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NBSIR 73-105

Environmental Evaluation of Polyurethane

Foam Core Sandwich Panel Construction

J. R. Shaver, L. W. Masters, T. W. Reichard, J. H. Pielert

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

December 1972

Final Report

Prepared for Office of Research and Technology

Department of Housing and Urban Development

Washington, D. C 20410

NBSIR 73-105

ENVIRONMENTAL EVALUATION OF POLYURETHANE

FOAM CORE SANDWICH PANEL CONSTRUCTION

J. R. Shaver, L. W. Masters, T. W. Reichard, J. H. Pielert

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

December 1972

Final Report

Prepared for Office of Research and Technology

Department of Housing and Urban Development

Washington, D. C. 20410

U. S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS. Richard W. Roberts. Director

SI Conversion Units

In view of the present accepted practice in this country for

building technology, common U. S. units of measurement have

been used throughout this paper. In recognition of the

position of the United States as a signatory to the General

Conference on Weights and Measures, which gave official

status to the metric SI system of units in 1960, assistance

is given to the reader interested in making use of the

coherent system of SI units by giving conversion factors

applicable to U. S. units used in this paper.

Length

1 in = 0.0254 meter (exactly)

1 ft = 0.3048 meter (exactly)

Force

1 lb (lbf) = 4.448 Newtons (N)

Pressure

1 lbf/ft 2 = 47.88 N/m 2

1 lbf/in 2 = 6894 N/m2

Temperature °C = 5 (Temperature °F - 32)

"9*

i
Environmental Evaluation of Polyurethane

Foam Core Sandwich Panel Construction

by

J. R. Shaver

L. W. Masters

J. H. Pielert

T. W. Reichard

Center for Building Technology

Institute for Applied Technology

Abstract

An environmental evaluation of a sandwich panel

bearing wall system for use in one of the Operation

BREAKTHROUGH housing systems is described. Two samples

of polyurethane foam core sandwich construction and four

full size wall panels were evaluated.

The samples of the sandwich construction were used

to evaluate the effect of extreme temperature and moisture

on this type of sandwich construction. The full size panels

were used to determine the behavior in service considering

the effects of adverse environmental conditions on ultimate

strength and mode of failure.

Key Words: Accelerated aging; compression; environmental

conditions; flexure; housing system; Operation

BREAKTHROUGH; polyurethane foam, sandwich

construction; wall system.
CONTENTS

Page

1.0 Introduction 1

1.2

1.1 Description of System

Scope of Evaluation 2

1

2.0 Panel Material Evaluation 4

2.1 Scope

2.2 Test Procedure

2.3 Test Results

3.0 Environmental Cycling of Full Size Panels

3.1 Scope

3.2 Test Specimen

3.3 Test Procedure

3.4 Test Results

4.0 Structural Testing of Full Size Panels

4.1 Scope

4.2 Flexural Tests

4.2.1 Moisture Conditioning Procedure

4.2.2 Test Specimen

4.2.3 Test Procedure

4.2.4 Test Results

11

iii
Page

4.3 Compressive Tests

4.3.1 Test Specimen

4.3.2 Test Procedure

4.3.3 Test Results

5.0 Summary and Conclusions

6.0 Acknowledgements

Figures

12

12

'13

13

iv
Environmental Evaluation of Polyurethane Foam

Core Sandwich Panel Construction

by

J. R. Shaver, L. W. Masters, J. H. Pielert, T. W. Reichard

1.0 Introduction

1.1 Description of System

"Operation BREAKTHROUGH , " a program sponsored by the

Department of Housing and Urban Development, has encouraged

the production of some new structural concepts in manufactured

housing systems. One of the proposed systems has as its

basic structural components a steel joist floor construction;

a composite steel deck construction for the roof; and a sandwich panel system for use as bearing walls as shown in

figure 1. Steel joists 24-in on center with a 3/4-in plywood

sub-flooring is used in the floor construction. The composite

roof is constructed by covering the steel roof deck with

1-in rigid insulation board overlaid with 1/2-in plywood.

