NBSIR 73-188

Structural Tests on Housing Components

of Glass Fiber Reinforced Polyester

Laminate

Thomas W. Reichard, William E. Greene, Jr., Louis E. Cattaneo,

Larry W. Masters

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

April 1973

Final Report

Prepared for Office of Research and Technology

Department of Housing and Urban Development

Washington. D. C. 20410

NBSIR 73-188

STRUCTURAL TESTS ON HOUSING COMPONENTS

OF GLASS FIBER REINFORCED POLYESTER

LAMINATE

Thomas W. Reichard, William E. Greene, Jr., Louis E. Cattaneo,

Larry W. Masters

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

April 1973

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
Structural Tests on Housing Components

of

Glass Fiber Reinforced Polyester Laminate

by

:^ Thomas W. Reichard, William E. Greene, Jr.

Louis E. Cattaneo and Larry W. Masters

of

Structures, Materials and Life Safety Division

Center for Building Technology

Abstract

This report describes a series of structural evaluation tests

performed on housing components made with a glass fiber

reinforced polyester (FRP) laminate. The components tested

were: 1) The FRP laminate used for the facings and the

corrugated core of the basic panel, 2) the adhesive bond

between the facing and core, 3) typical wall panels and

4) typical roof panels. Test data include: 1) the effect

of temperature and moisture on the tensile and compressive

strength of the FRP laminate, 2) the effect of temperature,

accelerated aging and sustained loads on the tensile shear

strength of the facing - to -core polyester adhesive bond,

3) the short-term strength of the wall panels under compressive

and in-plane shear loading, 4) the long-term strength of the

wall panels under sustained compressive loading and 5) the

short-term and long-term performance of the roof panels under

flexural loading.

ii
Key Words: Adhesive bond; Aging; Composites; Compression;

Flexure; Glass fiber; Housing system; Innovations;

Laminate; Operation Breakthrough; Racking;

Reinforced plastics; Reinforced polyester;

Sustained loading; Tensile shear.

iii
SI Conversion Units

In view of the present accepted practice in this country for

building technology, common US 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 US units

used in this paper.

Length

1 in = 0.0254 meter (exactly)

1 ft = 0.3048 meter (exactly)

Force

1 lb (Ibf) = 4.44 8 Newtons (N)

Pressure

1 psf = 47.88 N/m^

1 psi = 6894 N/m^

Temperature °C = 5/9 (Temperature - 32)

iv
CONTENTS

Structural Tests on Housing Components

of Glass Fiber Reinforced Polyester Laminate

Page

Abstract ii

SI Conversion Units iv

1.0 Introduction 1

1 . 1 Obj ect ive 1

1.2 System Description 1

1.3 Scope of Testing 2

2.0 Tests 3

2.1 FRP Laminate Tests 3

2.1.1 Scope 3

2.1.2 Test Procedure 3

2.1.3 Conditioning of Specimens 4

2.1.4 Test Results 4

2.2 Polyester Adhesive Bond Tests 5

2.2.1 Introduction 5

2.2.1.1 Objective 5 2.2.1.2 Scope 5

2.2.2 Test Specimens 5

2.2.2.1 Preparation of Specimens 5

2.2.2.2 Specimen Grouping 6

2.2.3 Test Apparatus and Procedures 7

2.2.3.1 Testing Machine 7

2.2.3.2 Sustained Loading Apparatus 7

V
Page

2.2.3.3 Test Conditions 7

2.2.3.4 Accelerated Aging Procedure f< 2.2.4 Test Results 9

2.2.4.1 Bond Strength Versus Temperature ^ 2.2.4.2 Bond Strength Versus Adhesive Thickness 10

.. 2.2.4.3 Bond Strength after Aging 10

2.2.4.4 Bond Strength Versus Rate of Loading 10

2.2.4.5 Bond Strength Under Sustained Loading 11

2.2.5 Discussion of Polyester Adhesive Bond Tests 1

1

3 Wall Panel Tests . 13

2.3.1 Introduction - 13

2.3.2 Racking Tests 15

2.3.2.1 Test Specimen 15

2.3.2.2 Test Apparatus and Procedures 15

2.3.2.3 Racking Test Results 17

2.3.3 Short-Term Compressive Tests 1

9

2.3.3.1 Test Specimens 19

2.3.3.2 Test Apparatus and Procedure 20

2.3.3.3 Test Results 22

2.3.4 Long-Term Compressive Tests 2

3

2.3.4.1 Test Procedure 23

2.3.4.2 Test Results 24

2.3.5 Discussion of Wall Panel Test Results 25

4 Roof Panel Tests 26

2.4.1 Introduction 26

2.4.2 Test Specimens 2

7

2.4.3 Test Apparatus and Procedure 27

2.4.3.1 Short-Term Flexural Tests 27

2.4.3.2 Long-Term Flexural Tests 29

2.4.4 Test Results 30

2.4.4.1 Short-Term Test Results 30

2.4.4.2 Long-Term Test Results 30

vi
Page

2.4.5 Discussion of Roof Panel Tests 30

2.4.5.1 Short-Term Tests 30

2.4.5.2 Long-Term Tests 31

3.0 Summary and Conclusions 32

vii

structural Tests on Housing Components

of Glass Fiber Reinforced Polyester Laminate

by

Thomas W. Reichard, William E. Greene, Jr.

Louis E. Cattaneo, Larry W. Masters

1.0 Introduction

1.1 Objective.

One phase of the Department of Housing and Urban Development's

"Operation BREAKTHROUGH" Program was an evaluation of the

structural adequacy of each proposed system. The system

considered here employs roof and wall sandwich panels constructed

from laminated sheets of polyester reinforced with chopped strands of glass fiber (FRP) . The basic panel consists

of an FRP sheet (facing) bonded to each side of a corrugated

FRP sheet (core) with a polyester adhesive.

The structural evaluation process included a consideration of

the transfer of stresses through and from the thin FRP sheets

into other structural components. To investigate this behavior,

tests were performed on wall and roof panels as well as on

typical adhesive bonded connections.

1.2 System Description.

Figure 1.2.1 is a schematic of a typical building cross section

employing the structural system. The wall and roof panels

1
are very similar except for overall thickness. The thicknesses

shown in figure 1.2.1 are nominal. All wall-to-roof and wallto-floor connections are made with an epoxy adhesive. The roof

is waterproofed with either a factory applied elastomeric

coating or a field applied roofing membrane. The exterior

surfaces of the walls are normally sprayed with a polymeraggregate coating for architectural effect. Rock wool insulation

is placed in the voids formed by the corrugated cores of the

panels. The nominal thicknesses of the FRP sheets are 0.08

in for the facings of the panels and 0.05 in for the corrugated

core. The polyester resin content of the FRP sheets was

reported by the manufacturer to be 45 percent by weight

(approximately 671 by volume). The composition of the polyester

resin is not known.

