Failure of Foam Core Sandwiches: Numerical Simulation by Microplane Model

Zdenek P. Bazant; Michele Brocca

doi:10.1115/IMECE2000-2032

Failure of Foam Core Sandwiches: Numerical Simulation by Microplane Model

Zdenek P. Bazant, Michele Brocca^*

^*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

Abstract

The paper presents a new constitutive model for closed-cell polymeric foams. The model is of the microplane type. In this model, the constitutive law is characterized in terms of vectors rather then tensors. The conceptual simplicity of this 'first-principles' approach makes it possible to base the model more directly on the physical phenomena occurring in the microstructure, in this case the elastic bending of the cells idealized as spheres in contact. The model is then employed in a finite element analysis of three point bending tests of sandwich beams failing by core indentation. Good agreement of the numerical results with the experimental observations is achieved. The softening and size effect engendered by the reduction of tangential bending stiffness due to the geometrically nonlinear effect of core indentation is discussed.

Original language	English (US)
Title of host publication	Mechanics of Sandwich Structures
Publisher	American Society of Mechanical Engineers (ASME)
Pages	51-67
Number of pages	17
ISBN (Electronic)	9780791819241
DOIs	https://doi.org/10.1115/IMECE2000-2032
State	Published - 2000
Externally published	Yes
Event	ASME 2000 International Mechanical Engineering Congress and Exposition, IMECE 2000 - Orlando, United States Duration: Nov 5 2000 → Nov 10 2000

Publication series

Name	ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)
Volume	2000-AA

Conference

Conference	ASME 2000 International Mechanical Engineering Congress and Exposition, IMECE 2000
Country/Territory	United States
City	Orlando
Period	11/5/00 → 11/10/00

Funding

The following are the conclusions drawn from the above investigation • A new co-injection resin infusion molding technique is introduced to fabricate foam-core sandwich panels. • Sandwich with higher density foam demonstrates higher buckling load than the ones with lower density foams having similar face sheet constructions. However, if the core densities are low, the variation in their failure loads is seen to be minimal. • Presence of core-skin disbonds slightly reduces the buckling load, initiates extensive delamination, and significantly changes the post-buckling behavior. • Implanted teflon also reduces the amount of core shear as part of the input energy is presumably expended to continue the delamination growth. • Higher density foam arrests core-skin delamination and core-shear phenomena almost entirely during buckling. • The correlation between experimental, analytical and FEM results are excellent in case of sandwiches without implants. However, modification of the FE model, and formulations of analytical equations in case of panels with teflon will be required for more accurate predictions. Acknowledgements The authors would like to appreciate the Office of Naval Research (ONR) to support this grant through grant No. N00014-90-J-11995. Dr. Y. D. S. Rajapakse is the Technical Monitor.

ASJC Scopus subject areas

Mechanical Engineering

Access to Document

10.1115/IMECE2000-2032

Cite this

@inproceedings{11e5325e6ce745798b45665f32fad3c2,

title = "Failure of Foam Core Sandwiches: Numerical Simulation by Microplane Model",

abstract = "The paper presents a new constitutive model for closed-cell polymeric foams. The model is of the microplane type. In this model, the constitutive law is characterized in terms of vectors rather then tensors. The conceptual simplicity of this 'first-principles' approach makes it possible to base the model more directly on the physical phenomena occurring in the microstructure, in this case the elastic bending of the cells idealized as spheres in contact. The model is then employed in a finite element analysis of three point bending tests of sandwich beams failing by core indentation. Good agreement of the numerical results with the experimental observations is achieved. The softening and size effect engendered by the reduction of tangential bending stiffness due to the geometrically nonlinear effect of core indentation is discussed. ",

author = "Bazant, {Zdenek P.} and Michele Brocca",

note = "Funding Information: The following are the conclusions drawn from the above investigation • A new co-injection resin infusion molding technique is introduced to fabricate foam-core sandwich panels. • Sandwich with higher density foam demonstrates higher buckling load than the ones with lower density foams having similar face sheet constructions. However, if the core densities are low, the variation in their failure loads is seen to be minimal. • Presence of core-skin disbonds slightly reduces the buckling load, initiates extensive delamination, and significantly changes the post-buckling behavior. • Implanted teflon also reduces the amount of core shear as part of the input energy is presumably expended to continue the delamination growth. • Higher density foam arrests core-skin delamination and core-shear phenomena almost entirely during buckling. • The correlation between experimental, analytical and FEM results are excellent in case of sandwiches without implants. However, modification of the FE model, and formulations of analytical equations in case of panels with teflon will be required for more accurate predictions. Acknowledgements The authors would like to appreciate the Office of Naval Research (ONR) to support this grant through grant No. N00014-90-J-11995. Dr. Y. D. S. Rajapakse is the Technical Monitor. Publisher Copyright: {\textcopyright} 2000 by ASME.; ASME 2000 International Mechanical Engineering Congress and Exposition, IMECE 2000 ; Conference date: 05-11-2000 Through 10-11-2000",

