# Analysis of Dynamic Properties and Johnson–Cook Constitutive Relationship Concerning Polytetrafluoroethylene/Aluminum Granular Composite

## TL;DR

This paper studies the mechanical behavior of a PTFE/Al composite under dynamic loading and models its properties using the Johnson–Cook constitutive model.

## Contribution

The study provides a constitutive model for PTFE/Al granular composites based on experimental and numerical analysis.

## Key findings

- The strain rate significantly affects the yield stress, ultimate strength, and limited strain of the PTFE/Al composite.
- The Johnson–Cook model accurately describes the stress–strain relationship of the composite based on experimental data.
- Numerical simulations using ANSYS/LS-DYNA align well with the experimental results.

## Abstract

The polytetrafluoroethylene/aluminum (PTFE/Al) granular composite, a common formulation in impact-initiated energetic materials, undergoes mechanochemical coupling reactions under sufficiently strong dynamic loading. This investigation discusses the dynamic properties and the constitutive relationship of the PTFE/Al granular composite to provide a preliminary guide for the research on mechanical properties of a series of composite materials based on PTFE/Al as the matrix. Firstly, the 26.5Al-73.5PTFE (wt.%) composite specimens are prepared by preprocessing, mixing, molding, high-temperature sintering, and cooling. Then, the quasi-static compression and Hopkinson bar tests are performed to explore the mechanical properties of the PTFE/Al composite. Influences of the strain rate of loading on the yield stress, the ultimate strength, and the limited strain are also analyzed. Lastly, based on the experimental results, the material parameters in the Johnson–Cook constitutive model are obtained by the method of piecewise fitting to describe the stress–strain relation of the PTFE/Al composite. Combining the experimental details and the obtained material parameters, the numerical simulation of the dynamic compression of the PTFE/Al composite specimen is carried out by using the ANSYS/LS-DYNA platform. The results show that the computed stress–strain curves present a reasonable agreement with the experimental data. It should be declared that this research does not involve the energy release behavior of the 26.5Al-73.5PTFE (wt.%) reactive material because the material is not initiated within the strain rate range of the dynamic test in this paper.