Brittle matrices reinforced with polyalkene films of varying elastic moduli |
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Authors: | D C Hughes D J Hannant |
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Affiliation: | (1) Construction Materials Research Group, Department of Civil Engineering, University of Surrey, Guildford, UK |
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Abstract: | The inclusion of polyalkene films of different moduli in a cement-based matrix has shown the benefits to be gained, in terms of increased stress at a given strain, from the use of films of high elastic modulus. Further, the concept of load-bearing cracks is used to explain the transition region between the limit of proportionality and the bend-over point on the tensile stress-strain curve, which is found to exist with high film modulus composites. This transition region could be an important factor affecting the choice of film to be used in a commercial composite.Nomenclature
E
c
uncracked composite modulus
-
E
m
matrix modulus
-
E
f
film modulus
-
V
m
matrix volume-fraction
-
V
t
film volume-fraction
-
V
f(crit)
(E
c
mu)/
fu
-
A
c
cross-sectional area of composite
-
(E
m
V
m/E
fVf)
-
m
matrix strain
-
mu
matrix cracking strain
- mu
average matrix cracking strain, (#x03C3;co)/E
c
-
mc
strain at end of multiple cracking
-
fu
ultimate fibre stress
-
cu
ultimate composite stress
-
co
average composite cracking stress (assumed at a strain of
mc/2)
- S4
81 draw ratio polypropylene film
- S8
181 draw ratio polypropylene film
- E3H
polyethylene film
- LOP
limit of proportionality (stress at first crack, assumed to be a departure from linearity of the tensile stress-strain curve of a perfectly straight and uniform test specimen. However, this point cannot be reliably determined from the stress-strain curve because of the clamping strains induced in warped specimens)
- BOP
bend-over point (stress at which the approximately horizontal portion of multiple cracking region commences. The BOP is generally higher than the LOP and is a much more reliable point to determine experimentally than the LOP) |
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Keywords: | |
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