Tensile and fatigue behavior of Al-based metal matrix composites reinforced with continuous carbon or alumina fibers: Pa
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INTRODUCTION
THE efforts devoted to adapt metal casting processes to the infiltration of preforms and the availability of high-performance continuous alumina or carbon fibers have led to the development of high fiber volume fraction metal matrix composites (MMCs) offering attractive specific mechanical properties for aerospace applications.[1–9] Moreover, the possibilities of obtaining near net shape parts and of tailoring the thermal conductivity or the coefficient of thermal expansion of such MMCs constitute essential advantages. However, when used in the form of unidirectional (UD) composites, these materials present limitations, such as inhomogeneous fiber distribution due to fiber clustering during metal infiltration and very low transverse properties leading to a strong anisotropy. Quasiunidirectional (quasi-UD) composites reinforced by a woven fabric preform with 90 pct fibers in the longitudinal direction and 10 pct fibers in the transverse direction constitute an efficient alternative to the UD composites, since the quasi-UD preform prevents fiber movements during infiltration and improves the transverse mechanical properties, whereas it nearly maintains the longitudinal performances.[10,11] Completely reinforced mechanical parts, which generally necessitate a less anisotropic behavior, may be manufactured from cross-ply laminates consisting in the stacking of such quasi-UD preforms oriented at 0, 45, 90 deg.[2] In this context, knowledge of the specific behavior and of the damage mechanisms of the quasi-UD composites is a prerequisite to the further
M. JACQUESSON, formerly with ONERA-DMSC, F-92322 Châtillon Cedex, France, is with CNES, F-91023 Evry Cedex, France. A. GIRARD is with ONERA-LEM, F-92322 Châtillon Cedex, France. M.-H. VIDAL-SÉTIF and R. VALLE are with ONERA-DMSC. Contact e-mail: [email protected] Manuscript submitted March 12, 2004. METALLURGICAL AND MATERIALS TRANSACTIONS A
investigation of the mechanical properties of the quasi-UD (0, 45, 90 deg) laminates. Although the study of the mechanical properties and damage mechanisms of the quasi-UD composites represents a broader investigation involving acoustic emission monitoring,[10,11] only those of the results that are essential in the understanding of the specific behavior of this type of composite are reported in the present article (Part I). The next article (Part II[12]) will be devoted to the quasi-UD (0, 45, 90 deg) laminates. Moreover, at a more theoretical viewpoint, due to the presence of the fibers and to the specific aspect of the quasi-UD preform, an exacerbation of the fatigue mechanisms occurring in the matrix, even more severe than in “model” UD composites,[13,14,15] may be expected.
II. EXPERIMENTAL A. Materials Each quasi-UD composite plate (260 130 3 mm in size) is a 16-ply laminate, each ply being a quasi-UD woven fabric (taffeta) with about 90 pct fibers in the longitudinal direction and 10 pct fibers in the transverse direction. The specific aspect of this laminate is that all the plies are oriented in the same 0 deg
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