Implication of Anisotropy of Face-Sheets and Core Layer Materials on the Load Carrying Capacity of Advanced Sandwich Panels: Linear and Nonlinear Responses

2000 ◽  
Author(s):  
Liviu Librescu
Keyword(s):  
Carrying Capacity ◽  
Sandwich Structure ◽  
Sandwich Panels ◽  
Core Layer ◽  
Anisotropic Materials ◽  
Load Carrying Capacity ◽  
The Core ◽  
Load Carrying ◽  
The Face ◽  
Sandwich Shells

Abstract This paper deals with a comprehensive geometrically nonlinear theory of shallow sandwich shells that includes also the effect of the initial geometric imperfections. It is assumed that the face-sheets of the sandwich structure are built-up from anisotropic materials layers, whereas the core layer from an orthotropic material. As a result of its features the structural model can provide important information related to the load carrying capacity of sandwich structures in the pre- and postbuckling ranges. Moreover, by using the directionality properties of face-sheets materials, possibilities of enhancing the load carrying capacity of sandwich shells/plates are reached. Selected numerical illustrations emphasizing these features are presented and pertinent conclusions on the beneficial implications of anisotropy of face-sheets and core layer materials upon the load-carrying capacity of sandwich panels are emphasized. Under the present study, the sandwich structure consists of a thick core-layer bonded by the face-sheets that consist of composite anisotropic materials, symmetrically laminated with respect to the mid-surface of the core-layer. The initial geometric imperfection consisting of a stress free initial transversal deflection, will be also incorporated in the study. The loads under which the nonlinear response will be analyzed consist basically of uniaxial/biaxial compressive edge and lateral loads.

scholarly journals Experimental and Numerical Analysis of Nonlinear Flexural Behaviour of Lattice-Web Reinforced Foam Core Composite Sandwich Panels

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Jiye Chen ◽  
Hai Fang ◽  
Weiqing Liu ◽  
Yujun Qi ◽  
Lu Zhu
Keyword(s):  
Numerical Analysis ◽  
Carrying Capacity ◽  
Sandwich Panels ◽  
Foam Core ◽  
Load Carrying Capacity ◽  
Flexural Behaviour ◽  
Composite Sandwich Panels ◽  
Composite Sandwich ◽  
Load Carrying ◽  
The Face

This paper conducted experimental and numerical analysis of the nonlinear flexural behaviour of lattice-web reinforced foam core composite sandwich panels. Composite sandwich panels composed of a polyurethane (PU) foam core with glass fibre-reinforced polymer (GFRP) composites as the face sheets and lattice webs were fabricated through the vacuum infusion moulding process (VIMP). The flexural behaviour of these composite sandwich panels were experimentally investigated under both uniformly distributed and concentrated loading scenarios. The results showed that reinforced lattice webs can significantly increase the flexural stiffness and load-carrying capacity of sandwich panels and effectively postpone the onset of interfacial debonding failure between the face sheets and core. The effects of the lattice-web height and spacing on the ductility and load-carrying capacities of the sandwich panels were also analysed. Several numerical simulations on lattice-web reinforced foam core composite sandwich panels under concentrated loadings were also conducted. The effectiveness of the finite element (FE) model was validated by the experimental work. Parametric studies indicated that thicker face sheets and lattice webs can remarkably increase the load-carrying capacity. Moreover, the load-carrying capacity and midspan deflection were hardly affected by the foam density.

