Catálogo de publicaciones - libros

In this investigation, three-point bend tests were performed on pre-cracked and unnotched sandwich structures offering a wide range of fracture toughnesses. It has been shown that an areas-based method is the most appropriate for characterizing the fracture toughness of the sandwich structures. It has also been shown that tough core materials are less sensitive to delaminations between core and skin than their more brittle counterparts.

In this study in plane shear tests on sandwich plates were performed using two different experimental set-ups. Failure modes, as well as maximum failure loads were compared with predictions using sandwich calculation equations given by Zenkert and Plantema. It could be shown, that the prediction of failure load and mode was quite consistent with measurements for panels of 10mm thickness or more. Very thin panels could not be predicted correctly.

Face/core debond damaged sandwich panels exposed to uniform and non-uniform compression loads are studied experimentally. The panel geometry is full-scale rectangular with a centrally located circular prefabricated debond. The results show a considerable strength reduction with increasing debond diameter, with the failure mechanisms varying between buckling driven debond propagation and face compression failure for large and small debonds respectively.

This paper presents a FEM based numerical model for prediction of residual strength of damaged sandwich panels. As demonstrated, the model can predict the maximum load carrying capacity of real-life panels with debond damages, where the failure is governed by face-sheet buckling followed by debond growth. Comparison of the theoretical predictions is carried out against a series of large-scale experiments described in Lundsgaard-Larsen et al. [1].

Fastenings are an essential part of the sandwich constructions. Mechanical f fastenings are needed to fix the panels to the frame of a building and fasteners are used to mount additional covering and components to a face of a sandwich panel. The paper studies failure modes on typical fastenings and introduces models to evaluate the resistance and to adjust the test results for design equations.

Application of GRP/PVC-Foam sandwich structures on naval ships strongly depends on the mechanical strength and collapse behaviour of the joints of the structure. Quasi-static and dynamic experiments were executed to determine the failure modes and failure progression of T-joints. The results were used to determine the focus of the material tests, and to determine the main properties of failure models that were developed.

The deformation mechanism of an aluminium foam core/thermoplastic composite facing sandwich structure was compared with an equivalent polymer foam core sandwich structure under 4pt bend loading. Full field strain analysis showed the metal core deformed extensively mid-beam while the polymer foam had high strain concentrations under the load rollers.

Hail strikes of possibly exceeding an energy level of 50 Joules may cause multiple-site damage to thin gauged composite airplane structures. If not repaired properly, they may trigger an extensive damage to airplane structures and disruptions to airline operations, and therefore posing a major maintenance and repair concern for the airlines. It is important both for the OEM and the airlines to be able to classify the hail strike damage for appropriate repair procedure. Therefore, this study presents a methodology to assist engineers in the classification of the repair type for hail strike damage. The methodology involves an accurate prediction of the stress and strain fields, and residual strength prediction.

Polymer sandwich configuration is now extensively used in many engineering structural applications such as ships, boats, spacecraft and aircraft. The design and manufacturing aspects of such materials are well known and regulations and codes exist to help designers, producers and operators of such artifacts. However, maintenance and repair are issues that have received relatively little attention. The aim of the research is to understand the influence of BVID upon structural repairs made to advanced composite sandwich structures and to determine whether a tapered scarf repair is as damage resistant and damage tolerant as the original structure.

Dynamical transient behavior of a shallow sandwich panel subjected to impulsive pressure load is studied. Governing equations and boundary conditions are derived from the Hamiltonian of this mechanical system. The problem is solved by the use of finite difference (FD) technique, which is illustrated by an example