1.3 Scope of Testing.

The testing performed for the evaluation is divided into

material property tests and structural component performance

tests as follows

1. The tensile and compressive strengths of the basic

FRP laminate and the effects of temperature, humidity and sustained loading on these strengths.

2. The tensile and compressive shear strengths of

the facing- to-core polyester adhesive bond and the effects

on these strengths of temperature, accelerated aging,

and sustained loading.

3. The short-term performance of wall panels under axial

compressive in-plane-shear (racking) forces and the

sustained loading (creep) performance of the wall

^ panels under an axial compressive force.

I

2
4. The short-term and long-term flexural performance

of the roof panels.

In addition, an evaluation of the epoxy adhesive bond between the

FRP facing and the wood members has been undertaken by another

laboratory.—'^ This evaluation is not covered by this report.

2.0 Tests

2.1 FRP Laminate Tests

2.1.1 Scope . Five sheets (each approximately 40 in

X 140 in) of the FRP laminate, intended for use as facings

in the wall and roof panels, were received from the

housing systems producer. Half of each sheet

was shipped to the Forest Products Laboratory for testII ing and the results are reported in [1].— Specimens

for the tests reported herein were cut from two of the

remaining half -sheets.

Tensile and compressive strength measurements were

made on specimens conditioned by three different

methods and tested at two different temperatures.

2.1.2 Test Procedure . The tensile test procedure

of Federal Test Method No. 406, Method 1011 [2] was

used in testing the FRP specimens which had a test-section

width of 1.00 in. The compressive test procedure of

-- Naval Civil Engineering Laboratory, Port Hueneme, Calif.

1/ Numbers in brackets indicate the references listed at the

end of this report.

3
Method 1021 \2] was used -^or "specimens 0.50 in wide

X 3.00 in long. Both procedures are shortterm tests. The test conditions were either 73.4°F (23®

C) and 50% rh , or 160°F (72°C) and 41 rh.

2.1.3 C onditioning of Specimens . The specimens

were cut from the sample sheets after conditioning

by one of the following methods:

1. At 73.4°F and 50% rh for 1 week.

2. Soaked in water at 122°F for 48 hours with

edges <=ealed by a mixture of rosin and beeswax.

3. Soaked in water at 122°F for 48 hours with

edges not sealed.

The specimens were cut to size then stored for about

2 hours at the test conditions described in 2.1.2.

2.1.4 Test Results . The test results are presented

in Table 2.1.1. The average strength values in

this table are for sets of 10 specimens and are based

on the thickness of each specimen. The thickness of

the laminate specimens varied from 0.065 in to 0.107

in with the average being close to the nominal 0.080 in.

The variability in these short-term strength values was so

high that the effect, if any, from the water-soak conditioning or the elevated test temperature is not obvious.

It was expected that temperature would have an effect on the

strength and Boiler [1] concluded that the sustained4
load strength of this laminate is considerably less at

160®F than at room temperature. However, he attributed a portion of this loss to the effect of the high humidity

(100% rh) which accompanied the elevated temperature.

2.2 Polyester Adhesive Bond Tests

2.2.1 Introduction

2.2.1.1 Obi ective . A study was initiated to evaluate

the polyester adhesive used to bond the corrugated

FRP core material to the two FRF laminate sheets

used as the sandwich panel facings and to determine

the effect on the bond strength of: (1) temperature;

2) adhesive thickness; 3) accelerated laboratory aging

4) rate of loading; and 5) sustained loading.

2.2.1.2 Scope . Lap joint specimens were tested in

tensile shear at various temperatures up to 180°F,

at several rates of loading and under sustained

loads. Specimens were separated into four groups

depending upon the adhesive thickness at the lap

joint. Normally, several specimens were tested

at each increment of adhesive thickness and temperature, and the average value and the standard

deviation computed.

2.2.2 Test Specimens

2.2.2.1 Preparation of Specimens . Test specimens

1/2 in wide and 7 in long were cut from a sandwich

panel at the area where the facing was bonded to the

nodes of the corrugated core sheet. Notches were

cut in the specimens with a band saw in such a way

as to provide a lap type, tensile shear specimen with

an effective bond area of 0.50 sq in at the lap.

5
The first eighteen specimens were notched as illustrated by figure 2.2.1 and are referred to in the text

as "notch type 1."

Tensile shear tests of these specimens at room temperature resulted in failure in the facing FRP laminate

parallel to the adhesive bond. The tensile shear

tests of these specimens at 120°F and 180°F produced

failure of the polyester adhesive bond to the node

of the corrugated core laminate. These results are

summarized in table 2.2.1.

To provide additional stability to the FRP laminate

during the tests, additional specimens were notched

in such a way that notch "A" was made through the

core laminate but not through the adhesive. This

type of notch will be referred to as "notch type

2" and is illustrated in figure 2.2.2. All specimens

tested, except those listed in table 2.2.1, were

prepared by the "notch type 2" technique.

2.2.2.2 Specimen Grouping

The polyester adhesive thickness at the bond area of the

lap joint in various specimens varied from 0.25 to 5.0 mm.

In order to effectively evaluate the adhesive bond the

specimens were grouped in the following way: Group A,

adhesive thickness less than 1.0 mm; Group B, 1.0 to

2.0 mm; Group C, 2.0 to 3.0 mm; and Group D, 3.0 to 5.0 mm.

The highest percentage of specimens was in Group B.

6

!

I
2.2.3 Test Apparatus and Procedures

2.2.3.1 Testing Machine . The tensile shear tests

o£ most specimens were conducted using a testing

machine equipped with a temperature chamber shown

in figure 2.2.3. The rate at which the load was

applied was approximately 300 Ib/min. This rate

of loading was used in all tests except for the

studies of strength versus rate of loading.

2.2.3.2 Sustained Loading Apparatus . Most sustained

loading tests were performed with dead weights in

place of the testing machine. The dead weight

apparatus consisted of 6 individual frames placed

on shock absorbent pads in a chamber controlled at

150**F. Each specimen was suspended from a frame

and loaded with a bag of lead shot. This apparatus

is illustrated in figure 2.2.4. Timer switches

were installed under each bag so that the timers

were turned off when the specimen failed.

