The purpose of this research is to examine the effect that high strain rates have on carbon nanotube impregnated epoxy resins, as well as to characterize the material properties of the composites. The main goals of the research are outlined here: describe the effects of applying high strain rates to epoxy impregnated with MWCNTs, determine the strain rate sensitivity of the specimens by comparing values from quasi-static and dynamic loading tests, find properties of specimens through quantitative and qualitative analysis of the specimens before and after testing. High strain rate testing is important when a material can withstand high-speed impacts or impulses. To investigate the strain rate sensitivity of the composites, a Split Hopkinson Pressure Bar (SHPB) will be used. This machine is able to apply high rates to specimen’s using a compressed air gas gun. The SHPB is made of two main bars to transmit the strain wave through the specimen, the incident and transmission bar. Specimens mounted onto the SHPB are placed between the incident and transmission bars with Petrolatum to ensure that they are allowed to expand freely. The data from the two strain gauge rosettes mounted on the incident and transmission bars is then collected by a computer and run through a Matlab code which outputs the stress vs strain curves, average and max strain rate applied, strain vs time, strain rate vs time, etc. To compare this data to quasi-static loading conditions a nanoindenter is used. A nanoindenter allows for precise measurement of the hardness and reduced modulus at the nanoscale. To ensure consistent and repeatable results the specimens the top 0.5 mm was polished off the specimens. This polishing allowed the inner material of the specimen to be tested which did not contain any of the defects or impurities on the surface. It was found that the composites tested were strain rate sensitive but not in an expected manner. The Young’s modulus of the specimens decreased with strain rate which is opposite of what was expected. The quasi-static results for Young’s modulus were 6 GPa while Young’s modulus found on the Split Hopkinson Bar was 4.4 G Pa. To further study this behavior more tests will have to be performed in a lower range of strain rates using dynamic mechanical analysis (DMA). Due to the manufacturing process, it is suspected that the bonding between the MWCNTs and the epoxy is only mechanical and not a chemical, thus allowing the formation of multiple cracks are reducing the structural integrity of the composite under impact loads. This theory will be confirmed by fracture surface microscopic analysis through scanning electron microscopy (SEM) before the conference.


Mechanical Coupling of Mwcnt/epoxy Interfaces Subjected to High Strain Rate Effects

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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