Effect of Geometric Constraint on Fracture Toughness of PVC Foam Core Sandwich Beams

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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Low temperature mixed-mode debond fracture and fatigue characterisation of foam core sandwich

Journal of Sandwich Structures & Materials ◽

10.1177/1099636218779420 ◽

2018 ◽

Vol 22 (4) ◽

pp. 1039-1054 ◽

Cited By ~ 2

Author(s):

Arash Farshidi ◽

Christian Berggreen ◽

Leif A Carlsson

Keyword(s):

Fracture Toughness ◽

Growth Rate ◽

Low Temperature ◽

Mixed Mode ◽

Room Temperature ◽

Sliding Mode ◽

Fatigue Tests ◽

Mode I ◽

Foam Core ◽

Climatic Chamber

This paper experimentally investigates the effects of low temperature on fracture toughness and fatigue debond growth rate in foam core sandwich composites. Mixed-mode bending specimens were statically and cyclically tested inside a climatic chamber at a low temperature (−20°C) and at room temperature (23°C) as a reference. Testing was conducted in mode I (opening) and mixed-mode I/II (opening-sliding) mode mixities. The fatigue tests results are presented according to the modified Paris–Erdogan relation. Results showed substantial fracture toughness reduction due to low temperature. Low temperature furthermore elevated the cyclic crack growth rate.

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An Investigation on Mechanical Behavior of Tooth-Plate-Glass-Fiber Hybrid Sandwich Beams

Advances in Polymer Technology ◽

10.1155/2020/6346471 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

Honglei Xie ◽

Li Wan ◽

Bo Wang ◽

Haiping Pei ◽

Weiqing Liu ◽

...

Keyword(s):

Glass Fiber ◽

Failure Modes ◽

Bending Strength ◽

Fibrous Composite ◽

Strain Energy Release ◽

Metal Plate ◽

Plate Glass ◽

Foam Core ◽

Sandwich Beams ◽

Tooth Plate

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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