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The authors write:
“Tow-placement technology expands the range of manufacturable laminate designs by allowing fibre-tows to be steered throughout each lamina. Since the fibre orientation defines the stiffness (and many of the intrinsic) properties of a laminate, composite panels with in-plane variations of the fibre angle were termed variable stiffness panels (Fig. 1). These panels demonstrate great potential for improving the structural performance of composite structures in terms of stiffness, buckling, and failure loads.”
FROM:
C.S. Lopes (1 and 2), P.P. Camanho (2), Z. Gürdal (1) and B.F. Tatting (3)
(1) Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft, The Netherlands
(2) DEMEGI, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal
(3) ADOPTECH Inc., Blacksburg, VA 24060, USA
“Progressive damage analysis of tow-steered composite panels in postbuckling”, 16th International Conference on Composite Materials, July 2007
ABSTRACT: Machines capable of individually controlling fibre tows and placing them onto the surface of a laminate with curvilinear topology are available nowadays. Due to the variation of properties along their surface, such structures are termed variable-stiffness composite panels. Experimental research demonstrated that properly designed tow-steered panels buckle at higher loads than traditional straight-fibre laminates. Also, numerical analyses by the authors demonstrated that first-ply failure of these designs is remarkably postponed. The focus of this paper is to extend those analyses into the postbuckling progressive damage behaviour and final structural failure. A user-developed continuum damage model implemented in the finite element code ABAQUS is employed in the characterisation of damage initiation and propagation. As with damage initiation, failure of curvilinear-fibre panels is remarkably postponed as compared with straight-fibre laminates. Tow-steered panels also show to be more tolerant to notches than traditional laminates. By taking into account the residual thermal stresses, not only predicted and experimented buckling loads show remarkable agreement but also predicted final failure loads of tow-steered panels in postbuckling are within 12% of the experimental results.
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