The load-carrying capacity of sandwich beams in different collapse mechanisms

2020 ◽  
pp. 109963622092011
Author(s):  
Lu Guo ◽  
Renwei Mao ◽  
Shiqiang Li ◽  
Zhifang Liu ◽  
Guoxing Lu ◽  
...  
Keyword(s):  
Carrying Capacity ◽  
Sandwich Beam ◽  
Sandwich Beams ◽  
Load Carrying Capacity ◽  
The Core ◽  
Shear Mechanism ◽  
Collapse Mechanisms ◽  
Continuity Equations ◽  
Load Carrying ◽  
The Face

The load-carrying capacity of the symmetrical and asymmetrical sandwich beams, under a quasi-static central load, is investigated in this paper. Three collapse mechanisms such as face yield, core shear and indentation are considered for symmetrical sandwich beams. Core shear mechanism is taken into account for fully clamped asymmetrical sandwich beams. Continuity equations are established by simple ‘equal area’ method for the postyield behavior of the sandwich beams in face yield and core shear mechanisms at different boundary conditions. In indentation mechanism theoretical model, the effect of the local denting on the large deflection of the sandwich beam is taken into account. Then, finite element simulations are carried out to verify the validity of the proposed analysis, and a good agreement is presented. It is shown that in the core shear mechanism under fully clamped condition, no plateau phase is presented. The effect of the core thickness on the response of the symmetrical beams is discussed in detail. For asymmetry beams in core shear mechanism under fully clamped condition, the effect of the asymmetric factor (strength or thickness) for face-sheets on the load–deflection behavior of the postyield beams can be neglected, if the sum of the strength or thickness of the face sheets is constant.

Structural Performance of Fiber-Reinforced Polymer Honeycomb Sandwich Panels: Evaluation of Size Effect and Wrap Strengthening

2003 ◽  
Vol 1845 (1) ◽  
pp. 191-199 ◽  
Author(s):  
Ondrej Kalny ◽  
Robert J. Peterman ◽  
Guillermo Ramirez ◽  
C. S. Cai ◽  
Dave Meggers
Keyword(s):  
Carrying Capacity ◽  
Ultimate Load ◽  
Sandwich Panels ◽  
Fiber Reinforced Polymer ◽  
Load Carrying Capacity ◽  
Flexural Capacity ◽  
Reinforced Polymer ◽  
Load Carrying ◽  
Honeycomb Sandwich ◽  
Ultimate Load Carrying Capacity

Stiffness and ultimate load-carrying capacities of glass fiber-reinforced polymer honeycomb sandwich panels used in bridge applications were evaluated. Eleven full-scale panels with cross-section depths ranging from 6 to 31.5 in. (152 to 800 mm) have been tested to date. The effect of width-to-depth ratio on unit stiffness was found to be insignificant for panels with a width-to-depth ratio between 1 and 5. The effect of this ratio on the ultimate flexural capacity is uncertain because of the erratic nature of core-face bond failures. A simple analytical formula for bending and shear stiffness, based on material properties and geometry of transformed sections, was found to predict service-load deflections within 15% accuracy. Although some factors influencing the ultimate load-carrying capacity were clearly identified in this study, a reliable analytical prediction of the ultimate flexural capacity was not attained. This is because failures occur in the bond material between the outer faces and core, and there are significant variations in bond properties at this point due to the wet lay-up process, even for theoretically identical specimens. The use of external wrap layers may be used to shift the ultimate point of failure from the bond (resin) material to the glass fibers. Wrap serves to strengthen the relatively weak core–face interface and is believed to bring more consistency in determining the ultimate load-carrying capacity.

Experimental investigations on the sandwich composite beams and panels with elastomeric foam core

2017 ◽  
Vol 21 (3) ◽  
pp. 865-894 ◽  
Author(s):  
AR Nazari ◽  
H Hosseini-Toudeshky ◽  
MZ Kabir
Keyword(s):  
Carrying Capacity ◽  
Sandwich Structures ◽  
Failure Mechanisms ◽  
Composite Beams ◽  
Core Material ◽  
Foam Core ◽  
Sandwich Beams ◽  
Load Carrying Capacity ◽  
The Core ◽  
Load Carrying

