Experimental Study on Static Strength and Fatigue of CNT-Modified CFRP Laminates

In this paper, an experimental study on the static strength and fatigue of carbon fiber-reinforced polymer (CFRP) laminates with ply angles of 0°, ±15° and ±45° and single-walled carbon nanotubes (SWCNTs) of 3% mass fraction in epoxy matrix has been presented to systematically demonstrate the SWCNT-modified effect on the static tensile properties and fatigue behavior of the CFRP laminates. The results of pseudo-static tensile tests show that the addition of SWCNTs increases the tensile strength of the three laminates by 37%, 43%, and 34%, respectively, and the elastic modulus by 5%, 62%, and 35%, respectively. The S-N curves obtained by the fatigue tests at various stress levels under graded tension–tension cyclic loads demonstrate that the SWCNT-modified laminates sustain higher stress levels than those without SWCNTs at the same fatigue cycles, and with the most obvious improvement of ±15° laminates. The fracture surface observations of the laminates indicate that the enhanced performance is attributed to the synergistic effects of matrix modification, interfacial bonding improvement and crack bridging by SWCNTs. Therefore, moderate addition of SWCNTs in the epoxy matrix of CFRP laminates is an effective approach for improving both the static strength and fatigue performance of the laminates.