Unconstrained shape recovery

The CTH approach is able to control the crack width, which can be closed by controlling the compression pre-strain level. A simple equation has been established by Li et al. [54] to correlate the crack width to be closed and the pre-strain level during compression programming. Cracks with different opening widths can be closed based on the level of compression programming (of course it is limited by the maximum allowed compression pre-strain level). In the unconstrained shape recovery approach such as the SMASH approach, it has not been demonstrated that it can close a wide-opened crack with constrained boundary. Also, it cannot control the crack width that can be closed because it depends on the external load to perform programming and relies on the shape recovery ratio and boundary condition of specimens to perform crack closing. 

Once the specimens were programmed, an unconstrained free shape recovery test was implemented, where the eompressed SMP specimen was heated to Thigh = 79 °C at an average heating rate of = 0.82 °C/min. The same LVDT system as given in Reference [41] was used to... 

C.M. Yakacki, R. Shandas, C. I anning, B. Rech, A. Eckstein, K. Gall, Unconstrained recovery characterization of shape-memory polymer networks for cardiovascular appheations. Biomaterials 28 (2007) 2255. 

Yakacki, C.M., Shandas, R., Lanning, C., Rech, B., Eckstein, A., and Gall, K. (2007) Unconstrained recovery characterization of shape-memory polymer networks for cardiovascular applications. Biomaterials, 28, 2255-2263. 

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