No abstract

No abstract

The application of non-geodesic filament winding significantly enlarges the design space for composite structures. The formulation and evaluation of these trajectories however, is a rather complicated problem. In this paper, under the limitation of exclusively considering generic shells of revolution, we present the basic equations supporting such a path description. These equations are already known but the emphasis of the derivation presented here is mainly oriented towards the relation between basic geometric quantities (metrics and curvatures) and the resulting fibre path orientation (winding angle distribution). In addition, we propose here the idea of formulating the friction distribution along the tow in such a way that the resulting path can be analytically described. Furthermore, we provide analytical results for some basic shapes.

No abstract

ABSTRACT:The design procedure of nongeodesic filament wound products requires well-determined values for the available friction situated between the applied roving and the supporting surface. In this paper, we propose a mandrel shape with a specially designed meridian profile that enables a linearly proportional relation between the feed eye carriage translation and the measured values for the coefficients of friction. As a result of this property, the optically or chronometrically obtained measurements can directly be translated into coefficients of friction. Additional features of this approach are the high accuracy, repeatability, low experimental costs, and simple machine control strategies. With the proposed mandrel, we performed several experiments corresponding to the variation of typical filament winding-related process parameters: fiber speed, roving tension, roving dimensions, wet versus dry winding, and surface quality of the mandrel. The results indicate that the surface quality of the mandrel and the type of winding process (wet vs. dry fibers) have a considerable influence on the obtained data. The influence of the fiber speed, roving tension, and fiber material on the other hand, is negligible.

No abstract

The sandwich composites fuselages appear to be a promising choice for the future aircrafts because of their structural efficiency and functional integration advantages. However, the design of sandwich composites is more complex than other structures because of many involved variables. In this paper, the fuselage is designed as a sandwich composites cylinder, and its structural optimization using the finite element method (FEM) is outlined to obtain the minimum weight. The constraints include structural stability and the composites failure criteria. In order to get a verification baseline for the FEM analysis, the stability of sandwich structures is studied and the optimal design is performed based on the analytical formulae. Then, the predicted buckling loads and the optimization results obtained from a FEM model are compared with that from the analytical formulas, and a good agreement is achieved. A detailed parametric optimal design for the sandwich composites cylinder is conducted. The optimization method used here includes two steps: the minimization of the layer thickness followed by tailoring of the fiber orientation. The factors comprise layer number, fiber orientation, core thickness, frame dimension and spacing. Results show that the two-step optimization is an effective method for the sandwich composites and the foam sandwich cylinder with core thickness of 5 mm and frame pitch of 0.5 m exhibits the minimum weight.

No abstract