behavior of Al₂O₃ceramic and PMMA. Thedeformation fields were measured and the failure mode under different loading conditionwas studied. The dynamic tensile strengths were achieved, and its loading rate dependencewas analyzed. The dynamic damage and fracture mode of Al₂O₃ceramic and PMMA wasinvestigated by using the FBD test, three-point bending test and semi-circular bending （SCB）test. The crack growth path was analyzed based on the deformation fields provided by DIC.The results of dynamic fracture toughness under different loading rates were measured andits loading rate dependence was also analyzed. Based on the dynamic compression tests onthe Al₂O₃ceramic block specimens of different high/width ratios, the effect of specimenshape on the failure mode was also analyzed.The stress wave propagation of gel, FPTE, PMMA and Al₂O₃ceramic was also studiedby SHPB technique combined with high-speed DIC method. From the displacement,deformation and velocity fields of the long bar specimens, the stress wave propagation and its evolution were analyzed. The stress wave velocities of different materials were calculated,and the stress wave attenuation was analyzed and the attenuation coefficients were obtained.Thanks to the fields provided by DIC method, the spalling phenomenon of PMMA andAl₂O₃ceramic by the effect of the reflected strength wave was observed. The stress wavepropagation, the position of spalling, and the spalling strength were analyzed.