Adhesion joints fracture

FIG. 8—Schematic of a typical geometry for DCB adhesive joint fracture specimens (shown with adherends of equal thickness) that was analyzed and experimentally tested. The forces (P) were applied by an Instron Universal Testing Machine. 

Fig. 4.14. Some adhesive joint fracture mechanics specimens, (a) Tapered double cantilever beam (TDCB). (b) Thick double cantilever beam (DCB). (c) Thin double cantilever beam or wedge cleavage specimen, (d) Independently loaded mixed-mode specimen (ILMMS). (e) Scarf joint.

Kinloch, A. J. (1972) Mechanics and Mechanisms of Adhesive Joint Fracture, University of London, Queen Mary College. 

Example of an adhesive joint fracture surface showing the influence of the lighting condition... 

The path of failure of an adhesive joint can give information about the mechanism of failure if analysis of the elemental and chemical composition can be conducted along the path. Several authors have performed such analyses by loading the adhesive joint until it fractures and then using XPS to analyze each side of the fracture. 

Usually tj/ is very much larger than Fq. This is why practical fracture energies for adhesive joints are almost always orders of magnitude greater than works of adhesion or cohesion. However, a modest increase in Fq may result in a large increase in adhesion as and Fo are usually coupled. For some mechanically simple systems where is largely associated with viscoelastic loss, a multiplicative relation has been found ... 

Eqs. 1-5 hold whether failure is interfacial or cohesive within the adhesive. Furthermore, Eq. 5 shows that the reversible work of adhesion directly controls the fracture energy of an adhesive joint, even if failure occurs far from the interface. This is demonstrated in Table 5, which shows the static toughness of a series of wedge test specimens with a range of adherend surface treatments. All of these samples failed cohesively within the resin, yet show a range of static toughness values of over 600%. 

Ripling, E.J., Mostovoy, S. and Patrick, R.L. (1964). Measuring fracture toughness of adhesive joints. Mater. Research and Standards, p. 129. 

Daghyani, Fl.R, Ye. L. and Mai, Y.W. (1995a). Mode 1 fracture behaviour of adhesive joints, I, Relationship between fracture energy and bond thickness. J. Adhesion 53, 149-162. 

The N(ls) spectra of these films show that the amines present in the regions of the film close to the aluminum oxide surface were protonated, an effect similar to that seen in the N(ls) spectra of the adhesive near the fracture surface of unprimed adhesive joints [15]. Figure 5 shows the spectra obtained from two... 

Papini M, Femlund G Spelt JK, Effect of crack growth mechanism on the prediction of fracture load of adhesive joints. Comp. Sci. Tech., 52, 1994, 561. 

Whilst test methods to measure the mode I fracture resistance of polymer fibre-composites [1] and stmctural adhesive joints [2,3] have now proceeded to full standards, the efforts to standardise a mode II method have been beset by a number of problems. Firstly, there exist a number of competing tests e.g. the end-loaded split (ELS), the end-notched flexure (ENF), the four point end-notched flexure (4-ENF) and the stabilised end-notched flexure (S-ENF) have all been proposed and have been subjected to various inter-laboratory evaluations. However, the results of these programmes have always revealed a very large scatter in the values of Gnc measured e.g, [4], and this scatter has been variously attributed to friction... 

Paraschi, M., A fracture mechanics approach to the failure of adhesive joints, PhD thesis. Department of Mechanical Engineering. 2002, Imperial College, University of London London. 

Fracture Mechanics, Wood adhesive joints, shear loading, cohesive failure. 

In bonded joints, a damage area, the size of which is often linked to the joint thickness and the adhesive properties, may appear ahead of the crack tip before fracture [1,2, 3]. In the case of wooden adhesive joints, the overall behaviour of the structure may be affected by the presence... 

Sheppard, A., Kelly, D., Tong, L., (1998), Int. J. of Adhesion and Adhesives 18, 385. Wemersson, H., (1994), Fracture characterization of wood adhesive joints. Report TVSM-1006, Lund University, Division of Structural Mechanics, Lund, Sweden, Simon, F., Morel, S., Valentin, G. (1997). In Proceedings of the Euromech Colloquium 358, Mechanical behaviour of adhesive joints, analysis, testing and design, Pluralis, Paris, pp. 341-351. 

It is my great pleasure to introduce the proceedings of the ESIS TC4 conference, Fracture of Polymers, Composites and Adhesives , which was held in the mountain resort of Les Diablerets, Switzerland between 15-18 September 2002. This was the third conference organised by TC4 and, as on the two previous occasions, it reflects the main activities of the committee which are focussed on developing fracture mechanics test methods for polymers, adhesive joints and composites. 

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