The effect of local bending stiffness on the wrinkling of sandwich panels

2003 ◽  
Vol 217 (2) ◽  
pp. 111-119
Author(s):  
L Fagerberg
Keyword(s):  
Elastic Modulus ◽  
Sandwich Panel ◽  
Volume Fraction ◽  
Fibre Volume Fraction ◽  
Fibre Volume ◽  
Bending Stiffness ◽  
Face Sheet ◽  
Stacking Sequence ◽  
The Core ◽  
The Face

The use of the face sheet elastic modulus versus the face sheet local bending stiffness while designing against wrinkling is discussed in this paper. It shows that there are several ways to improve the critical wrinkling load of a sandwich panel without replacing the core. It is often possible to increase the wrinkling load by as much as 25 per cent without virtually any increase in weight or cost of the sandwich. This is achieved by improving the local bending stiffness of the sandwich face sheet by either optimizing the stacking sequence, lowering the fibre volume fraction or adding some extra layers of a cheap fibre material to the sandwich face, creating a minisandwich within the face sheet. Experiments are performed that clearly show the potential for increasing the critical wrinkling load by means of altering the face sheet.

scholarly journals Geometrical Analysis of 3D Integrated Woven Fabric Reinforced Core Sandwich Composites

2019 ◽  
Vol 27 (1(133)) ◽  
pp. 45-50
Author(s):  
Abdul Jabbar ◽  
Mehmet Karahan ◽  
Muhammad Zubair ◽  
Nevin Karahan
Keyword(s):  
Cross Sections ◽  
Volume Fraction ◽  
Structural Parameters ◽  
Fibre Volume Fraction ◽  
Slope Angle ◽  
Fibre Volume ◽  
Woven Fabric ◽  
Sandwich Composites ◽  
The Core ◽  
Core Thickness

The variability of the internal geometry parameters, such as the waviness of yarns, cross sections of yarns and local fibre volume fraction of 3-dimensional (3D) integrated woven core sandwich composites affects their mechanical properties. The objective of this study was to define the geometrical and structural parameters of 3D integrated woven core sandwich composites, including the fold ratio of pile threads, the fabric areal weight and the fibre volume fraction by changing the core thickness of 3D sandwich core fabric. 3D fabrics with different core thicknesses were used for reinforcement. It was confirmed that the pile fold ratio, slope angle and pile length increase with an increase in the core thickness of the fabric. The difference between the calculated and experimental areal weights of fabrics was in the range of 5-13%. A novel approach was also presented to define the fibre volume fraction of 3D woven core sandwich composites.

Numerical Modelling of Impact Behavior of Composite Sandwich Panel With Honeycomb Core

2019 ◽  
Author(s):  
Shah Alam ◽  
Aakash Bungatavula
Keyword(s):  
Sandwich Panel ◽  
Sheet Thickness ◽  
Face Sheet ◽  
Honeycomb Core ◽  
Impact Performance ◽  
Composite Sandwich ◽  
The Core ◽  
The Face ◽  
Core Height ◽  
The Impact

Abstract The goal of this paper is to find the best impact response of the composite sandwich panels with honeycomb core. The focus of the study is to find the effects of changing the face sheet thickness and the core height of the sandwich panel subjected to variable velocities on impact performance. Initially, honeycomb core sandwich panel with 1mm thick face sheet is modelled in Abaqus/explicit to calculate the energy absorption, residual velocity, and deformation at four different velocities. Then, the process is repeated by changing the face sheets thickness to 2mm and 3mm to see the effects of changing the thickness on the impact performance of a composite sandwich panel. The honeycomb core height is also changed to see its effect on the performance. In all models, Al 7039 is used in the core and T1000G is used in the face sheets.

scholarly journals Damping Performance of Thermoplastic-Elastomer Interleaved Cfrp - Effect of Viscoelasticity of the Inter-Laminar Films and Stiffness of the Intra-Laminar Region -

2005 ◽  
Vol 14 (3) ◽  
pp. 096369350501400 ◽  
Author(s):  
Hajime Kishi ◽  
Manabu Kuwata ◽  
Satoshi Matsuda ◽  
Toshihiko Asami ◽  
Atsushi Murakami
Keyword(s):  
Elastic Modulus ◽  
Viscoelastic Properties ◽  
Volume Fraction ◽  
Fibre Volume Fraction ◽  
Local Strain ◽  
Thermoplastic Elastomer ◽  
Considerable Effect ◽  
Fibre Volume ◽  
Damping Properties ◽  
And Control

The objective of this study is to characterize damping performance of carbon-fibre reinforced interleaved toughened laminates using two types of thermoplastic-elastomer films as the interleaf materials. The damping properties of interleaved laminates depend not only on the viscoelastic properties of the interleaf films but also on the laminate sequence. The stiffness of the intra-laminar region, which can be determined by the fibre volume fraction, the elastic modulus of the fibres and the fibre arrangements, would give considerable effect on the local strain of the interleaf films and control the damping properties of the whole interleaved laminates.

