Curved Interface Tensile Test

If no closed form analytical solution is available for the specific mechanical problem, a finite element analysis can be used for the determination of K, provided 

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Determination of the Interface Strength of Polymer-Polymer Joints by a Curved Interface Tensile Test... 

Chapter 8 Curved Interface Tensile Test of Polymer-Polymer Joints... 

Figure 6. Specimen geometry for the curved interface tensile test case of a circular interface (r, = a) with supporting soft material at the edge.

Figures 1, 2, 3, 4, and 5 reprinted from Compos. Interfaces, Vol. 10, 2003, Authors B. Lauke, K. Schneider, T. Schuller, Title Determination of interface strength of polymer-polymer joints by a curved interface tensile test, p. 1, Copyright (2004), with permission from VSP, International Science Publishers. 

Various mechanical testing methods have been used to assess the bioadhesive properties of materials and formulations. Review of the literature reveals that the technique most commonly used is the tensile test [82,85]. This test provides the measure of the force needed to detach a layer of the tested material or formulation from a mucosal substrate as a function of the displacement occurring at the bioadhesive interface. Besides maximum force of detachment, another parameter provided by tensile test is the work of adhesion calculated as the area under the force versus displacement curve. Such a parameter gives more complete... 

Abstract The effects of the amount of rubber, the concentration of fibres and the state of the fibre/matrix interface upon the mechanical behaviour of short glass fibre-reinforced rubber-toughened nylon 6 ternary blends are described. First, tensile tests were carried out on different intermediate materials and then on the ternary blends to derive the stress-strain curves and document the damage mechanisms. Fracture toughness tests were implemented on compact tension specimens and the results were correlated to fractographic observations and acoustic emission analysis to assess the role of the different constituents. 

The work of Bussu and Irving on 6.35 mm (0.25 in.) thick 2024-T351 Al sheet is illustrative of hardness variations following FSW in 2024-T351 Al (Ref 12). In their work (Fig. 5.3), hardness is illustrated both as a function of distance from the joint interface and depth from the top surface. As shown, a typical W -shaped hardness curve is created. Due to the close relationship between hardness profiles and tensile test results, this composite of hardness results has implications for resultant mechanical properties. The studies in this work show four distinct hardness zones ... 

Figure 2 shows the general test set-up of the two-material sample under tensile load with the coordinate systems irsed for calcirlation of the stress distribution along the interface. Two polymer mat ials are bonded by a curved interface with the cylindrical coordinates r=r and 6. Because of symmetry, only half of the sample needs to be considered, i.e., 0 < jc < a and 0 < 0< 90 . By choosing different radii r, different curvatures of the line and consequently different angles 0, respectively 02, can be realized at.r = a. The geometrical situation near the points = a is shown at the right hand side of Figure 2. If the curvature of the interface in the very vicinity of that point is neglected, the typical open wedge problem of two-material interfaces is faced.

O Figure 22.6a shows the geometry for the tensile test. In the tensile test, two rigid cylinders are bonded end to end with adhesives, and the joint is tested by applying tensile forces on both cylinders and measuring the resulting stress-strain curves. Though the test method looks quite simple, special care has to be paid for the data analysis. In practice, the stress distribution at the adhesive-substrate interface is not uniform (see Fig. 22.6b), but depends on the elasticity (modulus and Poisson s ratio) of the cylinder and the adhesive, and also on the aspect ratio (thickness/diameter) of the adhesive (Adams et al. 1978 Anderson et al. 1977). Due to this reason, the tensile test has to be performed under (at least) controlled thickness conditions. 

For the pull-out test, a single crystal of Cgo was vapour deposited on high modulus pitch-based carbon fibres (Young s modulus 700 GPa, Tohnen Co. Ltd.) by the above-mentioned method. The fibres have a diameter of 10 m and their surface structure is similar to that of the CNTs. The shear strength of the interface was estimated from the load-displacement (L-D) curve of the pull-out test, which was performed in an Instron-type tensile testing machine (Autograph AGS-D Type 3, Shimadzu) at room temperature with a cross head speed of 0.5 mm/min. 

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