Evaluating Shear Creep Behavior Of Ceramic Adhesive Layer Based On The Cross-bonded Method

Ceramics have excellent properties such as high strength,high temperature resistance,corrosion resistance,and wear resistance,and play an important role in aerospace,architecture,medicine and many other fields.In engineering applications,a single ceramic often needs to be used after bonding with other materials,and it is easy to withstand shear stress for a long time during service,resulting in shear creep.The creep of ceramic is usually very small,and the creep mainly comes from the adhesive layer.Long term creep will lead to interface bonding failure,resulting in components falling off,and bring security risks to the whole system.In order to improve the safety of bonded structure,it is necessary to characterize the shear creep behavior of ceramic adhesive layer.Commonly used shear creep test methods are single lap method and double-notched method.However,the single lap method has peeling stress on the bonding surface of the sample,which will cause test errors;the double-notched method is only suitable for composite material testing,and sample preparation is difficult.In this paper,testing the shear creep behavior of ceramic adhesive layer by cross-bonded method was proposed.Supporting fixtures were designed to fix cross-bonded samples of different sizes,avoiding errors due to rotation and deformation of the samples,and improving the accuracy and simplicity of the test.The shear creep behavior of two types of ceramic adhesive layer composed of rigid epoxy resin adhesive and flexible silicone structural adhesive were tested at room temperature.The creep curves under different stress levels at 20-30℃ were obtained.The time-hardening model and Burgers model were selected to fit the creep curves,and the coefficients of determination were all above 0.95,which quantitatively described the shear creep of behavior of the adhesive layer.According to the creep curves obtained,it was predicted that it will take about 184 days and 3680 days for the silicone structural adhesive to produce 1 mm shear creep displacement under the stress levels of 0.2 N/mm~2 and 0.01 N/mm~2,respectively.The results showed that the shear creep rate of the ceramic adhesive layer increases with the increase of temperature and stress level.The shear creep behavior of the epoxy resin adhesive layer conforms to the time-hardening model,while the shear creep behavior of the silicone structural adhesive layer conforms to the Burgers model.The cross-bonded method was used to test the shear creep of the ceramic adhesive layer composed of silicate high-temperature adhesive at high temperature,and the shear creep curves of the samples at 600℃,700℃ and 800℃ were obtained respectively.The time-hardening model was used to fit the creep curves,and the coefficients of determination were all above 0.95.By comparing the difference in the creep behavior of the adhesive layer at different temperatures,combined with SEM morphology,element analysis and XRD phase analysis,the reason for the change in the high temperature creep properties of the adhesive layer were explained.The results showed that the shear creep rate of silicate high-temperature adhesive increases with increasing temperature.At high temperatures,the glass phase in the high-temperature adhesive softens.Between 700-800℃,the crystal phase in the high-temperature adhesive undergoes a crystal structure transformation.The shear creep mechanical properties of the ceramic adhesive layer at room temperature and high temperature environment can be evaluated accurately by the cross-bonded method,and the life prediction of in service bonding component can also be realized.Therefore the cross-bonded method shear creep test can guide engineering practice and has important practical value.