Complex stamp forming of advanced thermoplastic composites

The inherent advantages of thermoplastics over the traditional thermoset composite systems are well recognized in the aeronautics community. The main advantages are the much faster processing and the higher toughness. The current advanced thermoplastic material systems provide excellent mechanical performance but their main disadvantage is the difficult processing. Ideally, future aircraft subcomponents with complex shapes can be readily formed on the basis of pre-consolidated tailored laminates based on uni-directional plies. However, to exploit the full potential of thermoplastic composites models are to be developed in order to predict the process feasibility and product performance in an early stage of development. This paper addresses a number of steps to increase the accuracy of stamp forming simulations and highlights promising results for identifying intra-ply shear and tool-ply behavior of thermoplastic composites. A comparison of the forming behavior of a doubly curved reference part with simulations will be presented. The paper concludes with remarks on necessary future researc

Pull-off strength assessment of co-consolidated AS4/PEEK T-joints

Various joining methods are available for composite structures, with anticipated benefits for the most obvious way of exploiting the nature of thermoplastic materials: melting and reconsolidation. A proper joint selection and detailed design, however, will require quantitative results obtained in an objective and reproducible procedure. The objective of this paper was to develop benchmark procedures and results for the characterization of joining methods for composite materials.\ud AS4 carbon/PEEK joints (UD tape) were manufactured in T-configurations by autoclave processing. Two types of T-joints were co-consolidated on the skin, from a flat strip with an injection molded nugget (“butt joint”) or from a pre-consolidated T-stiffener, respectively.\ud RTD, CTD and HW experiments were performed on both types of configurations. The pre-consolidated T-stiffeners have a higher pull-off load and more gradual damage development than the flat strip/nugget configuration, at the cost of added mass. Also here CTD and RTD performances are similar, whereas the flat strip/nugget configuration shows no significant strength reduction in HW conditions, against 30% for the pre-consolidated T-stiffener configuration

FibreChain: characterization and modeling of thermoplastic composites processing

Thermoplastic composites feature the advantage of melting and shaping. The material properties during processing and the final product properties are to a large extent determined by the thermal history of the material. The approach in the FP7-project FibreChain for process chain modeling of thermoplastic composites is presented

Ising Field Theory on a Pseudosphere

We show how the symmetries of the Ising field theory on a pseudosphere can be exploited to derive the form factors of the spin fields as well as the non-linear differential equations satisfied by the corresponding two-point correlation functions. The latter are studied in detail and, in particular, we present a solution to the so-called connection problem relating two of the singular points of the associated Painleve VI equation. A brief discussion of the thermodynamic properties is also presented.Comment: 39 pages, 6 eps figures, uses harvma