Effect of the Hole on the Tensile Fatigue Properties of CFRP Laminates

Abstract The current study assessed the effect of a bolt hole on tensile fatigue properties of CFRP laminates. Two specimens, i.e. [(0/90)3]S, [(0/45/90/–45)2]S, were analyzed using a finite element method and were experimentally tested for cases, both with and without a hole, whose diameter corresponded to 0.12 times the specimen width. Delamination positions predicted by a 3-dimensional static finite element analysis were matched well to those observed by an ultrasonic imaging system in the middle of fatigue test. A hole whose diameter corresponds to 0.12 times the specimen width caused the fatigue strength to decrease by 9% and 11% under 5 Hz loading frequency, and by 22% and 25% under 10 Hz loading frequency for [(0/90)3]S and [(0/45/90/–45)2]S, respectively. Because the decrease in sectional area due to the hole was normalized in calculation of the tensile strength, a stress concentration around the hole is believed to induce the strength degradation of fatigue specimens. From the finite element analyses, the stress concentration factor around a hole was expected as 8.8 and 9.5 for [(0/90)3]S and [(0/45/90/–45)2]S, respectively. Keywords: CFRP (CARBON FIBER REINFORCED PLASTIC)FATIGUESTRENGTHBOLT HOLEFINITE ELEMENT ANALYSISINFRARED IMAGING SYSTEM