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Research Papers

Test Method Development and Determination of Three-Dimensional Strength and Failure Modes of Polyvinyl Chloride Structural Foams

[+] Author and Article Information
Akira Miyase

National Wind Energy Center,
University of Houston,
5000 Gulf Freeway,
Building 3, Room 152B,
Houston, TX 77204-0931
e-mail: amiyase@uh.edu

Su Su Wang

National Wind Energy Center,
University of Houston,
5000 Gulf Freeway,
Building 3, Room 152B,
Houston, TX 77204-0931
e-mail: sswang@uh.edu

Contributed by the Materials Division of ASME for publication in the JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY. Manuscript received August 30, 2016; final manuscript received January 30, 2017; published online March 27, 2017. Assoc. Editor: Erdogan Madenci.

J. Eng. Mater. Technol 139(3), 031006 (Mar 27, 2017) (7 pages) Paper No: MATS-16-1246; doi: 10.1115/1.4036068 History: Received August 30, 2016; Revised January 30, 2017

A comprehensive study has been conducted to develop proper test methods for accurate determination of failure strengths along different material directions of closed-cell polymer-based structural foams under different loading modes. The test methods developed are used to evaluate strengths and failure modes of commonly used H80 polyvinyl chloride (PVC) foam. The foam's out-of-plane anisotropic and in-plane isotropic cell microstructures are considered in the test methodology development. The effect of test specimen geometry on compressive deformation and failure properties is addressed, especially the aspect ratio of the specimen gauge section. Foam nonlinear constitutive relationships, strength and failure modes along both in-plane and out-of-plane (rise) directions are obtained in different loading modes. Experimental results reveal strong transversely isotropic characteristics of foam microstructure and strength properties. Compressive damage initiation and progression prior to failure are investigated in an incremental loading–unloading experiment. To evaluate foam in-plane and out-of-plane shear strengths, a scaled shear test method is also developed. Shear loading and unloading experiments are carried out to identify the causes of observed large shear damage and failure modes. The complex damage and failure modes in H80 PVC foam under different loading modes are examined, both macroscopically and microscopically.

Copyright © 2017 by ASME
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References

Figures

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Fig. 1

Coordinates for directionally dependent strength properties of H80 PVC foam

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Fig. 2

Foam compression test specimen geometry with reduced gauge section

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Fig. 3

Foam tensile test specimen geometry and dimensions

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Fig. 4

Shear test specimen geometry and dimensions

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Fig. 5

Rise-direction compressive stress–strain curves of H80 PVC foam specimen with different gauge section dimensions

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Fig. 6

Effect of gauge-section aspect ratio, LGS/WGS, on compressive failure strengths of H80 PVC foam

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Fig. 7

Compressive stress–strain behavior and failure strength of H80 PVC foam in (a) one-direction and (b) two-direction (specimens with different gauge-section dimensions)

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Fig. 8

Out-of-plane (rise-direction) tensile stress–strain behavior and failure strength of H80 PVC foam (in specimens with different gauge-section geometry)

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Fig. 9

Effect of gauge-section aspect ratio on tensile strengths of H80 PVC foam

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Fig. 10

Tensile stress–strain behavior and failure strength in (a) one-direction and (b) two-direction of H80 PVC foam in specimens with different gauge section geometry

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Fig. 11

Directionally dependent compressive stress–strain behavior and failure strength of H80 PVC foam (WGS = 19 mm, LGS/WGS = 1.60)

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Fig. 12

Rise direction (out-of-plane) compressive stress–strain development in H80 PVC foam under loading–unloading cycles (WGS = 19.1 mm, LGS/WGS = 1.60)

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Fig. 13

Tensile stress–strain behavior and failure strength in different loading directions of H80 PVC foam

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Fig. 14

In-plane and out-of-plane shear stress–strain curves and failure strengths of H80 PVC foam

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Fig. 15

In-plane (2-1 plane) shear stress–strain behavior of H80 PVC foam in repeated incremental loading–unloading cycles

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Fig. 16

In-plane strain recovery of H80 PVC foam after the 11th repeated incremental shear loading–unloading cycle

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Fig. 17

Glass transition temperature of H80 PVC foam polymer from differential scanning calorimeter (DSC) experiment

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Fig. 18

Compression failure modes in H80 PVC foam: (a) bulge band in test specimen and (b) microscopic damage with crimpled and collapsed cells

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Fig. 19

Tensile failure modes of H80 PVC foam: (a) fractured test specimen (WGS = 12.7 mm) and (b) foam cells near fracture surface

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Fig. 20

Microscopic cell damage and failure modes in foam transverse shear failure (specimen subjected to shear strain, γ23 = 0.29)

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