Shear Strength ASTM

The reinforcing fabrics used were aramid (Kevlar DuPont) and poly(p-pheny-lene-2,6-benzobisoxazole) (PBO) (Zylon Toyobo). The fabrics were first treated with a 1.5% solution of HB PAMAM (AD-102), dried, then interleaved with an epoxy film structural adhesive (epoxy stage B on polyester net), and compression-molded for 90 min at 120 °C. For the aramid-based composite, FM-73 (Cy-tec) was used as the matrix. For the PBO-based composite, AF-191 (3M) was used as the matrix. The laminates were cut into strips and tested for interlaminar shear strength (ASTM D-2344) using a three-point bending instrament. 

Table 15.8 Interlaminar shear strength (ASTM D-2344) for laminates with and without HMW PAMAM.

Shear strength— ASTM D732. Shear strength is rarely a factor in molded and extruded plastic products due to their relatively thick wall sections, however, it can be important in film and sheet products. In this test, 2-in-diameter or 2-in-square specimens, ranging in thickness from 0.005 to 0.500 in are placed in a punch-type shear fixture. Pressure is applied to the punch at the rate of 0.005 in/min until the moving part of the sample clears the stationary part. The force divided by the area sheared determines the shear strength. 

Test Procedure Shear Strength ASTM D1002/DIN EN 1465 [1, 2] Substrate Grit blasted mild steel lap shears Cure procedure 1 week at 22 °C... 

The routine compositional and functional testing done on the adhesives includes gas chromatographic testing for purity, potentiometric titrations for acid stabilizer concentrations, accelerated thermal stabiUty tests for shelf life, fixture time cure speed tests, and assorted ASTM tests for tensile shear strengths, peel and impact strengths, and hot strengths. 

We have also looked at the lap shear strength of selected EB-ciirable epoxy adhesives. Because the adhesives being developed were being used for both aluminum-to-aluminum and composite-to-composite applications the lap shear strengths for both adherends was measured. Aluminum adherends were T2024 phosphoric acid anodized according to ASTM 3933. The composite adherends... 

Corrosion Testing. Salt spray testing (ASTM-B-117-52,54) was used to determine durability of adhesive bond in corrosive environment. Lap shear samples were exposed to salt spray for 14 days and then immediately tested for lap shear strength. 

ASTM D 2344 (1989). Test method for apparent interlaminar shear strength of parallel fiber composites by short-beam method. 

ASTM D 3846 (1985). Test method for in-plane shear strength of reinforced plastics. 

In-Plane Shear Properties. The basic lamina in-plane shear stiffness and strength is characterized using a unidirectional hoop-wound (90°) 0.1 -m nominal internal diameter tube that is loaded in torsion. The test method has been standardized under the ASTM D5448 test method for in-plane shear properties of unidirectional fiber-resin composite cylinders. D5448 provides the specimen and hardware geometry necessary to conduct the test. The lamina in-plane shear curve is typically very nonlinear [51]. The test yields the lamina s in-plane shear strength, t12, in-plane shear strain at failure, y12, and in-plane chord shear modulus, G12. 

Two other variations are used to avoid the bending forces that occur with simple ASTM D 1002 specimens the laminated lap shear specimen (ASTM D 3165) shown in Fig. 20.6a and the double-lap specimen (ASTM D 3528) shown in Fig. 20.6b. These specimens minimize the joint eccentricity and provide higher strength values than does the singleoverlap specimen. For the specimen in Fig. 20.6a, the overlap joint can be made from saw cuts in the top and bottom substrates of a bonded laminate. This process negates the effects of extruded adhesive at the edges of the lap and the sheared edge of the standard type of lap shear specimen. As a result, the chances of deformation and uneven surface preparation are lessened. 

ASTM D 732-90 Standard Test Method for Shear Strength of Plastics by Punch Tool, 3 pp (DOD Adopted) (FSC 9330) (MR) (Conun D-20)... 

Laboratory tests to determine shear strength are the direct shear test, the unconfined compression test, and the triaxial test. ASTM Standards give complete details of these tests. Triaxial tests yield the most reliable results. The manner in which these tests define the failure line as shown in Figure 2.4. 

Shear strength is a measure of the load required to cause failure in the area of the sheared specimen in accordance with ASTM-D732-46. The shear strength is equal to the load divided by the area. 

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