Study On The Fracture Failure And Synergetic Icephobic Mechanisms Of The CNTs/GNPs Modified Polymer Materials

Polymer-matrix composite materials had been applied in some critical engineering fields about aerospace,transportation due to their excellent specific strength,modulus,and designability,which were served widely in various production activities of human beings.However,the fracture failure of the composite component was often caused in practical engineering applications due to the complexity of loading and structure.Especially under strong and dynamic loadings such as explosion and impact,the mechanical responses of the composite are significantly different from that under quasi-static loading.The inertia effect of stress waves also makes the dynamic fracture process more complicated than the quasi-static fracture.Hence,it is of great significance and engineering value to study the mechanical failure behavior of composites under different loading conditions.In the meantime,the composite materials served in the alpine-cold region such as north pole would also suffer from the problem of surface icing.If the ice accumulation cannot be effectively removed,the service function of the composite materials might be affected adversely.While enhancing the mechanical properties,carbon nanoparticles can also endow the as-prepared composite materials with excellent multifunctional characteristics,which provide conveniences for the composite materials to solve icing problems and realize the overall design of structure and function.Therefore,in this thesis,different types of carbon nanoparticles are studied to improve the fracture failure behavior and overcome the icing problem of polymer-matrix composite,in order to find an effective method to prevent the fast crack propagation within the composite materials and to explore the method of composite materials solving the icing problem by its functional characteristics.As a result,the main contents of this thesis include the following aspects:（1）The surfactant treatment of Triton^TM X-100 constructed a novel 3-D hybrid reinforcement system about the CNT@X+GNPs filler through the physical modification method in the composite materials.Subsequently,the mechanical failure behavior of single-phase and hybrid-phase filled composite systems with and without physical modification were characterized under different loading conditions.The relationships between the types,contents,interfacial properties of multi-scale nanoparticles and the macro-mechanical properties of composite materials were established,and the collaborative toughening mechanisms,as well as the general design principles about the novel 3-D hybrid reinforcement system in composite materials,were also revealed.（2）Two-dimension Digital Image Correlation（2-D DIC）technology together with high-speed photography was used to investigate the dynamic fracture properties of above composite specimens with and without physical modification,evaluating the pre-crack growth history,and extracting mode-I and-II dynamic stress intensity factor histories from the orthogonal displacement fields near the real-time crack tip.The research results verified that the mode-I dynamic fracture initiation toughness of the T@X+G/EP＿7/3 composite specimen increased by more than 200%compared with the neat epoxy matrix,the pre-crack initiation time was delayed by 120%,and the steady crack-tip velocity was also decreased by 179%.（3）The failure mechanisms of multi-scale nanoparticles in the epoxy matrix were revealed by the micromorphology analysis:（I）1-D CNTs were pulled out;（II）1-D CNT@X has two failure modes:instantaneous fracture or pulled out first and then fracture;（III）2-D GNPs can cause the crack tip to deflect or the interlayer failure;（IV）the novel 3-D hybrid reinforcement system will lead to a large range of shear deformation of the matrix,which can consume a lot of fracture energy.（4）The paper further investigated the active de-icing properties of the CNTs/EP和CNTs/PMIA composite materials about interfering with the adhesive stability of the ice-solid interface based on the electro-thermal behavior,analyzed the internal relationships between the electro-thermal response,surface temperature distribution and applied voltage,and focused on the effect rule of electro-thermal behavior on the adhesive strength and slide time of ice.（5）By constructing the biomimetic micro-column structure on the SCNTs/PDMS composite surface,it was investigated that the three-line synergetic icephobic abilities of pre-icing,icing,post-icing stages.Subsequently,the phase transition process of the water droplets on the composite surfaces with different wettability was quantitatively analyzed,and the synergetic icephobic mechanisms based on the electro-thermal behavior and the bionic surface was revealed,which provides a new idea for composite materials to realize the integrated design of active and passive icephobic function.