Formation of tough composite joints

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Description

Joints which exhibit tough fracture behavior were formed in a composite with a Si/SiC matrix reinforced with Textron SCS-6 fibers with either boron nitride or silicon nitride fiber coatings. In composites with BN coatings fibers were aligned uniaxially, while composites with Si{sub 3}N{sub 4}-coated fibers had a 0/90{degree} architecture. Lapped joints (joints with overlapping fingers) were necessary to obtain tough behavior. Geometrical requirements necessary to avoid brittle joint failure have been proposed. Joints with a simple overlap geometry (only a few fingers) would have to be very long in order to prevent brittle failure. Typical failure in these joints is ... continued below

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27 p.

Creation Information

Brun, M.K. May 1, 1997.

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Author

  • Brun, M.K. GE Corporate Research and Development, Schenectady, NY (United States)

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Publisher

  • Knolls Atomic Power Laboratory
    Publisher Info: Knolls Atomic Power Lab., Schenectady, NY (United States)
    Place of Publication: Schenectady, New York

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Description

Joints which exhibit tough fracture behavior were formed in a composite with a Si/SiC matrix reinforced with Textron SCS-6 fibers with either boron nitride or silicon nitride fiber coatings. In composites with BN coatings fibers were aligned uniaxially, while composites with Si{sub 3}N{sub 4}-coated fibers had a 0/90{degree} architecture. Lapped joints (joints with overlapping fingers) were necessary to obtain tough behavior. Geometrical requirements necessary to avoid brittle joint failure have been proposed. Joints with a simple overlap geometry (only a few fingers) would have to be very long in order to prevent brittle failure. Typical failure in these joints is caused by a crack propagating along the interfaces between the joint fingers. Joints of the same overall length, but with geometry changed to be symmetric about the joint centerline and with an extra shear surface exhibited tough fractures accompanied with extensive fiber pullout. The initial matrix cracking of these joints was relatively low because cracks propagated easily through the ends of the fingers. Joints with an optimized stepped sawtooth geometry produced composite-like failures with the stress/strain curves containing an elastic region followed by a region of rising stress with an increase of strain. Increasing the fiber/matrix interfacial strength from 9 to 25 MPa, by changing the fiber coating, increased matrix cracking and ultimate strength of the composite significantly. The best joints had matrix cracking stress and ultimate strength of 138 and 240 MPa, respectively. Joint failure was preceded by multiple matrix cracking in the entire composite. The high strength of the joints will permit building of structures containing joints with only a minor reduction of design stresses.

Physical Description

27 p.

Notes

INIS; OSTI as DE99001888

Source

  • 99. annual meeting of the American Ceramic Society, Cincinnati, OH (United States), 4-7 May 1997

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Identifier

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  • Other: DE99001888
  • Report No.: KAPL-P--000161
  • Report No.: K--97042;CONF-970568--
  • Grant Number: AC12-76SN00052
  • DOI: 10.2172/319832 | External Link
  • Office of Scientific & Technical Information Report Number: 319832
  • Archival Resource Key: ark:/67531/metadc687594

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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.

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Creation Date

  • May 1, 1997

Added to The UNT Digital Library

  • July 25, 2015, 2:20 a.m.

Description Last Updated

  • May 16, 2016, 3:53 p.m.

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Brun, M.K. Formation of tough composite joints, report, May 1, 1997; Schenectady, New York. (digital.library.unt.edu/ark:/67531/metadc687594/: accessed November 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.