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Title: Properties of Syntactic Foam for Simulation of Mechanical Insults.

Abstract

Syntactic foam encapsulation protects sensitive components. The energy mitigated by the foam is calculated with numerical simulations. The properties of a syntactic foam consisting of a mixture of an epoxy-rubber adduct and glass microballoons are obtained from published literature and test results. The conditions and outcomes of the tests are discussed. The method for converting published properties and test results to input for finite element models is described. Simulations of the test conditions are performed to validate the inputs.

Authors:
 [1];  [1];  [1];  [1]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1367482
Report Number(s):
SAND-2017-1828
654068
DOE Contract Number:
AC04-94AL85000
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Hubbard, Neal Benson, Haulenbeek, Kimberly K., Spletzer, Matthew A., and Ortiz, Lyndsy. Properties of Syntactic Foam for Simulation of Mechanical Insults.. United States: N. p., 2017. Web. doi:10.2172/1367482.
Hubbard, Neal Benson, Haulenbeek, Kimberly K., Spletzer, Matthew A., & Ortiz, Lyndsy. Properties of Syntactic Foam for Simulation of Mechanical Insults.. United States. doi:10.2172/1367482.
Hubbard, Neal Benson, Haulenbeek, Kimberly K., Spletzer, Matthew A., and Ortiz, Lyndsy. Wed . "Properties of Syntactic Foam for Simulation of Mechanical Insults.". United States. doi:10.2172/1367482. https://www.osti.gov/servlets/purl/1367482.
@article{osti_1367482,
title = {Properties of Syntactic Foam for Simulation of Mechanical Insults.},
author = {Hubbard, Neal Benson and Haulenbeek, Kimberly K. and Spletzer, Matthew A. and Ortiz, Lyndsy},
abstractNote = {Syntactic foam encapsulation protects sensitive components. The energy mitigated by the foam is calculated with numerical simulations. The properties of a syntactic foam consisting of a mixture of an epoxy-rubber adduct and glass microballoons are obtained from published literature and test results. The conditions and outcomes of the tests are discussed. The method for converting published properties and test results to input for finite element models is described. Simulations of the test conditions are performed to validate the inputs.},
doi = {10.2172/1367482},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 2017},
month = {Wed Feb 01 00:00:00 EST 2017}
}

Technical Report:

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  • This project was started early in the redevelopment of the carbon syntactic foam. The new mixture of carbon microballoons with the APO-BMI resin had not been fully characterized, but that was the actual purpose of this effort. During the forming of the billets for these tests, a problem began to surface; but full understanding of the problem did not evolve until samples were cured and tests were conducted. Material compressive strengths varied between 200 and 990 psi where anything below 700 was rejected. The cure cycle was adjusted in an iterative manner in an attempt to maximize the material strength.more » The result of this effort was that the material strength was almost doubled and was achieving strengths of 1,500 psi toward the end of the parts produced. As a consequence, some of the strength tests actually run and reported in the text of this report may not reflect data that would be obtained today. The material strength was continuously being improved over the entire year. A complete series of compression test data is reported, but subsequent tensile and flexural strength tests were not repeated. At a time when it is considered that there are no further changes to be incorporated, a repeat of these tests would be warranted. Some development remains to be done on the carbon microballoon material. Improved carbon material is now available and its effect of the material strength should be evaluated.« less
  • Triaxial compression testing is a means for mechanical characterization of a material. A unique feature of the triaxial compression test is the application of two different magnitudes of compressive pressures on the material simultaneously. The material behavior under these different compressive pressures can be monitored over time. Several important characteristics of the material, such as stress yield values and the shear failure envelope may then be determined. Also mechanical properties such as Poisson’s ratio, Young’s modulus and bulk modulus can be determined from the triaxial compression test. The triaxial compression test was employed in this investigation to characterize the shearmore » behavior, shear failure envelope, and mechanical properties of a syntactic foam. Los Alamos National Laboratory (LANL) supplied a total of 36 samples of APO-BMI syntactic foam to the University of New Mexico, Department of Civil Engineering for testing between December 2003 and May 2004. Each sample had a diameter of 1.395±0.005 in. (3.543±0.013cm.) and a length of 2.796±0.004 in. (7.102±0.010 cm.). The samples had an average density of 0.295 g/cm3. Additional information about the material tested in this investigation can be found in the “Specimen Description” section contained in Chapter 1. The nomenclatures used in this study is presented in Chapter 1. In addition to designing and implementing triaxial compression tests capable of up to 2,000 psi. confining pressure (minor principal stress) and roughly 13,000 psi. in axial pressure (major principal stress), a pure tension test was designed and conducted on the foam material. The purpose of this pure tension test was to obtain maximum tensile stress values to enhance the characterization of the shear envelope in the stress space. The sampling procedure and specimen preparation for a standard test can be found in the American Society for Testing Materials (ASTM) D 5379/ D 5379 – 93. The above tests mentioned and their procedures are discussed in Chapter 2. Chapter 2 contains the types of tests performed and the apparatus used for testing the material. Chapter 2 also has a brief explanation of the equipment and the procedures used for conducting the tests. In Chapter 3, the material characteristics and mechanical properties obtained from the tests are described; composite plots of deviatoric vs. mean stress and deviatoric stress vs. longitudinal strain are also included. The plots of deviatoric stress vs. mean stress clearly identify the shear envelope for the material. Chapter 4 summarizes the vital information obtained from the tests and the conclusions made. All the necessary plots and the data generated during the testing have been included in the Appendix. The information in the appendix includes plots of: Strain vs. Time, Stress vs. Time, Stress vs. Strain, Mean Stress vs. Volumetric Strain, Lateral Strain vs. Longitudinal Strain, and q vs. p. Bulk modulus, Poisson’s ratio, and Young’s modulus are displayed in the appropriate plots in each appendix.« less
  • HE ignition caused by shear localization is the principal concern for safety analyses of postulated mechanical insults to explosive assemblies. Although prompt detonation from shock is certainly a concern, insults that lead to prompt detonation are associated with high velocity, and correspondingly rare. For high-density HMX assemblies, an impact speed (by a steel object) of 400 m/s is needed to develop a detonation in a run distance less than 30 mm. To achieve a steady plane shock, which results in the shortest run distance to detonation for a given peak pressure, the impactor diameter must exceed 60 mm, and thicknessmore » approach 20 mm. Thinner plates and/or smaller diameter ones require even higher impact velocity. Ignitions from shear localization, however, have been observed from impacts less than 50 m/s in Steven tests, less than 30 m/s from spigot impact tests, and less than 10 m/s from various drop tests. This lower velocity range is much frequent in postulated mechanical insults. Preliminary computer simulations and analyses of a variety of such tests have suggested that although each is accompanied by shear localization, there are differing detailed mechanisms at work that cause the ignitions. We identify those mechanisms that may be at work in a variety of such tests, and suggest how models of shear ignition, such as HERMES, may be revised and calibrated to conform to experiment. We suggest combining additional experiments with computer simulations and model development to begin confirm or uncover mechanisms that may be at work in a specific postulated event.« less
  • A manufacturing process developed for parylene coating syntactic parts has resulted in several improvements. Thin edges have been strengthened, which minimizes breakage during the manufacturing process and subsequent assembly; part and surface toughness has been improved; the coefficient of friction during assembly has been reduced; and the bonding of the pads, shoehorn, and clips has been enhanced. Improvements in the tensile strength and flexural strength of the syntactic composite as a result of the coating are discussed, and coated parts and deposited films produced by laboratory and production coaters are compared.