A solution for the problem of load introduction in biaxial fatigue tests

Abstract

The concept of introduction of biaxial loads in a specimen made of sheet material using soft clamps of unidirectional aramid composite sheet is presented. Using this concept it is possible to generate realistic biaxial tensile stress states in specimens made of sheet materials without the introduction of unwanted fatigue critical areas.

Recent Development of Planar Cruciform Experiment on Biaxial Tensile Deformation and Failure of Unidirectional Glass/Epoxy Composite

“…Proper design of multiaxial composite specimens is a complex task [13][14][15][16][17][18][19][20][21][22][23][24][25]. Basic requirements for the design are [1]:…”

“…Cruciform specimens are, in theory, well suited [5,6] for biaxial composite tests under combined in-plane transverse and longitudinal stresses, when the fiber orientation is aligned with specimen loading arms. Proper specimen design is complicated by load sharing and differential deformations between the gage section and adjacent loading arms due to Poisson's effect [13][14][15][16][17][18][19][20]. Cruciform specimens have been used successfully to study cross-ply and other multidirectional laminates [13][14][15].…”

“…Related designs with thickness-tapered tabs have been used to study multidirectional laminates [1,13]. The stiffness anisotropy of unidirectional laminates may also be used to reduce loading arm transverse stiffness [17,18]. Other specimens feature a thickness-tapered gage section machined from a thicker laminate plate [14,15].…”