2.2.3.3 Test Conditions . The humidity conditions

within the temperature chambers were not controlled

but were a function of the laboratory air conditions

(73 +^ 2°F, 50 + 2% rh) and the operating temperature

of the chamber. Thus, the relative humidity within

the chamber varied from about 50 percent at 73°F to

4 percent at 160°F. Specimens with "notch type 2"

were tested to determine the minimum test temperature

7
which would result in adhesive failure to the FRP

laminate. Tensile shear tests of twelve specimens

at laboratory temperature did not consistently

yield failure at the polyester adhesive bond, although

three specimens did fail at the bond. As for the

other nine specimens- -three failed by an internal

separation of the outer FRP laminate and six failed

as a result of shear of the FRP laminate at notch B.

(Figure 2.2.2). The tensile shear results are presented

in table 2.2.2. Figure 2.2.5 illustrates the types

of failure that were observed. Tests conducted at

temperature increments of five degrees from 75° to

110°F indicated that adhesive bond failure could be

obtained consistently at 105*'F. Therefore, temperatures

of 105, 120, 150, and 180°F were chosen for the tests

to evaluate the effect of temperature on bond strength.

Specimens were placed in the grips of the machine,

which were enclosed in the temperature chamber,

before testing. An equilibration time of approximately

twenty minutes was used to permit the specimen to

reach the chamber temperature before the test was

started.

2.2.3.4 Accelerated Aging Procedure . The accelerated

aging was ASTM Laboaratory Aging Test C-481, Cycle A [3].

One cycle of the aging consists of the following steps:

1) Total immersion in water at 120 _+ 3°F

for one hour.

2) Spray with steam and water vapor at

200 + '^"F ^or 3 ^ours

.

8
3) Store at 10 + 5°F for 20 hours.

4") Heat in dry air at 210 + 3°F for 3 hours.

5) Spray with cteam and water vapor at 200

+_ 5**? for 3 hours.

61 Heat in dry air at 210 + 3*F for 18 hours.

The complete aging procedure consists '^f repeating

^he cycle six times an'^ auilibrating the specimens

at 73 + 2*F and 50 + 2% rh to constant weight. The

tensile shear tests were '^arried out at temperatures

of 73, 105, 120, 150 and 180*'F immediately following

the equili>^ration ^eriod.

2.2.4 Test Results

2.2.4.1 Bond Strength Versus Temperature . Approximately seventy specimens were tested in "^ensile shear

at temperatures of 105, 120, 150, and 180°F. The

failure for all specimens was in the oolyester

adhesive bond to the node of the corrugated core

FRP laminate. The results of these tests are presented

in table 2.2.3.

The effect '^f increasing temperature on the adhesive

bond strength was extracted from tables 2.2.2 and 2.2.3

and is illustrated •'n figure 2.2.6. The adhesive

bond «^rength 'decreased significantly with increasing

temperature with the bond strength at 180°F averaging

about 25 percent nf the strength at 73®F. The noint

'^n each curve at 73**F represents a less -than-maximum

bond strength at that temperature since the FRP

"aminate failed in most room temperature tests. The

adhesive was observed to be more pliable at elevated

temperatures than room temperature.

9
2.2.4.2 Bond Strength Versus Adhesive Thickness . Figure 2.2.7 is a graph o£ polyester adhesive bond

strength versus adhesive thickness. The data for these

curves were extracted from Table 2.2.3. This graph

indicates that the adhesive bond strength decreased

significantly with increasing adhesive thickness.

Decreasing strength with increasing adhesive thickness

has been "oted in a previous study [4].

'?.2.4.3 Bond Strength After Aging . Sixteen specimens

with "notch type 2" were subjected to the ASTM Laboratory

Aging Test, C-481, Cycle A, before obtaining bond

strength values at temperatures of 73, 105, 120,

150 and ISO'F. The resulting bond strength values

are summarized in table 2.2.4. Table 2.2.5 contains

a comparison of the average values obtained in the

tests with and without laboratory aging. This comparison

indicates that the accelerated aging did not significantly reduce the bond strength of the polyester

adhesive. The values at 73**F were again indicative of

FRP laminate failure rather than adhesive bond failure.

2.2.4.4 Bond Strength Versus Rate of Loading . Additional samples with "notch type 2" were tested in tensile

shear at various loading rates and the data obtained are

presented in table 2.2.6. The data from samples

requiring approximately 0.4 minutes to fail were

extracted from table 2.2.3. Figure 2.2.8 graphically

illustrates the data in table 2.2.6 for Group B.

The data for other groups provide similar curves.

The data obtained from Group B samples at 150**F were

plotted by the modified Prot method [5, 6, 7] described

by Boiler [6]. The results indicate that the change

10
in failure load with rate of loading is too large

for the Prot method to be applicable to this particular

system.

2.2.4.5 Bond Strength Under Sustained Loading . Thirty- two Group B (1.0-2.0 mm adhesive thickness)

specimens were tested at 150**F with sustained loads

in tensile shear to determine the endurance limit.

Sustained loads of 100, 60, 50 and 40 lbs were

applied with the testing machine. Other sustained

loads of 40, 35, and 25 lbs were applied by

suspending the lead shot weights from the specimens.

All failures observed were in the polyester adhesive

bond to the core FRP laminate. The data obtained are

presented in table 2.2.7. Figure 2.2.9 is a graph

of the sustained load versus time to failure. Three

specimens were tested in the sustained load apparatus

at 35 lb and three at 2 5 lb. One specimen loaded

at 35 lb failed at 296 hours and one specimen loaded

at 25 lb failed at 728 hours. The other two specimens

''t each of these loads exhibited no failure at 3000

and 3500 hours, respectively. Extrapolation of the

curve of figure 7. 2. 9 to 10,000 hours yields an

endurance limit of 30 lbs r60 psi).

2.2.5 D iscussion of Polyester Adhesive Bond Tests . When interpreting the bond test results of this report,

it should be remembered that the test specimens were

specially made for these tests and that quality control

factors used in fabricating the panel material are

variables which were not included in this study. The

strength of these bonds would be significantly affected

by fabrication and handling practices as well as by the

type and composition of the materials. The quality

11
control factors critical to the strength and durability

of the adhesive bond include the quality of the substrates

(FRP sheets); the condition of the substrate surfaces

(contamination, moisture, temperature, porosity, etc.);

the composition and mix proportions of the adhesive; age

at application and pot life of the mixed adhesive; time,

temperature and humidity during the curing process; and

the age of the bond when panel is loaded.

