Suppression of Delamination Crack Propagation in Laminated Composites by Using Thin SMA Plates

The use of thin actuator plates bonded to surfaces of laminated composites to suppress the growth of delamination cracks is investigated.A composite beam analysis was performed to estimate the effect of actuation strains on the strain energy release rate of delamination cracks.When compared at the same value of actuation strain, the increase in the apparent crack growth resistance is larger for smaller FRP thickness and for smaller value of the critical strain energy release rate of FRP without actuators, Gcr, under both mode I and II loadings.Mode I delamination suppression tests of unidirectional CFRP laminates were conducted by using thin SMA actuators.The value of the apparent crack growth resistance, Giapp, under actuation strains of about 0.1% was 2.5 times larger than fracture toughness of CFRP and was also about 1.5 times as large as that just before actuation.