Effect of thermal-mechanical cycling on damping capacity of B/Al composite

Abstract

B/Al composites possess high strength and stiffness with a low density, having an application as high performance structural materials in aircraft and spacecraft components [1, 2]. In many cases, the components in such applications are subjected to externally applied loads under conditions of varying temperature. The property degradation caused by “thermal-mechanical cycling (TMC)” can sometimes limit the service reliability of the composites [3–5]. Furthermore, fiberreinforced metal matrix composites (FMMCs) exhibit a lower damping capacity compared with other metal matrix composites, hence limiting their applications and performance in dynamic structures. The damping capacity of FMMCs is closely associated with the interfacial internal-friction [6]. The interface slip contributes strongly to the damping capacity. The weaker the interface bonding, the higher the damping capacity, including the logarithmic decrement δ and the inverse quality factor Q−1 . The damping capacity of the B/Al composites could be optimized by tailoring the interfacial strength, while maintaining the high-modulus and high-strength property of the composites. The material used in this study was an aluminum alloy 5A06 (AA5A06) matrix composite unidirectionally reinforced by boron fibers with a diameter of 140 μm, which was fabricated by the vacuum hotisostatic press/diffusion bonding technique. A stack of 9 foil-fiber plies with an average of 56 fibers/cm for each ply was pressed to 1.4 mm thick B/Al sheet. The nominal fiber volume fraction was 50 vol%. The size of the specimens for the TMC tests was 125 × 10 × 1.4 mm3. The longitudinal direction of the specimens was parallel to the fiber direction. After polishing and cleaning, the specimens were mounted on a pure copper clamp plate, one end of which was fixed to the rigid frame and the opposite end was loaded with an external stress of 110 MPa. The applied stress was parallel to the longitudinal direction of the specimens. The TMC with 2000 cycles was carried out in temperature intervals from 20 to 270 ◦C with the heating rate of 1.25 ◦C/s and the cooling rate of 2.5 ◦C/s. The hold-time at both the lower and upper temperatures was 60 s. Specimens for the damping and the modulus measurements were taken after every 500 TMC cycles. The damping measurements were carried out using a can-