Rate of debonding

The rate of debonding decreases as the number of debonded particles increases and as the stress increases. The debonding constants characterize the interaction and the influence of neighboring particles. Their values depend on the filler concentration and on the adhesion of the filler to the matrix. The volume increase due to debonding is given by the equation ... 

A probe tack test may be regarded as a mechanical thumb in which a disc or hemisphere of standard material (e.g. brass) is brought into contact with the adhesive surface under a fixed load for a specified dwell time (e.g. 1 s) and then removed at a specified rate. The maximum force of removal is usually taken as the tack value, although sometimes the work or energy of separation is reported. In such a test, it is important to control accurately the variables probe material and finish, probe diameter and shape, load on probe, thickness of adhesive, dwell time, rate of debonding of probe from adhesive, and... 

Rate and Temperature Effects. Adhesion of a soft crosslinked polymer to a rigid substrate is found to increase markedly as the rate of debonding is increased. An example is shown in Fig. 31. The strength also increases as the temperature is reduced, Fig. 31. Thus,... 

In fact, the same increase in joint strength that is obtained with a simple viscoelastic adhesive on increasing the rate of debonding, can be achieved by a suitable reduction in test temperature. This is referred to as the principle of rate-temperature equivalence. For amorphous glass-forming liquids above their glass transition temperature Tg, Williams, Landel, and Ferry (WLF) proposed a universal relationship for the ratio of corresponding test rates at temperatures Tand Tgi ... 

The rate of the cathodic reaction is not the only factor influencing the debonding however. Consider the IN NaOH solution. 

The fiber modulus and matrix shear modulus are also required for the analysis. The fiber s coordinates are recorded directly from the stage controllers to the computer. The operator begins the test from the keyboard. The x and y stages move the fiber end to a position directly under the debonder tip the z stage then moves the sample surface to within 4 yum of the tip. The z-stage approach is slowed down to 0.04 jan/step at a rate of 6 steps/s. The balance readout is monitored, at a load of 2 g the loading is stopped, and the fiber end returned to the field of view of the camera. The location of the indent is noted and corrections are made, if necessary, to center the point of contact. Loading is then continued from 4 g in approximately 1 g increments. Debond is determined to have occurred when an interfacial crack is visible for 90-120° on the fiber perimeter. The load at which this occurs is used to calculate the interfacial shear stress at debond. 

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