Boeing wedge-test

Figure 9 Boeing wedge test and typical results.

Fig. 13. The Boeing wedge-test for assessing joint durability. Typical exposure to the hot/wet environment is I h, or longer, at 50° or 60°C, and 100% relative humidity. The environmental crack growth, Aa, is then determined, which is a measure of joint durability.

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In the BOEING wedge test, the test specimens are immersed in water at 50°C for progressive periods of time, and the length of the crack is measured after each period with a microscope. If the siuface preparation was not good enough, then the crack will progress quickly and far, and the aircraft constructors have their own specifications for this test that they perform with various surface preparations such as PAA (phosphoric acid anodization), CAA (chromic acid anodization), etc. 

Figure 37 Cleavage test also called crack propagation (ISO 10354) or BOEING wedge test (a) test specimen (all dimensions in mm) (b) wedge (c) Test specimen after the test wedge has been pushed inside the test specimen (at a speed of 1 mm/min, for instance) original opening was o, which increased by Aa so that crack propagation was Aa (Aa is measured very accurately with a microscope).

Figure 16 Boeing Wedge Test after ASTM Test Method D3762.

Figure 8.10 Crack growth versus time in environment of water at 60 from the Boeing wedge-test. Epoxy/aluminium alloy joints with three different pretreatments used for the aluminium alloy substrates [42].

In one sense all tests are time-dependent since, even with the single lap joint, time to fracture is usually specified as being about 1 min. The Boeing wedge test is clearly a measure of crack initiation and propagation over a period of some hours. 

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