Shape memory hybrids : mechanism and design for tailored properties

The concept of shape memory hybrid (SMH) is proposed. The underlying mechanism and performance are investigated. The flexibility and versatile in design and fabrication of SMHs with tailored properties are demonstrated in a silicone based system. All types of shape memory phenomena, namely dual-shape memory effect (SME), triple-SME, and mechanical two-way SME, which are most likely found separately in some individual existing shape memory materials (SMMs), but not all in one material, are reproduced in SMHs made of silicone-paraffin wax (S-PW). The underlying mechanisms behind all these phenomena are revealed in details. In addition, the performance of S-PW SMHs is systematically characterized. Multiple-stimuli-responsive SME is achieved in a silicone-sodium acetate trihydrate (S-SAT) SMH, which is not only thermo-responsive and water-responsive, but also pressure-responsive. The last shape memory feature has never been realized in any existing SMMs. Beside the ability for mechanical two-way actuation, shape fixation of S-SAT SMHs can also be quickly achieved by means of tapping. Silicone and melting glue (S-MG) SMHs developed here are not only rubber-like at both high and low temperatures, but also have excellent SME and repeated instant self-healing function. It is proved that while micro sized MG inclusions play a part in the SME, tangled molecular chains of MG (and silicone) contribute to the rubber-like phenomenon and repeated instant self-healing function. Based on the working principle of SMHs, electrically conductive SMHs which are suitable for joule heating and with over-heating protection function, SMHs with a narrow transition temperature range (within 4.5oC), impact-responsive SMHs, high temperature SMHs, and heating/cooling-responsive SMHs are developed. This project presents a systematic study in design, fabrication and characterization of SMHs with tailored properties and features.DOCTOR OF PHILOSOPHY (MAE