The proposed panel system for the bearing walls consists of

4-ft by 8-ft by 3-in panels of sandwich construction interlocked by an aluminum "H" section. The panels are fabricated

by placing the face materials in a frame constructed with

aluminum extrusions and filling, by a continuous process, the

space between the faces with a polyurethane foam. The

exterior face is 1/8-in cement-asbestos board covered with

1
an epoxy adhesive for the attachment of decorative stone.

Plywood, 1/4-in thick, is used for the interior face. The

wall panels are connected to the floor by attaching matching

aluminum extrusions to the plywood sub-flooring and then sliding

an aluminum "H" section through the extrusions as shown

in figure lb. The wall panels are connected to the roof

deck by inserting sheet metal screws through the steel deck

and a matching aluminum extrusion as shown in figure la.

The aluminum MH" section is used to form an interlocking

vertical joint between the panels as shown in figure 2.

A synthetic rubber seal is then inserted to fill gaps in

the joint where an "H" section is used as the connector.

After erection, the interior face of the panels is covered

with gypsum drywall.

1.2 Scope of Evaluation

A structural review of the main load carrying components

in the system indicated that the floor and roof elements

satisfied strength and serviceability requirements. The

load carrying capacity of the panel system used in the

bearing walls was also assessed as being adequate. However,

there was concern that the environmental conditions of moisture

and temperature experienced during service could produce

damage sufficient to degrade the structural integrity of

the panels

This concern arises from the fact that one function of

the polyurethane core in a panel is to act as a stabilizer

for the faces and thereby increase their ability to transmit

a compressive load. The degree of stabilization is dependent

on the strength and character of the bond between the core

and faces. Regardless of the precautions taken, moisture

can accumulate over a period of time in the interior

of a panel and this moisture, in combination with high

2
temperature, will generally produce a reduction in bond

strength

Reduction in bond strength when subjected to the environmental

service conditions of temperature and moisture is referred

to as an aging process and the rate at which this process

takes place is often dependent upon the severity of the

environmental conditions. This process can often be evaluated

by taking small specimens of the panel and subjecting them

to moisture and temperature conditions more severe than

those normally encountered in service on the basis that

these conditions may cause acceleration of the aging process.

An accelerated aging procedure was used in this study and

the results obtained are presented in Section 2.0, Panel

Material Evaluation.

The accelerated aging procedure used in this study

on small specimens is especially pertinent when mechanical

incompatibility between the elements of a sandwich is expected.

Unfortunately, the temperatures used in this accelerated

aging procedure may be too severe for some materials such

that the panel is completely disrupted during the aging

procedure while under typical service temperatures the

panel may be satisfactory. Hence, a physical simulation

on a full-scale wall segment was also performed to evaluate

the effect of actual service conditions on this sandwich

construction. A description of the test specimen and the

test procedure along with the behavior of the specimen during

the test is given in Section 3.0, Environmental Cycling

of Full Size Panels.

Subsequent to this simulated environmental test the

panels used in the wall segment were subjected to physical

tests to evaluate their strength. Two additional panels

were tested in flexure to determine the effect of moisture

conditioning. The results of these physical tests along

with the procedures used are given in Section 4.0, Structural

Testing of Full Size Panels.

3
2.0 Panel Material Evaluation

2.1 Scope

Two samples of the sandwich panel, which were fabricated

by the producer, were evaluated to determine their resistance

to environmental factors

.

Sample 1 specimens were prepared with aluminum extrusions

surrounding the perimeter in the same manner as in the

full scale panels. Ten specimens measuring 6 x 6 in and

ten measuring 6 x 23 in were received for testing.

Sample 2 specimens were cut by the producer from a full

scale panel after foaming the core. These specimens

did not have aluminum extrusion surrounds. Ten specimens

measuring 6 x 6 in and ten measuring 6 x 23 in were received

for testing.

