Catálogo de publicaciones - libros

The present study is concerned with a probabilistic homogenization analysis of polymeric cellular media to be used as core materials for sandwich structures. The approach is based on a randomized representative volume element in conjunction with a Monte Carlo simulation. The results for stiffness and strength are evaluated by stochastic methods.

Driven by the desire to understand the influence of various mechanical properties and geometric features of foam materials, on the stiffness, failure mechanisms and fatigue life of sandwich materials, 3D finite element models of amorphous cellular structures have recently been developed and analyzed. Different algorithms were used to generate seed points of Voronoi tessellations, such as randomly distorted regular lattice distributions and totally random distributions. Periodic boundary conditions were used on representative volume elements containing hundreds of cells. Some comparison with experimental data from real foam materials was made and the agreement was found to be good. In the presented paper discrepancies between the used models and real foams are discussed and it is concluded that the adopted approach has substantial potential although there are some obvious routes for further improvement.

The present work investigates the possibilities and drawbacks when applying sandwich as opposed to single skin composites in the flanges of the load carrying spar in a future 180 m wind turbine rotor. FEA is applied to investigate two basic designs with single skin and sandwich flanges respectively. For a single skin design, buckling is critical compared to other design criterions. By introducing sandwich, a significant weight reduction and increased buckling capacity is obtained. Tower clearance now becomes critical. Proper choice of core material and thickness is important to prevent face wrinkling and large tip deflection. Geometric non-linear analysis showed sensitivity to imperfections.

Hurling is one of the fastest team games and related to a long term tradition in rules and practice. Former attempts to manufacture composite hurleys by the process of liquid composite molding (RTM) or injection molding failed. With the compression molding process the mechanical properties required, the traditional game performance, and target costs were matched.

The aim of the present research is to extend the knowledge of mechanical properties both on single components and on complete structure employed for snowboard. Flexural and torsion tests are performed to acquire important comparison parameters between snowboard sandwich structures that differ for the core material employed (wood, PVC foam core). A simplified FEM model is proposed to simulate the flexural tests of the sandwich structure showing good predictive capability.

In this paper the complete development and testing of an innovative composite bicycle frame is presented. The frame comprises epoxy resin, glass and carbon fabrics, foam core and metallic inserts produced by the resin transfer moulding technique in a closed mould. The new frame is lighter, stiffer and cheaper from the corresponding aluminium tube frame.

This article deals with the design, manufacturing and testing of new innovative load introductions into sandwich structures consisting of fibre reinforced plastics. Vitally new to these load introductions is the principle of local through-the-thickness reinforcements by threads, resulting in an excellent connection of both face sheets and core and, if necessary, also the load introduction element itself. The threads are introduced into textile face sheets and the core by stitching process. After stitching, the textile face sheets and the threads are impregnated with the polymer matrix using a liquid composite moulding process. The resulting mechanical out-of-plane properties of the so-called IDAK load introductions outperform current state-of-the-art load introductions.

Studies are presented on the performance of insert assemblies of the sandwich structures with localized through-the-thickness compressive loading. Through-the-thickness and partially inserted fully potted inserts are studied. Insert material considered are: aluminum and 3D woven composite. Experimental results are compared with analytical predictions. It is observed that the specific strength of 3D woven composite inserts is more than that of aluminum inserts.

Phenolic resin has excellent properties of fire resistance, low smoke during burning, and it also has a good balance between its cost and mechanical properties compared with other types of resin used in FRPs. If phenolic resin can be employed as a matrix of FRP, such FRP can have a higher fire safety factor which will be a desirable property in the structures of vessels and railway carriages. However, for the case of the resole type of phenolic resin, water due to condensation reaction remains in the matrix, and this water evaporates resulting in the formation of voids during curing process. In order to develop a new type of phenolic composite that be able to overcome this weakness, we used a foam type of phenolic resin and glass fibers as the matrix and as the reinforcement, respectively. We then developed a new pultrusion technique for the new composite, namely the phenolic foam composite (PFC) and examined its mechanical properties and thermal conductivity. In this paper, we reported a new technology to mold not only a phenolic foam composite but also a sandwich beam in which the PFC as a core and a thin phenolic GFRP or CFRP as facelayers were used. We also examined thermal and bending properties of this sandwich beam.

The topic of this investigation deals with experimental and numerical analysis of different configurations of hollow and of PMI foam-filled A-stringers/A-formers under axial compression load and bending moment. In this connection the Finite-Element-Analysis (FEA) program ANSYS® is used for the numerical approach. The result of this analysis is that PMI foam-filled A-profiles show significant higher buckling loads in comparison to hollow ones. These improvements depend on the loading conditions, e.g. bending moment and axial compression, as well as the geometry of the A-profile.