Uniaxial Fatigue Tests on Polyamide Reinforced with Short Glass Fibre

In the automotive sector, composite materials are gaining greater interest, in particular for application to car body components, thanks to their lightweight potential, which can lead to significant fuel consumption reduction and performance enhancement. In order to be suitable for automotive applications, fatigue properties have to be carefully investigated to properly design structural components. Having in mind the automotive application, a particular composite material, a polyamide reinforced with 18%wt short glass fibres, has been considered. Uniaxial fatigue tensile tests with load ratio R = 0.1 were carried out on flat specimens made of the selected material. The experimental tests were performed using a hydraulic fatigue testing machine, in stress-controlled mode, with a loading frequency in the range of 0.5–3 Hz depending on the stress amplitude. P-S-N curves and endurance limit were determined according to the ISO standard 12107. Moreover, an innovative approach based on the Maximum Likelihood Principle (MLP) was used to estimate the P-S-N curves as well as the endurance limit. Obtained results showed that the estimation made with the MLP, reduces the total time of the test campaign and data fitting is more effective. Moreover, the material tested exhibits interesting properties for automotive applications.