Fatigue life predictions in polymer particle composites

Abstract

This paper presents a study on fatigue life predictions in three polymer particle composites with different volume fractions of filler and different particle sizes. Central hole notched specimens were analysed using a fracture mechanics approach. A solution for the stress intensity factor of corner cracks at a hole was obtained using the finite element method and considering quarter-circular and quarter-elliptical cracks of different sizes. The solution was compared with a literature solution and significant differences were found. Fatigue crack propagation tests were performed at room temperature and constant loading amplitude, for stress ratios R=0 and R=-0.75. Finally, fatigue lives, crack shape evolution and final crack length were predicted assuming an initial crack size and considering that the crack maintains a quarter-elliptical shape. The comparison with experimental fatigue lives indicated the presence of initial defects larger than the silica particles; however, these large sizes can be explained by the residual stresses measured near the hole.