Influence of loading rate on hardening process of Al–Zn metal layered composite

In the paper the influence of the loading rate of metal layered aluminium–zinc (Al–Zn) composite on its mechanical properties was tested. Loading, as monotonic tension with constant rate of the stress increment was carried out on plane specimens of Al–Zn composite, aluminium, zinc and Al–Zn set when the layers were not joined permanently on the measuring length in the range σ˙=0.6–18.0MPa/s. Connection of layers in Al–Zn composite was obtained by gluing aluminium and zinc strips together using glue for metal named JB Weld CX-80 (on the basis of epoxy resin). Additionally, the above mentioned specimens were tested at kinematic forcing, with the rate of loading ε˙=2×10-31/s. It was found, that applying a specific method of loading significantly influenced the shape of deformation characteristics of all the tested materials and on the values of coefficients of their hardening curves. The data obtained from the experiments was compared with the values calculated from the law of mixtures. It was noticed, that only for rapid tests carried out on samples with loading rate ε˙=2×10-31/s and σ˙=0.6MPa/s the law of mixtures correctly describes mechanical properties of Al–Zn composite and Al–Zn set. In the paper, values of the uniform strain ɛu   (correspond to the unstable state of Al–Zn composite), determined on the basis of the experiment were compared with the values obtained analytically by using the condition of the maximum loading. The coefficient of material sensitivity to the change of the loading rate σ˙ was defined and determined for tested materials.

► The influence of the loading rate σ˙ of Al–Zn composite on its mechanical properties was tested.
► The coefficient of the material sensitivity for the change of the loading rate σ˙ was defined.
► Condition of the maximum load offers a good prediction of the uniform strain ɛu   of the Al–Zn composite.
► Selection of materials for composite layers allows to reduce its sensitivity of the change σ˙ rate.
► Hardening process of Al–Zn composite occurs more intensively at the slow σ˙ rate than for ε˙.