The effect of core geometry on flexural stiffness and transverse shear rigidity of weight‐wise identical corrugated core sandwich panels reinforced with 3D flat spacer knitted fabric

2020 ◽  
Vol 41 (9) ◽  
pp. 3638-3648
Author(s):  
Hamid Abedzade Atar ◽  
Mohammad Zarrebini ◽  
Hossein Hasani ◽  
Jalil Rezaeepazhand
Keyword(s):  
Transverse Shear ◽  
Sandwich Panels ◽  
Knitted Fabric ◽  
Flexural Stiffness ◽  
Shear Rigidity

scholarly journals Determination of corrugated core sandwich panels elastic constant based on three different experimental methods and effect of structural integrity on flexural properties

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Hamid Abedzade Atar ◽  
Mohammad Zarrebini ◽  
Hossein Hasani ◽  
Jalil Rezaeepazhand
Keyword(s):  
Elastic Constants ◽  
Transverse Shear ◽  
Structural Integrity ◽  
Sandwich Panels ◽  
Flexural Stiffness ◽  
Shear Rigidity ◽  
Knitted Fabrics ◽  
Load Carrying ◽  
Modulus Method

AbstractThis study deals with the investigation of flexural stiffness and transverse shear rigidity in the direction of corrugation of the integrated and non-integrated corrugated core sandwich panels with the rectangular core. The non-integrated sandwich panels were reinforced with conventional 2-D fabrics in which resin provides the bond between core and skins. The integrated sandwich panels were reinforced with 3-D weft knitted fabrics in which bonding of the core wall to skins was carried out by combined efforts of knitted loop and resin. Using weft knitting technical capabilities, samples of the integrated and non-integrated structures were manufactured with the uppermost degree of resemblance in terms of geometry and mass. Flexural stiffness and transverse shear rigidity of the structures based on the known and unknown facing modulus of ASTM D7250 standard and Nordstrand–Carlsson methods were calculated. The estimated elastic constants based on unknown facing modulus and the Nordstrand–Carlsson methods were found to be highly compatible. However, the unknown facing modulus method is prone to disclose the statistical significant differences between the elastic constants of the structures with fewer tests. Regarding the unknown facing modulus method, it was found that the flexural stiffness and transverse shear rigidity of the non-integrated structure in the direction of corrugation were higher than those of the integrated structure. Results also indicated that the load-carrying capacity in the direction of corrugation was significantly higher in case of the non-integrated rectangular core structure compared with that of the integrated structure.

Buckling of sandwich panels with transversely flexible core: Correction of the equivalent single-layer model using thick-faces effect

2018 ◽  
Vol 22 (5) ◽  
pp. 1612-1634 ◽  
Author(s):  
J Jelovica ◽  
J Romanoff
Keyword(s):  
Finite Element ◽  
Transverse Shear ◽  
Sandwich Panels ◽  
Shear Deformation Theory ◽  
Single Layer ◽  
Element Model ◽  
Layer Model ◽  
The Core ◽  
Truss Core ◽  
Single Layer Model

Modeling a periodic structure as a homogeneous continuum allows for an effective structural analysis. This approach represents a sandwich panel as a two-dimensional plate of equivalent stiffness. Known as the equivalent single-layer, the method is used here to analyze bifurcation buckling of three types of sandwich panels with unidirectional stiffeners in the core: truss-core, web-core and corrugated-core panels made of an isotropic material. The transverse shear stiffnesses of these panels can differ by several orders of magnitude, which cause incorrect buckling analysis when using the equivalent single-layer model with the first-order shear deformation theory. Analytical solution of the problem predicts critical buckling loads that feature infinite number of half-waves in the direction perpendicular to the stiffeners. Finite element model also predicts buckling modes that have non-physical, saw-tooth shape with infinite curvature at nodes. However, such unrealistic behavior is not observed when using detailed three-dimensional finite element models. The error in the prediction of the critical buckling load is up to 85% for the cases considered here. The correction of the equivalent single-layer model is proposed by modeling the thick-faces effect to ensure finite curvature. This is performed in the finite element setting by introducing an additional plate with tied deflections to the equivalent single-layer plate. The extra plate is represented with bending and transverse shear stiffness of the face plates. As a result, global buckling is predicted accurately. Guidelines are proposed to identify the sandwich panels where ordinary model is incorrect. Truss-core and web-core sandwich panels need the correction. Corrugated-core panels without a gap between plates in the core have smaller shear orthotropy and do not need the correction. Modeling the thick-faces effect ensures correct results for all cases considered in this study, and thus one should resort to this approach in case of uncertainty whether the ordinary equivalent single-layer model is valid.