The bond test results presented in this report (Fig. 2.2.7)

show that the thickness of the adhesive is a significant

quality control factor. For this panel material in which

the quantity of adhesive per unit length of bond is a constant (gun applied) the thickness of the adhesive in

the joint affects the bond area, the bond strength and

the stress level. Thus, in a thicker adhesive joint the

bond area will be smaller, the bond strength will be lower,

and the stress level will be higher. For the panel

materials tested for this report the width of the bond

between the FRP facings and the core nodes usually varied

from 1/2 in to 1-1/2 in, but at a few bond areas the width

was considerably less than 1/2 in.

These bond test results also clearly indicate that the

results from short-term tests at ordinary laboratory

conditions are insufficient when estimating the expected

service performance of such panel material. This is

especially true for roof panels where the temperature

and humidity within the panel can reach 160**F and

100 percent relative humidity and where appreciable loads

must be sustained for extended periods of time.

The data shown in figure 2.2.6 are especially pertinent

for roof panels because of the indication that the shortterm bond strength for this polyester adhesive at 160*F

is only about 1/3 as high as it is at 73*F.

12
Boiler's data [1] for sustained loading under 100 percent

relative humidity on specimens cut from the same panels

indicate a significantly greater loss of bond strength

than the data of figure 2.2.9 which was for sustained

loading under low humidity conditions. These data indicate

that high humidity degrades the bond strength over

and above the effect of the sustained loading and elevated

temperatures. Furthermore, Boiler's data also indicate

a reduction in the bond strength with aging. His procedure

(ASTM C481) is the same as was used in developing the

data of tables 2.2.4 and 2.2.5 which indicate no significant

effect from the aging. However, Boiler's data are considered

to be more reliable because of the larger number of

specimens.

In conclusion, these results indicate that the sustained

shear stress in the polyester adhesive bond of the roof

panels identical to those tested should not exceed 5 psi.

Because of the variability in the bond area the shear

stress in the bond of a typical roof panel can only be

approximated, and so, when computing design stresses this

variability should be considered. The long-term effect

of high humidities on the strength of these polyester

adhesive bonds is probably very significant, but was not

fully investigated. Additional testing is being performed

on this effect, but some development work is needed towards

improving the long-term reliability of the bond between

the FRP facing and core.

2.3 Wall Panel Tests

2.3.1 Introduction . The purpose of this part of the

phys-Scal testing program was to evaluate the nerforraance

13
of wall panel specimens under the action of racking loads

and of short-term nd long-term compressive loads. Tn

service, wall panels receive such loads from the

tributary areas '*f floors and roofs supported by them

and from other in-plane or trans"erse walls. Such

cumulative loads were "imulated in separate static tests

to determine the "^hort-term and long-term load carrying

capacities of the wall panels. Five wall r>anels ^ere tested:

one in racking, two in short-term compression and two in

long-term compression.

Wall panel specimens ^ere fabricated by the housing system

producer and were ready for testing when received. Panels

were typical of those intended for use in the building

system, but did incorporate some additional wood members

at the top and bottom edges to facilitate test simulation nf

service loading. These additional wood members were iudged

to provide a satisfactory simulation of the in-service

load distributing surfaces ^floor and roof) without unduly

reinforcing the wall panel specimens. A wall panel specimen

consisted of two thin facings "lade of the FRP laminate

separated by a vertical stiffening core which was a corrugated

sheet of the same material (Fig. 2.3.1). The corrugated

core was bonded to the two facings with a polyester adhesive.

Each test panel contained a 2 x 4 (1-1/2-in x 3-1/2-in)

wood top plate and sole plate. These wood members were

bonded to the facings with an epoxy adhesive and were

completely within and flush with the top and bottom edges

of the FRP facings. Examination after the tests showed

that the wood plates did not touch the ends of the core

corrugations. The additional wood members attached for

test purposes to the top and bottom of each panel are

described below.

14
In order to obtain engineering data on the wall panels

in a generally recognized manner, test methods for

determining short-term compressive and racking characteristics

followed ASTM Designation E72-68 TS]. Wherever techniques

or equipment differed from E72 recommendations, they

are described in the appropriate sections below. All

load-displacement measurements in short-term tests were

recorded automatically on magnetic or punched paper tape

for computer processing.

2.3.2 Racking Tests

2.3.2.1 Test Specimen . One specimen of

wall panel construction was tested in a normal

vertical position by subjecting it to horizontal

racking forces. The specimen was 7 ft-1 1/2 in

wide by 8 ft (nominally) high by 3-7/8 in thick,

(See Fig. 2.3.1). The 96-in height of the panel

proper was increased by two 2 x 4's nailed and

adhesive bonded (flat-wise) along the top edge

and the bottom edge of the panel. These attached

members (See section C-C of fig. 2.3.1) were intended

to distribute the racking load and its reaction

horizontally along the top and bottom edges of the

test panel. The entire specimen consisted of two

narrower panels connected by the producer. This

connection had been made by polyester adhesive bonding

external FRP joint cover plates to the individual

panel facings (See section B-B of fig. 2.3.1).

2.3.2.2 Test Apparatus and Procedures . The loading apparatus, assembled as shown in figures

2.3.1, 2.3.2, and 2.3.3 for three different test

15
arrangements, consisted of 30-ton hydraulic rams

attached to a structural steel framework connected

to the laboratory tie-down test floor. The specimen

was bolted and clamped (by the two bottom 2 x 4's)

between steel channels which, in turn, were bolted

to the test floor. A toe stop connected to the

floor was also used to prevent sliding of the specimen

under horizontal load. Lateral guides were provided

in the form of caster wheels mounted on rigid steel

plates and applied to the sides of the panel top at

mid-length. Additional vertical hold-down of the

specimen in the second and third tests was accomplished

by hydraulic rams attached to the test frame. All ram

loads were applied through roller bearings (Fig. 2.3.4)

and were measured to the nearest 10 lb by an electric

strain gage pressure transducer which had been

calibrated in combination with the rams. Panel

displacements and deformations were measured by

electric displacement transducers (linear variable

differential transformers- -LVDT) to the nearest

0.0001 in. The LVDT's, which measured panel

deformation, were mounted in aluminum tubes and

pin-connected to the wall panel (using a hot-melt

adhesive) as shown in figures 2.3.3 and 2.3.4.

Diagonal eage lengths were 118.25 in, vertical gage

lengths were 88.88 in, and horizontal gage lengths

were 78.63 in. The LVDT's, which measured wall

panel displacements at the outer extremities of

the panel, were mounted on rigid stands resting

on the test floor. Three racking tests were performed

on the one specimen by re-setting the specimen

between tests. In all tests the racking load was

applied in increments of 1000 lb.