It was planned to determine the shear (parallel to the

plane of the sandwich) and flatwise tension (perpendicular to

the plane of the sandwich) strengths of the specimens from

each sample before and after accelerated aging.

2.2 Test Procedure

All specimens were tested after being brought to equilibrium with laboratory conditions (73 +_ 3°F and 50 + 1% rh) .

. Half of the specimens were stored in the laboratory while the

other half were artificially aged using the standard procedure

of ASTM C481-62, Test for Laboratory Aging of Sandwich

Construction . i/

— Part 16, 1971 Annual Book of Standards; American Society

for Testing and Materials; Philadelphia, Pennsylvania.

4
The C481-62 procedure contains two cycles, Cycle A and

Cycle B, of which Cycle A is considered to be more severe.

Cycle A was used to age the Sample 1 specimens and the less

severe Cycle B was applied to the specimens from Sample 2.

Both Cycles A and B of the test procedure consist of

six repetitive cycles of the following steps: (1) warm water

soaking, (2) steam or hot water spraying, (3) freezing,

(4) drying, (5) steam or hot water spraying and (6) drying.

Although this procedure is widely used in evaluating sandwich

construction, there is as yet no acceptable correlation

with natural aging.

2.3 Test Results

2.3.1 Sample 1

All specimens of Sample 1 exhibited bowing and cracking

of the cement-asbestos board facing. The bowing was noted in

each specimen following the first dry heat step of the first

cycle of the aging procedure. Cracking of the cement -asbestos

board and the coating material had occurred in each specimen

by the end of the second dry heat step of the first cycle.

Figure 3 illustrates the type of failure that was observed.

The bowing and cracking of the cement -asbestos board was

caused by expansion of the foam core normal to the plane of

the panel since expansion of the core either length-wise or

width-wise was restrained by the aluminum perimeter extrusions.

The accelerated aging procedure was stopped at the end of

the first cycle when it was observed that all the specimens

had suffered severe damage. Because of the severe damage the

shear and flatwise strengths of the specimens were not obtained.

5
2.3.2 Sample 2

The first deterioration of Sample 2 specimens was noted

following the first dry heat step of the first cycle in a

6 x 23 in specimen. The observed damage was a delamination

of the cement-asbestos board from the polyurethane core.

By the end of four cycles all specimens showed partial delamination

of the cement -asbestos board from the core. Expansion of

the core material occurred in each specimen and some specimens

exhibited cracking within the polyurethane core. Figure 4

illustrates the delamination and cracking of the polyurethane

core and also shows that the foaming process must have occurred

in two steps. Much of the cracking in the core material was

noted to be at the interface which was a result of the two

step foaming process. Initial indication of damage or increased

degradation of the specimens was observed following one of

the dry heat steps in the cycle indicating that the elevated

temperatures were the primary factor causing the foam expansion.

Because visible damage had occurred in all specimens the

accelerated aging procedure was stopped at the end of the

fourth cycle. Again the damage was sufficient to preclude

obtaining strength of the specimens in shear and flatwisetension.

3.0 Environmental Cycling of Full Size Panels

3.1 Scope

Since there was concern that the results from the small

specimen tests, described in the previous section, did not

realistically assess the effects of temperature and moisture

conditions on this type of sandwich construction, an environmental test was performed on a wall segment. This test subjected

the specimen for a 30-day period to temperature and moisture

conditions and a loading representative of those

6
that the wall might experience during its service life. A

wall segment representative of that found in the housing

system was constructed from full-size panels and connectors

supplied by the manufacturer using their prescribed techniques.

3.2 Test Specimen

The test specimen consisted of two 4- by 8-ft sandwich

wall panels attached to a test frame by connection methods used

in the housing system. The wall test segment is shown in

figures 5, 6 and 7. Figure 8 shows construction details of the

test specimen. The sides of the test frame were made by

attaching 3/4-in plywood to a 1-3/4 x 4-in steel channel

with wood screws. The appropriate matching wall extrusions

were then connected to the plywood with sheet metal screws

.

