B. SANDWICH STRUCTURES
Presentation format to be decided
Prediction of Material Behaviour of Closed Cell Rigid Foams via Mesoscopic Modelling
R Schlimper, M Rinker, R Schäuble (IWM)
Deformation and failure behaviour of CFRP foam core sandwich structures was investigated experimentally and numerically. Prediction of strength has to take into account the observed damage progression in the foam material. Therefore the foam structure was modelled on the mesoscopic scale via a representative volume element (RVE) approach. (IB6:1)
Modelling of Auxetic Filled Adhesive System
G Chirima, K Alderson, A Alderson, K Zied, N Ravirala (Univ of Bolton)
The study uses a finite element modelling (ANSYS) tool to attempt to minimise the high material mismatch of joining an auxetic honeycomb to a fibre reinforced composite laminate. The paper seeks to modify the adhesive via the inclusion of auxetic particulate fillers. Modelling results are compoared to existing analytical models for filled systems. (IB6:2)
Non-Linear Behaviour of Foam Cored Curved Sandwich Panels Subjected to Thermo-Mechanical Loading
OT Thomsen (Aalborg Univ) Y Frostig (Technion)
The non-linear analysis of curved composite sandwich panels with a compliant foam core subjected to combined thermal and mechanical loading is considered. It is shown that the response remains linear when only thermal loading is involved, whereas the response becomes strongly non-linear with limit point behaviour when mechanical loading is applied at elevated temperatures. (IB6:3)
Nonlinearities in the Behaviour of Composite Sandwich Beams under Bending
E Gdoutos, I Daniel (Northwestern Univ)
The nonlinear stress distribution in composite sandwich beams made of unidirectional carbon/epoxy facings and PVC foam and aluminum honeycomb cores under bending was studied. It was obtained that the neutral axis of sandwich beams is displaced toward the tensile side of the beam. Experimental results corroborated the analytical predictions. (IB6:4)
Development of Standard Test Methods for Sandwich Composites under ASTM Committee D30
A Sawicki (The Boeing Co) C Rousseau (Lockheed Martin Aeronautics) R Fields (Lockheed Martin Missles & Fire Control) S Ward (SW Composites) W Bertelsen (Gougeon Brothers)
Sandwich composite standard test methods developed by ASTM D30 Committee on Composite Materials are discussed. Technical attributes of new and revised D30 sandwich standards are described to aid the international composites community in the selection and utilization of sandwich test methods. Ongoing sandwich test method development activities are discussed. (IB6:5)
Methods for Qualification of the Mechanical Properties of Sandwich Core Materials for Wind Turbine Blades
P Broendsted, H Toftegaard (TU Denmark)
Methods are suggested for measuring the properties of sandwich core materials for wind turbine blades. The basic properties of the core material in shear, tension and compression are measured under quasi static loading as well as in shear fatigue. The methods proposed are demonstrated on a reference PVC core material. (IB6:6)
Effects of Thermoforming on the Cell Morphology of a Thermoplastic Core
L Sorrentino, S Iannace (IMCB-CNR) M Aurilia (IMAST)
Thermoplastic foams, used as cores, are a promising solution in aeronautical applications such as in sandwich structures. They are characterized by reduced processing cycle time, final part price and can be post processed, mainly by thermoforming. In this work a foamed sheet was produced from an high performance semicrystalline polyester and the changes produced by the thermoforming process on cells morphology was evaluated and compared to the pristine one. (IB6:7)


Assessment of Effective Elastic Properties of Honeycomb Cores by Finite Element Analysis of Sandwich Panels
A Kayran, I Aydincak (Middle East Technical Univ)
Continuum models of regular hexagonal aluminum honeycomb cores are evaluated by finite element analysis. The evaluation is based on the comparison of total in-plane and out-of-plane reaction forces determined by the finite element analyses of the sandwich panels with the actual honeycomb core geometry and with the existing equivalent core models. (IB6:8)
Low-Velocity Impact Response of Sandwich Composites with Nanophased Foam Core
M Hosur, MA Bhuiyan, S Jeelani (Tuskegee Univ)
Low-velocity impact response of sandwich composites with nanophased foam core and braided carbon/epoxy face sheets was evaluated. Closed cell polyurethane foam modified with carbon nanofibers was used as core. Impact response was measured at 15, 30 and 45 J. Nanophased systems showed better impact response compared to neat counterparts. (IB6:9)
Effect of the Manufacturing Process and Skin-Core Adhesion Efficiency on the Mechanical Properties of a Thermoplastic Sandwich
S Pappadà, R Rametta, A Passaro (Consorzio Cetma) L Lanzilotto, A Maffezzoli (Univ of Salento)
In this memory the changes in the mechanical properties of a thermoplastic sandwich due to different manufacturing processes and skin-core adhesion efficiency were investigated. For this reason different composite sandwiches with PET foam core and Twintex skins were realized, tested and analyzed with Finite Element Method. (IB6:10)
A Three Dimensional Crack Analysis in Sandwich Specimens under Flexural Loading
E Theotokoglou (National Tech Univ of Athens)
Extending the two dimensional cracked problem which has been studied under plane strain conditions using the J integral evaluation in sandwich specimens under flexural loading, a three dimensional analysis is performed. A numerical method using commercial software based on a finite element implementation has been used. An investigation of the numerical results as well as a comparison with the two dimensional approach, is included in this study. (IB6:11)
Effect of Damage due to Thermal Shock Cycling and Hygrothermal Ageing on the Mechanical Behaviour of GFRP-Al Sandwich Structures
A Xepapadaki, G Papanicolaou, T Bakopoulos (Univ of Patras)
The effect of hygrothermal ageing and thermal shock cycling of GFRP-Al sandwich structures on their flexural behavior has been investigated. In addition, the interfacial stress distribution along the skin-core interfacial length was evaluated and analyzed by means of a theoretical model. All the above-mentioned experiments were executed to both the GFRP core material, and the GFRP-Al sandwich structure as a whole. (IB6:12)
Residual Strength in Bending of Damaged Hybrid Sandwich Panels with an Aluminium Foam Core
KR Kabir, T Vodenitcharova, M Hoffman (Univ of New South Wales)
Aluminium foam-cored sandwich panels laminated with thin aluminium skins were subjected to hemispherical indentation, and their residual strength was investigated by four-point bending tests. The failure modes/loads and the deformation behavior was also studied. Analytical and numerical models were developed to confirm the experimental results. (IB6:13)
Morphology Observation of PC/ABS Sandwich Injection Moldings
Y Makata, LY Wei, H Hamada (Kyoto Inst of Tech) K Tomari, K Yamada (Osaka Municipal Tech Res Inst)
Sandwich co-injection molding was performed by using a closed spiral flow mold and a twin-barrel injection molding machine. Both the skin and core layers consist of PC/ABS blend. The main objective is to observe the morphology of the deformation and dispersion of the dispersed ABS phase at the interfacial region between the skin and core layers. (IB6:14)