On a damage approach for microcracking modeling in continuous fiber composites

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:175446

Ladeveze, P; Allix, O; Cluzel, C H; Grasser, A ^[1]

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1. Laboratorie de Mecanique et Technologie, Cachan (France)

The studied material is a woven SiC (Nicalon)/SiC (CVI) composite. Its behavior is elastic-damageable in tension and brittle-linear-elastic in compression (this response does not depend on a previous damage in tension). The damage state is described with a second-order symmetric tensor H. In plane stress state, H is represented by a symmetric 2x2 matrix in an orthogonal basis. The evolution of H is linked to both microcracking mechanisms. To have better results in the modeling of biaxial tests, some improvements, taking account of these mechanisms, have been introduced with respect to. To take into account the difference between tension and compression due to the closure of the microcracks, the strain energy is separated into a {open_quotes}tension energy{close_quotes} and a {open_quotes}compression energy{close_quotes}. Only the {open_quotes}tension energy{close_quotes} is affected by the damage. With this approach, the strain energy is differentiable, and the strain is continuous. The 0{degrees} and 45{degrees} uniaxial tension-compression tests, at room temperature, are not sufficient to identify the model. A biaxial test, like a combined tension test (0{degrees} test followed by a 90{degrees} test, for example), is necessary. The model is validated with an internal pressure test on tube and is able to describe the crack array evolution. This model, valid for complex loadings, can be adapted to other materials and to temperature (including creep) or cyclic loadings. To model the temperature effects, a coupling damage-viscoplasticity is introduced. The model is built upon the {open_quotes}effective stress{close_quotes} and the {open_quotes}effective inelastic stain rate{close_quotes}. In an initial approach, the evolution of the effective inelastic stain rate is described with isotropic hardening. The damage evolution takes into account the specific damage mechanisms due to creep or aging (structural evolution of the interphases and the fibers).

• OSTI ID: 175446
• Report Number(s): CONF-950686--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COMPRESSION
CRACKS
CREEP
HARDENING
MECHANICAL PROPERTIES
SILICON CARBIDES
STRESSES