Accession Number : ADA268275


Title :   Direct Observation of Fracture of Cas-Glass/SiC Composites and Processing of Toughened Alumina


Descriptive Note : Final rept. 1 Apr 91-31 Mar 92,


Corporate Author : CAMBRIDGE UNIV (UNITED KINGDOM) DEPT OF ENGINEERING


Personal Author(s) : Shercliff, H R ; Vekinis, G ; Ashby, M F ; Beaumont, P W


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a268275.pdf


Report Date : Sep 1992


Pagination or Media Count : 99


Abstract : The first part of the report describes the continuation of a test series which has been undertaken on the laminated CAS-glass SiC fibre reinforced material provided by the USAF Materials Laboratory, Dayton, Ohio. Fracture mechanisms have been studied in four-point bend and in two geometries - double cantilever beam and double edge-notched tension. Dynamic in-situ scanning electron microscopy has enabled a clear characterization of sub-critical damage, and crack interactions prior to final failure, both of which have a strong influence on the material failure strength. The second part of the report describes preliminary studies on the fracture behavior of alumina toughened with ductile metal reinforcements. Specimens of alumina reinforced with discrete particles (mainly cobalt) have been produced by pretreating metal powders and mixing them with alumina powder followed by sintering under protective atmospheres. Processing conditions have been developed, and fracture surfaces studied in the scanning electron microscope. Crack bridging by metal ligaments has been observed. The ligaments fail by necking and/or shearing. The materials and processing route appear to be promising, especially in terms of controlling the interfacial reactions and strength.


Descriptors :   *COMPOSITE MATERIALS , *CERAMIC MATRIX COMPOSITES , *GLASS , *LAMINATED GLASS , *SILICON CARBIDES , *ALUMINUM OXIDES , TEST AND EVALUATION , METALS , CALCIUM , MEASUREMENT , SCANNING ELECTRON MICROSCOPES , CRACKS , TOUGHNESS , LIGAMENTS , COBALT , POWDER METALS , ATMOSPHERES , SILICATES , MIXING , TENSION , PARTICLES , SURFACES , UNITED KINGDOM , FIBER REINFORCEMENT , SINTERING , CANTILEVER BEAMS , FAILURE , DAMAGE , MODELS , INTERACTIONS , DYNAMICS , MATERIALS , PROCESSING


Subject Categories : Ceramics, Refractories and Glass
      Laminates and Composite Materials
      Optics
      Mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE