Biaxial Fatigue Loading of Notched Composites

Abstract

Thin-walled, 2.54-cm diameter tubular specimens of graphite/epoxy (Fiberite T300/1034) were fatigue cycled in combinations of axial, torsion al, and internal pressure loading. Two different four-ply layup configura tions were tested: [0/90] s and [±45]s; each tube contained a 0.48-cm diameter circular hole penetrating one wall midway along the tube length. S-N curves were developed to characterize fatigue behavior under pure axial, torsional, or internal pressure loading, as well as combined loading fatigue. A theory was developed based a plane stress model which enabled the S-N curve for combined stress states to be predicted from the S-N data for the uniaxial loading modes. Correlation of the theory with the experi mental data proved to be remarkably good.

Fatigue of fiber reinforced composites under multiaxial loading

“…Francis and coworkers [10] extended Hill's anisotropic yielding criterion [69] to fatigue for [AE45] graphite/epoxy tubes. The TsaieWu criterion [70] was used by Fujii and Lin [35] to calculate failure envelopes at constant fatigue lives for tensionetorsion data on glass/polyester tubes.…”

“…In spite of the importance that notches and stress concentrations can have in the design of structural parts, their influence on multiaxial fatigue strength has rarely been investigated [10,15,16,29,32,33]. It is difficult to draw general design indications from the few data available; however, from at least one of the papers cited, some interesting conclusions can be obtained.…”

Fatigue of fiber reinforced composites under multiaxial loading

“…Examples are reported in refs [8,30,39,40,43,44,46,54,55,57,[78][79][80][81][82][83][84][85][86] and some of them are briefly discussed below. Examples are reported in refs [8,30,39,40,43,44,46,54,55,57,[78][79][80][81][82][83][84][85][86] and some of them are briefly discussed below.…”

“…in spite of the importance that notches and stress concentrations can have in the design of structural parts, their influence on multiaxial fatigue strength has rarely been investigated [30,35,36,49,52,53]. in spite of the importance that notches and stress concentrations can have in the design of structural parts, their influence on multiaxial fatigue strength has rarely been investigated [30,35,36,49,52,53].…”

Fatigue Life Prediction of Notched Composite Components

“…Using the macrostress component So, at each point on the periphery of the hole, the microstress components oij at the same location were determined using the unit block approach and equations (21) and (22). The microstresses were not uniformly distributed in the block and the highest concentration of the shear oI3 and normal cII stresses occurred in the matrix adjacent to the fibre at X2 +O.…”