Post-bonding testing

If the adhesive layer was always to represent the weakest link in the joint, the quality of the assembly would be limited to an assessment of the cohesive properties of that layer. Unfortunately it is the interface which tends to be of greater concern because it is here that joint failure is more commonly encountered, particularly after ageing. The most useful tests for indicating interfacial quality are in fact pre-bonding surface inspection procedures, which can nevertheless suggest potential joint performance. The tests used for assessing cohesive properties of the adhesive layer must necessarily be post-bonding activities. 

The measurement of the strength of adhesion between adherend and adhesive requires a measurement of the intermolecular forces of attraction this is not currently possible. This aspect of quality control is therefore essentially reduced to assessing the adherend surface characteristics prior to bonding, although some post-bonding simple mechanical tests are appropriate. 

ASTM D429-02, Method D, Post Bond Vulcanisation butt test [16]. Parts are clamped in a jig and put into an autoclave or oven. 

The results described in this paper were all obtained from tests on E-glass reinforced composite materials produced by hand lay-up. This is the manufacturing route most frequently used for marine structures. For the majority of the tests reported here the E-glass fibres were either quasi-unidirectional (250 g/m with 1 g/m of polyester fibres bonded in the 90° direction to keep the UD fibres in place) or stitched quadrlaxial (0/45/907-45° 1034 g/m ) cloths. The same uniaxial ply is used in both cloths. The resin is based on DGEBA epoxy (SRI500) with an amine hardener (2505) from Sicomin, France. All epoxy specimens were post-cured at 90°C for 6 hours. Some results are also shown for a woven glass (0/90° 500 g/m ) reinforced isophthalic polyester for comparison, as this is the traditional marine... 

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