(255f) Early Damage Detection in Epoxy Matrices Via a Dimeric Anthracene Mechanophore

Catastrophic damage in materials, whether it
be in an aerospace, mechanical, or consumer application, often occurs suddenly
and without warning, resulting in loss of mechanical properties, complete functionality,
or even loss of life. Thus, the ability to observe and quantify the amount of
damage sustained by a material before ultimate failure is quite desirable in
these applications. We have completed the synthesis, characterization, and
validation of multiple mechanophores, which are compounds possessing mechanically
sensitive chemical moieties that act as sensors for applied stress or strain. In
particular, we have employed cyclooctane-based mechanophores, created by the
dimerization of anthracene moieties with UV light, to detect damage in epoxy
matrix composites. For the dimeric anthracene mechanophore studied, when damage
is applied and cracks are formed, there is spontaneous bond cleavage in the
cyclooctane rings, resulting in an observable fluorescent signal via the recovery
of the monomeric structure. The utilization of the anthracene chemistry
features a number of advantages compared to other fluorescent mechanophores, including
an increase in quantum fluorescence yield, damage detection deep within the
matrix, and, most notably, early damage precursor detection before the yield
point in compression tests. Overall, the application of this self-sensing
mechanophore into epoxy polymer matrix composites has been successful.