| Aviation materials are the basic guarantee for the continuous improvement and development of aircraft performance.With the continuous development of hypersonic aircraft in China among which adhesives play an important role,the requirements for the extreme environmental resistance of aviation materials are also continuously improved.Phosphate adhesives have excellent adhesion properties and can be used in the temperature range from-183? to 2900?.They have been widely used in high-temperature adhesion,static sealing and dynamic sealing of hypersonic and reusable aircrafts.However,due to the harsh curing conditions of phosphate adhesive and the parameter mismatch during bonding,its application is limited in large high-temperature bonding structures such as aerospace and ships.Therefore,aiming at finding effective means to improve the curing efficiency,thermal performance and bonding performance of adhesives,this paper studies the mechanical behavior of high-temperature-resistant phosphate adhesives through curing parameters and load environment.At the same time,the thermal mismatch of high temperature bonding was studied to reveal the mechanism of the influence of residual stress on the properties of high temperature bongding.Based on the preparation technology of high temperature phosphate adhesives,the toughening modification method of phosphate adhesives and the modification of curing agents including nano-CuO,nano-TiO2 and nano-AlN was studied firstly.The phenolic resin toughening modification of phosphate resins was carried out.Then the micro-structure,thermal and mechanical behavior of phosphate adhesives prepared after toughening modification were assessed.In order to study the mechanical behavior of phosphate adhesives before and after toughening modification,the tensile shear strength,microstructure and thermal properties of phosphate adhesives at different temperatures were analyzed.The ratio of phosphate resin to curing agent was studied,and the reasonable amount of curing promoter was optimized.The formulation optimization of ultra-high temperature phosphate adhesive was explored,and its shear strength was tested and analyzed in high temperature environment or heat treatment at ultra-high temperature.In this paper,in order to characterize the residual stresses in the bonded joints,the residual stresses of phosphate adhesive bonded silicon carbide single lap joints were measured and analyzed by micro-Raman spectroscopy combined with Raman imaging and energy fluorescence spectroscopy,and the relationship between Raman frequency shift and the residual stresses in the single lap joints was analyzed.At the same time,in order to study the thermal match of high temperature bonding,6 kinds of curing temperature schemes are designed.Then the residual stress distribution of single lap joint specimens is analyzed through combining experiment with finite element method.In order to evaluate the high temperature bonding performance of adhesives conveniently,the concept of engineering residual stress was put forward and analyzed with the shear strength of bonded joints.The relationship between residual stress and bonding strength was given,thus the mechanism of thermal matching and bonding strength was revealed. |
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