STRESS CORROSION CRACKING RESPONSE OF HAND LAY-UP GRY COMPOSITES

Abstract

Stress corrosion cracking is the consequence of tensile stress actions, from any sources, simultaneous with corrosion on a structural component above certain critical tensile stress levels in specific corrosive media. Hand lay-up glass reinforced plastics (GRP) composites coupon samples (30% fibre volume content) were immersed for twenty-four hours in the following chemicals:0.50M H₂S0₄,0.50M Chromic Acid, 50% Acetic Acid, 0.50M Ethanol, and 0.50M Methanol They were subsequently subjected to tests at Constant tensile stresses using a bending stress rig while the corrosive fluid dripped on a filter paper wrapped on the stressed specimen. The location of the maximum tensile stresses due to bending was identified very close to the supporting clamp. A constant load was applied for a duration of 100 seconds at 50%, 60%, 70%, 75% and 80% of the dry laboratory temperature average tensile strength of the GRP composites (about 128 MPa). In each corrosive medium except Methanol there was no observable indication of stress corrosion cracking. Only those coupon samples immersed in 0.50M methanol exhibited stress corrosion cracking with brittle fracture below 90MPa (about 70% of the tensile strength) of the GRP composites.