- Volume 12 Issue 1
The effect of structure size on the nominal strength of unidirectional fiber-polymer composites, failing by propagation of a kink band with fiber microbuckling, is analyzed experimentally and theoretically. Tests of novel geometrically similar carbon-PEEK specimens, with notches slanted so as to lead to a pure kink band (without shear or splitting cracks), are conducted. The specimens are rectangular strips of widths 15.875, 31.75. and 63.5 mm (0.625, 1.25 and 2.5 in and gage lengths 39.7, 79.375 and 158.75 mm (1.563, 3.125 and 6.25 in.). They reveal the existence of a strong (deterministic. non-statistical) size effect. The doubly logarithmic plot of the nominal strength (load divided by size and thickness) versus the characteristic size agrees with the approximate size effect law proposed for quasibrittle failures in 1983 by Bazant This law represents a gradual transition from a horizontal asymptote, representing the case of no size effect (characteristic of plasticity or strength criteria), to an asymptote of slope -1/2 (characteristic of linear elastic fracture mechanics. LEFM) . The size effect law for notched specimens permits easy identification of the fracture energy of the kink bandand the length of the fracture process zone at the front of the band solely from the measurements of maximum loads. Optimum fits of the test results by the size effect law are obtained, and the size effect law parameters are then used to identify the material fracture characteristics, Particularly the fracture energy and the effective length of the fracture process zone. The results suggest that composite size effect must be considered in strengthening existing concrete structural members such as bridge columns and beams using a composite retrofitting technique.
- Int.J.Solid Struct. v.29 no.9 The role of material orthotropy in fracture specimens for composites Bao G.;Ho.S.;Suo Z.;Fan B.
- IUTAM Prager Symposium on Mech.of Geomaterials: Rocks.Conc.Soils Fracture in concrete and reinforced concrete Bazant Z.P.;Z.P.Bazant(ed.)
- J.of Engrg.Mech.ASCE v.110 Size effect in blunt fracture: concrete,rock,and metal Bazant Z.P.
- J.of Engrg.Mech.ASCE v.119 no.9 Scaling laws in mechanics of failure Bazant Z.P.
- Int.J.of Fracture v.83 no.1 Scaling of quasibrittle fracture: Asymptotic analysis Bazant Z.P.
- Stability of structures: Elastic,Inelastic,Fracture and Damage Theories Bazant Z.P.;Cedolin L.
- J.of Engrg.Materials and Technology ASME v.118 no.3 Size effect and fracture characteristics of composite laminates Bazant Z.P.;Daniel I.M.;Li Z.
- Int.J.of Rock Mech.Mining Science & Geomechanical Abstracts v.28 no.1 Identification of nonlinear fracture properties from size effect tests and structural analysis based on geometry-dependent R-curves Bazant Z.P.;Gettu R.;Kazemi M.T.
- Int.J.of Fracture v.44 Determination of fracture energy,process zone length and brittleness number from size effect.with application to rock and concrete Bazant Z.P.;Kazemi M.T.
- J.of merican Ceramic Society v.73 no.7 Size effect in fracture of ceramics and its use to determine the fracture energy and effective process zone length Bazant Z.P.;Kazemi M.T.
- Computers and Strct. v.16 no.1-4 Micromechanics Budianski B.
- Composites Part B-Engrg. v.27 no.6 Compressive R-curve of a carbon fiber-epoxy matrix composite Fleck N.A.;Sutcliffe M.P.F.;Sivashanker S.;Xin X.J.
- Advances in Appl.Mech. v.33. Compressive failure of fiber composites Fleck N.A.
- Stress Analysis of Cracks Handbook(Second Edition) Tada H.;Paris P.C.;Irwin G.R.