Continuous parallel alumina fiber-reinforced metals produced by pressure in
filtration are tested in tension/compression along the fiber axis with a go
al of measuring the influence exerted by long fibers on the flow stress of
their matrix. In this configuration, the equistrain rule of mixtures, modif
ied to take into account stresses due to differential lateral contraction,
can be used to back-calculate the matrix flow stress from that of the compo
site. This method provides the least physically ambiguous measurement of ma
trix flow stress in the composite; however, experimental uncertainty can be
high. This uncertainty is evaluated in detail for the present experiments,
in which matrix in situ stress-strain curves are measured for cast 3M NEXT
EL 610 and DUPONT FIBER FP reinforced pure and alloyed aluminum- and copper
-based matrices of varying propensity for recovery and cross-slip. Within e
xperimental uncertainty, data show no enhanced matrix work-hardening rates
such as those those that have been measured with tungsten fiber-reinforced
copper. It is found that the fibers alter the matrix plastic flow behavior
by increasing the flow-stress amplitude of the matrix, and by rendering ini
tial yield in compression more progressive than in initial tension. Essenti
ally, all observed features of matrix/fiber interaction can be rationalized
as attributable to dislocation emission in the matrix caused by thermal mi
smatch strains within the material during composite cooldown from processin
g temperatures.