Journal Published Online: 01 December 1991
Volume 13, Issue 4

The Effects of Nonlinear Intralaminar Shear Behavior on the Modeling Accuracy of [(0/90) ,0] and [(+45/−45)] Pin-Loaded Laminates



The effects of nonlinear intralaminar shear behavior on the modeling accuracy of pin-loaded [(0/90)3,0]s and [(+45/−45)]3s fiberglass epoxy composite laminates was quantitatively examined. The comparison of net, bearing, and shearout sectional strains from linear and nonlinear elastic three-dimensional finite-element approximations with similar front surface experimental geometric moire sectional strains formed the basis of this investigation.

Three-dimensional constitutive equations for the [(0/90)3,0]s laminate were developed from actual lamina properties and classical laminate plate theory. A material axes transformation of similar [(0/90)]3s constitutive equations was used to derive the [(+45/−45)]3s laminate constitutive equations. The validity of these equations and the effects of nonlinear intralaminar shear behavior were experimentally investigated by comparing them with laminate uniaxial tensile test data.

Nonlinear elastic [(+45/−45)]3s finite-element results exhibited a nonlinear material response in both the net and bearing sections. Similar results were observed in the [(0/90)3,0]s laminate shearout section. Both pin proximity and load level intensified these effects. Net section [(+45/−45)]3s experimental moire strains agreed well with nonlinear elastic finite-element results at low pin-load level, but surpassed them at higher pin-load levels near the pin. Similar trends were observed in the [(+45/−45)]3s bearing and [(0/90)3,0]s shearout sections, but were slightly skewed by unsymmetric experimental pin boundary conditions.

Variations in nonlinear elastic finite-element and experimental moire sectional strains were examined by a qualitative determination of material damage made with a backlit liquid penetrant experimental arrangement. Material failure was observed in those regions where experimental moire and nonlinear elastic finite-element sectional strains diverged, thus signifying the presence of a discontinuous stress-strain material behavior.

Author Information

Serabian, SM
Mechanics and Structures Branch, Army Materials Technology Laboratory, Watertown, MA
Pages: 13
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Stock #: CTR10232J
ISSN: 0884-6804
DOI: 10.1520/CTR10232J