The wall panels were connected to the extrusions on the frame

by "H" sections in a manner prescribed by the manufacturer

with rubber sealing strips inserted along all vertical

connections and along the base connection on both the interior

and exterior sides of the panel. The face of the specimen,

on the interior side, was covered completely with gypsum drywall in the manner prescribed by the system manufacturer.

Threaded rods were placed horizontally across the specimen

on both sides and attached to the steel channel on the side

members of the frame at the quarter, mid, and three-quarter

height to provide lateral support. A small amount of tension

was introduced into the horizontal rods as the purpose of

this horizontal restraint was to simulate the lateral restraint

provided by adjacent panels in the actual structure. Threaded

rods were attached vertically on botli sides to the steel

channel at the center and at 32-in offsets on either side of

the center. The vertical rods were used to simulate the load

7
a floor and/or roof system would apply to the wall. Polystyrene insulation was placed around the test specimen in

order to provide a thermal and moisture barrier between

the two faces.

Eight dial gage extensometers were used during

the test to measure the displacement of the wall test segment.

All extensometers were located at midheight of the specimen

as follows: 3 each on the interior and exterior faces at

the center of the panels and test specimen; and 1 on each

of the vertical frame members on the interior side. Strain

gages were attached to the vertical rods so that the load

applied to the wall by introducing tension in these rods

could be monitored during the test. The temperature and

humidity of the air on both sides of the test specimen were

checked during the test by a motorized psychrometer . Thermocouples were attached to both sides of the specimen so that

the face temperature of the wall could be continuously recorded

during the test. The instrumentation is shown in figures 9

and 10.

3.3 Test Procedure

The test specimen was loaded with a 1.0 DEAD + 0.5 LIVE test

load of 375 lb per ft by tensioning the vertical threaded rods and

conditioned in the environmental chamber for 72 hrs at 75°F and

501 rh prior to the start of the test. During the 30 day test

period the interior side (face to which the gypsum wall board is

attached) was maintained at 75° + 5°F and 62 + S% rh. The temperature in the test chamber to which the exterior side (face

covered with exposed aggregate epoxy matrix) was exposed was

cycled between 115 + 6°F and 13 + 8°F. Each cycle took place

in 24 hours and was broken approximately into an 8 hr period

8
at the high temperature and a 16 hr period at the low

temperature. A plot of the air temperature and average

wall surface temperature for both the interior and exterior

sides during a typical cycle is shown in figure 11. Figure 12

exhibits the maximum and minimum surface temperatures on

the exterior face during the 30 day test period. The

relative humidity in the test chamber to which the exterior

side was exposed varied during the cycle from 50% in the

low temperature segment to 20% in the high temperature

segment

.

3.4 Test Results

The lateral movement of both the interior and exterior

sides of the test wall were recorded during the test and the

average displacements for a typical 5 day segment of the

test are shown in figure 13. The corresponding maximum and

minimum average temperatures on the interior and exterior

surfaces are shown for the same period in figure 14. The

equivalent uniform load ranges for this period are shown in

figure 15.

The only visible indication of any undesirable effect

during the test period was moisture condensation on the surface

of the gypsum drywall along the base through-wall extrusion

during the low temperature portion of the thermal cycle as can be seen in figure 16.

4.0 Structural Tests of Full Size Panels

4.1 Scope

A physical testing program was undertaken to verify

the structural performance of full size panels after they

were subjected to various environmental conditioning procedures.

The effect of environmental conditioning on the strength of the

9
panel in compression and flexure and an evaluation of panel

stiffness in flexure was determined. For the flexure test

a simulated in-service moisture conditioning procedure was

used while the compression test was performed on the panels

used in the environmental test.

