Cleavage tests

Spalt-versuch, m. Min.) cleavage test, -win- el, m. Cryst.) cleavage angle, -zunder, m. high-tension detonator. 

Cleavage products, 10 569 Cleavage reaction, in phenol manufacture, 25 749-750 Cleavage tests, 2 514 (+)-Cleavamine, 2 98 Clenbuterol, 23 14-15 Clentiazem, 5 121... 

The cleavage test utilizes a specimen where the load is intentionally placed on one edge of the bonded area. The test method is described in ASTM D 1062. The specimen is usually loaded at a rate of 0.05 in/min until failure occurs. The failing load is reported as breaking load per unit area in pounds per square inch. A standard test specimen is illustrated in Fig. 20.9. Because cleavage test specimens involve considerable machining, peel tests are usually preferred where possible. 

FIGURE 20.9 Cleavage test specimen. (From ASTM D 1062.)... 

Procedures. Preparation of Cast Double-Cantilever Cleavage Test Specimens. 

Fracture Surface Energy Calculation Berry s Method (8). The dimensions of double cantilever test specimen and techniques are illustrated in Ref. 3. We determined the surface work by substituting the measured quantities from the cleavage tests into Griffiths equation. Three cantilever bars were used. 

Heat Distortion Test. Two remaining bars from the cleavage tests are used to determine heat distortion temperature in accordance with ASTM D-621 test methods. These thermal-mechanical tests are necessary to determine whether a brittle resin has been truly toughened or whether it has been merely flexibilized. The morphology of the resin also effectively describes a true toughening situation and can aid immeasurably in explaining departures from true toughening. 

Electron Microscopy. We replicated the surfaces developed from the double cantilever cleavage test and the surface developed from the tensile test specimen. Replicas are first taken with a gelatin solution from the fracture surface (9). A typical electron micrograph of a CTBN-epoxy system is shown in Figure 1. This micrograph is from a surface of a fractured cantilever cleavage specimen. It shows a uniformly dispersed rubber phase in a brittle epoxy matrix. 

Table IV shows test results of samples with various levels of piperidine and a constant amount of Hycar CTBN. The data on fracture energy in the table show conclusively an increase in crack resistance with increasing amounts of piperidine, but there is no corresponding increase in the Gardner impact. This system shows a rate sensitivity. The slow rate cleavage test for fracture energy improves although a fast rate impact test does not. Also there is a greater deterioration of mechanical properties when the additional piperidine is used.

The expression for the parallel cleavage test, for example, may be written in this form ... 

Gagliano, J. M., "An Improved Method for the Fracture Cleavage Testing of Adhesively-Bonded Wood," Wood Science and Forest Products. Virginia Tech, Blacksburg, VA. 2001. 

For an approximate (since the experimental conditions are not identical) yet rapid comparison of the relative efficiencies of the manganese complexes toward DNA cleavage, the circular supercoiled plasmid cleavage test is convenient. About the same yield of plasmid cleavage was reached with 100 pM of 29 (Ih, 37° C) 181), or 10 pM of 28 (5 min, 37° C) 174) and finally, 250 nM of Mn-TMPyP (1 min, 20° C) 182). 

The crack initiation energy can readily be determined from a mode I cleavage test using a double cantilever beam specimen [1,2]. This method has been applied to wood-adhesive joints by many researchers [3 17]. The test requires the beam compliance (C), load at crack initiation (P ), crack length at initiation (a), specimen thickness (/), and change in beam compliance = change in displacement of load points/change in... 

Fig. 3.14. Performance of emery cloth abraded adherends, and the influence of a silane primer, in stressed cleavage tests (Ref. 4). (a) Aromatic amine cured epoxy, (b) Aliphatic amine cured epoxy, (c) Epoxy polysulphide.

Cleavage strength BS 5350 Part Cl 1986 ASTM 01062-72(83) ASTM 03433-75(85) ASTM 03762-79(83) ) Compact tension specimen ) Parallel- or tapered doublecantilever-beam joint for determining the adhesive fracture energy, G c Wedge cleavage test (for aluminium adherends)... 

ISO 19993 Timber structures. Glued laminated timber. Face and edge joint cleavage test. 

Cleavage tests and tests based on fracture mechanics... 

The ASTM D1062 cleavage test uses the specimen configuration shown in Fig. 19. The specimen is fabricated from two identical metal pieces that are adhesively bonded to form the bond line to be tested. The load is applied off-axis... 

Fig. 19. Cleavage test for metal-to-metal adhesive bonds (ASTM D1062).

The test methods used for structural adhesives in fracture mechanics studies are often those based on either cleavage or torsion loading. Cleavage tests will produce a pure Mode I loading. Other test methods may be used to induce a mixture of Modes I and II. 

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