Rigid Square Inclusion Embedded within an Epoxy Disk: Asympototic Stress Analysis

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The asymptotically singular stress state found at the tip of a rigid, square inclusion embedded within a thin, linear elastic disk has been determined for both uniform cooling and an externally applied pressure. Since these loadings we symmetric, the singular stress field is characterized by a single stress intensity factor, and the applicable calibration relationship has been determined for both fully bonded and unbended inclusions. A lack of interfacial bonding has a profound effect on inclusion-tip stress fields. A large radial compressive stress is generated in front of the inclusion tip when the inclusion is well bonded, whereas a large ... continued below

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Guess, T.R. & Reedy, E.D. February 2, 1999.

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  • Sandia National Laboratories
    Publisher Info: Sandia National Laboratories, Albuquerque, NM, and Livermore, CA
    Place of Publication: Albuquerque, New Mexico

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Description

The asymptotically singular stress state found at the tip of a rigid, square inclusion embedded within a thin, linear elastic disk has been determined for both uniform cooling and an externally applied pressure. Since these loadings we symmetric, the singular stress field is characterized by a single stress intensity factor, and the applicable calibration relationship has been determined for both fully bonded and unbended inclusions. A lack of interfacial bonding has a profound effect on inclusion-tip stress fields. A large radial compressive stress is generated in front of the inclusion tip when the inclusion is well bonded, whereas a large tensile hoop stress is generated when the inclusion is unbended, and frictionless sliding is allowed. Consequently, an epoxy disk containing an unbended inclusion appears more likely to crack when cooled than a disk containing a fully bonded inclusion. Elastic-plastic calculations show that when the inclusion is unbended, encapsulant yielding has a significant effect on the inclusion-tip stress state. Yielding relieves stress parallel to the interface and greatly reduces the radial compressive stress in front of the inclusion. As a result, the encapsulant is subjected to a nearly uniaxial tensile stress at the inclusion tip. For a typical high-strength epoxy, the calculated yield zone is embedded within the region dominated by the elastic hoop stress singularity. A limited number of tests have been carried out to determine if encapsulant cracking can be induced by cooling a specimen fabricated by molding a square, steel insert within a thin, epoxy disk. Test results are in qualitative agreement with analysis. Cracks developed only in disks with mold-released inserts, and the tendency for cracking increased with inclusion size.

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  • Journal Name: International Journal of Fracture

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  • Other: DE00003339
  • Report No.: SAND99-0290J
  • Grant Number: AC04-94AL85000
  • Office of Scientific & Technical Information Report Number: 3339
  • Archival Resource Key: ark:/67531/metadc682310

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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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  • February 2, 1999

Added to The UNT Digital Library

  • July 25, 2015, 2:20 a.m.

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  • Dec. 1, 2016, 4:45 p.m.

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Guess, T.R. & Reedy, E.D. Rigid Square Inclusion Embedded within an Epoxy Disk: Asympototic Stress Analysis, article, February 2, 1999; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc682310/: accessed December 15, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.