Transverse properties

The film tube is collapsed within a V-shaped frame of rollers and is nipped at the end of the frame to trap the air within the bubble. The nip roUs also draw the film away from the die. The draw rate is controlled to balance the physical properties with the transverse properties achieved by the blow draw ratio. The tube may be wound as such or may be sHt and wound as a single-film layer onto one or more roUs. The tube may also be direcdy processed into bags. The blown film method is used principally to produce polyethylene film. It has occasionally been used for polypropylene, poly(ethylene terephthalate), vinyls, nylon, and other polymers. 

Table 24. Long Transverse Properties of Wrought Aluminum Alloy Products...

R. L. Foye, An Evaluation of Various Engineering Estimates of the Transverse Properties of Unidirectional Composites, Proceedings of the 10th National Sympo-... 

With ladle plunging or additions through a degassing unit, the costs per ton can go as high as 12.00 per ton for guaranteed sulfide shape control and maximum transverse properties which generally require a RE/S equal to U instead of 3. 

Experimental determination of the properties of any material is very important. This is particularly true in the case of fibrous materials because general insufficient data are available for them. Fibers have one very long dimension and the other two extremely small. This makes determination of their properties, physical and mechanical, far from trivial. In particular determination of their transverse properties, i.e. in the direction of the fiber diameter, can be difiicult. In this chapter we describe experimental techniques to determine some physical and mechanical properties of fibers. 

Therefore, moisture absorption has a larger effect on the transverse properties of a typical composite system. Despite this, the strength of a 0° composite is also affected by moisture ingress since the reloading of a broken fibre occurs through shear stress transfer Ifom the interphasal matrix. To achieve isotropy, unidirectional plies are stacked at a set of angles such as 0°, 45° and 90° to form a laminate. In this situation, moisture ingress will modify the residual stress state in the individual laminae. 

These values, for example, might correspond to a roving-reinforced panel employing an intermediate TS polyester plastic. When the orthotropic material is balanced, the longitudinal and transverse properties are the same, that is, Ei= Ej and Vu- = Vji. The properties are symmetrical about the 45° angle, as shown in Figure 8.25 in which the following values were used ... 

Finally, a word about the fracture properties of poly(p-benzamide) fibre. Not unexpectedly it appears that the extreme axial properties of the fibre have to be paid for in terms of very poor transverse properties. Indeed the higher the modulus the greater is the tendency for the fibre to exhibit a failure mode consisting of fibrillation and splintering. Words cannot describe this as well as the Stereoscan photograph (Fig. 10) and Fig. 11 which compares fracture surfaces in a glass fibre-epoxy composite (a) and a poly(p-benzamide)-epoxy composite (b) prepared in the authors laboratories. 

Fibers and films possess anisotropic mechanical properties. Hence a discussion of this subject should include tensile and compression properties in at least two different directions, viz. in longitudinal and transverse direction to the filament axis. However, in general little is known of the transverse properties of fibers and films. 

One final point to be remembered is that if the fibre orientation is largely unidirectional, and hence the transverse properties are relatively low, forming a hole through the material can significantly reduce its strength. 

This method does not explicitly contain terms associated with the degree of bonding, fibre spacing, fibre shape, packing geometry and other influential factors which can significantly affect the shear moduli and transverse properties of the lamina. However, as this method is conservative, the actual properties will always be higher than those predicted. 

For the transverse properties the reinforcing effect of the fibres is ignored and the failure strength is taken as that of the matrix. 

Pitch based carbon fibers, however, do have a higher yield of 85% with a high resultant modulus but, due to their more graphitic nature, they will have poorer compression and transverse properties as compared to PAN based carbon fibers. 

Biaxial orientation is imparted to the coextruded LCP layer, greatly improving transverse properties and eliminating splitting and thinning of the LCP layer. 

Question by E. W. Johnson, Alcoa I am under the impression that the properties which you have determined are largely or entirely longitudinal. Work done at NASA indicates that transverse properties of the austenitic stainless steels are substantially or significantly lower. Does your test program include an investigation of the orientation effect ... 

Molecular orientation is another important factor influencing mechanical properties of coextruded films (11). Biaxial orientation can greatly improve film strength. However, uniaxial or highly unbalanced orientation causes poor transverse properties, which result in easy splitting of coextruded films in the machine direction. This tendency may occur even when a relatively thin layer responds to unidirectional orientation and propagates failure to thicker adjacent layers. 

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