4.2 Flexural Tests

4.2.1 Description of Moisture Conditioning Procedures

Each of the two full-size wall panels to be tested in

flexure were moisture conditioned by a different procedure

before being subjected to short-term flexural tests. The

two procedures were:

1. 501 relative humidity at 75 3°F for five days,

2. 95% relative humidity at 73 +_ 3°F for five days by

storage in a fogroom with the panel draped with a plastic film to prevent the deposition of liquid

water

4.2.2 Description of Test Setup

The wall panel was tested with an air bag located

between it and the laboratory floor as shown in figures 17

and 18. The overall panel length was 96 in and the supportto-support dimensions was 95 in. The specimen supports were

square tubular tie down beams with a roller at one end and

a knife edge at the other.

Three linear variable differential transformers (LVDT)

were placed at midspan to record vertical movement with one

over each side extrusion and one at the centerline of the

10
specimen. X-Y recorders plotted air bag pressure versus

mid-span deflection.

4.2.3 Description of Test Procedure

A preload of 15 psf was applied and removed in order

to "seat" the panel in the test fixture. Load was then

increased in 5 psf increments to the design wind load of

25 psf and removed. Next the load was cycled ten times

between 0 and 25 psf. Load was then increased to 48.75

psf and removed before increasing the load until failure

occurred. The 48.75 psf is the ultimate load obtained by

multiplying the wind load factor (1.3W) by the modifier

2 /

(1 + 1.5v) where v is the variability factor.— Instrumentation

readings were continuously taken during each load increment.

4.2.4 Short Term Flexural Test Results

The wall panel conditioned by Procedure 1 was subjected

to a uniformly applied load until failure which occurred

at approximately 136 psf. Figure 19 shows the average loaddeflection history of the midspan LVDT's. Failure occurred

as the aluminum side extrusions separated from the panel

at the quarter point leading to longitudinal cracking of

the cement asbestos board on the compression face of the

panel (see figures 20 and 21). Ten cycles of the load between

0 and 25 psf did not lead to a progressive increase in deflection

— Based on a normal distribution, the increase of the panel

design load (1 . 3W) by a factor of 1+ 1 . 5v means that

approximately 95 percent of the panels would have no less

than the required capacity.

11
The wall panel conditioned by Procedure 2 was subjected

to a uniformly applied load until failure which occurred

at approximately 168 psf. Figure 22 shows the average load

deflection history of the midspan LVDT's. Failure occurred

as the aluminum side extrusion separated from the panel at

one end (see figures 23 and 24). Again, ten cycles of the

load between 0 and 25 psf did not lead to a progressive increase

in deflection.

4.3 Compression Tests

4.3.1 Test Specimen

Both panels used in the environmental test were subjected

to a short-term compressive test using simulated in-service

end conditions. The length of each test specimen was 96-

in. To prevent the crushing of the aluminum extrusions at

each end of the panel and to insure a uniform bearing surface,

both ends of each test specimen were embedded in a highstrength plaster. One end of the panel was set in a 1-

3/4 - in deep by 3-in wide by 48-in long aluminum channel.

The channel was attached to a 2 x 8 x 48-in wood base which

in turn was bearing on the platen of the hydraulic testing

machine. The rotational restraint produced by this test

condition at the bottom of the panel is probably greater

than that which the panel would experience in the actual

structure. The load was applied to the top of the wall

through a 2 x 6 x 48-in steel plate. The load was applied

to this plate through a 6-in wide flange beam and a 3/4-

in half-round steel rod along a line of action offset from

the center of the panel 1/3 of the panel thickness to the

inside face as indicated in figure 25. This end condition

allowed for some end rotation and a load eccentricity that

the top of the wall might experience in service.

12
4.3.2 Test Procedure

A 250 lb load was applied to the panel and maintained

for a short time in order to "seat" the specimen in the

test fixture. Load was then continuously applied at a rate

of approximately 5000 lb per minute up to the point of no

further increase. The specimen was allowed to deform as the load decreased until half of the maximum load remained.

