Synthetic aliphatic polyamide 6, or PA 6, exhibits high strength, wear, chemical, and heat resistance,&nbsp;excels&nbsp;in uncommon areas for most polymers; this makes it ideal for engine parts, bearings, wearable, and solid-state electronics. Due to its versatility and capability to be enhanced with second phase inclusions, this material is of great interest and demand in engineering. In this research high strain rate impact testing of polyamides PA6 &nbsp;with different inclusions and processes is performed to assess the material response to increasing impact loads. Polyamides are used in mechanical and tribological applications in industry, including automotive, electronics where crashworthiness under high strain rates is sought. Here, strain-rate dependent, thermoplastic, cast PA6 variants of PA6 are investigated to evaluate their response. Testing groups are divided into four categories depending on their inclusions and process: no inclusions, heat stabilized with no inclusions, oil &amp; Molybdenum disulfide (MoS2), and glass fiber/solid lubricant. Five samples of each testing group are tested in dynamic compression using Split Hopkinson Pressure Bar (SHPB). Each testing group is evaluated at pressures of 100, 110, 120, 140, and 160 Psi producing strain rates varying from 1500-2500 s-1. Microscopic imagery is taken to evaluate crack formation in samples and sample deformation. Computational analysis is performed to obtain material properties such as dynamic modulus and stress-strain behavior from SHPB tests. The test groups were evaluated based on their average dynamic modulus at the same pressure range. All PA6 specimens except for the glass fiber/solid lubricant presented increase in dynamic modulus with an increase in strain rate. &nbsp;The glass fiber/solid lubricant demonstrated a decreasing trend in dynamic modulus after strain rates of 1800 s-1. The heat stabilized &nbsp;PA6 presented high dynamic modulus results at lower strains than the other materials. For the 100 psi tests, the heat stabilized &nbsp;PA6 exhibited the highest average dynamic modulus, 2.66 GPa at 1604 s-1and the PA6 with no inclusions displayed the highest dynamic modulus value, 2.94 GPa at 1641 s-1. For the 110 psi tests, the PA6 no inclusions exhibited the highest value of dynamic modulus 3.03 GPA, and the highest average value at 2.97 GPA out of the calculated averages of dynamic modulus at this pressure. For the 120, 140 tests, the heat stabilized PA6 presented the highest results and lowest strains with values of 3.33 GPa at 1792 s-1 and 3.02 GPa at 1918 s-1, respectively. Multiple side and edge cracks were developed from the specimens starting from the 120 psi tests; however, shattering of specimens was not experienced until above 2300 strain rates were achieved. At first, the edge cracks are formed, then side cracks that span from one face to face of the specimen develops, and lastly, at higher strain rates, the specimen shatters completely. Out of the test groups, the molybdenum-filled PA6 was the first to experience shattering at 160 psi and 2354 s-1; however, the other specimen types experienced only edge cracks. It is concluded that tested specimens experienced hardening trends at higher testing pressures and strain rates, while all, except for the glass fiber/ solid lubricant-filled PA6s, experienced an increase in dynamic modulus. A computational analysis is underway to establish the effect of heat stabilization and lubricant inclusions in PA6 strain rate-dependent mechanical response.

Effect of Heat Stabilization and Solid Lubricants on High Strain Rate Response of Polyamide 6

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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