On the micromechanics of low temperature strength and toughness of intermetallic/metallic microlaminate composites

• Published in: Acta materialia Vol. 44; no. 11; pp. 4289 - 4299
• Main Authors: Heathcote, J., Odette, G.R., Lucas, G.E., Rowe, R.G., Skelly, D.W.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.11.1996; Elsevier Science
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Fatigue, brittleness, fracture, and cracks; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Metals. Metallurgy; Physics; Hardness test; Intermetallic compounds; Tensile tests; Mechanical properties; Laminated structure; Brittle material; Experimental study; Microhardness; Niobium; Tensile strength; Fracture toughness; Crack opening displacement; Composite materials; Niobium base alloys; SEM; Rupture strength; Fractography; Strength
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/1359-6454(96)00112-7

Tensile strength and fracture resistance curves were measured for different combinations of brittle intermetallic/ductile metallic microlaminates. Metal layer bridging, characterized by the closure stress (σ)-crack opening ( u) displacement function, produced toughening by factors of 2–5. The key composite property, σ( u), was evaluated by fitting resistance curves using a large scale bridging code coupled with independent estimates of the maximum stress and ligament height. These functions were used in a bridging-crack stability analysis of tensile strength controlled by pre-existing processing defects. Assuming similar flaws, the composites are roughly 4–6 times stronger than the intermetallic, with predicted strengths in agreement with experiment within a standard deviation of 45 MPa. Composite strength is primarily sensitive to the intermetallic toughness and the constrained strength of the metal layer. Greater strength can also be achieved by better control of the growth defects.