Sharp Notch Stress Corrosion Cracking of B/Al and G/Al Composites.

摘要

Sharp notch stress corrosion properties of transverse loaded, uniaxially aligned B/6061-T6 Al, B/6061-F Al, B/2024-F Al and G/201 Al/2024 Al composites have been evaluated in a salt water environment and in laboratory air. For both environments, delayed time fractures were observed in those B/Al specimens that were dead weight loaded to stress intensities greater than approximately 80% of the overload fracture toughness. Fractures did not occur, within the 1000 hour time limit, for specimens subjected to lower stress intensities. Based on comparisons of the data for salt water and air exposures, analyses of the crack- opening-displacement versus time data, and appearances of the fracture surfaces, it is concluded that the delayed time failures in B/Al were caused by room temperature creep. For the G/Al composite, load carrying capacity was reduced about 25% due to 1000 hour immersion in salt water. Delayed time failures were attributed to the combined effects of room temperature creep and pitting corrosion adjacent to the crack tip. (Author)