B. Moser

Nextel? 610 alumina fibre reinforced aluminium: Influence of matrix and process on flow stress

Abstract Continuous alumina fibre reinforced aluminium matrix composites are produced using two different liquid metal infiltration methods, namely direct squeeze casting and gas pressure infiltration. Net-shape fibre performs for longitudinal parallel tensile bars are prepared by winding the Nextel™ 610 alumina fibre (3M, St Paul, MN) into graphite moulds. High purity aluminium, two binary (Al–6% Zn and Al–1% Mg) and one ternary (Al–6% Zn–0.5% Mg) aluminium alloys are used as matrix materials. The composite is tested in uniaxial tension–compression, using unload–reload loops to monitor the evolution of Youngs modulus. A linear dependence between Youngs modulus and strain is observed; this is attributed, by deduction, to intrinsic elastic non-linearity of the alumina fibre. This conclusion is then used to compare on the basis of the in situ matrix flow curve the influence of matrix composition and infiltration process on the composite stress–strain behaviour.

Transmitted light microscopy of a fibre reinforced metal

A method is presented for studying fibre damage in continuous fibre reinforced composites. It is based on contrasting the transmission of light through intact translucent fibres with the light through fractured or dead‐ended fibres. The method is applied in order to detect processing‐induced fibre fractures in aluminium reinforced with continuous alumina fibres.

The influence of non-linear elasticity on the determination of Weibull parameters using the fibre bundle tensile test

We address the influence of individual fibre stress‐ strain non-linearity on the extraction of Weibull-parameters from fibre bundle tensile tests. We extend the statistical theory of fibre bundle strength to include the non-linear elastic behaviour observed in many technically important fibres, e.g. glass-, carbon-, and alumina-fibres. It is shown that neglecting this non-linearity may lead to significant errors in determining the shape and scale parameters of the fibre fracture strength Weibull-distribution. A refinement of the existing extraction technique, accounting for this effect, is presented. The error resulting from neglecting the non-linear behaviour is assessed through a parametric study of the Weibull parameters for different levels of non-linearity. Explicit calculations are performed for two fibres of technical importance, namely Nextel 610e a-alumina fibre and a T300 carbon fibre. q 2003 Elsevier Ltd. All rights reserved.

Swift and inverse swift effect in alumina fiber reinforced aluminum wires

Abstract The change in length during torsion is examined (i.e. the Swift effect) of an aluminum wire reinforced with 45% continuous Nextel ® 610 alumina fibers at ambient temperature, and also its rotation under applied tensile stress after pre-twisting (i.e. the inverse Swift effect). The wire is shown to shorten when twisted away from its initial configuration in which all fibers are parallel. The shortening is proportional to the square of the twisting angle over a large range of angles. Reversal of the shear from a given pre-twist elongates the wire again, up to its initial length when zero cumulated twist is reached. In the inverse Swift experiment the wire increasingly untwists as the external load is increased. Analytical models for both Swift and inverse Swift behavior of the wire are presented, and are shown to be in good agreement with the experiments.