Study On Preparation And Service Behavior Of Buckypaper Composites

Buckypaper is a three-dimensional network structure film formed by the van der Waals force between carbon nanotubes overlapping each other.And it is a typical mesoporous material that has an excellent infiltration property with high performance resin matrix,which can be integrated with composite material and prepared into a multifunctional structural composite material with stealth,flame retardant and self-sensing.However,the application environment of composite materials has a great impact on the life of materials.The hygrothermal environment is the most common one.It is easy to cause structural parts deformation and damage,because of the complex forming process and the load change of composite materials in service.In this paper,the wet and heat aging behavior of buckypaper composites was studied systematically,based on the on-line monitoring of the curing process,deformation behavior and service behavior of typical structural parts of by buckypaper sensors.The preparation process of buckypaper composite was presented,and the buckypaper was prepared by vacuum filtration method firstly.Then the molding forming process was used to fabricate the composite laminates.And no buckypaper,single side buckypaper and double side buckypaper composite laminates were prepared respectively.The solidification behavior of composites was monitored by buckypaper sensor.The change information of physical parameters,such as the lowest viscosity temperature and gel temperature of resin curing was obtained.The relationship between resin curing behavior and resistance of buckypaper sensor was analyzed,which provided technical support for optimizing the curing process of composite materials.At the same time,it is proved that buckypaper has high stability and high application prospect in curing behavior monitoring of composite materials.The method to improve the moisture and heat resistance of the composite materials was proposed,through coverd the surface of the composites with buckypaper.the hygroscopic behavior of no buckypaper,single sided buckypaper and double sided buckypaper composite materials was studied by accelerated aging method.The influences of moisture and heat time and moisture absorption rate on interlaminar shear strength,bending strength and glass transition temperature of composite were analyzed,based on the mathematical modelestablished to describe the hygroscopicity of composite materials.Finally,the fracture morphology of the composite was analyzed by scanning electron microscope(SEM).The results show that the hygroscopicity of the three kinds of buckypaper composites does not change significantly and conforms to Fick's second law at the early stage of heat and humidity.The saturated moisture absorption rate and moisture absorption rate of the composites coverd with buckyaper decreased by 7.6% and 8.5%,respectively.And after hygroscopic saturation,the interlayer strength,bending strength and glass transition temperature were increased by9.5%,7.3% and 9.2%,respectively.The improvement of moisture and heat properties of composites is obvious.Composite materials embedded in buckypaper sensors at different positions were prepared and tensile and bending tests were carried out for loading and unloading.The change law of resistance rate of buckypaper with time was revealed in the process of stretching and bending of composite material.The strain sensing coefficient of buckypaper sensor was obtained by fitting method,and the synergism of composite materials during deformation is clarified.The tensile and bending tests of the composite material show that the resistance change of buckypaper sensor is related to the phase state of resin matrix in the composite material.The buckypaper sensor can monitor different deformation forms and degrees effectively in different interface layers.And it has unique technical advantages in the field of real-time monitoring of composite deformation.Through integrated preparation of the developed buckypaper sensor with typical composite structural parts,the impact,fatigue and other multi-mode static/dynamic mechanical tests and monitoring on the structural parts were completed.The buckypaper sensor has excellent response characteristics under different impact energy.The influence mechanism of damage evolution on microstructure and resistance of buckypaper sensor was analyzed.The reliability of buckypaper sensor for damage localization and evaluation when the cylinder is impacted can be analyzed qualitatively.The pressure cycle test of composite pressure vessel shows that the buckypaper sensor has excellent linearity and following ability under different pressure and frequency.Composite material design life is 3000 times,and the results of 3000 cycles of pressurization and pressure relief tests show that the buckypaper sensor has stable pressure monitoring capability in the whole life stage.