Shear Properties of Wool Plain-Knitted Fabrics

1976 ◽  
Vol 46 (4) ◽  
pp. 265-272 ◽  
Author(s):  
R. J. Hamilton ◽  
R. Postle
Keyword(s):  
Shear Force ◽  
Hysteresis Loops ◽  
Shear Behaviour ◽  
Knitted Fabric ◽  
Shear Rigidity ◽  
Knitted Fabrics ◽  
Fabric Structure ◽  
Applied Tension ◽  
Constant Tension ◽  
Applied Relaxation

An instrument is described for the measurement of shear in knitted fabrics under conditions of constant tension and “equal length of side.” Shear hysteresis loops were obtained for a series of wool plain-knitted fabrics of different tightness factors. Typical curves and fabric parameters (shear rigidity and coercive shear force) are presented for the fabrics tested in two states of relaxation using several values of applied tension. The results have been analyzed statistically and a simple friction-elastic rheological model of the shear behaviour is examined. This model is interpreted in terms of the knitted fabric structure and the changes that occur when a shear deformation is applied. Relaxation was found to reduce the values of both the shear rigidity and the coercive shear force. The effect of tension was investigated, and suitable levels of tension are recommended for testing knitted fabrics in shear.

Evaluation of Transverse Shear Moduli of Composite Sandwich Beams Through Three-Point Bending Tests

2018 ◽  
Author(s):  
Özgün Şener ◽  
Oğuzhan Dede ◽  
Oğuz Atalay ◽  
Mert Atasoy ◽  
Altan Kayran
Keyword(s):  
Finite Element ◽  
Transverse Shear ◽  
Sandwich Beam ◽  
Image Correlation ◽  
Core Material ◽  
Flexural Stiffness ◽  
Element Analysis ◽  
Bending Tests ◽  
Shear Moduli ◽  
Composite Sandwich

Transverse shear moduli of the sandwich core and flexural stiffness of all-composite sandwich constructions are determined with three-point beam bending tests, and compared with the analytical and finite element analysis solutions. Additionally, Digital Image Correlation (DIC) system is employed to validate the experimental results by monitoring the displacements. The effect of orientation of the composite core material with respect to the beam axis on the shear modulus of the core material itself, flexural stiffness of the sandwich beam, maximum loading, and the maximum stresses on the sandwich panel are also examined. Comparable results are achieved through experiments, finite element and analytical analyses.

Experimental and analytical behavior of sandwich composite beams: Comparison of natural and synthetic materials

2016 ◽  
Vol 20 (3) ◽  
pp. 287-307 ◽  
Author(s):  
Pedram Sadeghian ◽  
Dimo Hristozov ◽  
Laura Wroblewski
Keyword(s):  
Composite Beams ◽  
Bending Test ◽  
Synthetic Fiber ◽  
Sandwich Composite ◽  
Flexural Stiffness ◽  
Fiber Types ◽  
Shear Rigidity ◽  
Sandwich Composites ◽  
Core Materials ◽  
Natural And Synthetic

In this study, the flexural behavior of sandwich composite beams made of fiber-reinforced polymer (FRP) skins and light-weight cores are studied. The focus is on the comparison of natural and synthetic fiber and core materials. Two types of fiber materials, namely glass and flax fibers, as well as two types of core materials, namely polypropylene honeycomb and cork, are considered. A total of 105 small-scale sandwich beam specimens (50 mm wide) were prepared and tested under four-point bending. Test parameters were fiber types (flax and glass fibers), core materials (cork ad honeycomb), skin layers (0, 1, and 2 layers), core thicknesses (6–25 mm), and beam spans (150 and 300 mm). The load–deflection behavior, peak load, initial stiffness, and failure mode of the specimens are evaluated. Moreover, the flexural stiffness, shear rigidity, and core shear modulus of the sandwich composites are computed based on the test results of the two spans. An analytical model is also implemented to compute the flexural stiffness, core shear strength, and skin normal stress of the sandwich composites. Overall, the natural fiber and cork materials showed a promising and comparable structural performance with their synthetic counterparts.