The specimen was then unloaded.

4.3.3 Test Results

Panel No. 1 had a maximum equivalent load of 11,750

lb per ft while Panel No. 2 had a maximum equivalent load

of 12,500 lb per ft. The design load for these panels

(Dead plus Live) as bearing walls in the proposed housing

configuration is 576 lb per ft. Thus it can be seen that the

capacity of the panel is greatly in excess of that required

by the design. A better simulation of in-service end restraint

during the test would probably reduce the ultimate load capacity

of the panel. However, it is judged that the capacity of the

panel would not be substantially reduced. Both panels bowed

toward the interior (plywood) side during the test. The

vertical aluminum extrusions in both panels visibly deformed

during the decrease in load segment of the test. The cementasbestos facing fractured in Panel No. 2 near the restrained

end during the decrease in load segment of the test.

The "coin tapping" test was performed on both panels

after the compression test to detect if any unbonded areas

between the core and faces existed. No indication of

delamination was found in Panel No. 1. Panel No. 2 exhibited

an area of approximately 5%. This was verified by stripping

the panel faces from the core after removing the extrusions.

The unbonded area occurred on the cement-asbestos side of the

panel at the end where the foam is introduced during the

13
manufacturing process and its appearance indicated it was a manufacturing defect rather than an unbonding from environmental

exposure. There was no visual evidence of moisture accumulation

in the interior of the panel.

5,0 Summary and Conclusions

An environmental evaluation of a foam-core sandwich

panel construction intended for use in bearing walls in a housing system proposed for "Operation Breakthrough" is

described in this report. The sandwich panel is constructed

by placing sheets of cement- asbestos board and plywood in

an extruded aluminum frame and filling the space between

them with a polyurethane foam.

Small representative panel specimens were subjected to

an aging procedure to assess the effect of high humidity and

temperature. A test wall segment typical of the bearing

wall found in the housing system was constructed in an

environmental chamber and subjected to 30 days of environmental

cycling to evaluate the validity of the aging procedure on

this type of sandwich construction. Full size panels were tested

in compression and flexure to ascertain the effect of different

simulated environmental conditioning procedures on strength

and stiffness.

The following conclusions can be made from the test

results

1. The equivalent load at failure obtained in axial

compression after the simulated in-service test

was well in excess of the required design load.

2. The high-humidity conditioning procedure did not

have an adverse effect on the flexural strength of

the wall panel.

14
Failure in compression and flexure occurred as the

aluminum side extrusions separated from the panel

indicating the attachment of the frame to the panel

faces is a significant factor in maintaining structural integrity.

The performance of the wall segment under load

during the simulated in-service environmental

conditions was satisfactory.

For this type of sandwich panel construction, the

aging process cannot be properly evaluated by the

currently accepted accelerated aging procedures

for small specimens.

15
6.0 Acknowledgement

Acknowledgement must be made for the cooperation and

assistance given by J. W. Grimes, W. J. Mulroy, B. L. Shomaker,

and D. K. Ward of the Thermal Engineering Systems Section during

the environmental test of the wall segment.

USCOMM-NBS-DC

16
EPOXY MATRIX

FOR EXTERIOR

SURFACE

CEMENT ASBESTOS BOARD

.MEMBRANE ROOFING

PLYWOOD

^RIGID INSULATION

POLYURETHANE FOAM

GYPSUM DRYWALL

PLYWOOD

a. ROOF WITH CONNECTED WALL

^4" DEEP STEEL DECK

WITH RIBS <§) 16" o.c.

