Two β-NiAl plus α -Re alloys with near eutectic composition were produced by rapid solidification and then consolidated through a powder extrusion process. Microstructures of the rapidly solidified, as-consolidated, and deformed alloys were characterized by transmission electron microscopy. Both compression and tensile properties of these alloys were determined over the temperature range of 300–1300 K. The Re additions were found to greatly enhance low and intermediate temperature yield strengths when compared to other β-NiA1 alloys. This enhancement was attributed to a combination of solid solution strengthening, precipitate hardening, and grain size refinement. Above 1200K the strength of these Re-modified alloys was comparable to the binary β-NiAl compound.

This paper describes the development of a graphite/epoxy wing skin configuration capable of sustaining limit load following damage from a 23-mm high-explosive (HE) projectile impact. The skin configuration incorporates information learned in sawcut and ballistic fracture testing, and consists of a ±45 graphite/epoxy laminate with integral spanwise and chordwise crack-arresting pads formed by adding 0-deg glass/epoxy between the plies of graphite/epoxy. The ±45-ply orientation provides enhanced battle damage tolerance because of its higher residual strain-to-fracture capability relative to quasi-isotropic 0/±45/90 laminates. This permits developing the full load-carrying capability of the spar chords before unstable crack propagation can occur in the damaged skin. The 0-deg glass/epoxy was added to further enhance this capability, and concentrated into pads to avoid undesirable ballistic damage augmentation caused by the glass fibers, and to provide a controlled failure mode under blast pressures. The optimum graphite-to-glass ratio and the required width of the crack-arresting pads were determined using a new analysis method for predicting fracture in laminates containing high-strength 0-deg fibers. The effectiveness of the damage tolerance concept was demonstrated by firing a 23-mm HEI projectile into the tension surface of a full-scale wing-box test component loaded in combined bending and torison. Following damage, limit load was achieved as a result of successful crack arrestment.