OLE THYBO THOMSEN

This paper discusses recent work on the development of multimaterial structural details based on unidirectional carbon fibre-reinforced plastics (UD CFRP) adhesivelly bonded to thin-walled aluminium box-section extrusions. Numerical analyses have been developed to predict the performance of these structures and to identify key material properties, failure modes and structural limitations. The effects of linear-elastic and non-linear properties of the adhesive on the structural behaviour of the beams have been considered. Both experimental test and theory have demonstrated optimum performances in terms of strength, ductility and preferred failure modes by varying the thickness, stiffness or length of the CFRP reinforcing laminate and adhesive’s tensile modulus.

Abstract

The paper provides experimental data on vibration damping of adhesively bonded single-lap joints with steel adherends. Modal testing has been performed with several joints, using different adhesive materials. Additionally, the adhesive materials mechanical and damping characteristics have been determined in a DMTA test. The mechanical properties of the adhesives have been measured also in a tensile test. Finally, the lap shear strength of the single-lap joints was measured.

Abstract

Polymer based composite systems are nowadays widespread in many industrial applications, from aerospace, aeronautical, naval, automobile, building to medical prosthesis. Nevertheless these materials are limited in these applications due to the lack of confidence in the prediction of the residual properties in a long-term basis, i.e., for a given loading history and environmental conditions. Much work have been done to overcome these difficulties, improving the theoretical models and establishing efficient and reliable experimental methodologies to determine the relevant properties.

Polymers exhibit a time-dependent behavior as a consequence of its viscoelastic nature. The composite systems due to the advanced fiber reinforcement form a high-performance structural material. Reinforcements, as carbon fibers, exhibit a negligible viscoelastic behavior and even when combined with a viscoelastic matrix that results in plies which exhibit very small amount of creep or stress relaxation in the reinforcement direction. However these plies may exhibit considerable amounts of creep in transverse and shear directions. When these plies are combined to form a laminate it results in a structure that exhibit creep, stress relaxation and delayed failure.

IJSBRAND J. VAN STRAALEN

Abstract

This paper deals with adhesive bonded joints in thin-gauge steel sheeting used for building applications. It is noticed that available design codes do not give any guidelines for this type of joints. For this reason TNO and Delft University of Technology have started the project 'Adhesive joints in thin-gauge steel sheetings', to draw up design rules for building applications. In this paper a proposal is given for the process of drafting design rules for adhesive bonded joints. This proposal is based on the current adhesive bonding technology and the so called structural reliability methodology, which takes the stochastic nature of materials and geometry into account. For practical applications a design rule based on the partial safety factor approach is most convenient. One of the main aspects of drafting design rules is the calibration of the partial safety factors and correction factors. To illustrate this process, an example of calibrating the partial safety factor for a specific overlap joint is discussed.

IJSBRAND J. VAN STRAALEN

Abstract

This paper gives a comprehensive overview of theories for sandwich panels, dealing with the mechanical behaviour. The classical theories are mainly formulated during the fifties and sixties. The derived analytical solutions are based on simplified assumptions. To study local effects near supports, load points and other discontinuities, superposition approaches and higher-order theories have been developed during recent years. Mostly these derivations can only be solved with use of numerical solving techniques. Finite-element methods developed during the last two decades, are an alternative for the analytical solutions. The three-layer models seems to be very popular, but also more detailed three-dimensional models are usefull. One application of sandwich panels is discussed more in detail; for the building sector the development of design rules is reviewed. It is observed that the rules used nowadays, are mainly based on classical theories. To illustrate the advantages of the other theories in case of local sandwich behaviour, an example of a sandwich beam under three point bending is presented. This paper concludes with suggestions how to make use of these recently developed sandwich theories.

A.J. MENDES FERREIRA, A. TORRES MARQUES, J. CÉSAR DE SÁ

Abstract

In this paper it is presented a finite element model for the analysis of reinforced concrete with external FRP strengthening.

The model is based on a concrete material model, on external unidirectional composites, on the Ahmad Shell element and on geometric and material non-linearities. The first-order shear-deformation theory is used, in order to describe the deformation of the shell under the total lagrangian formulation. An example of a RC plate without and with external FRP reinforcement is presented and discussed.

Francisco J. Q. de Melo

LOME, Laboratory of Optics and Experimental Mechanics

Faculty of Engineering of the University of Porto

Abstract

This paper presents a hybrid formulation for the classical solution by Theodore von Karman on the problem of the uniform bending of curved tubes. His method consisted on assuming a trigonometric shape function approach for the deformed surface of the shell, having the calculation of the unknowns been carried out minimizing the total potential energy involved in the deformation process of the shell. The present solution deals with unknown membrane forces, following the longitudinal direction and unknown displacements for the ovalization of the curved pipe. The results are discussed and commented in the sequel.

This paper presents results from a round robin exercise aimed at comparing predictive methods for sandwich panel behaviour. The case studied is a wide sandwich beam loaded under uniform pressure. First, results from different analytical methods and finite element codes are compared. Then test results are presented for a glass/epoxy facing-PVC foam core sandwich panel. Finally predicted strains and out-of-plane displacements are correlated with experimental results.