Failure Modes of Foam Core Sandwich Beams under Static and Impact Loads

Tooth-plate-glass-fiber hybrid sandwich (TFS) is a type of sandwich composites fabricated by vacuum-assisted resin infusion process, in which glass fiber facesheets reinforced by metal plate are connected to foam core through tooth nails. Bending properties and interlaminar properties of TFS beams with various foam densities were investigated by flexural tests and DCB (double cantilever beam) tests. The test results showed that by increasing the foam core density from 35 kg/m3 to 150 kg/m3, the peak strength of TFS beams significantly increased by 168% to 258% compared with similar sandwich beams with fibrous composite facesheets. With the change of foam density and span length, the main failure modes are core shear and facesheet indentation beneath the loading roller. The interlaminar strain energy release rates of TFS specimens also increased by increasing the density of the foam. In addition, an analytical model was used to predict the ultimate bending strength of TFS beams, which were in good accordance with the experimental results.

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Failure of Composite Sandwich Beams

Advanced Composites Letters ◽

10.1177/096369350201100301 ◽

2002 ◽

Vol 11 (3) ◽

pp. 096369350201100 ◽

Cited By ~ 6

Author(s):

I. M. Daniel ◽

E. E. Gdoutos ◽

K.-A. Wang

Keyword(s):

Failure Modes ◽

Foam Core ◽

Sandwich Beams ◽

Composite Sandwich ◽

Four Point Bending ◽

Constituent Material ◽

Closed Cell ◽

Failure Envelopes ◽

Geometrical Dimensions ◽

Cell Foam

A thorough investigation of failure behaviour of composite sandwich beams under three- and four-point bending was undertaken. The beams were made of unidirectional carbon/epoxy facings and a PVC closed-cell foam core. The constituent materials were fully characterised and in the case of the foam core, failure envelopes were developed for general two-dimensional states of stress. Various failure modes including facing wrinkling, indentation failure and core failure were observed and compared with analytical predictions. The initiation, propagation and interaction of failure modes depend on the type of loading, constituent material properties and geometrical dimensions.

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The Failure Behavior of Geometrically Asymmetric Metal Foam Core Sandwich Beams Under Three-Point Bending

Journal of Applied Mechanics ◽

10.1115/1.4027200 ◽

2014 ◽

Vol 81 (7) ◽

Cited By ~ 17

Author(s):

Jianxun Zhang ◽

Qinghua Qin ◽

Weilong Ai ◽

Huimin Li ◽

T. J. Wang

Keyword(s):

Failure Mechanism ◽

Failure Modes ◽

Metal Foam ◽

Minimum Weight ◽

Failure Behavior ◽

Foam Core ◽

Sandwich Beams ◽

Three Point Bending ◽

Initial Failure ◽

Core Height

The failure behavior of geometrically asymmetric sandwich beams with a metal foam core is analytically and experimentally investigated. New initial failure modes of the asymmetric sandwich beams are observed under three-point bending, i.e., face yield, face wrinkling, core shear A, core shear AB, core shear A-AB, and indentation. It is shown that the initial failure modes of sandwich beams depend on the span of the beam, the thicknesses of top and bottom face sheets, core height and material properties. We derived the analytical formulae for the initial failure loads and then constructed the initial failure mechanism maps for the geometrically asymmetric sandwich beams. It is shown that the analytically predicted initial failure mechanism maps are in good agreement with the experimental results, which are clearly different from the symmetric sandwich beams. As a preliminary application, the minimum weight designs are presented for asymmetric metal sandwich beams.

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Failure modes of composite sandwich beams

Theoretical and Applied Mechanics ◽

10.2298/tam0803105g ◽

2008 ◽

Vol 35 (1-3) ◽

pp. 105-118 ◽

Cited By ~ 22

Author(s):

E. Gdoutos ◽

I.M. Daniel

Keyword(s):

Failure Modes ◽

Failure Behavior ◽

Foam Core ◽

Sandwich Beams ◽

Composite Sandwich ◽

Four Point Bending ◽

Constituent Material ◽

Closed Cell ◽

Failure Envelopes ◽

Geometrical Dimensions

A thorough investigation of failure behavior of composite sandwich beams under three-and four-point bending was undertaken. The beams were made of unidirectional carbon/epoxy facings and a PVC closed-cell foam core. The constituent materials were fully characterized and in the case of the foam core, failure envelopes were developed for general two-dimensional states of stress. Various failure modes including facing wrinkling, indentation failure and core failure were observed and compared with analytical predictions. The initiation, propagation and interaction of failure modes depend on the type of loading, constituent material properties and geometrical dimensions.