In this paper, the load-carrying capacity and failure mechanisms of sandwich beams and panels with elastomeric foam core and composite laminate face sheets are investigated. For this purpose, the flexural behavior of laminated composite beams and panels (applied as face sheets) is firstly investigated under three-point bending and central concentrated loads, respectively. Then, the same examination is conducted for the sandwich beams and panels, in which the proposed elastomeric foam is utilized as the core material. It is shown that the failure mechanisms which are associated to the core in the sandwich structures with crushable foams are not considered in the examined sandwich structures. The collapse of the sandwich specimens, examined here, is observed due to the failure of the skins in some steps. By multi-step collapse of these specimens via separately failure of the top and bottom skins, a considerable amount of energy is absorbed between these steps. Due to non-brittle behavior of the core material under loading, a large compression resistance is observed after failure of the top skin which led to the recovery of the load-carrying capacity in the sandwich beams. A similar behavior for the sandwich panels led to the increase of the ultimate strength after appearance of the failure lines on the top skin. The general outcomes of this investigation promise a good influence for the application of elastomeric foam as core material for sandwich structures.

Application and Experimental Study on Seismic Behavior of Composite Core Walls with STRC Columns

2012 ◽  
Vol 446-449 ◽  
pp. 395-399
Author(s):  
Hong Ying Dong ◽  
Wan Lin Cao ◽  
Jian Wei Zhang
Keyword(s):  
Experimental Study ◽  
Carrying Capacity ◽  
Structural Design ◽  
Seismic Behavior ◽  
Steel Tube ◽  
Load Carrying Capacity ◽  
The Core ◽  
Load Carrying ◽  
Energy Dissipation Capacity ◽  
Steel Trusses

According to the structural design in a project in Dalian, experimental study on seismic behavior of composite core walls with steel tube-reinforced concrete (STRC) columns were carried out. Five 1/6 scale composite core wall specimens with different steel reinforced details in the walls and different openings on the walls were designed and tested under cyclic loading. Based on the experiment, hysteretic property, load-carrying capacity, ductility, energy dissipation capacity and damage characteristics of the five specimens were compared and analyzed. The results show that the core walls with STRC columns have good seismic behavior. And the seismic behavior can be greatly improved by setting concealed steel trusses in the walls.

DYNAMICS AND BUCKLING OF SANDWICH PANELS WITH STEPPED FACINGS

2011 ◽  
Vol 11 (04) ◽  
pp. 697-716 ◽  
Author(s):  
CODY H. NGUYEN ◽  
RAMANJANEYA R. BUTUKURI ◽  
K. CHANDRASHEKHARA ◽  
VICTOR BIRMAN
Keyword(s):  
Carrying Capacity ◽  
Sandwich Panel ◽  
Sandwich Panels ◽  
Structural Response ◽  
Blast Loading ◽  
Attractive Alternative ◽  
Equal Weight ◽  
Load Carrying Capacity ◽  
Structural Problems ◽  
Load Carrying

Sandwich panels have been developed to either produce lighter structures capable of carrying prescribed loads or increase the load-carrying capacity subject to limitations on weight. In these panels, facings carry bending and in-plane loads while the core functions similarly to the web of a beam, mostly resisting transverse shear. Improvements in the load-carrying capacity of sandwich panels can be achieved through modifications in their geometry, boundary conditions, and material distribution. One of the methods recently considered by the authors is based on using facings with a step-wise variable thickness that increases at the critical region of the structure.1 It was illustrated that the strength of a sandwich panel can be considerably enhanced using such stepped facings, without a detrimental increase of the weight. The present paper expands the study of the feasibility of the stepped-facing sandwich panel concept concentrating on three structural problems, i.e. a possible improvement in stability, changes in the natural frequencies, and forced dynamic response to the explosive blast. It is illustrated that the stepped-facing design can improve stability of the panel and its response to blast loading. However, fundamental frequencies of stepped-facing panels decrease compared to those in their conventional equal-weight counterparts. Such decrease is detrimental in the majority of engineering applications representing a limitation of stepped-facing panels. Nevertheless, the usefulness of the stepped-facing design is proven in the problems of bending, stability, and blast loading. Numerous examples presented in the paper validate our suggestion that the combination of a relatively simple manufacturing process and an improved structural response of sandwich panels with stepped facings may present the designer with an attractive alternative to conventional sandwich structures.

