Environmentally assisted cracking behaviour of Al–Zn–Mg–Cu–Cr alloy bonded with polymer matrix composite stiffener

Abstract Studies were conducted to investigate the effect of polymer matrix composite stiffener (patch) on environmentally assisted cracking (EAC) susceptibility of pre-cracked alclad Al–Zn–Mg–Cu–Cr alloy in 3.5 wt.% NaCl environment. The EAC threshold stress intensity of the peak and two-step aged alloy was reduced from 26 to 7 MPa m 1/2 and 31to 8 MPa m 1/2 respectively under the influence of patch. The plateau crack velocity was increased from 2.5 × 10 −9 to 5.1 × 10 −9  m/s for peak aged and 1.2 × 10 −9 to 2.0 × 10 −9  m/s for two-step aged tempers in patched condition. The significant increase in EAC susceptibility was attributed to crevice effect generated by the stiffener.