16
In the first test (Fig. 2.3.1) the racking load

was increased monotonically until an indication of

impending failure was observed. No vertical holddown from above the wall was supplied in this test

in order to allow possible rotational failure to

develop at the bottom. Upon application of each

successive load increment, displacements were measured

and recorded.

In the second test the racking load was applied

incrementally and reduced to zero after each additional increment was applied. The racking load

was increased until failure developed. Additional

vertical hold-down was supplied at the loading corner

by a hydraulic ram which was loaded to maintain the

specimen in static rotational equilibrium. (Fig. 2.3.2).

The third test wa« conducted in the same manner as the

preceding test except that the vertical hold-down above

the wall was provided by six equally spaced rams operated

simultaneously by a common pump. The vertical resultant

of these rams was always such as to maintain the

specimen in static rotational equilibrium. (Fig. 2.3.3).

2.3.2.3 Racking Test Results . The first test

was conducted without the vertical hold-down recommended in ASTM Method E-72 in an effort to evaluate

the performance of the bond between the FRP panel

facings and the wood sole plate. However, the test was

terminated at a maximum total racking load of

5700 lb (800 lb/ft) beyond which the load could not

be increased. The failure which prevented greater

load development occurred in the bond between the two

17
extra bottom 2 x 4's with no apparent damage to

the FRP facing bond. Figure 2.3.5 shows the failure

at the bottom trailing corner (heel) of the specimen

where uplift was being measured. The graph of figure

2.3.6 shows the relationship between racking load

and net horizontal drift (corrected for uplift and

sliding) ; and between racking load and rotational uplift

for test No. 1.

After re-setting and re-clamping the bottom edge of

the wall, the second test was performed in the manner of

ASTM Method E72; i.e., with vertical restraint

provided at the loading corner. The maximum total

racking load which could be developed was 7200

lb (1010 lb/ft). The observed failure was in the

epoxy adhesive bond between the FRP facings and the

top plate at the loading corner of the specimen

(Fig. 2.3.7). Figure 2.3.8 shows racking load versus

net drift under load; and versus net residual drift

(set) measured at no-load upon removal of each

incremental load. Note that the dotted portions

of the curves represent the concluding part of this

test in which displacement readings are considered

unreliable. The apparent stiffening (reduction of

displacement with increase in load) is attributed

to the development of greater distortions at locations

on the specimen other than those instrumented.

The third test which employed a vertical hold-down

distributed along the top of the wall (instead of

the ASTM E72 hold-down) , developed a maximum total

racking load of 6800 lb (950 lb/ft). The failure

was in the epoxy adhesive bond between the FRP facings

18
and the wood sole niate at the bottom leading

corner (toe) of the specimen (Fig. 2.3.9).

Measured observations of drift (as described for

the preceding test) are shown for test No. 3 in

figure 2,3.10.

In addition, the sequence of figures 2.3.11, 2.3.12,

2.3.13 shows for each test, the relationship of

racking load to extension and to shortening in

the major diagonals of the wall panel. Transducer

measurements made over the horizontal and vertical

gage lengths of the specimen were not considered

significant and, consequently, are not reported. '

2.3.3 Short-Term Compressive Tests

2.3.3.1 Test Specimens . Two specimens of wall

panels were tested in axial compression. Each

specimen was 40 in wide by 96 in (nominal) high

by 3-7/8 in thick (Fig. 2.3.14). In addition to

the 96-in height (used as reported height of test

specimen), each specimen had two 2 x 4's nailed

and adhesive bonded (flatwise) along the bottom

edge of the panel. In addition, along the top edge

of each specimen, there was nailed and adhesive

bonded (to the wall panel top plate and to each

other) one 2 x 4 on edge beside one 2x2

(1-1/2 in X 2 in) as shown in section B-B of

figures 2.3.14. The additional members at the bottom

and top were intended to simulate the bearing conditions

at the portions of the floor and ceiling to which

the wall panel would be attached.

19
2.3.3.2 Test Apparatus and Procedure . Tests were

performed in a 600,000-lb compression testing machine

(as shovm in figure 2.3.14) following ASTM Method

E72. Specimens were positioned vertically in the

machine so that the line of load application was

centered on the 1-1/2-in side of the upper 2x4

resting on edge. This resulted in a load eccentricity of 1 in (i.e., an eccentricity ratio, or fraction

of panel thickness, equal to 0.26).

Each panel was tested as a column having a flat

end at the bottom and bearing on a steel plate which

rested on the platen of the testing machine. Loads

were applied along the top end through a 3/4-in

X 2-in steel plate on which rested a 3/4-in halfround steel bar with the flat side toward the wall.

A 6-in WF beam transmitted the load from the testing

machine head to the assembly described above. The

tare weight of the above loading fixtures (111 lb,

i.e., 33 lb/ft) was not included in recorded load

observations. The loading rate corresponded to

a testing machine crosshead movement of 0.03 in/min.

Vertical wall shortening measurements were made

by four compressometers made of LVDT's mounted

in aluminum tubes attached to the faces of the wall

panels near the four vertical edges. Tubes were

pin-connected to the panel at the top. The

compressometer gage lengths were 92 in. Locations

of compressometer attachment were chosen to coincide

with locations of the facing-corrugation junctions

nearest to the edges of the wall. These locations

were chosen in order to have the compressometers

20
mounted on braced skin areas to avoid regions which

might possibly buckle prematurely. Distances of the

compressometers from vertical wall edges ranged from

4 in to 8 in. Locations of the facing-to-corrugation

junctions were determined by observing the shadows

produced by a flood light projected through the

translucent wall structure. In order to aid visual

detection of skin buckling during the test, ink lines

were drawn on the panel faces horizontally at intervals

of 12 in, and vertically at locations midway between

facing-to-corrugation junctions (intervals of about

6 in +^ 1 in)

.

Lateral deflections were measured with two LVDT

displacement transducers. Each was mounted transversely

at the middle of a 92 -in aluminum tube which was

pin-suspended at the top end along the mid-thickness

of a wall edge. The bottom ends of these tubes were

attached with rubber bands to guides fastened to the

wall on the thickness centerline which permitted the

tubes to slide as the wall shortened under load.

Lateral deflections and wall shortening displacements

were measured to the nearest 0.001 in.

In addition, measurements of vertical strain were

made at the centers of both surfaces of the wall

panels by use of 6-in electrical resistance strain

gages.

Compressive load was applied to the specimens in

increments of 500 lb and reduced to a holding load

of 500 lb after each incremental increase. Deformations

measured by all transducers were recorded at each

21
incremental load increase and at the subsequent reduction

to the holding load. This observation of load deformations and residual deformations was continued beyond

the wall panel design ultimate load to a value of

2100 lb/ft. Beyond this point the specimens were loaded

monotonically up to their ultimate load carrying capacity.

