Block-shear test

Figure 5 Modified ASTM D905 specimens for block-shear test, (a) Phenolic FRP-wood specimen (b) epoxy FRP-wood specimen.

D-3110. Specification for Adhesives Used in Nonstructural Glued Lumber Products. Employs the D-0905 block shear test and a finger joint test, along with several exposures, to evaluate interior and semi-exterior adhesives, in end, edge and face bonded joints, especially for the molding and millwork field. Most of the applicable adhesives are based on polyvinyl acetate. 

Fig. 8. Wood block shear test head and specimen (D-0905).

Where applicable, perhaps use long term loading with the new block-shear test (D-4501) or consider the creep test methods now used for construction adhesives in the specification for adhesives used in bonding wood in mobile homes (D-3930). 

Fig. 11. Effect of polyolefin primers on bond strength of ethyl cyanoacrylate to plastics. All assemblies tested in accordance with ASTM D 4501 (block shear method). ETFE = ethylene tetrafluoroethylene copolymer LDPE = low-density polyethylene PFA = polyper-fluoroalkoxycthylene PBT = polybutylene terephthalate, PMP = polymethylpentene PPS = polyphenylene sulfide PP = polypropylene PS = polystyrene PTFE = polytetrafluoroethylene PU = polyurethane. From ref. [73].

ISO 11003-1 2001 Adhesives - Determination of shear behaviour of structural adhesives -Part 1 Torsion test method using butt-bonded hollow cylinders ISO 11003-2 2001 Adhesives - Determination of shear behaviour of structural adhesives -Part 2 Tensile test method using thick adherents ISO 13445 2003 Adhesives - Determination of shear strength of adhesive bonds between rigid substrates by the block-shear method... 

A shear test using a quadruple block test piece as shown in Figure 8.17 is standardised as ISO 1827117 and BS 903 Part A14118. There is not an ASTM equivalent. 

Among many shear-type tests the following are representative the mallet friction test, the sliding-block friction test, and the emery-paper friction test of the Explosives Research and Development Establishment, England, the U.S. Bureau of Mines pendulum friction test, and the Julius Peters friction test. Each of these can be used to test primary explosives, and some may be used also on secondary explosives. 

Polyurethane adhesives were prepared by mixing polyol, diisocyanate (MDI, TDI or HDI), solvent (DMF, benzene or ethylace-tate), and catalyst (T-9) in the following fashion The diisocyanate dissolved in half of the total solvent volume was mixed with two-thirds of the polyol in one-fourth of the solvent in the presence of a trace of the catalyst. The mixture was heated to 50°C until an exothermic reaction starts then, heat was temporarily removed and reapplied for 10 min to maintain a temperature of 80°C. The rest of the polyol, catalyst, and solvent were then added and mixed completely. The resin was ready for application when the consistency of the mixture had reached a suitable level. The adhesive was spread on 11 3/4" x 4 1/2" x 3/4" wood (hard maple or southern pine) strips. The moist adhesive-coated surfaces were exposed to ambient air (vented hood) for 20-30 seconds if DMF was used as solvent, or for 3-5 minutes if either benzene or ethylacetate was used. After pressing (100 psi), the strips were cut into small shear blocks and tested according to ASTM Standard D905-49. Polyurethane coatings were prepared by mixing the polyol (80 parts) in ethylacetate (60 parts) and toluene (40 parts), with a solution of TDI (53 parts) in 80 parts ethylacetate and 30 parts toluene, and T-9 catalyst... 

In practice, block copolymer based PSA are often formulated from base polymer blends of triblock and diblock copolymers in various proportions. Setting aside cost considerations, the reasons for using a certain blend or even a pure triblock copolymer are typically based on performance in standardized PSA tests such as loop tack, peel, or shear tests. Yet, the effects of adding diblocks to a triblock copolymer on the details of the mechanisms of debonding are not known. 

One method used to evaluate the upper working temperature of block copolymer systems is to measure the shear adhesion failure temperature (SAFT), a useful method to discover exactly what has been gained in the upper working temperature limits when resins are added to the styrene domain of polystyrene end-block systems to increase the effective glass transition temperature. Typically the test is set up as a standard shear test, either to the standard stainless steel panel or to polyester, with a 1 in. by 1 in. (25 mm by 25 mm) area and a load of 1 kg. The set-up is placed in an oven that can be accurately controlled so that the temperature is increased by 2.0°C (3.6°F) per minute, the temperature at which failure occurs being recorded as the SAFT. 

In order to gain some knowledge about the degradation of the adhesive layer during the delamination test, the specimens which successfully passed the test were further tested in compression shear (Fig. 24). For these tests, blocks with a cross section of 50 by 50 mm were cut out of the tested specimens. As a control, specimens of a similar size were cut from the part of the original sample which had not been subjected to the delamination tests. The compression shear tests conhrmed that the five adhesive layers which passed the delamination tests did not suffer any degradation during the harsh treatment. Their shear resistance was hardly reduced after the harsh delamination tests. 

In an in situ shear test, a block of rock is sheared from a rock surface while a horizontal jack exerts a vertical load. It is advantageous to make the tests inside galleries, where... 

An adhesively bonded structure is considered in shear when the applied loads act in the plane of the adhesive layer. The loads tend to produce sliding of the adherends and this results in sliding or shearing of the adhesive. These shear stresses should not be confused with pure shear stresses, which are typical of uniform blocks of a homogeneous material. Interactions between adhesive thickness, adherend thickness and yield strength, and bond geometry produce nonuniform stresses. When this occurs, the shear bond may actually be dominated by tensile stresses rather than shear stresses. However, in service, adhesive structures rarely encounter these pure shear conditions. Therefore, standard shear tests provide adequate duplication of conditions which may exist in an actual structural adhesive application. 

Another compressive shear test used for wood joints is ASTM D905-49. Test joints are prepared by bonding two blocks of wood, free from defects, with the grain of each block parallel to the length direction. Test specimens are cut from this bonded joint and tested in a special shearing apparatus (Figure 13). Loads are applied using a crosshead movement of 0.015 inch/min. The shear stress is calculated with the failure load and bonded shear area. 

ASTM D 4501-85 Test Method for Shear Strength of Adhesive Bonds Between Rigid Substrates by the Block-Shear Method. 

Fig. 1. Block flow sheet of the vibrational shear test equipment.

D-3024. Specification for Protein-Base Adhesives for Structural Laminated Wood Products for Use Under Interior (Diy Use) Exposure Conditions. Employs the D-0>905 block shear, D-0906 plywood shear, and D-4300 mold resistance tests to evaluate mostly casein-base adhesives for use in interior grade laminated beams. 

D-4317. Specification for Polyvinyl Acetate-Based Emulsion Adhesives. Somewhat similar in scope to D-3110, this standard employs the D-0905 block shear and D-0906 plywood shear tests in evaluating polyvinyl acetate based adhesives for common wood gluing applications. 

D-4501. Test Method for Shear Strength of Adhesive Bonds Between Rigid Substrates by the Block-Shear Method. Fig. 9 shows the two specimen configurations and the test head for this new, general-purpose, compression shear test which should be suitable for testing adhesives for plastics, metals, glass, wood, and other substrates. 

Fig. 9. New block shear specimens (top) and test head (bottom) (D-4501).

Honeycomb Flatwise Tensile 50 X 50 mm specimens are cut from similar sandwich panels as are prepared for the beam shear test. These are then bonded to rigid blocks, generally using a paste adhesive having a cure temperature at ambient or, at least, lower than that used to cure the adhesive under test. The whole is then loaded in such a manner as to subject the bond between honeycomb and skin to tensile stresses (Fig. 52). 

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