Large debond energy

Large Debond Energy. For LDE (Fig. 1.23), when cr< crs, the unloading modulus depends on both r and T, (Fig. 1.26). There are also linear segments to the unloading and reloading curves. These segments can be used to establish... 

According to the detailed examination of the cryofractured surfaces under SEM and TEM, the volume strain mainly comes from the interfacial debonding, which transformed into microcavities under large applied strain. However, large volume strain does not mean high energy dissipation. Conversely, the energy dissipation... 

In conclusion, when such an adhesive is debonded from a high energy surface such as steel, the high-strain properties of the adhesive control the formation and extension of the fibrillar structure which provides the bulk of the work necessary to detach the adhesive from the surface, and hence the major part of the peel force. We have seen that the level of the plateau stress can be predicted quantitatively by a simple tensile test. From the studies on cavitation, we know that the nominal stress at the plateau corresponds also to the cavity growth stress for large initial defects. 

Scanning electron microscopy (SEM) can offer a good depth of held, good resolution, and easy specimen preparation. It can be used for immiscible polymer blends, where the phases are sufficiently large and can be easily debonded. Information on surface topography, size, and distribution of the dispersed phase and interfacial interaction between phases can be elucidated with this technique. Elemental analysis on the blend components can also be obtained if the SEM equipment includes an energy dispersion X-ray spectrometer (EDX). 

The fiber or whisker pull out has the potential for the greatest toughening effect and consists in a debonding of fiber from the adjacent matrix consuming large energy. This mechanism depends strongly on the aspect ratio of the second phase and is favored by weak interface bonds. 

For CNTs not well bonded to polymers, Jiang et al. [137] established a cohesive law for CNT/polymer interfaces. The cohesive law and its properties (e g. cohesive strength and cohesive energy) are obtained directly fiom the Lennard-Jones potential from the vdW interactions. Such a cohesive law is incorporated in the micromechanics model to study the mechanical behavior of CNT-reinforced composite materials. CNTs indeed improves the mechanical behavior of composite at the small strain. However, such improvement disappears at relatively large strain because the completely debonded nanotubes behave like voids in the matrix and may even weaken the composite. The increase of interface adhesion between CNTs and polymer matrix may significantly improve the composite behavior at the large strain [138]. 

When two such particles approach through the solvent, there is a slight van der Waals attraction at large separations. But as the gap equates to two polymer molecule diameters, an increasing repulsion is observed. This eventually breaks down into the primary minimum if sufficient force is applied to debond the polymer molecules. Thus, there is a small seomdary minimum in this situation, separated from the primary minimum by a large energy barrier. Such particles behave very much like hard sjAeres, as shown in Fig. 10.20(c), because there is... 

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