Fracture toughness of adhesives

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

Lee, D.B., Ikeda, T. Miyazaki, N., and Choi, N.S. (2004) Effect of bond thickness on the fracture toughness of adhesive joints. Journal of Engineering Materials and Technology, 126, 14-18. 

Lint, W.W., Hatano, Y. and Mizumachi. H., Fracture toughness of adhesive joints I Relation between strain energy release rates in three different fracture modes and adhesive strength. J. Appl. Polym. Sci., 52, 967-973 (1994). 

The critical strain energy release rates measured in each test are shown in Fig. 15. The fracture toughness measured decreases as the mode II fracture component increased in the tests for this particular material system. This mode mixity dependence of the fracture toughness of adhesively bonded joints apparently is in contrast with the observations of other researchers for other material systems [49-54]. This contradiction can be explained through analyzing the locus of failure. As discussed in Swadener and Liechti [52] and Swadener et al. [53], the locus of failure in their studies was independent of the fracture mode mixity, and the size of the plastic deformation zone at the crack tip increased with the fracture mode mixity. This increased plastic zone was shown to be responsible for a shear-induced toughening mechanism, which consequently, caused the fracture toughness to increase with the mode II components in their studies. In this study, however, as... 

As pointed out by Pocius [60], the directional stability of cracks is significantly affected by the fracture toughness of adhesive bonds. An energy balance model used to analyze crack propagation predicted that directionally unstable cracks are more unlikely to occur as the fracture toughness of the adhesive bonds increase [32]. This energy balance model will be discussed in this chapter later. 

Ripling EJ, Mostovoy S et al (1964) Measuring fracture toughness of adhesive joints. N terials Research Standards (ASTM Bulletin) 4(3, March) 129-134 Swadener JG, Liechtiet KM et al (1999) Mixed mode fracture of automotive bonded joints. SAMPE-ACX2E-DOE Advanced Cpmposites Conference. Detroit MI... 

Nossek and Marzi (2009) have developed a CZM base method to predict the impact strength of adhesive joints for car structures. A trapezoidal traction-separation law was adopted. In this case, they expanded the CZM model from mode I condition to mode II and combined both stress conditions. In this study the fracture toughness of adhesive joints was... 

Film Adhesion. The adhesion of an inorganic thin film to a surface depends on the deformation and fracture modes associated with the failure (4). The strength of the adhesion depends on the mechanical properties of the substrate surface, fracture toughness of the interfacial material, and the appHed stress. Adhesion failure can occur owiag to mechanical stressing, corrosion, or diffusion of interfacial species away from the interface. The failure can be exacerbated by residual stresses in the film, a low fracture toughness of the interfacial material, or the chemical and thermal environment or species in the substrate, such as gases, that can diffuse to the interface. 

Two wooden beams are butt-jointed using an epoxy adhesive (Fig. A1.3). The adhesive was stirred before application, entraining air bubbles which, under pressure in forming the joint, deform to flat, penny-shaped discs of diameter 2fl = 2 mm. If the beam has the dimensions shown, and epoxy has a fracture toughness of 0.5 MN mT , calculate the maximum load F that the beam can support. Assume K = cT Tra for the disc-shaped bubbles. 

Fig. 27. Fracture toughness of cracked-lap shear specimens made with FM-x5 adhesive. Adapted from Ref. [109].

Recently siloxane-imide copolymers have received specific attention due to various unique properties displayed by these materials which include fracture toughness, enhanced adhesion, improved dielectric properties, increased solubility, and excellent atomic oxygen resistance 1S3). The first report on the synthesis of poly(siloxane-imides) appeared in 1966, where PMDA (pyromellitic dianhydride) was reacted with an amine-terminated siloxane dimer and subsequently imidized 166>. Two years later, Greber 167) reported the synthesis of a series of poly(siloxane-imide) and poly(siloxane-ester-imide) copolymers using different siloxane backbones. However no physical characterization data were reported. 

Madhukar, M.S. and Drzal, L.T. (1992b). Fiber-matrix adhesion and its effect on composite mechanical properties IV. Mode 1 and Mode II fracture toughness of graphite/epoxy composites. J. Composite Mater. 26, 936-968. 

Ishai O., Rosenthal H., Sela N. and Drukker E. (1988). Effect of selective adhesive interleaving on interlaminar fracture toughness of graphite/epoxy composite laminates. Composites 19, 49-54. 

Sela N., Ishai O. and Banks-Sills L. (1989). The effect of adhesive thickness on interlaminar fracture toughness of interleaved CFRP specimens. Composites 20, 257-264. 

The dispersion of SiC-coated MWCNTs increases the microhardness and fracture toughness of SiC. The SiC coating on MWCNTs at 1150°C is effective in improving the weak adhesion between MWCNTs and the SiC matrix. SiC-coated MWCNT/SiC composites show elastic behavior due to the crack-bridging effect of MWCNTs. 

The type of failure for the XD4600 adhesive was found to alter with increasing test rate. Whereas all XD1493 adhesive TDCB joints failed in a stable continuous manner, TDCB specimens bonded with the XD4600 adhesive showed a transition to stick-slip behaviour at these increased test rates (Fig. 8). It is argued that this is probably due to the strain rate dependent fracture toughness of this adhesive. 

In the present work, a novel experimental method was proposed to evaluate the modes I-fll fracture toughness of the adhesive interface between concrete and carbon fiber sheets. The validity of the evaluation formula was studied on the basis of the results of finite element analysis. The mixed mode fracture toughness and fracture criterion of the adhesive interface were also studied on the basis of the results of fracture toughness test using the proposed method. 

Fig. 15. Mixed mode fracture toughness of the adhesive interface between concrete and carbon fiber sheets each plot is the average value of 5-10 test data.

The mixed mode fracture toughness of the acrylic resin adhesive interface was obtained by applying the proposed method. The mode II fracture toughness was more than twiee as high as the mode I fracture toughness. 

However, the fracture occurred microscopically in the concrete blocks. Consequently, the apparent fracture toughness of the adhesive interface was much lower than the adhesive resin itself. 

The mixed mode fracture toughness of the adhesive interface followed the linear fracture criterion. This result suggests that the principle of superposition was valid... 

The purpose of this work is to study the fracture toughness of a laminated material in relation to the adhesion between the layers. Load and extension were measured for a two-layer laminate specimen with a pre-crack as well as for the individual layers of the laminate. The same specimen geometry was used in all tests. For comparison, measurements were also done for the laminate without any adhesion between the layers. 

The use of accelerated aging tests to predict the durability of phenolic adhesive joints has been critically examined to establish the dependence of fracture toughness of the joints on cure chemistry... 

After initiation of a crack, the further propagation is determined by the stress field in the scale and the fracture toughness of the material. Because of the higher fracture toughness of the metallic substrate, the cracks are presumably arrested at the oxide-metal interface. When the oxide-metal adhesion is not too weak, the cracks do not de-... 

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