• Tatting, Bf
• Camanho, Pp
• Gurdal, Z.
• Lopes, Cs

Abstract

The recent developments on tow-placement technology have led to the production of machines capable of controlling fibre tows individually and placing them onto the surface of a laminate with curvilinear topology. Due to the variation of properties along their surface, such structures are termed variable-stiffness composite panels. In previous experimental research tow-steered panels have shown increased buckling load capacity as compared with traditional straight-fibre laminates. Also numerical analyses by the authors showed that first-ply failure occurs at a significant higher load level. 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 identification of damage initiation and material stiffness degradation. By taking into account the residual thermal stresses, not only predicted and experimented buckling loads show remarkable agreement but final failure of tow-steered panels in postbuckling, due to material damage, is predicted to within 12% of the experimental results. Curvilinear-fibre panels not only show up to 55% higher strength values than straight-fibre laminates but also damage initiation is postponed. Tow-steered panels also show more tolerance to notches than traditional laminates.

Topics

• impedance spectroscopy
• surface
• strength
• composite