  One of the challenges in the widespread use of biocomposites for engineering
applications is the influence of environmental conditions on their mechanical
properties, particularly for a combination of aging factors such as
temperature, moisture, and mechanical stresses. Thus, the purpose of this paper
is to study the influence of coupled aging factors by focusing on a 100%
bio-based and biodegradable composites made of flax/poly(lactic acid) with
several fiber contents. The development of a specific testing setup enabled
continuous in-situ measurements and allowed comparing the effects of combined
aging factors to those of uncombined aging factors. It was confirmed that the
aging temperature in wet conditions led to a loss of elastic properties,
especially for higher fiber fractions. While creep tests in dry conditions
resulted in little decrease of elastic properties, it was observed that
mechanical loading of the materials combined with water immersion resulted in a
strong synergistic effect on the loss of stiffness. Finally, the presence of
fibers reduced environmental stress cracking mechanisms and increased the time
to failure.
