Material properties The deformation and failure response of closed-cell PMDI foams subjected to dynamic impact loading Behrad Koohbor a , Silas Mallon a , Addis Kidane a, * , Wei-Yang Lu b a Department of Mechanical Engineering, University of South Carolina, 300 Main Street, Columbia, SC 29208, USA b Sandia National Laboratories, Livermore, CA 94551-0969, USA article info Article history: Received 6 February 2015 Accepted 21 March 2015 Available online 7 April 2015 Keywords: Polymeric foam PMDI Dynamic loading Digital image correlation Shock tube abstract The present work aims to investigate the bulk deformation and failure response of closed- cell Polymeric Methylene Diphenyl Diisocyanate (PMDI) foams subjected to dynamic impact loading. First, foam specimens of different initial densities are examined and characterized in quasi-static loading conditions, where the deformation behavior of the samples is quantified in terms of the compressive elastic modulus and effective plastic Poisson's ratio. Then, the deformation response of the foam specimens subjected to direct impact loading is examined by taking into account the effects of material compressibility and inertia stresses developed during deformation, using high speed imaging in conjunction with 3D digital image correlation. The stress-strain response and the energy absorption as a function of strain rate and initial density are presented and the bulk failure mechanisms are discussed. It is observed that the initial density of the foam and the applied strain rates have a substantial influence on the strength, bulk failure mechanism and the energy dissipation characteristics of the foam specimens. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Foam materials have recently gained attention in engi- neering applications, particularly in those where light- weight structural design and/or energy dissipation are essential design parameters [1]. Polymer foams are widely used in applications such as sandwich structures, auto- motive industries and packaging. Many of these applica- tions inherently entail high loading rates, such as high speed vehicle accidents or impacts on packaged items. Due to unavailability of a well-defined material model at such high loading rates, these structures are usually designed based on their quasi-static behavior. However, material properties obtained from quasi-static testing may not accurately characterize the material response in real situ- ations at extremely high strain rate loading conditions, as the material response might be highly sensitive to the rate of deformation. The effect of strain rate on the material properties could be also depend on some of the material characteristics, such as the foam density and the cell structure [2e6]. At cellular scale, the deformation mecha- nism of foam materials include cell wall bending and stretching followed by post-yield wall buckling, while these microscale mechanisms contribute to the overall stiffness and strength of the material at larger scales. Thus, varying the cell structure and pore geometry in a foam specimen not only can change the material's bulk density, it will also substantially influence the stiffness, strength and bulk failure response of the material [1]. Researchers have been looking to understand the deformation behavior of foams at high strain rate loading conditions. So far, there have been both experimental and * Corresponding author. Department of Mechanical Engineering, University of South Carolina, 300 Main Street, Columbia, SC 29208, USA. Tel.: þ1 (803) 777 2502; fax: þ1 (803) 777 0106. E-mail address: [email protected] (A. Kidane). Contents lists available at ScienceDirect Polymer Testing journal homepage: www.elsevier.com/locate/polytest http://dx.doi.org/10.1016/j.polymertesting.2015.03.016 0142-9418/© 2015 Elsevier Ltd. All rights reserved. Polymer Testing 44 (2015) 112e124
The deformation and failure response of closed-cell PMDI foams subjected to dynamic impact loading
Jun 16, 2023
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Related Documents