Equivalent in-plane elastic modulus of honeycomb sandwich in the direction of cell vertical wall

2021 ◽  
pp. 109963622110235
Author(s):  
DH Chen ◽  
XL Fan
Keyword(s):  
Cell Wall ◽  
Elastic Modulus ◽  
Vertical Wall ◽  
Face Sheet ◽  
The Core ◽  
Proposed Model ◽  
Honeycomb Sandwich ◽  
The Face ◽  
Equivalent Modulus ◽  
Vertical Cell

The equivalent in-plane elastic modulus [Formula: see text] of a honeycomb sandwich in the direction of cell vertical wall can be assessed by the law of mixture from the modulus of face sheet [Formula: see text] and the equivalent modulus of honeycomb core [Formula: see text]. However, significant errors as large as 40% can be made depending on material and geometry parameters, when the used [Formula: see text] is obtained from a cellular model of core alone without considering the skin effect of face sheet. The main reason of the error is that the rigidity to deformation of y-direction is different greatly between the vertical cell wall of core and inclined cell wall of core. In the present paper, an analytical model is proposed to assess [Formula: see text] of honeycomb sandwich with considering the interference effect of the core with the face sheet. In the proposed model, the influence of the face sheet rigidity on [Formula: see text] is taken into account. The results demonstrate that the contribution of the core to [Formula: see text] is also dependent on the face sheet rigidity significantly. The validity of presented model is verified by comparing the results with numerical results of FEA.

The Strength of Fibres in All-Ceramic Composites

1986 ◽  
Vol 78 ◽  
Author(s):  
Kevin Kendall ◽  
N. Mcn. Alford ◽  
J. D. Birchall
Keyword(s):  
Elastic Modulus ◽  
Volume Fraction ◽  
Fibre Volume Fraction ◽  
Ceramic Composites ◽  
Fibre Volume ◽  
Matrix Cracking ◽  
Fibre Strength ◽  
All Ceramic ◽  
The Matrix ◽  
Fibre Matrix

ABSTRACTWhen considering the strength of a fibre reinforced ceramic composite, it is often assumed that the fibres retain their full strength of several GPa after cracking of the weaker matrix. The strength of the composite after matrix cracking is then calculated by the rule of mixtures as the product of fibre volume fraction and fibre strength. This paper demonstrates that such a calculation is not consistent with the principles of fracture mechanics for an isolated fibre embedded in an elastic matrix of the same elastic modulus, because the strength of the fibre is much reduced by the stress concentration arising from the matrix crack. Experimental measurements of the strength of a glass fibre embedded in a brittle matrix support the theory. The case of a fibre in a matrix of different elastic modulus is also considered, together with the proDlem of cracking along the fibre-matrix interface.

Elastic Interphase with Variable Properties in Fibrous Composites

1992 ◽  
Vol 11 (1) ◽  
pp. 82-97 ◽  
Author(s):  
A. V. Pournaras ◽  
G. C. Papanicolaou
Keyword(s):  
Distribution Function ◽  
Elastic Modulus ◽  
Theoretical Model ◽  
Volume Fraction ◽  
Fibre Volume Fraction ◽  
Fibre Volume ◽  
Elastic Fibre ◽  
Variable Properties ◽  
Longitudinal Elastic Modulus ◽  
Dirac Distribution

In the present work a theoretical model for composite materials with a Poisson's ratio v = 0.5 is developed in order to evaluate the mechanical stresses around a single cylindrical elastic fibre inclusion. The model considers a gradual and continuous variation of the longitudinal elastic modulus EL in the area between matrix and fibre, the former being under hydrostatic pressure po · EL is expressed as a Fermi-Dirac distribution function of important parameters such as the rate of variation of EL, the extent of the interphase and the fibre volume fraction. Results indicate a strong effect of the above parameters on the stress state developed around the fibre.

