New Sandwich Structures Consisting of Aluminium Foam and Thermoplastic Hybrid Laminate Top Layers

2015 ◽  
Vol 825-826 ◽  
pp. 797-805 ◽  
Author(s):  
Daisy Nestler ◽  
Heike Jung ◽  
Maik Trautmann ◽  
Bernhard Wielage ◽  
Guntram Wagner ◽  
...  
Keyword(s):  
Sandwich Structures ◽  
Core Layer ◽  
Shear Stiffness ◽  
Aluminium Foam ◽  
Main Task ◽  
Reinforced Plastics ◽  
The Core ◽  
Hybrid Laminates ◽  
Sandwich Materials ◽  
Hybrid Laminate

Sandwich structures consist of one light core layer and two top layers, which form the load-bearing structure. These layers have to be stiff and strong and have to protect the structure against indentations. The main task of the core layer is to keep the top layers in place and to generate a high shear stiffness. In order to obtain the required space between the top layers, the core layer has to have a high specific volume. Different sandwich materials with aluminium or steel top layers and cores of aluminium combs, corrugated aluminium sheets or aluminium foams are already known. In order to obtain better properties in terms of strength fibre-reinforced plastics (FRP) are utilised as top layers; this is the focus of numerous of the current research studies. The sole use of these materials leads to negative effects regarding the damage and impact behaviour. New top layers with high strength and high stiffness characteristics as well as good damage tolerances are to be expected by utilising metal layers in combination with endless fibre-reinforced plastics, so called hybrid laminates. These hybrid laminates combine the positive properties of metals (e.g. ductility) and fibre-reinforced plastics (e.g. tensile strength). The focus of this investigation lies on the production and characterisation of sandwich structures with aluminium foam core layers and hybrid laminate top layers. The foam cores consist of closed pore aluminium foams produced by utilising ingot and powder metallurgical techniques. The top layers consist of glass fibre-reinforced thermoplastics and aluminium layers. The production of the sandwich materials is realised by means of thermal pressing.

Homogenization of the core layer in stitched sandwich structures

2010 ◽  
Vol 70 (2) ◽  
pp. 350-355 ◽  
Author(s):  
B. Lascoup ◽  
Z. Aboura ◽  
K. Khellil ◽  
M. Benzeggagh
Keyword(s):  
Sandwich Structures ◽  
Core Layer ◽  
The Core

Design of Adaptive Cores of Sandwich Structures Using a Compliant Unit Cell Approach and Topology Optimization

2010 ◽  
Vol 132 (8) ◽  
Author(s):  
Jiangzi Lin ◽  
Zhen Luo ◽  
Liyong Tong
Keyword(s):  
Topology Optimization ◽  
Large Scale ◽  
Sandwich Structures ◽  
Core Layer ◽  
Problem Formulation ◽  
Unit Cell ◽  
Cell Network ◽  
The Core ◽  
Unit Cells ◽  
Scaled Models

This paper presents a new method in designing the core layer of adaptive sandwich structures. The proposed design formulation treats the core layer as a compliant unit cell network while the unit cell network is synthesized by repeatedly linked identical compliant unit cells. Each unit cell is designed to possess shape adaptive functions independently and through the accumulation of the number of cells within the network, the global adaptive functions are accumulated also. Therefore, the network is capable of achieving large scale shape adaptations of complex profile with high fidelity. Topology optimization is used to design the compliant unit cell. Depending on the problem formulation, topology optimization can perform the simultaneous design of both the host material and the actuation material in the defined environment. This research includes a numerical case study to illustrate the technical aspects of this design philosophy. This is followed by the rapid prototyping of two scaled models and experimental validation.

scholarly journals Mechanical Properties of Thermoplastic-Based Hybrid Laminates with Regard to Layer Structure and Metal Volume Content

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1430
Author(s):  
Maik Trautmann ◽  
Selim Mrzljak ◽  
Frank Walther ◽  
Guntram Wagner
Keyword(s):  
Mechanical Properties ◽  
Carbon Fibre ◽  
Volume Content ◽  
Layer Structure ◽  
Reinforced Plastics ◽  
Reinforced Plastic ◽  
Metal Volume ◽  
Hybrid Laminates ◽  
Static Tensile ◽  
Hybrid Laminate

Multi layered lightweight material compounds such as hybrid laminates are composed of different layers of materials like metals and unidirectional fibre-reinforced plastics and offer high specific strength. They can be individually tailored for applications like outer cover panels for aircraft and vehicles. Many characteristics especially layer structure, volume contents of the embedded materials as well as layer surface adhesion determine the performance of a hybrid laminate. In this study, the influence of layer structure and metal volume content are evaluated with regard to the mechanical properties of the recyclable hybrid laminate CAPAAL (carbon fibre-reinforced plastics/aluminium foil laminate), which consists of the aluminium alloy AA6082 and a graded structure of glass and carbon fibre-reinforced polyamide 6. Hybrid laminates with different ratios of the fibre-reinforced plastic and numbers of aluminium layers were manufactured by thermal pressing. The consolidation quality of in total four laminate structure variations, including 2/1 and 3/2 metal-to-fibre-reinforced plastic layer structures with fibre orientation variation, were investigated by light microscopy through cross-sections and further on computed tomography. For determination and evaluation of the mechanical properties metrologically instrumented quasi-static tensile and three-point bending tests, as well as tension-tension fatigue tests for the establishment of S-N curves were performed. The results were correlated to the microstructural observations, revealing significant influence by the consolidation quality. The layer structure proved to have a proportional impact on the increase of quasi-static tensile and flexure strength with a decrease in metal volume content. Orienting some of the fibre-reinforced plastic layers in ±45° leads to a more evenly distributed fibre alignment, which results in a higher consolidation quality and less anisotropic bending properties. Fatigue results showed a more complex behaviour where not only the metal volume content seems to determine the fatigue loading capability, but also the number of metal-fibre-reinforced plastic interfaces, hinting at the importance of stress distribution between layers and its longevity over fatigue life.

