Role of internal stresses in fracture behavior of engineering composites

Book · Sat Dec 31 04:00:00 EST 1994

OSTI ID:62962

Singh, J P; Singh, D; Kupperman, D S; Majumdar, S ^[1]

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1. Argonne National Lab., IL (United States). Energy Technology Division

The fracture behavior and microstructure of SiC(f)/Si{sub 3}N{sub 4} matrix composites, and of Ag-particle/YBa{sub 2}Cu{sub 3}O{sub x}(YBCO) superconductor matrix composites, together with internal residual strains in composite constituents, have been evaluated as a function of reinforcing fiber, particle content, and processing variables. Residual strains were measured by neutron diffraction with the Intense Pulsed Neutron Source and the General Purpose Powder Diffractometer at Argonne National Laboratory. Internal radial strains on SiC fibers in SiC(f)/Si{sub 3}N{sub 4} composites decreased from 0.0015 at 8.4 vol.% fibers to 0.0010 at 23.3 vol.% fibers. This decrease in radial strain with increasing fiber volume fraction is expected to reduce frictional, and hence interfacial sliding stresses between the SiC fibers and Si{sub 3}N{sub 4} matrix; this is in agreement with interfacial shear strengths measured by the fiber pushout technique. Similar relationships between residual strain and interfacial shear strength were observed in composites that were hot isostatically pressed (HIPed). For YBCO/Ag composites, tensile strain in the Ag phase was as high as 0.085%, whereas compressive strain in the YBCO phase reached 0.09%. The presence of compressive strain (stress) improved the strength of YBCO from {approx}190 to 223 MPa. Implications of the effects of residual stresses on interfacial characteristics and resulting composite mechanical properties and fracture behavior are discussed.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 62962
• Report Number(s): CONF-941016--; ISBN 0-87339-247-7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM OXIDES
COMPOSITE MATERIALS
COPPER OXIDES
EXPERIMENTAL DATA
FRACTURE PROPERTIES
FRICTION
INTERFACES
NEUTRON DIFFRACTION
RESIDUAL STRESSES
SAMPLE PREPARATION
SILICON CARBIDES
SILICON NITRIDES
SILVER
STRAINS
STRESSES
YTTRIUM OXIDES