Numerical simulation of pre-cracked thin aluminum alloy skin repaired with a FRP patch: Pre-crack length studies

The fatigue life of a thin pre-cracked aluminium-alloy panel, repaired with Carbon Fiber Reinforced Plastics (CFRP) patch on one side, is investigated using a numerical model. CFRP plies of different lengths are used to form patch which in turn repair pre-cracked aluminium skin. Numerical studies are performed to determine variation in stress intensity factor (SIF) range and bulging out deflection of specimen subjected to minimum and maximum fatigue load. Patch width to pre-crack and length to pre-crack ratio are kept constant for different pre-crack studies. Numerical simulations are carried out for three different pre-crack length. Three different patch configurations are studied for each pre-crack length. Maximum stress considered is at 50 % yield strength of aluminium skin. The numerical model is simulated by using ANSYS 15.0, a Finite Element Analysis package. The interface behaviour between the skin and the patch is simulated by using cohesive zone material model (CZM). Stress intensity factor (SIF) is determined from J-integral results. Relation between SIF range and crack length can be used to determine fatigue crack propagation by invoking the Paris law. It is found that with increasing the patch length, ΔKI decreased significantly which may result into the increase of the fatigue life.