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Carbon Foam Core Composite Sandwich Beams: Flexure Response

Journal of Composite Materials ◽

10.1177/0021998305048740 ◽

2005 ◽

Vol 39 (12) ◽

pp. 1067-1080 ◽

Cited By ~ 10

Author(s):

M. D. Sarzynski ◽

O. O. Ochoa

Keyword(s):

Carbon Foam ◽

Foam Core ◽

Sandwich Beams ◽

Composite Sandwich

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Creep Responses of Smart Sandwich Composites at Multiple Length Scales: Experiments and Modeling

Journal of Engineering Materials and Technology ◽

10.1115/1.4002643 ◽

2010 ◽

Vol 133 (1) ◽

Cited By ~ 4

Author(s):

Anaïs Farrugia ◽

Charles Winkelmann ◽

Valeria La Saponara ◽

Jeong Sik Kim ◽

Anastasia H. Muliana

Keyword(s):

Creep Behavior ◽

Composite Structures ◽

Effective Properties ◽

Micromechanical Model ◽

Foam Core ◽

Sandwich Beams ◽

Fiber Reinforced ◽

Polymer Foam ◽

Creep Tests ◽

Unique Challenge

In service, composite structures present the unique challenge of damage detection and repair. Piezoelectric ceramic, such as lead zirconate titanate (PZT), is often used for detecting damage in composites. This paper investigates the effect of embedded PZT crystals on the overall creep behavior of sandwich beams comprising of glass fiber reinforced polymer laminated skins and polymer foam core, which could potentially be used as a damage-detecting smart structure. Uniaxial quasi-static and creep tests were performed on the glass/epoxy laminated composites having several fiber orientations, 0 deg, 45 deg, and 90 deg, to calibrate the elastic and viscoelastic properties of the fibers and matrix. Three-point bending creep tests at elevated temperature (80°C) were then carried out for a number of control sandwich beams (no PZT crystal) and conditioned sandwich beams (with PZT crystals embedded in the center of one facesheet). Lateral deflection of the sandwich beams was monitored for more than 60 h. The model presented in this paper is composed by two parts: (a) a simplified micromechanical model of unidirectional fiber reinforced composites used to obtain effective properties and overall creep response of the laminated skins and (b) a finite element method to simulate the overall creep behavior of the sandwich beams with embedded PZT crystals. The simplified micromechanical model is implemented in the material integration points within the laminated skin elements. Fibers are modeled as linear elastic, while a linearized viscoelastic material model is used for the epoxy matrix and foam core. Numerical results on the creep deflection of the smart sandwich beams show good correlations with the experimental creep deflection at 80°C, thus proving that this model, although currently based on material properties reported at room temperature, is promising to obtain a reasonable prediction for the creep of a smart sandwich structure at high temperatures.

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

Journal of Sandwich Structures & Materials ◽

10.1177/1099636217701093 ◽

2017 ◽

Vol 21 (3) ◽

pp. 865-894 ◽

Cited By ~ 1

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.

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Mechanical Behavior of Sandwich Panels with Hybrid PU Foam Core

Advances in Civil Engineering ◽

10.1155/2020/2908054 ◽

2020 ◽

Vol 2020 ◽

pp. 1-8

Author(s):

Xudong Zhao ◽

Li Tan ◽

Fubin Zhang

Keyword(s):

Failure Modes ◽

Peak Load ◽

Hard Core ◽

Experimental Results ◽

Control Panel ◽

Foam Core ◽

Initial Stiffness ◽

Composite Sandwich ◽

Pu Foam ◽

Compression Area

The traditional composite sandwich structures have disadvantages of low shear modulus and large deformation when used in civil engineering applications. To overcome these problems, this paper proposed a novel composite sandwich panel with upper and lower GFRP skins and a hybrid polyurethane (PU) foam core (GHP panels). The hybrid core is composed of different densities (150, 250, and 350 kg/m3) of the foam core which is divided functionally by horizontal GFRP ribs. The hard core is placed in the compression area to resist compressive strength and improve the stiffness of the composite sandwich structure, while the soft core is placed in the tension area. Six GHP panels were tested loaded in 4-point bending to study the effect of horizontal ribs and hybrid core configurations on the stiffness, strength, and failure modes of GHP panels. Experimental results show that compared to the control panel, a maximum of 54.6% and 50% increase in the strength and bending stiffness can be achieved, respectively. GHP panels with the hybrid PU foam core show obvious secondary stiffness. Finally, analytical methods were proposed to predict the initial stiffness and peak load of the GHP panels, and the results agree well with experimental results.

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