Adhesive shear

The lap shear test involves measuring the adhesive shear strength between two surface fluorinated polyolefin sheet tokens that are adhesively secured with a reinforcement resin. The tokens are individually reinforced with steel backing plates to eliminate flexural distortion in the shear joint. Lap shear tests carried out with various reinforcing polyester-type resins, contrasting fluorination and oxyfluorination as surface treatment, are shown in Table 16.8. 

Flat laminated panels are manufactured using fluorinated sheet substrates. The manufacturing of these test panels simulates the production process used to manufacture the fiberglass-reinforced pipes. The BS6464 test prescribes a minimum adhesive shear and peel strength of 7 MPa and 7 N/mm, respectively. Representative values for both tests are given in Tables 16.9 and 16.10 below. 

Thus, fundamentally the interest is in testing the limits and theory of polymer behavior in end-tethered systems, e.g., viscoelastic behavior, wetting and surface energies, adhesion, shear forces relevant to tribology, etc. It should be noted that relevant surfaces and interfaces can also refer to polymers adsorbed in liquid-liquid, liquid-gas, solid-gas, and solid-liquid interfaces, which makes these polymer systems also of prime importance in interfacial science and colloidal phenomena (Fig. 2). Correspondingly, a wide number of potential applications can be enumerated ranging from lubrication and microelectronics to bioimplant surfaces. 

Pressure-sensitive adhesives are used in a great variety of applications, most commonly for adhesive tapes. In that case, they have to be tested by static shear test or dynamic shear test The difference between these two methods is that in static shear test a standard force is being applied to the test specimen and the adhesive failure is reported as the time it takes for failure to occur. The dynamic shear test involves a force being applied to the PSA tape at a specific rate of speed (typically 0.25 mm or 0.1 in. per minute). The value reported is as the peak force per unit area (Ib/in, also abbreviated as psi, and in SI units MPa) required to cause adhesive failure. The standards for adhesion shear tests are ASTM D3654, ISO EN 1943, and PSTC-107.i i ... 

D 5999 D 6004 D 6005 D 6105 Test Method for Noninterference of Adhesives in Repulping Test Method for Determining Adhesive Shear Strength of Carpet Adhesives Test Method for Determining Slump Resistance of Carpet Adhesives Practice for Application of Electrical Discharge Surface Treatment (Activation) of Plastics for Adhesive Bonding... 

Table II. Effect of Urea/Carbohydrate Mole Ratio (0.125 1) on Adhesive Shear Strength of Yellow Birch Panels...

Polybenzoxazole Adhesive Shear Force (N/mm ) Coating Type... 

ION. Maeno and M. Arakawa, Adhesion shear theoiy of ice friction at low sliding velocities, combined with ice sintering. Journal of Applied Physics, 2004, 95, 134. 

Tables 15.4 and 15.5 present the adhesion shear strength of epoxy (Epon 815C/Versamide 140)-bonded aluminum joints (anodized) and of PU (EN-4/EN-7)-bonded aluminum joints (anodized), respectively. Both types of adhesively bonded joints were primed with high MW HB PAMAM (AD-102). As is evident from the tables, significant improvements in shear strength were ob-...

Bonding, contact angle, heat-treated wood, penetration, phenol-formaldehyde adhesive, shear strength... 

Fig. 2.21. Temperature dependence of bulk adhesive shear strength (Ref. 25).

Goland and Reissner(16) was limited because the peel and shear stresses were assumed constant across the adhesive thickness, the shear was assumed a maximum at the overlap end (and not zero as it must be at a free surface), and the shear deformation of the adherends was neglected. Later, several analysts including Renton and Vinson(17) and Allman) 18) produced solutions where the adherends were modelled to account for bending, shear and normal stresses. Adhesive shear stress was set to zero at the overlap ends. Allman additionally allowed for a linear variation of the peel stress across the adhesive thickness, although his adhesive shear stress was constant. 

Fig. 4.4. Design of bonded lap joint (Ref. 19). (a) Idealised adhesive shear stress/strain curve. (f>) Design of bonded double-lap joints.

Physical wear may be loosely defined as the removal of surface material due to adhesion-shear cycles. The process may be divided into three general regimes light, medium or mild, and severe wear, depending on the extent of material loss or transfer and the general effect of the process on the nature of the surface produced (Fig. 18.15). 

Shear tests are very common because samples are simple to construct and closely dupUcate the geometry and service conditions for many structural adhesives. As with tensile tests, the stress distribution is not uniform and, while it is often conventional to give the failure shear stress as the load divided by the bonding area (Table 11.1), the maximum stress at the bond line may be considerably higher than the average stress. The stress in the adhesive may also differ from pure shear. Depending on such factors as adhesive thickness and adherend stiffness, the failure of the adhesive shear joint can be dominated by either shear or tensioa ... 

P(5) For brittle adhesives (shear strain to failure < 3%), Yn, shall not be taken as less than 1.5. 

Parameter for overlap Elastic adhesive shear straiu Partial safety factor for the load Partial material safety factor Plastic adhesive shear straiu... 

Plastic adhesive shear stress (N/mm ) allowable Allowable adhesive shear stress (N/mm ) Maximum adhesive shear stress (N/mm ) Adherend Poisson s ratio... 

Figure 5.27 A typical adhesive shear stress distribution in a lap joint according to elastic-plastic model (see reference 5.24, EUROCOMP Handbook).

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