On compression and damage evolution in two thermoplastics

Area of Science:

• Materials Science
• Polymer Physics
• Impact Dynamics

Background:

• The Taylor cylinder impact test is a standard method for studying material deformation under high strain rates.
• Previous research identified phase changes within polymers during impact, indicated by deformation variations.
• Understanding polymer behavior under extreme conditions is crucial for advanced material applications.

Purpose of the Study:

• To investigate the deformation and failure mechanisms of polytetrafluoroethylene (PTFE) and polyetheretherketone (PEEK) under impact conditions.
• To visualize and analyze the material phase changes and fracture zones within impacted polymer cylinders.
• To elucidate the continuous nature of polymer failure development and identify gaps in high strain-rate response understanding.

Main Methods:

• Conducting Taylor cylinder impact tests on PTFE and PEEK at various speeds.
• Utilizing Diamond synchrotron for high-resolution imaging of impacted polymer targets.
• Employing macroscopic high-speed photography and three-dimensional X-ray imaging to analyze deformation and fracture.

Main Results:

• High-speed and 3D X-ray imaging revealed detailed fracture zones in the impact region of recovered polymer cylinders.
• Evidence of material phase changes was observed through spatial and temporal deformation analysis.
• The study demonstrated a continuous range of failure responses rather than abrupt transitions in both PTFE and PEEK.

Conclusions:

• Polymer failure under impact is a continuous process involving competing mechanisms, not a discrete event.
• The observed behaviors in PEEK highlight significant gaps in the current understanding of polymer high strain-rate response.
• Advanced imaging techniques provide critical insights into material failure dynamics at extreme conditions.