In test No. 1 stops were made in the upper loading

range at intervals of 5000 lb to observe and record

deformations; instruments were removed when impending

failure became apparent. Later examination of this

data indicated jamming of instruments near the 10,000 lb

load. Instruments in test No. 2 were removed after

unloading from 7000 lb (2100 lb/ft).

2,3.3.3 Test Results . The two short-term compressive

specimens were used for duplicate tests. The first

specimen sustained a maximum compressive load of

20,800 lb (6240 lb/ft) and the second specimen,

19,750 lb (5925 lb/ft). Failure in the first specimen

occurred in the epoxy adhesive bond between the FRP

facing and the wood sole plate on the side closer

to the eccentric load (Fig. 2.3.15). In the second

specimen a similar failure occurred in the epoxy

adhesive bond between the FRP facing and the top

plate on the side closer to the load (Fig. 2.3.16).

Subsequent to these bond failures, secondary failures

occurred in both specimens when the facings buckled

near the bond separations.

Figures 2.3.17 and 2.3.18 show development of

average-shortening (4 transducers) in the two specimens

with increasing load. Residual deformations were

22
measured at a small holding load of 500 lb (150

lb/£t). Figure 2.3.19 shows the average deflections

(2 transducers) developed in 92 inches of specimen

length by the loading sequence of test No. 1. The

negative deflection shown in this graph was probable

accommodation of instruments upon application of the

initial load. Figure 2.3.20 shows the deflections

measured at only one side of the specimen in test No.

2. The second transducer was used for monitoring

the test by an X-Y recorder; the record was not

satisfactory for reproduction.

Figure 2.3.21 illustrates load versus mid-height surface

strains of both faces of the specimen for test No.

1 as measured with the electrical resistance strain

gages.

2.3.4 Long-Term Compressive Tests

2.3.4.1 Test Procedure . Two wall specimens identical

to those described in 2.3.3.1 above were tested

under a sustained load of 6000 lb (1800 lb/ft).

The load was applied along the center line of the

upright 2x4 member as was described in 2.3.3.2.

Two different support conditions were included.

The first condition was the ASTM E-72 flat bottom

support and is illustrated in figure 2.3.22. The

second condition was with the bottom supported

on a roller to provide the same eccentricity

as at the top. This second support condition is

shown in figure 2.3.23. These figures also show the

springs used to sustain the load as well as the

taut wire and mirrored scale used for measuring

the deflection.

23
i

Both wall specimens were originally loaded with

th*» '''"•^ bottom support. After 24 days a <?ingle i specimen was reloaded with the eccentric bottom

support.

2.3.4.2 T est Results . With the -Flat V>ottom support,

^ specimen 1 failed after 18 days under ^he 6000-

1b fl800 lb/ft*) sustained load. Failure "as due

*o loss of epoxy adhesive i^ond between the 2^4

'•ole Dlate and the FRP Danel facing. This bond failure

allowed the wall to rotate on the flat bottom support

until the 2 4 sole olate rested on the corrugated

core of the wall. This "»ode of failure was the «?ame

as described in 2.3.3.3 for the short-term compressive

test.

Snecimen No. 2 had «>lso been loaded with •he -^lat

bottom support, however, after 24 days under 6000 ib of

sustained load it did not show any sign failure.

Specimen No. 2 was then unloaded and reloaded to

6000 lb with the eccentric-bottom support. After

•^3 days under these conditions specimen No. 2 failed

in an identical manner as specimen No. 1. Figure

2.3.24 is a photograph of the bottom end of this

specimen after failure. Failures in both specimens

were gradual; i.e., there was a slight rotation

at the sole plate «?everal days before the epoxy

adhesive bond broke loose for the full ^''idth of the

specimen

.

Figure 2.3.25 is a plot of the midheight deflection

versus time-under-load for the three tests. Near

24
failure, the measured deflection was less than the

correct value because the rotation of the sole plate

moved the taut -wire attachment point in the direction

that reduced the measured value.

2.3.5 Discussion of Wall Panel Test Results . Probably

the most significant observation made during the wall

panel tests was the common mode of failure: i.e.,

separation of the FRP facing from the top or bottom 2x4

wood plates at the epoxy adhesive bond. Since there is a gap (as much as 1/4 in) between the corrugated core and

these wood plates (see section C-C, figure 2.3.1) all

forces acting on a wall must be transferred through this

epoxy adhesive bond. This method of transferring forces

precluded the development of the full -potential of this

type of structural sandwich.

The data from these wall panel tests were interpreted

in the absence of data needed to reflect the effects

of aging, environmental conditions, and variability

on this epoxy adhesive bond. The effects of these factors

on the sustained- load strength of this bond are being

studied by others (see footnote 1, page 3). If, in

considering variability, a conservative value of 0.4

is assumed as the coefficient of variation (v) , the

observed load capacities should be adjusted by a factor

1 3/ of Cj-qr-j—5^) which is equal to 0.625— . When this factor

is applied, the racking load capacity of the panels is

reduced to 600 lb/ft. However, this will probably be reduced

— Assuming a normal distribution, with known mean and standard

deviation, the requirement that structures be designed for

an overcapacity of (1 + l.Sv) times the required capacity

would mean that approximately 95 percent of that population

of structures would have at least the factored load capacity.

25
further when data for aging and environmental effects

become available. Similarly, the factored short-term

compression load capacity of the wall panels becomes

3800 lb/ft. Unlike racking loads which are usually of

short duration (e.g., wind) gravity compressive loads

often exist for prolonged periods. The rated capacity in

compression will, therefore, be governed by the long-term

test data (which will also be modified by pending test

data for aging and environmental effects). Projection

of the data in figure 2.3.25, together with factoring for

variability indicates that a long-term bearing load

should not exceed 830 lb/ft of wall. This is based on the

judgement that a proportionately smaller load will produce

in a period of 50 years a deflection equal to that

displayed by the test specimens at incipient failure.

Again, the calculated estimate was reduced by the conservative variability factor of 0.625.

All evidences of failures in the wall tests point toward

the need for improvement in fabrication methods at the

top and bottom of wall panels. In addition to improving

the adhesive bond between FRP facing and the 2x4 wood

plates, the gaps between the corrugated cores and the wood

plates should be eliminated in order to improve the

transfer of loads throughout the panel.

