• Glud, Jens Ammitzbøll
• Jakobsen, Johnny
• Krogh, Christian

Abstract

Composite parts made from pre-impregnated fiber mats, so-called prepregs,<br/>are frequently used in the aerospace industry due to their superior mechanical<br/>properties. Currently, woven prepregs are manually placed into a mold prior<br/>to curing. The manual layup process is costly and can yield significant quality<br/>variations in the final part. Thus, an automated layup solution is under<br/>development where a robot can manipulate and drape the prepregs into the<br/>mold.<br/>The success of this implementation relies on both accurate and computationally<br/>efficient models describing the mechanical behavior of the prepreg<br/>material which is the scope of the PhD project. The models will aid in<br/>generating feasible robot trajectories, i.e. draping sequences. Here feasible<br/>entails that the fiber plies do not deform undesirably while being manipulated<br/>by the robot as well as drapes onto the mold without wrinkles, air pockets and<br/>other defects. The models must, among other things, account for the nonlinear<br/>anisotropic constitutive behavior, viscoelasticity, possible plasticity,<br/>and contact which includes friction between the ply-mold and ply-end effector<br/>interfaces. The problem is path dependent and thus the transient aspect of the<br/>draping must be taken into account.<br/>The accurate modeling is accomplished with an explicit Finite Element (FE)<br/>scheme with shell elements. Material characterization in the form of uniaxial<br/>tensile tests, bias-extension tests (45 ° tensile test) and bending tests provide<br/>input for the model. With basis in an experimentally validated FE model and<br/>with improved knowledge of the mechanics of the plies, more efficient<br/>models and/or simple wrinkling criteria are to be developed at a later stage.

Topics

• impedance spectroscopy
• anisotropic
• composite
• viscoelasticity
• bending flexural test
• defect
• plasticity
• curing
• woven