2524-T3 aluminum alloy CFRP patches CP Ti Technology: general issues alloy 625 aluminum hand-hole artificial neural network corrosion crack branching behavior crack front shape crack growth rate crack propagation crack propagation path crack retardation design S-N curve environmentally assisted cracking failure analysis fatigue fatigue crack growth fatigue crack propagation fatigue test fatigue variability fish eye fractography fracture fracture toughness galvanic protection high cycle fatigue high strength steel high-entropy alloy