year = "2000",

doi = "10.1115/IMECE2000-2032",

language = "English (US)",

series = "ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)",

publisher = "American Society of Mechanical Engineers (ASME)",

pages = "51--67",

booktitle = "Mechanics of Sandwich Structures",

}

Bazant, ZP & Brocca, M 2000, Failure of Foam Core Sandwiches: Numerical Simulation by Microplane Model. in Mechanics of Sandwich Structures. ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), vol. 2000-AA, American Society of Mechanical Engineers (ASME), pp. 51-67, ASME 2000 International Mechanical Engineering Congress and Exposition, IMECE 2000, Orlando, United States, 11/5/00. https://doi.org/10.1115/IMECE2000-2032

Failure of Foam Core Sandwiches: Numerical Simulation by Microplane Model. / Bazant, Zdenek P.; Brocca, Michele.
Mechanics of Sandwich Structures. American Society of Mechanical Engineers (ASME), 2000. p. 51-67 (ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE); Vol. 2000-AA).

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

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T1 - Failure of Foam Core Sandwiches

T2 - ASME 2000 International Mechanical Engineering Congress and Exposition, IMECE 2000

AU - Bazant, Zdenek P.

AU - Brocca, Michele

N1 - Funding Information: The following are the conclusions drawn from the above investigation • A new co-injection resin infusion molding technique is introduced to fabricate foam-core sandwich panels. • Sandwich with higher density foam demonstrates higher buckling load than the ones with lower density foams having similar face sheet constructions. However, if the core densities are low, the variation in their failure loads is seen to be minimal. • Presence of core-skin disbonds slightly reduces the buckling load, initiates extensive delamination, and significantly changes the post-buckling behavior. • Implanted teflon also reduces the amount of core shear as part of the input energy is presumably expended to continue the delamination growth. • Higher density foam arrests core-skin delamination and core-shear phenomena almost entirely during buckling. • The correlation between experimental, analytical and FEM results are excellent in case of sandwiches without implants. However, modification of the FE model, and formulations of analytical equations in case of panels with teflon will be required for more accurate predictions. Acknowledgements The authors would like to appreciate the Office of Naval Research (ONR) to support this grant through grant No. N00014-90-J-11995. Dr. Y. D. S. Rajapakse is the Technical Monitor. Publisher Copyright: © 2000 by ASME.

PY - 2000

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N2 - The paper presents a new constitutive model for closed-cell polymeric foams. The model is of the microplane type. In this model, the constitutive law is characterized in terms of vectors rather then tensors. The conceptual simplicity of this 'first-principles' approach makes it possible to base the model more directly on the physical phenomena occurring in the microstructure, in this case the elastic bending of the cells idealized as spheres in contact. The model is then employed in a finite element analysis of three point bending tests of sandwich beams failing by core indentation. Good agreement of the numerical results with the experimental observations is achieved. The softening and size effect engendered by the reduction of tangential bending stiffness due to the geometrically nonlinear effect of core indentation is discussed.

AB - The paper presents a new constitutive model for closed-cell polymeric foams. The model is of the microplane type. In this model, the constitutive law is characterized in terms of vectors rather then tensors. The conceptual simplicity of this 'first-principles' approach makes it possible to base the model more directly on the physical phenomena occurring in the microstructure, in this case the elastic bending of the cells idealized as spheres in contact. The model is then employed in a finite element analysis of three point bending tests of sandwich beams failing by core indentation. Good agreement of the numerical results with the experimental observations is achieved. The softening and size effect engendered by the reduction of tangential bending stiffness due to the geometrically nonlinear effect of core indentation is discussed.

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U2 - 10.1115/IMECE2000-2032

DO - 10.1115/IMECE2000-2032

M3 - Conference contribution

AN - SCOPUS:85119841674

T3 - ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)

SP - 51

EP - 67

BT - Mechanics of Sandwich Structures

PB - American Society of Mechanical Engineers (ASME)

Y2 - 5 November 2000 through 10 November 2000

ER -

Failure of Foam Core Sandwiches: Numerical Simulation by Microplane Model

Abstract

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