Adhesive modulus

Cured adhesive Modulus Tensile strength increases and peel and impact decrease with increasing crosslink density... 

Flexural modulus is a measure of the strength of adhesives. Modulus data are most often used in stress analysis (one-dimensional or as an input to 3-D modeling). In addition to flexural modulus, elongation-at-break is also recorded. The standard test... 

A STUDY OF POLYETHYLENE-GLASS BEADS ADHESION Modulus of elasticity... 

The cubic equation (4.20) allows determination of the adhesive modulus of elasticity E2 in a plate made of three layers. For this purpose it is necessary to find the frequency of the natural vibrations of the three-layer plate under investigation with one edge fixed and the other free. 

The methods of controlling the edge stresses are based on adding substances that produce different mechanisms of adhesive cure in the bulk and at the interface with air. This results in alteration of the physical-mechanicsd properties of the adhesive depending on the distance to the edge—i.e., decrease of the adhesive modulus of elasticity at the edge and increase of the rate of relaxation of the internal stresses. 

Bai, Y. and Keller, T. (2011) Effects of thermal loading history on structural adhesive modulus across glass transition. Construct. Build Mater., 25, 2162-2168. 

Figure 16.21. Surface defining the transition between crack transmission and deflection at an interface depending on interface adhesion, modulus mismatch and residual strain.

The effective adhesive transverse modulus Ea takes into account the fact that adhesive properties are different in bulk and film forms. In a bonded joint the adhesive layer is a film. When loaded using through thickness tensile or compressive loads the adherends restrict the deformations of the adhesive, unlike when the bulk form of the adhesive is being similarly loaded. These restrictions in deformations tend to increase the adhesive modulus measured between the relatively stiff adherends. This effective modulus is difficult to establish theoretically. 

Keywords Adhesive modulus Adhesys expert system Co-axial joints Compression Concealed joints Creep Elastic limit Epoxy Epoxy composite Einite element analysis Glue line thickness Goland and Reissner Hart-Smith Heat exchanger Hooke s Law Joint designs Joint thickness Lap shear strength Peel Plastic behaviour Polyurethane Pipe bonding Shear stresses Shear modulus Stress distribution Thick adherend shear test Tubular joints Volkersen equation Young s modulus... 

Strain of the adhesive = modulus of the adhesive = CTE of the adhesive = the CTE of silicon AT = temperature difference... 

The empirical, quantitative relationship between PSA performance and adhesive modulus values was obtained by correlating adhesion properties in Figures 34-40 with their G value at ( ) = 0.1 rad/sec and slope, G (o) = 1(X))/G (< ) = 0.1), as shown in Figures 49-51. 

Adherend or Adhesive Modulus (103 MPa) Linear coefficient of expansion (10-6 m/moQ... 

Firstly, the adhesive thickness, /la, and adhesive modulus, E, both appear in Eq. 63 and when the adhesive layer is taken into account, this typically results in a relatively small decrease in the value of dUd/bda and once this effect is taken into account the value of G should be independent of the value of h. ... 

Comparison of dependence on temperature of joint strengths with mechanical properties of the adhesive. O dry joints, joints stored for 1,000 h at 100% relative humidity and 50°C adhesive modulus, adhesive tensile strength. The adhesive is DGEBA cured with DAPEE (Brewis et al. 1983)... 

Effect of the adhesive modulus on the adhesive stress distribution along the overlap... 

Al-Samhann and Darwish (2003) demonstrated with the FE method that the stress peaks typical of adhesive joints can be reduced by the inclusion of a weld spot in the middle of the overlap. They studied later (Darwish and Al-Samhann 2004) the effect of adhesive modulus and thickness and concluded that for rational design of weld-bonded joints, adhesives of low Young s modulus are recommended with the largest possible bondline thickness. Darwish (2004) also investigated weld-bonded joints between dissimilar materials and found that the introduction of an adhesive layer resulted in an increased joint strength and a better stress distribution. 

Peel tests intended for flexible adhesives are designed to measure resistance to highly localized stresses (Figure 12.1). Peel forces are therefore considered as being applied to linear fronts. The more flexible the adherend and the higher the adhesive modulus, the more nearly the stressed area is reduced to linearity. The stress then approaches infinity. Since the area over which the stress is applied is dependent on the thickness and modulus of the adherend and the adhesive, and is therefore very difficult to evaluate exactly, the... 

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