**3.2 Results and discussion**

374 Recent Trends in Processing and Degradation of Aluminium Alloys

The compact tension specimens were manufactured from rectangular plates conforming to

The fatigue tests were performed on a standard Mayes machine attached to a Pd system. The Pd system was switched on with the current circulating for 30 minutes before any readings were taken; the fatigue cycle was then begun. Data from the Pd system was exported into an excel spreadsheet and the number of cycles versus crack propagation was then plotted. From these results, values of stress intensity (ΔK) versus crack growth rate were then calculated. In order to calculate the stress intensity factor, a standard equation

> *PY <sup>K</sup> B W*

Where*, Y =* geometry factor*, ∆P =* change in cyclic load (Pmax - Pmin)*, B =* sample thickness and *W =* sample width*.* Fatigue tests were conducted in fully tension - tension and at a

<sup>Δ</sup> Δ = (14)

**3. Aluminium honeycomb sandwich panels and metallic foam** 

**3.1 Material and experimental procedure** 

BS 7448-1: 1991 as shown in Fig. 21.

Fig. 21. Compact tension specimen

was used.

constant frequency.

The results of fatigue testing of aluminium honeycomb sandwich panel both in air and in 3.5% sodium chloride solution, are plotted in Figure 22. A total of twenty cyclic deformation tests were conducted in fully tension-tension at a constant frequency of 2HZ, which is equivalent to two cycles per second. The results of fatigue testing of metallic foam sandwich panel both in air and in 3.5% sodium chloride solution, are plotted in Figure 23.

Fig. 22. Aluminium honeycomb fatigue data

Fig. 23. Metallic foam fatigue data