A realistic model for transverse shear stiffness prediction of composite corrugated-core sandwich structure with bonding effect

2021 ◽  
pp. 109963622199386
Author(s):  
Tianshu Wang ◽  
Licheng Guo
Keyword(s):  
Present Model ◽  
Shear Stiffness ◽  
Realistic Model ◽  
Torsional Stiffness ◽  
Fem Model ◽  
The Core ◽  
Bonding Effect ◽  
Stiffness Model ◽  
Bonding Area ◽  
The Relationship

In this paper, a shear stiffness model for corrugated-core sandwich structures is proposed. The bonding area is discussed independently. The core is thought to be hinged on the skins with torsional stiffness. The analytical model was verified by FEM solution. Compared with the previous studies, the new model can predict the valley point of the shear stiffness at which the relationship between the shear stiffness and the angle of the core changes from negative correlation to positive correlation. The valley point increases when the core becomes stronger. For the structure with a angle of the core smaller than counterpart for the valley point, the existing analytical formulations may significantly underestimate the shear stiffness of the structure with strong skins. The results obtained by some previous models may be only 10 persent of that of the present model, which is supported by the FEM model.

Material Selection for CFRP-Aluminium-Foam-Sandwiches Manufactured by a PUR Spraying Process

2017 ◽  
Vol 742 ◽  
pp. 317-324
Author(s):  
Peter Rupp ◽  
Peter Elsner ◽  
Kay André Weidenmann
Keyword(s):  
Manufacturing Process ◽  
Sandwich Structures ◽  
Bending Stiffness ◽  
Effective Density ◽  
Sandwich Composites ◽  
Open Cell ◽  
The Core ◽  
Bending Modulus ◽  
The Face ◽  
Spraying Process

Sandwich structures are ideal for planar parts which require a high bending stiffness ata low weight. Usually, sandwich structures are manufactured using a joining step, connecting theface sheets with the core. The PUR spraying process allows to include the infiltration of the facesheet fibres, the curing of the matrix and the joining of the face sheets to the core within one processstep. Furthermore, this manufacturing process allows for the use of open cell core structures withoutinfiltrating the core, which enables a comparison of different material configurations, assembled bythe same manufacturing process. The selection of these materials, with the aim of the lowest possiblemass of the sandwich composite at a constant bending stiffness, is displayed systematically within thiswork.It could be shown that the bending modulus calculated from the component properties matched theexperimentally achieved values well, with only few exceptions. The optimum of the bending modulus,the face sheet thickness and the resulting effective density could be calculated and also matched theexperimental values well. The mass-specific bending stiffness of the sandwich composites with corestructures of open cell aluminium foams was higher than with closed cell aluminium foams, but wasexceeded by sandwich composites with Nomex honeycomb cores.

A micromechanical model of carbon fiber-reinforced plastic and steel hybrid laminate composites

2021 ◽  
pp. 002199832110075
Author(s):  
Minchang Sung ◽  
Hyunchul Ahn ◽  
Jinhyeok Jang ◽  
Dongil Kwon ◽  
Woong-Ryeol Yu
Keyword(s):  
Carbon Fiber ◽  
Compressive Stress ◽  
Fracture Strain ◽  
Matrix Material ◽  
Micromechanical Model ◽  
Fiber Reinforced ◽  
Laminate Composites ◽  
Reinforced Plastics ◽  
Carbon Fiber Reinforced ◽  
Hybrid Laminate

The fracture strain of carbon fiber-reinforced plastics (CFRPs) within CFRP/steel hybrid laminate composites is reportedly higher than that of CFRPs due to transverse compressive stress induced by the steel lamina. A micromechanical model was developed to explain this phenomenon and also to predict the mechanical behavior of CFRP/steel hybrid laminate composites. First, the shear lag theory was extended to calculate stress distributions on fibers and matrix material in a CFRP under multiaxial stress condition, considering three deformation states of matrix (elastic and plastic deformation and fracture) and the transverse compressive stress. Then, the deformation behavior of CFRP was predicted using average stress in the ineffective region and the Weibull distribution of carbon fibers. Finally, the mechanical properties of CFRP/steel hybrid laminate composites were predicted by considering the thermal residual stress generated during the manufacturing process. The micromechanical model revealed that increased transverse compressive stress decreases the ineffective lengths of partially broken fibers in the CFRP and results in increased fracture strain of the CFRP, demonstrating the validity of the current micromechanical model.

Wave Propagation and Power Flow Analysis of Sandwich Structures With Internal Absorbers

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
J. S. Chen ◽  
R. T. Wang
Keyword(s):  
Wave Propagation ◽  
Power Flow ◽  
Wave Attenuation ◽  
Sandwich Structures ◽  
Flow Analysis ◽  
Flow Characteristics ◽  
Continuum Models ◽  
Sandwich Beams ◽  
The Core ◽  
In Series

This study examines wave attenuation and power flow characteristics of sandwich beams with internal absorbers. Two types of absorbing systems embedded in the core are considered, namely, a conventional spring-mass-dashpot system having a mass with a spring and a dashpot in parallel, and a relaxation system containing an additional relaxation spring added in series with the dashpot. Analytical continuum models used for interpreting the attenuation behavior of sandwich structures are presented. Through the analysis of the power flowing into the structure, the correlation of wave attenuation and energy blockage is revealed. The reduction in the power flow indicates that some amount of energy produced by the external force can be effectively obstructed by internal absorbers. The effects of parameters on peak attenuation, bandwidth, and power flow are also studied.

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