Crosslinked polymers play an important role in structural applications as adhesives. Due to their  
considerable advantages over other assembly methods (e.g. reduction in weight and stress  
concentration), their usage in different industries are becoming widespread, including aerospace,  
automotive and offshore equipment. Furthermore, structural adhesive must often endure detrimental  
conditions over long periods during its service life (e.g. cyclic loads, high temperature, etc.). These  
conditions lead to degradation and reduction of mechanical properties. Therefore, in-depth study of  
such effects seems necessary. In this article, we performed an experimental study to understand the  
effects of this high temperature i.e. thermo-oxidative aging on the mechanical behavior of polymers.  
Subsequently, the constitutive behavior, i.e. stress-strain relation of these adhesives before and after  
the accelerated aging tests were studied on samples aged at different levels of temperature and  
different time durations at zero humidity. The aging conditions and periods selected for the tests have  
been specifically designed to simulate the effects of aging under the working environmental conditions  
that the materials will be subjected to in their standard applications. The focus of this study is on the  
investigation of the effects of aging on the polymeric adhesived used in automotive applications.  
Consequently, four different polymeric adhesives (one silicon based, two polyurethane based and one  
acrylic type) has been chosen that are being used extensively in these applications. The quasi-static  
tensile loading was used on these four adhesives and the changes in the constitutive behavior was  
measured. During this investigation, cyclic test has been done to measure inelastic behavior of  
elastomeric materials, such as Mullins effect, permanent set and hysteresis. The failure tensile tests as  
well as the cyclic tensile tests were performed in our lab using a Test-Resources tensile testing machine.  
The temperatures that were used in this work are 60, 80 and 95°C for varying aging periods of 24hrs,  
240hrs and finally 720hrs. Then, all the data was collected and consequently analyzed, and the resulting  
behavior was compared to that of the unaged material, showing varying results depending on material,  
temperature and aging period. Different behaviors have been observed after aging. The polymers  
behavior were expanding from no effect to significant damage caused by aging conditions. To further  
understand the micro-structure of the phenomenon, we performed chemical tests such as differential  
scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), and cross-linking density  
test (CLD). This work provides the core understanding required for modeling the material behavior  
during aging and lay down the groundwork for further data-infused model free approaches.


Thermo-Oxidation Analysis of Structural Adhesives: An Experimental Study

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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