Roof Panel Tests

2.4.1 Introduction . The evaluation of the performance

of roof panel specimens when subjected to short-term and

long-term loading constitutes the purpose of this part of

physical testing program. Service gravity loads for roofs

result from snow, rain, sleet, hail, and from the workmen

26
who construct and repair roofs. Long-term loading

represents some portion of the short-term load that

is considered to remain on a roof for an extended period

of time. These loads were simulated in separate static

tests to determine: (1) deflection under loading which

might be encountered in service, (2) the overload

capacity, and (3) deflection under long-terra loading.

Two specimens were tested, one for service loading and

overload capacity, and one for deflection under longterm loading.

2.4.2 Test Specimens . The two roof specimens received for

testing consisted of flat panel sections, 3 ft- 4 in wide

by 12 ft long. The panels were a sandwich composite

fabricated by bonding the FRP laminate facings to a 5 3/4 inch

deep corrugated FRP laminate core with the polyester adhesive.

The ends of the facings were bonded with an epoxy adhesive

to wood closure assemblies which were fabricated from

nominal 2-inch thick (1-1/2 in actual) framing lumber,

as shown in figures 2.4.1, 2.4.2 and 2.4.3. The latter

figure indicates that the core is not connected to

the closure assemblies, therefore, the shear load path is

through the top and bottom facings and the closure assembly

to the supporting walls.

2.4.3 Test Apparatus and Procedures . 2.4.3.1 Short-Term Flexural Tests . The loads for the

short-term flexural tests were applied by the use of

air bags. This was accomplished by placing the roof

specimen upside down, approximately 2 inches above

the laboratory floor, with an air bag between the

specimen and the floor. The roof panel was supported

at one end by a rocker and at the other end by a roller.

27
LVDT's were attached to the test specimen to monitor

midspan deflection and end rotation. Figures 2.4.4

and 2.4.5 illustrate the test setup. The deflections

indicated by the two exterior LVDT's located at midspan

were plotted by X-Y recorders. This provided a realtime record of midspan deflection versus pressure.

The readings taken from the remaining LVDT's were

recorded on paper tape. A schematic diagram of the

instrumentation and recording equipment is presented

on figure 2.4.6.

The air bag pressures required to simulate serviceability

and safety loading were adjusted to include an allowance

for the inability to load the entire panel surface.

This adjustment was required due to weak longitudinal

panel edges, and also, as the panel deflects, to some

further reduction of area as a result of the increase

of radius in the air bag at the longitudinal edges of

the panel. The latter situation was found to be of

secondary importance for this specimen. A total

width reduction of 8 inches was used to calculate the

test pressures. This was later checked by taking

measurements from the edge of the panel to the edge

of the contact area at the safety loading pressure,

which was found to be approximately 7.75 in.

To insure that the ends of the panel were free to

rotate, a gap was provided between the reaction beams

and the end support assemblies as shown on 2.4.4.

Before starting the test, the air bags were pressurized

to approximately 5 psf (the panel dead load) to seat

the end supports against the reaction beams. Further

28
pressurization constituted the test loading.

The service load was applied and relaxed three times

to check for linearity and residual deflection. The

loading for structural safety however, was applied

only once.

2.4.3.2 Long-Term Flexural Tests . To simulate this

condition, one panel was loaded to 5 psf with the

appropriate depth of sand. Although the entire surface

area of the panel could not be loaded because of the

unsupported facing edges, the total panel load -was

achieved by increasing the depth of sand on the reduced

area. Wood slats three inches long were glued on the

panel surface along the centerline of the outermost

core corrugation to contain the sand. To avoid

increasing the structural stiffness of the panel,

1/8 inch gaps were left between the retaining slats.

These gaps were later covered with masking tape to

prevent sand leakage. Sand was then placed on the panel

and screeded to the top of the slats which had been

milled to the required height of 0.8 in. Figure 2.4.7

is a picture of the roof panel under long-term sustained

load test and figure 2.4.8 illustrates the test

apparatus and arrangement. To simulate simple

support end conditions, a rocker and a roller were

used as illustrated in figure 2.4.4.

Two deflection gages, located at midspan, were read

and recorded daily for the first two weeks; thereafter

readings were taken and recorded weekly. Temperature

and humidity were also recorded at the time of the

deflection readings.

29
2.4.4 Test Results . 2.4.4.1 Short-Term Test Results . The results of

this test are expressed in the form of load versus

midspan deflection plots which are presented in

figures 2.4.9 and 2.4.10. Figure 2.4.9 is a typical

example of one of the three cycles of serviceability

loading (20 psf live load + 5 psf dead load) which were

performed. Figure 2.4.10 is a plot of the ultimate load

test. The roof panel was not loaded to its ultimate,

' however, because the air bag failed first. At this

point the load on the roof panel had exceeded the

recommended ultimate load (65 psf) by a factor of

• 1.8.

2.4.4.2 Long-Term Test Results . The results of this

testing are presented on figure 2.4.11. Midspan

deflections, temperature and humidity readings were

taken for 280 days but only the first 100 days of the

test period are considered usable because a failure

in the temperature and humidity control unit resulted

in erratic environment conditioning after this initial

period. The data points for days 12 to 100 plot

approximately as a straight line when time is plotted

on a logarithmic scale. If this line is extrapolated

to 50 years, the calculated deflection is 0.35 inches.

This deflection, when added to the instantaneous

deflection caused by a live load of 20 psf, which was

determined to be 0.21 in, yields a total deflection of

0.56 in for a simulated long-term loading condition.

2.4.5 Discussion of Roof Panel Tests

2.4.5.1 Short-Term Tests . The load/deflection plots

shown in figures 2.4.9 and 2.4.10 indicate that the

structural behavior of the roof panel tested is

30
linear and, presumably, elastic up to a load o£

approximately 80 ps£. The assumption of elasticity

is further reinforced by the fact that the apparent

residual deflection indicated for the simulated

service loading (Fig. 2.4.9) would recover to

within 0.01 in. in a few hours after the load was

removed. This delayed recovery behavior is common

to many structural systems fabricated from FRP

materials

.

The loads imposed on the roof panel to simulate

service and ultimate loading were 20 psf and 65 psf,

respectively. The first value is consistant with

service loads which are specified in a large number

of building codes in the United States for single and

multiple dwelling flat roofs. The ultimate load

values, although not usually directly specified,

would exceed most building code requirements for

safety factors against failure. Most codes also

limit the midpoint deflection of a roof under service

load conditions. A common value in current use is

1/360 of the span or 0.33 in for this case. The

measured value (see fig. 2.4.9) was 0.21 in for a live load of 20 psf.

