Page 384 - T. Anderson-Fracture Mechanics - Fundamentals and Applns.-CRC (2005)

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364 Fracture Mechanics: Fundamentals and Applications

(a)

(b)

FIGURE 8.6 Effect of specimen width on K Q in two engineering plastics: (a) rigid PVC and (b) polycarbonate.
Taken from Cayard, M., “Fracture Toughness Testing of Polymeric Materials.” Ph.D. Dissertation, Texas A&M
University, College Station, TX, 1990.

Figures 8.8(a) and 8.8(b) are plots of fracture toughness vs. thickness for the PVC and the PC,
respectively [4]. Although all of the experimental data for the PVC are below the required thickness
(according to Equation (8.25)), these data do not exhibit a thickness dependence; Figure 8.8(a)
indicates that the E 399 thickness requirement is too severe for this material. In the case of the PC,
most of the data are above the E399 thickness requirement. These data also do not exhibit a thickness