Glass epoxy

Figure 1 Amplitude distribution of AE signals from model glass epoxy specimens...

Of course, in order to vary the mass transport of the reactant to the electrode surface, the radius of the electrode must be varied, and this unplies the need for microelectrodes of different sizes. Spherical electrodes are difficult to constnict, and therefore other geometries are ohen employed. Microdiscs are conunonly used in the laboratory, as diey are easily constnicted by sealing very fine wires into glass epoxy resins, cutting... 

In Figure 5.23 the finite element model predictions based on with constraint and unconstrained boundary conditions for the modulus of a glass/epoxy resin composite for various filler volume fractions are shown. 

Fig. 9. Pie2oelectric embedded inside a glass—epoxy laminate to form a composite smart stmcture.

A single ply glass/epoxy composite has the properties Usted below. If the fibres are aligned at 30° to the x-direction, determine the value of in-plane stresses, a, which would cause failure according to (a) the Maximum Stress criterion (b) the Maximum Strain criterion and (c) the Tsai-Hill criterion. 

To gain a visual appreciation for how the moduli vary, values typical of a glass-epoxy composite material are plotted from Equation... 

Several experiments will now be described from which the foregoing basic stiffness and strength information can be obtained. For many, but not all, composite materials, the stress-strain behavior is linear from zero load to the ultimate or fracture load. Such linear behavior is typical for glass-epoxy composite materials and is quite reasonable for boron-epoxy and graphite-epoxy composite materials except for the shear behavior that is very nonlinear to fracture. 

As an illustration of the results of the measurements just described, the mechanical properties for four unidirectionally reinforced composite materials, glass-epoxy, boron-epoxy, graphite-epoxy, and Kevlar 49 -... 

Glass-Epoxy Boron-Epoxy Graphite-Epoxy Kevlar -Epoxy... 

Most comparisons of a failure criterion with failure data will be for the glass-epoxy data shown in Figure 2-36 as a function of off-axis angle 0 for both tension and compression loading [2-21]. The tension data are denoted by solid circles, and the compression data by solid squares. The tension data were obtained by use of dog-bone-shaped specimens, whereas the compression data were obtained by use of specimens with uniform rectangular cross sections. The shear strength for this glass-epoxy is 8 ksi (55 MPa) instead of the 6 ksi (41 MPa) in Table 2-3. 

Figure 2-36 Measured Failure Data for Glass-Epoxy (After Tsai [2-21])...

As with the maximum stress failure criterion, the maximum strain failure criterion can be plotted against available experimental results for uniaxial loading of an off-axis composite material. The discrepancies between experimental results and the prediction in Figure 2-38 are similar to, but even more pronounced than, those for the maximum stress failure criterion in Figure 2-37. Thus, the appropriate failure criterion for this E-glass-epoxy composite material still has not been found. 

Results for this criterion are plotted in Figure 2-40 along with the experimental data for E-glass-epoxy. The agreement between the Tsai-Hill failure criterion and experiment is quite good. Thus, a suitable failure criterion has apparently been found for E-glass-epoxy laminae at various orientations in biaxial stress fields. 

The Tsai-Hill failure criterion appears to be much more applicable to failure prediction for this E-glass-epoxy composite material than either the maximum stress criterion or the maximum strain failure criterion. Other less obvious advantages of the Tsai-Hill failure criterion are ... 

For E-glass-epoxy, the Tsai-Hill failure criterion seems the most accurate of the criteria discussed. However, the applicability of a particular failure criterion depends on whether the material being studied is ductile or brittle. Other composite materials might be better treated with the maximum stress or the maximum strain criteria or even some other criterion. 

Figure 3-20 Bounds on E2 for a Glass-Epoxy Composite Material...

The experimental results for of a glass-epoxy composite material are shown along with the theoretical prediction from Equation (3.66) as a function of resin content by weight in Figure 3-44. Theoretical results are shown for contiguity factors of C = 0,. 2,. 4, and 1. Apparently, C = 0 is the upper limit of the data whereas C =. 4 is the lower limit. Thus, the concept of contiguity factor is further reinforced. 

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