FRACTURE OF FIBER-METAL LAMINATE GLARE 2

摘要

Low temperature regimes impose various constraints with regard to structural material performance. In this context, advanced composite materials and fiber-reinforced metal laminates (FML) have been considered to be appropriate candidates, and in some cases even a favored choice. As such, FML GLARE 2 was selected, as it has recently been examined for some applications in the aerospace industry. GLARE 2 was mechanically characterized with regard to low temperatures and orientation effects by monotonic loading of uniform and notched specimens, and by some results from cyclic loading. The mechanical tests were accompanied by supplementary characterization techniques [optical and SEM microscopy, acoustic emission (AE) combined with stress wave emission (SWE) monitoring, and fast Fourier transform (FFT) analysis] in order to clarify the controlled fracture mechanisms and the damage build-up profile, with regard to the dominant variables (temperature and orientation). The experimental results emphasized the anisotropic mechanical behavior of GLARE 2 in terms of tensile and fracture toughness properties. The distinct mechanical response at the various orientations was reflected by other supporting findings such as SWE shapes and the frequency of their appearance, event count rates, characteristic frequency, and fracture modes at some stress levels and at failure. These comprehensive data make it possible to point out the main fracture mechanisms, which govern damage accumulation, including temperature effects; these may be helpful in the composite processing design. In addition, it has been shown that the degree and progression of damage can be associated with AE event count rates. Similar tendency related to crack density has also been assessed using damage mechanics models.