  This work is based on the study of the behaviour of flax fibres twill
reinforced epoxy composites. The aim of the study is to determine the modulus
of elasticity, Poisson coefficients and strength of these composites materials
with image correlation. The specimens used in this work were manufactured by
the infusion vacuum process and after subjected to quasi-static tensile tests.
Two numeric cameras were disposed perpendicular to the front and to the side of
the specimen so as to achieve a sequence of visible digital pictures during the
test. The recorded pictures were analysed with the image correlation software
7D in order to calculate ad hoc measurements of displacements and strain
fields. To check the validity of the results, measurements were compared to
those obtained by classical extensometry. We found that, despite the low levels
of strains, results of identifications from optical extensometry were very
promising.
