With delamination

If, as in the fracture surface type shown in Fig. 3 on the left hand side, the width of the featureless delamination is increasing with delamination length this is also reflected in the R-curve (Fig. 5). There, values are dropping from relatively high cross-ply -values to a value typical of the unidirectional laminate. This could be a hint that energy release rates determined for the cross-ply laminates using the analysis developed for the unidirectional material are valid in the sense that relative proportions are conserved. 

Rarely problems with delamination and spalling in vivo. 

The mesoporous structure, with high surface area could provide simple accessibility of guest molecules to the active sites and increase their chances to receive light. One research group fabricated mesoporous photocatalysts with delaminated structure. The exfoliated layered titanate in aqueous solution was reassembled in the presence of anatase Ti02 nanosol particles to make a great number of mesopores and increase the surface area of Ti02 [370] (see Table 6). 

Of these failure mechanisms, the major ones associated with delamination include contaminated surfaces, inadequate adhesive coverage, stresses, voids, and moisture absorption. Many of these mechanisms are also responsible for other failure modes besides delamination. 

The many tests on coupons (with supported edges), and on stiffened compression panels, can reduce the residual strength by more than 70% [11]. Figure 9.6 shows the results of a series of tests by Olsson [12] conducted on panels of various thicknesses, edge conditions and materials. The decrease in residual strength with delamination width is dramatic. There is a modest increase in residual strength for the toughened epoxy (6376) and thermoplastic PEEK. 

The coloration that occurred however, was restricted to the near-surface region. Figure 12 shows an on-edge view of the pure polymer sample with delamination or peeling of the exposed surface. Similar observations were made for the nanocomposite samples. 

A mechanism which begins with delaminations that are initiated at opposite ends of a single grain, but on different basal planes. With further deformation, the torque separates the lamellae between the two delamination cracks to ultimately form crack bridges not unlike those shown in Figure 7.18b. 

However, the fracture toughness G nipact related to the delamination fracture toughness G y., since both are dealing with delamination damage. 

Sealed, 2mm-thick BTMs were applied with delamination scheduled for 28days however, spontaneous delamination and fragmentation were noted in several sites. Only two sites maintained a seal that could be delaminated by Day 28. The wounds contracted to 50% their original size. CCS was applied to delaminated BTMs to test... 

An alternative method of producing natural rubber based clay reinforced nanocomposites with outstanding properties is by using a spray drying technique. In this technique the siUcate layers of clay will be well dispersed in an irradiated polymer latex and this mixture will be sprayed through hot air to produce micrometre-sized liquid droplets. When the solvent is fully evaporated, micrometre-sized polymer spheres with delaminated clay silicate layers on their surface are produced. These spheres can later be melt blended with natural rubber to produce ternary nanocomposites. It is noteworthy that exfoliation of nanofillers can still be achieved without modification of the nanofiller surface, thus the expensive modification process can be eliminated. 

Figure 12.5 shows a schematic of the structure of a V-ribbed belt. The most commonly reported mechanical failure mode for this type of belt is wear, with delamination not generally perceived as a problem. This is of interest as most flexible composite elements will have a delamination failure mode of some description, and so the most obvious question to ask is why the V-ribbed belt does not. The probable answer is that the belt cord in a V-ribbed belt is isolated from the major distortions of the belt through its position above the belt/pulley interface. The large majority of the distortion of the belt takes place in the belt ribs, away from the cord. If the four shear stresses identified previously by Gerbert and Fritzson for a V-belt are considered, it can be seen that of the four i) and ii) do not apply to the cord layer in a V-ribbed belt. The cord layer in a V-ribbed belt therefore does not incur shear stress to the same extent as that in a V-belt. Thus the V-ribbed belt may be considered a better design in composite terms, with the individual elements of the composite more effectively employed and protected. 

In many particular cases, there is a direct correspondence between the Irwin and Griffith criteria, as was noted above an connection with the result in (4.27). However, the latter criterion has the distinct advantage that the energy release rate can often be determined, or at least estimated, without the need for a complete solution of the boundary value problem for the stress field in the body. For this reason, it is selected as the basis for the present discussion. Many of its special features and numerous extensions of the basic concept will become evident in the sections that follow, in the course of discussing various issues concerned with delamination and fracture in thin film configurations. 

The degradation in performance with MEAs 10 and 11 occurred at potentials of —1.8 and —1.9 V. The initial assumption concerning the cause of this fault was a problem with the cell orientation. When the cell was repositioned so that the water outlets were in a vertical position, a steady and continuous stream of fine gas bubbles was observed in the outlet stream. However further testing with subsequent MEAs found that this was more to do with delamination problems due to vigorous gas evolution. Thus the next series of tests were done at potentials of —1.7V. 

N. Widjojo, T.S. Chung, and W.B. Krantz, A morphological and structural study of Ultem/P84 copolyimide dual-layer hollow fiber membranes with delamination-free morphology. Journal of Membrane Science 294 (2007) 132-146. 

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