ALUMINUM

"H" SECTION

SYNTHETIC

RUBBER SEAL

7 1/2" DEEP

STEEL JOISTS

@ 24- IN O.C

PLYWC

ITH CONNECTED WALLS

FIGURE 1, STRUCTURAL COMPONENTS OF HOUSING SYSTEM

9 17
.EPOXY MATRIX FOR EXTERIOR FINISH

SYNTHETIC RUBBER SEAL

CEMENT ASBESTOS

BOARD

POLYURETHANE

FOAM

GYPSUM DRYWALL-t

FOR INTERIOR

FINISH

PLYWOOD

FIGURE 2, VERTICAL CONNECTION IN WALL PANEL SYSTEM

18

20
103"

FIGURE 5, SCHEMATIC FOR ENVIRONMENTAL TEST WALL

21

FIGURE 7. INTERIOR FACE

25

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INTERIOR

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AVERAGE DISPLACEMENT

INTERIOR FACE at MINIMUM TEMP.

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FIGURE 13. WALL DISPLACEMENT DURING TYPICAL 5 DAY

PERIOD OF TEST
40

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TIME, days

FIGURE 14. TEMPERATURE VARIATION DURING TYPICAL

5 DAY PERIOD OF TEST „
FIGURE 15. EQUIVALENT LOAD VARIATION DURING TYPICAL

5 DAY PERIOD OF TEST

31
32
33

0.5

pjrve beyond this point not obtained

because of instrumentation failure

10 1.5 2.0 2.5

MIDSPAN DEFLECTION, in

3.0

FIGURE 19. SHORT-TERM FLEXURAL TEST RESULTS ON SPECIMEN

CONDITIONED BY PROCEDURE 1 35


_J I I I I 1_

0.5 1.0 1.5 20 2.5 3.0

MIDSPAN DEFLECTION, in

FIGURE 22. SHORT-TERM FLEXURAL TEST RESULTS ON SPECIMEN

CONDITIONED BY PROCEDURE 2 38


T = PANEL THICKNESS

6WF BEAM

PLYWOOD INTERIOR

FACE

POLYURETHANE

FOAM CORE\

ALUMINUM CHANNEL

WOOD BASE

STEEL PLATE

HIGH-STRENGTH

GYPSUM

EXPOSED AGGREGATE

EPOXY MATRIX

CEMENT ASBESTOS

BOARD

HIGH -STRENGTH

GYPSUM

/// / / / // / / / r) i / /ay / // //////// / // / 1

LOAD LINE

FIGURE 25, SCHEMATIC FOR SHORT-TERM COMPRESSION TEST

ON FULL SIZE WALL PANEL

41

form NBS-H4A n-71)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

NRSTR 73-105

2. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Environmental Evaluation of Polyurethane Foam Core

Sandwich Panel Construction

5. Publication Date

6. Performing Organization Code

7. author(s) J„ R. Shaver; L. W. Masters; J. H. Pielert;

T. W. Reichard

8. Performing Organization

NRSTR 73-105

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/ Work Unit No. 4600443

11. rnnfr.irt/rir.inr Mn

IAA-H-16-70

12. Sponsoring Organization Name and Address

Department of Housing & Urban Development

Washington, D. C. 10410

13. Type of Report & Period

Covered

Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) An environmental evaluation of a sandwich panel bearing wall system for use in one

of the Operation BREAKTHROUGH housing systems is described. Two samples of polyurethane foam core sandwich construction and four full size wall panels were

evaluated.

The samples of the sandwich construction were used to evaluate the effect of extreme

temperature and moisture on this type of sandwich construction. The full size panels

were used to determine the behavior in service considering the effects of adverse

environmental conditions on ultimate strength and mode of failure.

17. KEY WORDS (Alphabetical order, separated by semicolons)

Accelerated aging; compression; environmental conditions; flexure; housing system;

Operation BREAKTHROUGH; polyurethane foam; sandwich construction; wall system

18. AVAILABILITY STATEMENT 19. SECURITY CLASS

(THIS REPORT)

21. NO. OF PAGES

[~Xl UNLIMITED.

UNCL ASSIFIED

1 I FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE

TO NTIS.

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

22. Price

USCOMM-DC 662 44-P71