Surface elastic moduli energy

As is true for macroscopic adhesion and mechanical testing experiments, nanoscale measurements do not a priori sense the intrinsic properties of surfaces or adhesive junctions. Instead, the measurements reflect a combination of interfacial chemistry (surface energy, covalent bonding), mechanics (elastic modulus, Poisson s ratio), and contact geometry (probe shape, radius). Furthermore, the probe/sample interaction may not only consist of elastic deformations, but may also include energy dissipation at the surface and/or in the bulk of the sample (or even within the measurement apparatus). Study of rate-dependent adhesion and mechanical properties is possible with both nanoindentation and... 

In summary, we can first say that there is no significant evidence that the low surface energy siloxane-modified epoxies reduce friction compared with the unmodified epoxy or the ATBN- and CTBN-modified epoxies. Based on the results of the steel ball-on-epoxy experiments, the most significant effect of the siloxane modifiers is the reduction of the elastic modulus associated with large closely spaced domains. The longer initiation times and lowest wear rates observed for the siloxane-modified epoxies were generally associated with a lower modulus. Epoxy modified with the CTBN of 18% AN content also showed lower wear rates with lower modulus but, in contrast with the siloxane-modified resins, had shorter initiation times with lower modulus. 

Extrudability, bulk density, flexural strength, modulus of elasticity, absorbed energy of specimens were examined. After bending tests, fractured surface was observed by SEM and porosity was measured. 

Compaction Microlevel Processes Compaction is a forming process controlled by mechanical properties of the feed in relationship to applied stresses and strains. Microlevel processes are controlled by particle properties such as friction, hardness, size, shape, surface energy, and elastic modulus (Fig. 21-86). The performance of compaction techniques is controlled by the ability of the particulate phase to uniformly transmit stress, and the relationship between applied stress and the compaction and strength characteristics of the final compacted particulate phase. 

This balance between interfacial propagation and bulk deformation has been described for linear elastic materials [56] and results from the competition between two mechanisms the velocity of propagation of an interfacial crack, which is controlled by the critical energy release rate Gc, and the bulk deformation, which is controlled by the cavitation stress and hence essentially by the elastic modulus E or G. In the hnear elastic model, the key parameter is the ratio GJE, which represents the distance over which an elastic layer needs to be deformed before being fuUy detached from the hard surface. This model has been verified experimentally for elastic gels [57]. 

A plate of high-density polyethylene has a surface crack 7.5 pm in one face. The plate fractures in a brittle fashion when a force of 6 X 10 N m is apphed in a direction perpendicular to the crack. The elastic modulus of the polyethylene is 0.95 GPa. Estimate the surface energy of the material. 

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