Investigation of elastomeric foam response applied as core for composite sandwich beams through progressive failure of the beams

2017 ◽  
Vol 21 (2) ◽  
pp. 604-638
Author(s):  
AR Nazari ◽  
MZ Kabir ◽  
H Hosseini Toudeshky
Keyword(s):  
Finite Element ◽  
Carrying Capacity ◽  
Progressive Failure ◽  
Core Material ◽  
Foam Core ◽  
Sandwich Beams ◽  
Load Carrying Capacity ◽  
Composite Sandwich ◽  
The Core ◽  
Load Carrying

In this paper an elastomeric foam is applied as core for the composite sandwich beams and load carrying capacity, load–deflection response, and progressive failure are examined through experimental and finite element studies. The objective of this study is to assess the efficiency of elastomeric foam-cored sandwich (EFCS) beams relative to crushable foam-cored sandwich (CFCS) beams. The experimental program consists of two phases. In the first phase, some characterization tests are conducted on the constituent materials of the sandwich beams such as tension, compression, and shear tests on the foam and bending test on the composite beams utilized as skins. Then in the second phase, the performance of the sandwich beams is examined under bending conditions. The load carrying behavior of the sandwich beams is considered dependent on two main features of the constituent materials: (1) the hyperelastic behavior of the foam core and (2) the progressive damage of the composite skins. These characteristics are simulated by the finite element models. Due to elastomeric rather than crushable deformation of the applied foam as the core, the conventional damage modes of the CFCS beams associated to the brittleness of the core material are omitted through load carrying capacity of the EFCS beams. So in the recent sandwich beams by omission of the core failure modes and utilization of compressive residual strength of the top composite skin, considerable energy is absorbed prior to failure of the bottom composite skin. By simulation of the test specimens using FE models, the response of the foam applied as core for the sandwich beams through progressive failure of the beams is investigated. The results show that the elastomeric foam core can provide superior features for the sandwich components especially for the cases in which high energy absorption capacity is required.

Effect of Core Thickness on Load Carrying Capacity of Sandwich Panel Behavior Beyond Yield Limit

2011 ◽  
pp. 171-181
Author(s):  
Salih N. Akour ◽  
Hussein Maaitah ◽  
Jamal F. Nayfeh
Keyword(s):  
Experimental Investigation ◽  
Finite Element ◽  
Carrying Capacity ◽  
Sandwich Panel ◽  
Core Material ◽  
Load Carrying Capacity ◽  
Yield Limit ◽  
The Core ◽  
Load Carrying ◽  
Core Thickness

Sandwich Panel has attracted designer’s interest due to its light weight, excellent corrosion characteristics and rapid installation capabilities. It has been implemented in many industrial application such as aerospace, marine, architectural and transportation industry. Its structure consists of two face sheets and core. The core is usually made of material softer than the face sheets. The current investigation unveils the effect of core thickness on the behavior of Sandwich Panel beyond the yield limit of core material. The core thickness is investigated by utilizing univariate search optimization technique. The load is applied in quasi–static manner (in steps) till face sheets reach the yield limit. Simply supported panel from all sides is modeled using a finite element analysis package. The model is validated against numerical and experimental cases that are available in the literature. In addition, experimental investigation has been carried out to validate the finite element model and to verify some selected cases. The finite element results show very good agreement with the previous work and the experimental investigation. The study presents that the load carrying capacity of the panel increases as the core material goes beyond the yield point. Also, increasing core thickness to a certain limit delays the occurrence of core yielding and gives opportunity to face sheets to yield first.

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