Study on V-Bending of Aluminium Foam Sandwich Panels

2011 ◽  
Vol 181-182 ◽  
pp. 281-286 ◽  
Author(s):  
Zhen Zhong Sun ◽  
Wei Feng He ◽  
Hai Bin Chen ◽  
Sheng Gui Chen ◽  
Rong Yong Li
Keyword(s):  
Shear Deformation ◽  
Transverse Shear ◽  
Final Stage ◽  
Sandwich Panels ◽  
Core Layer ◽  
Aluminium Foam ◽  
Transverse Shear Deformation ◽  
Acceptable Limit ◽  
Air Bending

The forming of the completed aluminium foam sandwich (AFS) panels would determine an improvement in the manufacturing of parts and panels. In this paper the authors have investigated the formability of AFS through experiments. the load versus punch stroke curve and deformation procedures of Aluminium foam sandwiche panels was investigated by performing V-bending experiments. A serious problem encountered in the V-bending was bending-induced large transverse shear deformation of the skin-core layer. It causes the delamination of the AFS. It was found from experimental observations that the large shear defomation progresses rapidly only at the final stage of V-bending. Consequently, the air-bending operation for Aluminium foam sandwiche panels is recommended for suppressing the shear deformation of skin-core layer to within an acceptable limit.

scholarly journals Core failure in sandwich structures subjected to water slamming loads

2019 ◽  
Vol 21 (5) ◽  
pp. 1751-1772
Author(s):  
MA Battley ◽  
TD Allen
Keyword(s):  
Transverse Shear ◽  
High Speed ◽  
Failure Modes ◽  
Sandwich Panels ◽  
Core Material ◽  
Polymeric Foams ◽  
Failure Mechanics ◽  
The Core ◽  
High Elongation ◽  
Core Materials

Sandwich composite materials are widely used within the marine industry, particularly as hull panels. Water impact loads, known as slamming, can be very significant for these structures, particularly for high-speed craft. These loadings generate local regions of high transverse shear forces near panel boundaries, which can result in transverse shear failures of core materials. The transient nature of slamming loads can cause stress rates that are high enough to affect the strength of the core material, particularly for polymeric foams. Despite the significant body of work on the constitutive behaviour and failure mechanics of sandwich core materials, there is a lack of understanding of how core materials fail in transverse shear during slamming events. There is also only very limited knowledge of how the core shear strengths measured using standardised, often quasi-static material coupon testing relate to their behaviour in a panel-slamming situation. This paper contributes in two novel areas; controlled experimental characterisation of the failure mechanics of sandwich panels subjected to water slamming to understand and quantify the strength of different polymeric core materials, comparison of the failure modes and transverse shear strength of slam-loaded sandwich panels to predictions from material coupon properties. Core types include low, medium and high elongation polymeric foams. The results demonstrate that the more ductile foams perform better as panel structures under slamming relative to their quasi-static properties compared with the more brittle cores. Prediction of the strength of a panel is shown to be highly dependent on the load distribution and whether the static or dynamic core strength is considered. The results support empirical experience that ductile foams perform well under slamming loads, and that high-elongation materials can perform better in slamming situations than predicted by their quasi-static strengths.

An Elastic Analysis of Multiroll Endless Web Systems

1979 ◽  
Vol 101 (4) ◽  
pp. 308-313 ◽  
Author(s):  
Tsai-Chen Soong ◽  
Chun Li
Keyword(s):  
Steady State ◽  
Transverse Shear ◽  
Shear Rigidity ◽  
Elastic Analysis ◽  
Pass Through ◽  
Parallel Strips ◽  
Contact Arc ◽  
The Web ◽  
Web Systems ◽  
Transient And Steady State

A procedure for analyzing a multiroll endless web system is presented. The web is divided into endless, parallel strips which are longitudinally elastic and possess shear rigidity. The strips are wrapped over frictional cylinders and then required to pass through predetermined points on the contact arc so that compatibility among neighboring strips is maintained. Contact is assumed to be nonslipping until transverse shear and belt tension components exceed friction. Transient and steady-state motions with and without edge guide can be studied. Problems concerning edge guide force, steering moment, pivoting cylinders, rate of drift, and effect of conicity of web, taper of cylinder, and initial unstretched length of the web, etc., can be analyzed.

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