Effect of fibre content on the mechanical properties of hemp fibre woven fabrics/polypropylene composite laminates

2021 ◽  
pp. 096739112110239
Author(s):  
Sheedev Antony ◽  
Abel Cherouat ◽  
Guillaume Montay
Keyword(s):  
Mechanical Properties ◽  
Polymer Matrix ◽  
Composite Laminates ◽  
Volume Fraction ◽  
Fibre Volume Fraction ◽  
Fibre Volume ◽  
Woven Fabrics ◽  
Fibre Content ◽  
Viscoelastic Behaviour ◽  
Hemp Fibre

Nowadays natural fibre composites have gained great significance as reinforcements in polymer matrix composites. Composite material based on a polymer matrix reinforced with natural fibres is extensively used in industry due to their biodegradability, recyclability, low density and high specific properties. A study has been carried out here to investigate the fibre volume fraction effect of hemp fibre woven fabrics/PolyPropylene (PP) composite laminates on the tensile properties and impact hammer impact test. Initially, composite sheets were fabricated by the thermal-compression process with desired number of fabric layers to obtain composite laminates with different fibre volume fraction. Uniaxial, shear and biaxial tensile tests were performed and mechanical properties were calculated. Impact hammer test was also carried out to estimate the frequency and damping parameters of stratified composite plates. Scanning Electron Microscope (SEM) analysis was performed to observe the matrix and fibre constituent defects. Hemp fabrics/PP composite laminates exhibits viscoelastic behaviour and as the fibre volume fraction increases, the viscoelastic behaviour decreases to elastic behaviour. Due to this, the tensile strength increases as the fibre content increases. On the other hand, the natural frequency increases and damping ratio decrease as the fibre volume fraction increases.

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.

scholarly journals Insulation Characteristics of Sisal Fibre/Epoxy Composites

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
A. Shalwan ◽  
M. Alajmi ◽  
A. Alajmi
Keyword(s):  
Volume Fraction ◽  
Fibre Volume Fraction ◽  
Thermal Characteristics ◽  
Fibre Volume ◽  
Point Of View ◽  
Natural Fibres ◽  
Epoxy Composites ◽  
Ongoing Research ◽  
Sisal Fibre ◽  
The Impact

Using natural fibres in civil engineering is the aim of many industrial and academics sectors to overcome the impact of synthetic fibres on environments. One of the potential applications of natural fibres composites is to be implemented in insulation components. Thermal behaviour of polymer composites based on natural fibres is recent ongoing research. In this article, thermal characteristics of sisal fibre reinforced epoxy composites are evaluated for treated and untreated fibres considering different volume fractions of 0–30%. The results revealed that the increase in the fibre volume fraction increased the insulation performance of the composites for both treated and untreated fibres. More than 200% insulation rate was achieved at the volume fraction of 20% of treated sisal fibres. Untreated fibres showed about 400% insulation rate; however, it is not recommended to use untreated fibres from mechanical point of view. The results indicated that there is potential of using the developed composites for insulation purposes.

New Development of Cattail Fibre in Composite Uses

2013 ◽  
Vol 746 ◽  
pp. 385-389
Author(s):  
Li Yan Liu ◽  
Yu Ping Chen ◽  
Jing Zhu
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Fibre Volume Fraction ◽  
Fibre Volume ◽  
Environmental Benefits ◽  
Bending Properties ◽  
New Development ◽  
Original Plant ◽  
Reinforcing Material ◽  
Pp Composites

This paper is aiming to develop the cattail fibre as reinforcing material due to its environmental benefits and excellent physical and insulated characteristics. The current work is concerned with the development of the technical fibres from the original plant and research on their reinforcing properties in the innovative composites. Polypropylene (PP) fibre was used as matrix in this research which was fabricated into fibre mats with cattail fibre together with different fibre volume fractions. Cattail fibre reinforced PP laminates were manufactured and compared with jute/PP composites. The tensile and bending properties of laminates were tested. The SEM micrographs of fracture surface of the laminates were analyzed as well. The results reveal that the tensile and bending properties of cattail/PP laminates are closed to those of jute/PP composites. The mechanical properties of cattail/jute/PP laminates with fibre volume fraction of 20/35/45 is betther than those of laminate reinforced with cattail fibers.

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