Publications Details

Dynamic mode-ii characterization using SHPB embedded with PVDF

Lu, Wei-Yang L.; Song, Bo S.; Jin, Huiqing J.

Quasi-static experimental techniques for fracture toughness have been well developed and end notched flexure (ENF) technique has become a typical method to determined mode-II fracture toughness. ENF technique also has been implemented to high-rate testing using SHPB (Split Hopkinson Pressure Bar) technique for dynamic fracture characterization of composites. In general, the loading condition in dynamic characterization needs to be carefully verified that forces are balanced if same equations are used to calculate the fracture toughness. In this study, we employed highly sensitive polyvinylidene fluoride (PVDF) force transducers to measure the forces on the front wedge and back spans of the three-point bending setup. High rate digital image correlation (DIC) was also conducted to investigate the stress wave propagation during the dynamic loading. After careful calibration, the PVDF film transducer was made into small square pieces that are embedded on the front loading wedge and back supporting spans. Outputs from the three PVDF transducers as well as the strain gage on the transmission bar are recorded. The DIC result shows the transverse wave front propagates from the wedge towards the supports. If the crack starts to propagate before reaching force balance, numerical simulation, such as finite element analysis, should be implemented together with the dynamic experimental data to determine the mode-II fracture toughness.