Accession Number : ADA308876

Title :   Fatigue Crack Growth Mechanisms in Titanium Metal Matrix Composites.

Descriptive Note : Final rept. Jun 92-Jun 95,

Corporate Author : RHODE ISLAND UNIV KINGSTON

Personal Author(s) : Ghonem, Hamouda

PDF Url : ADA308876

Report Date : FEB 1996

Pagination or Media Count : 237

Abstract : This report details studies carried out to identify the high temperature fatigue crack growth damage mechanisms in fiber-reinforced titanium metal matrix composites. The report consists of eight separate sections. In the first section, the fatigue and fatigue crack growth characteristics in neat laminates made of Timetal 21S were studied in relation to both temperature and loading frequency effects. The second section deals with the evolution of the thermal residual stresses in the composite when cooling from consolidation temperature or subjecting the composite to thermal cycles. A new mechanical simulation method capable of measuring the induced residual stress on real time basis has been developed in this study. The third section extends this issue to the time-dependent internal stress and strain states of MMCs under the thermomechanical loading conditions. Here, a new micromechanical model employing the four-phase concentric cylinder configuration has been proposed. Based on this model, the time-dependent behavior of continuous fiber reinforced metal matrix composites. It has been evaluated. These results are presented in the fourth section. The fifth, sixth and seventh sections of this report describe the influence of temperature and loading frequency on the crack growth process and suggest a fatigue-creep interactive mechanism acting at the crack tip during high temperature loadings. The last section of the report deals with the determination of the stress evolution in bridging fibers during the fatigue crack growth in SM 1240/Timetal-21S composite using the finite element method. Several parameters affecting this evolution were considered; namely, the process-induced residual stress, the creep characteristics of the matrix layer surrounding the fiber, the test temperature and the loading frequency.

Descriptors :   *METAL MATRIX COMPOSITES, *CRACK PROPAGATION, *FATIGUE(MECHANICS), *TITANIUM, TEST AND EVALUATION, THERMAL PROPERTIES, THERMOMECHANICS, FREQUENCY, SIMULATION, FIBERS, MECHANICAL PROPERTIES, TIME DEPENDENCE, REAL TIME, INTERACTIONS, HIGH TEMPERATURE, LAMINATES, FINITE ELEMENT ANALYSIS, COOLING, CYLINDRICAL BODIES, INTERNAL, CONFIGURATIONS, RESIDUAL STRESS, CREEP, EVOLUTION(GENERAL), THERMAL STRESSES.

Subject Categories : Inorganic Chemistry
      Physical Chemistry
      Laminates and Composite Materials
      Properties of Metals and Alloys
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE