Mechanical behavior and failure mechanism of polyurea nanocomposites under quasi-static and dynamic compressive loading

Abstract

Polyurea is an elastomeric material that can be applied to enhance the protection ability of structures under blast and impact loading. In order to study the compressive mechanical properties of SiC/polyurea nanocomposites under quasi-static and dynamic loading, a universal testing machine and split Hopkinson pressure bar (SHPB) apparatus were used respectively. The stress-strain curves were obtained on polyurea and its composites at strain rates of 0.001–8000 s−1. The results of the experiment suggested that increase in the strain rates led to the rise of the flow stress, compressive strength, strain rate sensitivity and strain energy. This indicates that all of the presented materials were dependent on strain rate. Moreover, these mechanical characters were enhanced by incorporating a small amount of SiC into polyurea matrix. The relation between yield stress and strain rates were established using the power law functions. Finally, in order to investigate the fracture surfaces and inside information of failed specimens, scanning electron microscopy (SEM) and micro X-ray computed tomography (micro-CT) were used respectively. Multiple voids, crazes, micro-cracks and cracking were observed in fracture surfaces. On the other hand, the cracking propagation was found in the micro-CT slice images. It is essential to understand the deformation and failure mechanisms in all the polyurea materials.

Keywords

• Polyurea nanocomposites
• Mechanical properties
• Strain rate
• Micro-CT
• Failure