Enhanced Fatigue Performance of a Polymer Nanocomposite under Spectrum Loads

Abstract

Abstract A thermosetting epoxy polymer was modified by incorporating 10 wt. % of silica nanoparticles, which were well dispersed in the polymer. Two different glass-fiber-reinforced plastic (GFRP) composite laminates were prepared to give: (1) a GFRP composite with an unmodified epoxy matrix (GFRP neat), and (2) a GFRP composite with a silica-nanoparticle-modified epoxy matrix (GFRP nano). Fatigue tests were undertaken employing a standard wind-turbine spectrum-load sequence, WISPERX. The fatigue life of the GFRP nanocomposite was about four times longer than that of the GFRP neat composite. This was reflected in (1) the development of matrix cracking, and (2) the rate of degradation of the stiffness of the composite, both being more severe in the GFRP neat composite, compared to the GFRP nanocomposite. The underlying mechanisms for the observed improvement in the spectrum fatigue life of the GFRP nanocomposite are discussed. Further, constant amplitude fatigue tests were conducted at various stress ratios. Using the static and fatigue data, constant life diagrams (CLD) were constructed. The spectrum fatigue life was then predicted following a standard procedure using the CLD. Very good correlation was observed between the predicted and experimental fatigue life for both GFRP neat and GFRP nanocomposites.