High Rate Compressive Behaviour of a Dilatant Polymeric Foam

• Author(s) / Creator(s)

  • Bhagavathula, Kapil Bharadwaj
  • Azar, Austin
  • Ouellet, Simon
  • Satapathy, Sikhanda
  • Dennison, Christopher R.
  • Hogan, James D.

• Polymeric foams are an essential part of personal protection equipment, such as helmets and body armor. In this work, the authors study the strain-rate dependent behavior of a dilatant polymeric foam, focusing on developing characterization and testing methodologies needed to better understand the links between microstructure and failure in these materials. The authors study these links for a commercially-available shear-thickening foam, named D3O LITE D. Prior to testing, the pore sizes (82 ± 26 µm), ligament thickness between pores (5–12 µm), and porosity (83 ± 5%) were quantified using scanning electron microscope images. Samples were then tested in compression under quasi-static conditions for a strain rate of 0.04 s−1 using an MTS testing apparatus, and in dynamic conditions using a split Hopkinson pressure bar apparatus for strain rates of 5280–5720 s−1. For both rates, strains upwards of 85% were achieved and this allowed us to examine a variety of material failure behaviors, including elastic collapse, localization, pore collapse, densification and post pore collapse hardening. These mechanisms are observed in-situ during compression experiments using high-speed photography, and linked back to stress–strain responses of the materials. In this material, the elastic collapse stress for quasi-static and dynamic compression conditions was found to be 120 ± 40 kPa and 243 ± 47 kPa, respectively, and elastic modulus were noted of 2.4 ± 0.7 MPa and 3.8 ± 1.2 MPa, respectively. Following the elastic collapse, some unique specimen-scale localization features were observed during the dynamic experiments. These features are unique to dynamic compression and were not observed for the quasi-static case, demonstrating a demonstrating a distinct high-rate behavior for this material, possibly linked to its “shear thickening” label. After densification, complete pore collapse followed by post pore collapse hardening were observed for both strain rates. These results represent some of the first studies on shear-thickening foams in the literature, and the testing methodologies developed in this study will serve as the foundation for additional experimental and computation studies across a broader range of foam materials.

• Date created

  2018-01-01

• Subjects / Keywords

  • Material behaviour
  • Shear thickening foam
  • High strain-rate
  • Kolsky bar
  • Dynamic compression
  • Ultra high-speed photography

• Type of Item

  Article (Draft / Submitted)

• DOI

  https://doi.org/10.7939/r3-3p0e-b664

• License

  This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: https://doi.org/10.1007/s40870-018-0176-0 © This is a U.S. government work and its text is not subject to copyright protection in the United States; however, its text may be subject to foreign copyright protection 2018