Evaluation of the MMCLIFE 3.0 code in predicting crack growth in titanium aluminide composites
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INTRODUCTION
MMCLIFE V3.0 is a multistage analysis routine for prediction of strength and life of fiber-reinforced metal matrix composite (MMC) when subjected to spectrum loads and thermal profiles. The MMCLIFE routine is based on a combination of micromechanics and macromechanics analyses: micromechanics analyses are used to determine elastic/plastic matrix behavior, lamina properties, and initial failure modes; and macromechanics analyses are used to determine laminate stresses, strains, and overall failure modes. This routine can be used to predict lamina and laminate stiffness, stresses about a notch and through the net section, laminate strength (notched or un-notched), crack initiation lives, and crack growth. The analyses are based on simple analytical methods and were programmed in FORTRAN for a Digital VAX computer with a VMS operating system and an IRIS workstation with a UNIX operating system. The approach in developing the metal matrix composite strength and fatigue analyses was to create a design tool to be used by engineers to obtain initial sizing requirements for specific MMC applications. This requires the use of simplified analytical procedures along with a limited amount of test data to provide a tool that executes quickly, yet provides accurate results. Detailed studies of micromechanical models were required to understand MMC maDAVID HARMON, formerly Principal Technical Specialist, The Boeing Company, St. Louis, MO 63166, is Project Engineer, Pratt & Whitney, East Hartford, CT 06108. JAMES M. LARSEN, Research Group Leader, is with the Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, OH 45433. ALONSO PERALTA, formerly Engineer, Allied Signal Engines, Phoenix, AZ 85072, is Graduate Student, Arizona State University, Tempe, AZ 85287. JAMES A. HALL, formerly Principal Materials Engineering, Allied Signal Engines, is Director of Process Engineering, Ormet-Wah Chang, Albany, OR 97321. This article is based on a presentation made in the symposium ‘‘Fatigue and Creep of Composite Materials’’ presented at the TMS Fall Meeting in Indianapolis, Indiana, September 14-18, 1997, under the auspices of the TMS/ASM Composite Materials Committee. METALLURGICAL AND MATERIALS TRANSACTIONS A
terial behavior when subjected to various loading conditions. Once the material response was understood, simpler expressions were derived to describe the phenomenon. In some cases, such as determination of failure mode initiation and location, simplified models were developed based on observation and interpretation of test data. The combined micromechanical and macromechanical analyses within MMCLIFE allow the code to be used to predict a wide range of MMC properties and behaviors. Trade studies can be performed to compare the predicted response of various fiber and matrix combinations. This requires input data describing the constituent material properties (i.e., fiber and matrix stiffness and strength, matrix fatigue life, and crack growth data). The analysis withi
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