Cavitation tensile deformation

In our case, these evaluations clearly point out an increase in volume (most presumably related to a cavitation process) during tensile deformation for all modifred products even under uniaxial loading conditions. This increase in volume can reach 15 %. In the same evaluations, the unmodified PET, either amorphous or semi-crystalline, shows little or no volume change. 

Schneider, K et al. (2006). The Study of Cavitation in HDPE Using Time Resolved Synchrotron X-ray Scattering During Tensile Deformation, Macromolecular Symposia Vol.236 (2006), 241-248... 

Pawlak A (2007) Cavitation during tensile deformation of high density polyethylene. Polymer 48 1397-1409. 

Lv R, Xu W, Na B, Zhang Q and Fu Q (2008) Large tensile deformation behavior of oriented high-density polyethylene A correlation between cavitation and lamellar fragmentation, J Polym Sci Polym Phys 46 1202—1206. 

Figures 1.2-1.3 are from Polymer, Vol. 48, 2007, Author Pawlak A, Title Cavitation During Tensile Deformation of High Density Polyethylene, pp. 1397-1409, Copyright (2007), with permission firom Elsevier Ltd., Oxford, UK.

Pawlak, A., Galeski, A. Cavitation during tensile deformation of polypropylene. Macromolecules 41, 2839-2851 (2008)... 

Fig. 11a-d TEM of a section through part of the fracture surface of a third generation HDPE tested with an initial K of 0.12 MPa m1/2 in Igepol. a Overview, b localised interla-mellar cavitation behind the fracture surface, c region of relatively diffuse deformation behind the fracture surface, showing both relatively coarse cavitation (i) and finer inter-lamellar cavitation (it) and d detail of deformation at the fracture surface (embedded in epoxy and stained in Ru04, tensile axis as indicated by the arrows) [73]... 

Figure 25 shows that the tensile behavior of PMMA and PS, stretched some 10-30 °C below Tg, is very similar to that of PC. Like PC both PMMA and PS exhibit extensive stress-whitening at high extension ratios, k", where the peak or inflection of the stress-strain curve is observed. In Table 3, the value of k" measured for PMMA is compared to the maximum extension ratio, k , of chains between entanglement points. The fact that k" = k provides further evidence that the cavitation in PMMA must be attributed to the same deformation mechanism as discussed in Section 4.2 for PC. The value of k" = kikj" = 6.8 measured for pre-oriented PS is higher than the theoretical value of k = 4.1 included in Table 3. This result is not... 

Goodier (42) showed that for a particle which possesses a considerably lower shear modulus than the matrix, the maximum stress concentration occurs at the equator of the particle. Rubbers are commonly found to undergo cavitation quite readily under the action of a triaxial tensile stress field. Thus, the microvoids are produced by cavitation around the rubbery particles during fatigue crack propagation, together with localized plastic deformation due to interaction between the stress field ahead of the crack and the rubber particles. 

Analyses have been carried out assuming a cavitated particle, that is, the particle is replaced by a void (see the section Cavitation of the Rubber Particles ). The analysis is applied to an annulus of epoxy resin. The volume fraction of the void is 20%. The elastic material properties used for the epoxy matrix are shown in Table I. The elastic-plastic material properties used are shown in Figure 4. Nonlinear geometric effects were included to take account of large deformations. Final failure of the cell was defined (23) to be the applied strain required for the maximum linear tensile strain in the resin to attain the value of 20%. 

Figure 12. Results of simultaneous SAXS and tensile testing of acrylic sheet materials. (a) Results for the AS material show the formation of crazes during deformation. (b) Results for RTAS-8 show that the deformation processes that induce yielding are dominated by particle cavitation. The contour scattering patterns were obtained at the points indicated on the stress-strain curves.

---