Offshore and Structural Mechanics

Characterization of the Compressive Behavior of Glass Fiber Reinforced Polyurethane Foam at Different Strain Rates

[+] Author and Article Information
Huiyang Luo, Yanli Zhang

School of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, OK 74078

Bo Wang

 Technology, American Bureau of Shipping (ABS), Houston, TX 77060

Hongbing Lu

Department of Mechanical and Energy Engineering, University of North Texas, Denton, TX 76207hongbing.lu@unt.edu

J. Offshore Mech. Arct. Eng 132(2), 021301 (Mar 10, 2010) (12 pages) doi:10.1115/1.4000396 History: Received July 03, 2008; Revised June 20, 2009; Published March 10, 2010; Online March 10, 2010

A glass fiber reinforced polyurethane foam (R-PUF), used for thermal insulation of liquefied natural gas tanks, was characterized to determine its compressive strength, modulus, and relaxation behavior. Compressive tests were conducted at different strain rates, ranging from 103s1 to 10s1 using a servohydraulic material testing system, and from 40s1 to 103s1 using a long split Hopkinson pressure bar (SHPB) designed for materials with low mechanical impedance such as R-PUF. Results indicate that in general both Young’s modulus and collapse strength increase with the strain rate at both room and cryogenic (170°C) temperatures. The R-PUF shows a linearly viscoelastic behavior prior to collapse. Based on time-temperature superposition principle, relaxation curves at several temperatures were shifted horizontally to determine Young’s relaxation master curve. The results show that Young’s relaxation modulus decreases with time. The relaxation master curve obtained can be used to convert to Young’s modulus at strain rates up to 103s1 following linearly viscoelastic analysis after the specimen size effect has been considered.

Copyright © 2010 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.



Grahic Jump Location
Figure 1

R-PUF cylindrical specimens and the fiber orientations. (a) An undeformed specimen with axial direction in the z-direction; speckles are used for deformation measurements using DIC. (b) A compressed specimen after compression at 40% strain on a SHPB test at a strain rate of 1100 s−1.

Grahic Jump Location
Figure 2

Schematic of the split Hopkinson pressure bar for testing R-PUF at high-strain rates

Grahic Jump Location
Figure 3

Optical micrographs of the PU foam surface: (a) x-y plane and (b) x-z plane

Grahic Jump Location
Figure 4

SEM micrographs of the R-PUF: (a) x-y plane and (b) x-z plane

Grahic Jump Location
Figure 5

DMA schematic setup for the measurement of the flexural properties of the R-PUF in the z-direction

Grahic Jump Location
Figure 6

DMA testing results for the R-PUF in the z-direction

Grahic Jump Location
Figure 7

Reference and deformed images of a foam in the z-direction compressed at a strain rate of 0.01 s−1. (a) t=0 s(εz=0), (b) t=10 s(εz=0.10), (c) t=20 s(εz=0.20), and (d) t=30 s(εz=0.30).

Grahic Jump Location
Figure 8

Contours of displacements and strains in the z-direction measured using DIC. (a) Displacement field W(1 pixel=86.1 μm), (b) displacement field U(1 pixel=86.1 μm), (c) strain field εz, and (d) strain field εx.

Grahic Jump Location
Figure 9

Axial strain as a function of subset size (1 pixel=86.1 μm)

Grahic Jump Location
Figure 10

Compressive stress-strain curves of the R-PUF in the z-direction after scaling for the specimen size effect (23°C at a strain rate of 0.01 s−1). The curves represent the results for a large sample with diameter of 76.2 mm and length of 76.2 mm, and a small sample with diameter of 17.8 mm and length of 12.7 mm.

Grahic Jump Location
Figure 11

Size factors for Young’s modulus and yield strength of the R-PUF at low-strain rates

Grahic Jump Location
Figure 12

Typical SHPB testing results of a R-PUF specimen. (a) Original oscilloscope recording and (b) stress equilibrium check and strain rate history.

Grahic Jump Location
Figure 13

Compressive stress-strain curves of the R-PUF in the z-direction (high-strain rate data were corrected with the size factor shown in Fig. 1): (a) at 23°C and (b) at −170°C

Grahic Jump Location
Figure 14

Compressive stress-strain curves of the R-PUF in the x-direction (high-strain rate data were corrected with the size factor shown in Fig. 1): (a) at 23°C and (b) at −170°C

Grahic Jump Location
Figure 15

Compressive properties of the R-PUF at different strain rates (data at high-strain rates were scaled using the size factor in Fig. 1): (a) Young’s modulus and (b) yield strength. (Note that the sudden change in property at 20–40 s−1 is due to the dynamic buckling of glass fibers at these high-strain rates.)

Grahic Jump Location
Figure 16

Typical deformed images of the R-PUF under compression at a high-strain rate obtained using high-speed photography. (a) εz=0%, (b) εz=2.73%, (c) εz=5.29%, (d) εz=10.8%, (e) εz=21.4%, and (f) εz=29.1%.

Grahic Jump Location
Figure 17

Compressive stress-strain curves from bar signals and image analysis using DIC, and transverse strains corresponding to different axial strains. The dynamic Poisson’s ratio of the foam when compressed in the z-direction is determined as 0.054.

Grahic Jump Location
Figure 18

Axial strain filed measured using DIC on an area of 250×50 pixels; axes are given in number of pixels, 1 pixel=37.74 μm in this case

Grahic Jump Location
Figure 19

SEM micrographs of a failed R-PUF specimen compressed on a SHPB by 40% at a strain rate of 1100 s−1: (a) loading in the z-direction and (b) loading in the x-direction

Grahic Jump Location
Figure 20

Relaxation modulus data of the R-PUF. (a) Young’s relaxation modulus curves at several temperatures. (b) Relaxation master curve referred to 23°C. The inset is the shift factors at several temperatures.

Grahic Jump Location
Figure 21

Comparison of Young’s modulus between direct experimental measurement and calculated value using Eq. 9 from master curve in Fig. 2 for the foam in the z-direction



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In