Influence of temper condition on the nonlinear stress-strain behavior of boron-aluminum

The influence of temper condition on the tensile and compressive stress-strain behavior for six boron-aluminum laminates was investigated. In addition to monotonic tension and compression tests, tension-tension, compression-compression, and tension-compression tests were conducted to study the effects of cyclic loading. The laminates studied were [0], [90], [±45]_S, [0/±45/0]_S, [0/±45]_S, and [±45/0]_S, and the temper conditions were "as received" or F, T6 and T6N which was T6 followed by cryogenic exposure. It is shown that the T6 heat treatment increases the yield stress in both tension and compression. Tensile strength results are a function of the laminate configuration; unidirectional laminates were affected considerably more than other laminates with some strength values increasing and others decreasing. In general, cryogenic exposure of laminates with 0° plies increased the tensile yield stress and reduced the compressive yield stress, but other laminates were not significantly affected. Results from the cyclic tests show that the linear range of material behavior was increased by cyclic loading to a maximum value for all laminates and temper conditions. Typically, a maximum linear range was established which remained constant except in those cases where material degradation was indicated. Only those laminates with ±45° plies exhibited significant material degradation.