Abstract
WE have measured values of the fracture surface energy (γ) at + 20° C of a sample of high molecular weight poly(methyl methacrylate) sheet (‘Perspex’, manufactured by Imperial Chemical Industries, Ltd., Plastics Division). In order to measure γ over a wide range of crack propagation velocities (ċ), we used three different experimental techniques: (1) A modification of the static loading method described by Van den Boogaart and Turner1 in which the crack length was measured as a function of time. From the results it was possible to deduce the relation between γ and ċ by assuming a value for Young's modulus (E = 2.85 × 1010 dynes/cm2). This technique covered the range of velocities from comparatively slow rates (≃ 10−4 cm/sec) up to about 1 cm/sec. Beyond this the crack propagation rate increased rapidly and the specimen failed catastrophically. (2) A modification of the cleavage technique described by Broutman and McGarry2 which produced controlled crack growth at various lead screw speeds. (3) Charpy impact tests on sharply notched specimens. γ was taken as the ratio of the energy to break to the area of the new surfaces created during crack growth. Although ċ was not measured accurately, it is between the pendulum velocity at the point of impact (240 cm/sec) and tho maximum possible crack propagation velocity (∼ 105 cm/sec). Thus it is substantially higher than in the other experiments.
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References
Van den Boogaart, A., and Turner, C. E., Trans. J. Plast. Inst., 31, 109 (1963).
Broutman, L. J., and McGarry, F. J., J. App. Polymer Sci., 9, 589 (1965).
Berry, J. P., Fracture Processes in Polymeric Solids, edit. by Rosen, B., 221 (Interscience, 1964).
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VINCENT, P., GOTHAM, K. Effect of Crack Propagation Velocity on the Fracture Surface Energy of Poly(methyl methacrylate). Nature 210, 1254 (1966). https://doi.org/10.1038/2101254a0
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DOI: https://doi.org/10.1038/2101254a0
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