Internal stresses in planar random fiber aluminum composites. 2: Mean stress hardening and relaxation

Journal Article · Fri Dec 01 04:00:00 EST 1995 · Acta Metallurgica et Materialia

DOI:https://doi.org/10.1016/0956-7151(95)00117-E· OSTI ID:178002

Johannesson, B; Ogin, S L ^[1]

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1. Univ. of Surrey, Guildford (United Kingdom). Dept. of Materials Science and Engineering

The hardening rate of the matrix mean stress in planar random fiber aluminum composites with a range of fiber volume fractions is measured in cyclic Bauschinger experiments at room temperature and 77 K. A particular problem with predicting the mean stress hardening rate in these composites is that the plastic strain is not isotropic in the transverse directions. A method for quantifying the experimentally determined plastic flow in a form useful for this analysis is proposed. The difference between the predicted and measured mean stress hardening rates is smallest for low fiber volume fractions at 77 K. A model for relaxation of the plastic mean stress in the matrix is developed. It is based on the assumption that the rate controlling mechanism in these composites is cross slip of screw dislocations. The measured activation energy is independent of fiber volume fraction but the activation volume decreases with increasing fiber content. The magnitudes of activation energy and activation volume support the assumptions of the model.

• OSTI ID: 178002
• Journal Information: Acta Metallurgica et Materialia, Journal Name: Acta Metallurgica et Materialia Journal Issue: 12 Vol. 43; ISSN 0956-7151; ISSN AMATEB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ACTIVATION ENERGY
ALUMINIUM
ALUMINIUM OXIDES
CHEMICAL COMPOSITION
COMPOSITE MATERIALS
HARDENING
MATHEMATICAL MODELS
PLASTICITY
PREDICTION EQUATIONS
SCREW DISLOCATIONS
SLIP
STRAINS
STRESS RELAXATION
STRESSES