Fatigue crack growth of SLS polyamide 12: Effect of reinforcement and temperature

The evaluation of the fatigue crack propagation at room and low temperature of neat polyamide 12 and its composite reinforced with short fibers processed by selective laser sintering (SLS) has been carried out. The linear fracture mechanics approach was successfully applied. The crack growth rate curves obeyed the Paris law, and their parameters were determined. It was found that at −50 °C fiber reinforcement improves the fatigue resistance of SLS polyamide 12 significantly while at room temperature similar fatigue behavior between the pure polyamide and the composite is observed. The polyamides microstructure and fracture surfaces obtained from the fatigues tests were analyzed using SEM. The differences in fracture micromechanisms at room and low temperatures in the PA12 composite were attributed to the different thermal expansion coefficients of the fibers as well as the crystalline and amorphous regions of the granular structure of the matrix.