Study On The Properties And Applications Of Shape Memory Epoxy(SMEP) And Its Composites

As a new type of smart material,shape memory epoxy(SMEP)has excellent mechanical properties compared with thermoplastic shape memory material;however,insufficient recovery force,narrow performance tuning range,simple shape memory effect and deformation structure limit the development and practical application of SMEP.In this dissertation,SMEP and its composites with high performance and application value are systematically studied.Epoxy matrix materials were carefully selected and designed,nano/micro composites were prepared,and multiple shape memory effects of 2D/3D structures were implemented.The carried-out research and results are as follows:(1)SMEP materials with high recovery force and wide tuning range of performance were designed and prepared.According to the mechanism of shape memory effect,curing degree and adjustable range of the system are the key to achieve excellent shape memory effect and performance regulation.Shape memory switch temperature and recovery force of SMEP cured with anhydride can be adjusted in a wide range of 65-140 ~oC and 3-24 MPa,by changing the composition and analyzing curing kinetics,which is better than that of other reported curing systems.(2)SMEP composites with superior mechanical properties were fabricated.Smart behavior of shape memory polymers is realized in response to temperature change.This process is accompanied by a sharp drop in mechanical properties and the resultant low modulus makes materials lose their practical value.The SMEP composites with good filler dispersion and interfacial properties were prepared by adding carbon nanotube(CNT)and carbon fiber(CF),and the mechanical stiffness was improved by 1-3 orders of magnitude.The results show that CNT exhibits"slip-fracture"behavior in the matrix,which prolongs the fracture process of the matrix and strengthens and toughens the composite above the switch temperature.The crack propagation path is blocked by the CF with appropriate aspect ratio which lead to improvement in the mechanical properties.(3)Design and preparation of SMEP with multiple shape memory effects and complex structure.SMEP is criticized for its small recovery strain,simple material structure and non-sophisticated SME.Through novel fabrication methods including splicing of materials with wide switch temperature range,design of casting mold and preparation of 3D printable inks,the structure with quadruple shape memory effects that can grasp and fasten object,the spring structure with high strength and large deformation to drive high temperature alarm device,as well as the 4D complex structure with filler orientation and excellent shape memory effect were achieved.These examples represent breakthrough in design and processing technology of SMEP.Moreover,the relationship between the structure and property of SMEP was studied under the philosophy of structural design-material construction-performance characterization-applicational exploration.