In this paper, we demonstrate a fabrication method for ordered self-assembly using pre-programmed shape memory
polymer (SMP) as the substrate in an organic-inorganic bi-layer structure. By heating the hybrid structure above the
SMP's shape recovery temperature, the substrate expands because of positive CTE in one direction, while in the
perpendicular direction it shrinks due to shape memory effect overpowering thermal expansion. Consequently, the thin
film is subjected to an orthogonal compression-tension stress field and forms unidirectional wavy patterns. We further
validate our conceptual design by adjusting the strain level of pre-programmed SMP substrates. The present study is
expected to offer a convenient and simple path of fabricating unidirectional wavy patterns. Moreover, selective growth
and ordering of patterns can become possible.
In this paper, the influence of disbonds on Lamb wave propagation in GLARE composites is described. Guided Lamb
waves were launched and detected with Polyvinylidene Fluoride (PVDF) comb transducers. Disbond defects were
introduced with ball drop test to study their influence on the Lamb wave signals. The amplitudes of the detected Lamb
wave signals show distinct differences with and without disbonds, which can be used to monitor the disbond growth. In
addition, a thermal imaging technique was applied to inspect the disbond region so as to cross-correlate the disbond size
with its influence on the Lamb wave signals measured by the PVDF sensors. It is demonstrated that the amplitudes of the Ao mode Lamb wave decrease exponentially with increasing disbond size.
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