Laser-ultrasonic evaluation of damage in unidirectional ceramic matrix composites

Conference · Mon Apr 01 04:00:00 EST 1996

OSTI ID:219493

Liu, Y M; Mitchell, T E ^[1]; Wadley, H N.G. ^[2]

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1. Los Alamos National Lab., NM (United States). Center for Materials Science
2. Univ. of Virginia, Charlottesville, VA (United States). Dept. of Materials Science and Engineering

Ceramic matrix composites (CMCs) have attracted great attention because of their potential for high temperature structural applications. Among these materials, calcium aluminosilicate (CAS) glass ceramic and similar composites reinforced by Nicalon{trademark} SiC fiber with carbon-rich interface have been under active investigation because of their {open_quotes}notch-insensitivity{close_quotes}: stress near holes and notches can be redistributed by inelastic deformation in the form of multiple matrix cracking. Therefore, stress concentration is alleviated near these sites. Understanding the damage mechanism in these composites is very important for the development of constitutive modeling. To achieve this goal, monitoring damage initiation and accumulation in-situ are especially critical. In most of the previous work, the change of elastic modulus along loading direction was used to characterize the damage. However, the overall anisotropic damages such as fiber-matrix debonding or shear deformation were unknown. In this study, we have pursued an in-situ nondestructive laser-ultrasonic technique to assess the overall anisotropic stiffness degradation under loading. When a laser pulse is brought to sample surface, high frequency acoustic waves can be generated by thermal or ablation mechanisms depending on the incident power intensity. The propagation of the elastic waves through anisotropic media is characterized by the well-known Christoffel equation.

• Research Organization: Los Alamos National Lab., NM (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States); Department of Defense, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 219493
• Report Number(s): LA-UR--96-899; CONF-9604124--1; ON: DE96009777
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM SILICATES
CALCIUM COMPOUNDS
COMPOSITE MATERIALS
DEFORMATION
ELASTICITY
GLASS
INTERFACES
LASERS
MATHEMATICAL MODELS
MECHANICAL PROPERTIES
SHEAR
SILICON CARBIDES
TENSILE PROPERTIES
ULTRASONIC WAVES
WAVE PROPAGATION