Influence of uniaxial compression on the shape memory behavior of vitrimer composite embedded with tension-programmed unidirectional shape memory polymer fibers

Tension programmed shape memory polymer (SMP) fibers have been used as sutures for closing wide-opened cracks per the close-then-heal strategy. However, the composite may be subjected to compression loading during service. These compression loads can reduce the amount of recoverable strain in these pre-tensioned fibers, limiting their ability to close cracks. The purpose of this study is to investigate the effect of in-service compression loading on the shape memory effect (SME) of composites consisting of SMP fiber and SMP matrix. To this end, pre-stretched shape memory Polyethylene Terephthalate (PET) fibers were embedded into a shape memory vitrimer to obtain composite samples with different fiber volume fractions. The SME of both the PET fiber and the vitrimer was investigated. The effect of compression load on the SME of the composite was studied. It is found that, uniaxial compression on the composite along the fiber direction significantly reduced the shrinking ability of the embedded pre-tensioned SMP fibers. Hence, this is a factor that needs to be considered when designing such types of self-healing composites.