Titanium adherends

The steps used to produce an anodized surface on titanium adherends are similar to those used for aluminum adherends. Initially, the adherend must be degreased to remove organic contaminants. This is followed by an acid etch to remove the oxide scale. The anodization (if used) is done at constant voltage and the adherend is rinsed and dried. The details of the procedure are presented in Tables 4 and 5. Oxide morphologies resulting from the CAA, SHA, and AP processes are presented below. 

Processing Steps of the Alkaline-Peroxide Surface Treatment 

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Since the m,m -DABP polyimide is known to be an outstanding adhesive, lap shear strength tests employing titanium-titanium adherends and metal ion filled polyimides were conducted. Tests were performed at room temperature, 250°C and 275°C employing either DMAC or DMAC/Diglyme as the solvent. At room temperature regardless of the metal ion employed adhesive strength is de-... 

Table IV Lap Shear Tests Titanium-Titanium Adherend BTDA-m,m -DABP...

Metal ion modified polyimide films have been prepared to obtain materials having mechanical, electrical, optical, adhesive, and surface chemical properties different from nonmodified polyimide films. For example, the tensile modulus of metal ion modified polyimide films was increased (both at room temperature and 200 0 whereas elongation was reduced compared with the nonmodif ied polyimide (i). Although certain polyimides are )cnown to be excellent adhesives 2) lap shear strength (between titanium adherends) at elevated temperature (275 0 was increased by incorporation of tris(acetylacetonato)aluminum(III) (2). Highly conductive, reflective polyimide films containing a palladium metal surface were prepared and characterized ( ). The thermal stability of these films was reduced about 200 C, but they were useful as novel metal-filled electrodes ( ). 

Mahoon, A., Titanium adherends. Durability of Structural Adhesives (A.J. Kinloch, ed.). Applied Science Publishers, London, 1983. 

Depth profiles of one or both sides of the failure may also be helpful, or even necessary, depending on the situation. Figure 16 shows an example of an interfacial or near-interfacial failure between the oxide and the titanium adherend. Because the freshly exposed metal surface oxidized immediately, the initial surface spectra could not distinguish between the interfacial failure and a failure entirely within the oxide.<86,87) Depth profiles may also be needed in the analysis of complex structures, such as those comprising many layers. In these cases, the sample interface chemistry might occur at several different points. However, a profile through several layers should allow the specific locus of failure to be identified.<87)... 

In the following sections, we first discuss briefly some of the analytical techniques used in the study of adherend surface preparation. Aluminum adherend preparations are discussed next in Section 2 and titanium adherends in Section 3, including processing, oxide morphology and chemistry, and bond durability. Section 4 contains a discussion of the preparations that have been used with steel adherends to improve surface morphology for bonding. 

More related information on titanium adherends can be found in Chapters 6 and 8 in this volume, and the chapter by Mahoon on the durability of titanium structural joints in Durability of Structural Adhesives. ( 36)... 

Most of the polyimides discussed in this paper were evaluated as adhesives for bonding titanium adherends. Recently, however, a need for polyimide adhesives for use with polyimide composites has developed. Preliminary studies for the BTDA-3,3 -DABP polyimide adhesive system with composites show promising results as reflected in Table V. 

Fig. 4. Ti-6A1-4V titanium adherend tensile stress-strain curves.

Let us also consider the titanium adherend joint with FM350NA adhesive, because it showed the widest variation of applied load. Fig. 12 shows the maximum principal stresses, averaged across the adhesive thickness, for joints loaded to the failure load normalised by dividing by the applied tensile stress. 

Unlike aluminum, titanium adherends are stable under conditions of moderately elevated temperatures and humidity. In the wedge test results of O Fig. 8.3, the adherend surfaces underwent no change in morphology. Failure of the CAA specimens remained within the adhesive, with the physical bonds provided by the microscopically rough oxide remaining intact. For moderate conditions, the key requirement for a titanium treatment is a convoluted nanorough surface to promote physical bonding. 

Davis GD, Whisnant PL, Venables JD (1995b) Plasma sprayed coatings as surface treatments of aluminum and titanium adherends. J Adhes Sci Technol... 

Davis GD, Groff GB, Zatorski RA (1997) Plasma sprayed coatings as treatments for aluminum, steel, and titanium adherends. Surfece Inter Anal 25 366 Davis GD, Krebs LA, Drzal LT, Rich MJ, Askeland P... 

Mahoon A. Titanium adherends. In Kinloch AJ, ed. Durability of Structural Adhesives. London and NY Applied Science Publishers 1983. 

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