โ Scribed by Andrzej Pawlak; Andrzej Galeski
No coin nor oath required. For personal study only.
Microphotoelasticity gives the possibility of determining stresses in systems with small inclusions. We studied four systems with the same matrix (epoxy resin) and different inclusions of spherical shapes. The distributions of stresses and pressure, after the application of external tensile forces, were determined. In a matrix with a hard inclusion, tensile stresses concentrated at the pole. For a soft inclusion, that is, a poly(vinyl acetate) bead or an air bubble, the tensile stresses concentrated at the equator with some compression at the pole. The soft inclusion promoted the stress relaxation by the change in its shape. In the matrix with a stiff inclusion, such as a steel or glass bead, debonding was observed at the interface near the pole area. In such a case, the stress concentration region moved toward the tip of the debonding. For a hard inclusion, the pressure at all points of the interface was negative, and the maximum was found at the pole near the inclusion surface from โ6 to โ10 MPa. This region was sensitive to the initiation of destruction processes such as cavitation and debonding. For a soft inclusion, the pressures at the pole and equator were comparable, but the signs were opposite, being positive at the pole (compression) and negative at the equator (expansion). ยฉ 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1436โ1444, 2002
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