Thermal, chemical, and mechanical response of rigid polyurethane foam

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Rigid polyurethane foams are frequently used as encapsulants to isolate and support thermally sensitive components within weapon systems. When exposed to abnormal thermal environments, such as fire, the polyurethane foam decomposes to form products having a wide distribution of molecular weights and can dominate the overall thermal response of the system. Mechanical response of the decomposing foam, such as thermal expansion under various loading conditions created by gas generation, remains a major unsolved problem. A constitutive model of the reactive foam is needed to describe the coupling between mechanical response and chemical decomposition of foam exposed to environments such as ... continued below

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20 p.

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Hobbs, M.L. December 1, 1997.

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Description

Rigid polyurethane foams are frequently used as encapsulants to isolate and support thermally sensitive components within weapon systems. When exposed to abnormal thermal environments, such as fire, the polyurethane foam decomposes to form products having a wide distribution of molecular weights and can dominate the overall thermal response of the system. Mechanical response of the decomposing foam, such as thermal expansion under various loading conditions created by gas generation, remains a major unsolved problem. A constitutive model of the reactive foam is needed to describe the coupling between mechanical response and chemical decomposition of foam exposed to environments such as fire. Towards this end, a reactive elastic-plastic constitutive model based on bubble mechanics describing nucleation, decomposition chemistry, and elastic/plastic mechanical behavior of rigid polyurethane foam has been developed. A local force balance, with mass continuity constraints, forms the basis of the constitutive model requiring input of temperature and the fraction of the material converted to gas. This constitutive model provides a stress-strain relationship which is applicable for a broad class of reacting materials such as explosives, propellants, pyrotechnics, and decomposing foams. The model is applied to a block of foam exposed to various thermal fluxes. The model is also applied to a sphere of foam confined in brass. The predicted mechanical deformation of the foam block and sphere are shown to qualitatively agree with experimental observations.

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20 p.

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OSTI as DE98001701

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  • 27. international symposium on combustion, Boulder, CO (United States), 2-7 Aug 1998

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  • Other: DE98001701
  • Report No.: SAND--97-3139C
  • Report No.: CONF-980804--
  • Grant Number: AC04-94AL85000
  • Office of Scientific & Technical Information Report Number: 658120
  • Archival Resource Key: ark:/67531/metadc712105

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

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  • December 1, 1997

Added to The UNT Digital Library

  • Sept. 12, 2015, 6:31 a.m.

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  • Nov. 25, 2015, 5:34 p.m.

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Hobbs, M.L. Thermal, chemical, and mechanical response of rigid polyurethane foam, article, December 1, 1997; United States. (digital.library.unt.edu/ark:/67531/metadc712105/: accessed August 15, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.