2.4.5.2 Long-Term Tests . Most current U.S. codes

covering residential construction do not have

specific requirements for long-term loading because

they are oriented toward the use of conventional

structural materials such as wood, concrete, masonry

and steel. The lack of a specific requirement in

this area probably stems from the knowledge that the

durability of conventional materials, when properly

protected, will generally exceed the useful life of the

building. However, when unconventional materials

and structural systems are used for residential

31
construction, some attempt at evaluating the behavior

o£ such structures over a long period of time must

be made. This was done by extrapolating the data

for 50 years as described in section 2.4.4.2, and

resulted in a calculated midspan deflection of

0.56 in. This deflection is slightly less than

^ 1/240 of the span, which is the maximum allowed

by many codes for roofs subjected to short-term

loads of 1 dead plus 1 live.

3.0 Summary and Conclusions

This report describes a series of structural evaluation tests

on housing components made with a glass fiber reinforced

polyester (FRP) laminate. The components tested were: 1) The

FRP sheet laminate used for the facings and corrugated core

of the basic panel, 2) the polyester adhesive bond between

the facing and core, 3) typical wall panels and 4) typical

roof panels. Test data include: 1) the effect of temperature

and moisture on the tensile and compressive strength of the

FRP laminate, 2) the effect of temperature, accelerated aging

and sustained loads on the tensile shear strength of the

facing- to-core polyester adhesive bond, 3) the short-term

strength of the wall panels under compressive and in-plane

shear loading, 4) the long-term strength of the wall panels

under sustained compressive loading and 5) the short-term

and long-term performance of the roof panels under flexural

loading

The test data presented in this report indicate the following

conclusions

1.) Water-soaking at 122°F for 48 hours and/or testing

at 160°F had no significant effect on the tensile

strength of the FRP laminate.

32
2. ) The temperature and thickness of the polyester

adhesive had a significant effect on the tensile shear

strength of the bond between the FRP laminate facing

and core. The short-term bond strength at 160"?

was only about one-third of the strength at 73°F.

The short-term bond strengths in specimens with an

adhesive thickness of 3 to 5 mm was only about

half of those with an adhesive thickness of

1 mm or less. The variability in adhesive thickness,

which is a quality control factor in fabrication,

must be considered in the design of such panels.

3. ) The shear strength of the bond was much less under

sustained loading than under short-term loading.

4. ) Accelerated aging by ASTM C-481 had no significant

effect on the polyester adhesive bond strength.

However, Boiler's data [1] for the same material

indicate that high humidity will significantly

reduce the bond strength.

5. ) Failures in the wall panels under short-term and

long-term compressive loading and under short-term

in-plane shear loading were in the epoxy adhesive

bond between the FRP facing and the 2x4 wood plate.

6. ) The long-term edgewise compressive strength of the

wall panel was less than one-third of the short-term

strength.

7. ) The performance of the roof panel would satisfy

building codes with a requirement for a live load

of 20 psf.

8. ) The effects of quality control variables and of high

humidity for extended periods on the performance

of these panels '-'ere "ot fully evaluated. However

they are considered to be highly significant

factors

.

33
REFERENCES

1. BOLLER, K. H., "Effect of Exposure on a Proposed GlassReinforced Plastic Laminate to be Used in Building

Constructions," Forest Products Laboratory, Madison,

Wisconsin, Aug. 1972. (Available as NTIS No. PB211314)

2. Federal Test Method Standard No. 406, "Plastics: Methods

of Testing", General Services Administration, Washington,

D.C. , 1961.

3. ASTM Book of Standards, Part 16, "Structural Sandwich

Constructions; Wood; Adhesives.", ASTM, Philadelphia,

Pa. , 1970.

4. BRYANT, R. W. , and DUKES, W. Q., "The Effect of Joint

Design and Dimensions on Adhesive Strength", Structural

Adhesives Bonding , Edited by Michael J. Bodnar

,

Interscience Publishers, New York, N.Y. , 1966.

5. PROT, E. Marcel, "Fatigue Testing Under Progressive

Loading, A New Technique for Testing Materials",

Wright Air Development Center Technical Report 52-148.

6. BOLLER, K. H., "Application of Prot Test Method to

Stress-Rupture Curves of Glass -Reinforced Plastic

Laminates", Forest Products Laboratory Report #2118,

September 1958.

7. LOVELESS, Harold S. , DEELEY, Charles W. , and SWANSON,

Donald L. , "Prediction of Long-Term Strength of

Reinforced Plastics", SPE Transactions , p. 126, April 1962.

8. ASTM Book of Standards, Part 14, "Thermal Insulation;

Accoustical Materials; Fire Tests; Building Constructions."

ASTM, Philadelphia, Pa., 1970.

34
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33
Table 2.2.1 Preliminary Polyester Adhesive Bond Test Results Using

Specimens with Tyi^e 1 Notch (Tensile Shear Test)

SPECIMEH

NDMBn

ADHESIVE

THICKRISS

TEST

TIMF

MAXIMDM

LOAD TYPE OF FAILURE

m °F lbs

1-1 2.0-2.5 73 182

Delami nation within

facing laminate

parallel to bond

2-1 2.0 73 132

4-1 2.5-3.0 73 161 M

11-1 2.0 73 176

16-1 1.0 73 165 M

18-1 1.25-1.50 73 195

8-1 2.5 120 130

Adhesive bond to core laminate

9-1 2.0-2.5 120 135 II

10-1 2.0 180 101

Adhesive bond to core laminate

13-1 1.5 180 126 II

17-1 1.5-1.75 180 73 II

36
Table 2.2.2 Polyester Adhesive Bond Test Results at 73°F Using

Specimens with Notch Type 2 (Tensile Shear Test)

SPECIMEN

NUMBER

ADHESIVE

THICKNESS

MAXIMUM

LOAD TYPE OF FAILURE

nnn lbs

1-2 2.5-4.0 171

Adhesive bond to core laminate

L—i o A o n 1 1 c llD It

3-2 2.5 213 II

19 1.0 220

Tensile failure in core laminate at Notch B

1 f\ lU

Delamination within

facing laminate

parallel to bond

12 1.5-1.75 264

Tensile failure in core laminate at Notch B

13 1.0-2.5 237 II

15 2.0 168 II

9 2.0-2.5 283 II

4 3.5-4.0 154 II

157 0.5-1.25 *284

Delamination within

facing laminate

parallel to bond

187 0.75 351 II

*Some weakening in laminate noted before test.

37
0)a. H

Q O

eu • 3 in o I Ci o

CJ •

o o Ol, • Si

o

0 I 01 O

o •

3 O

C • OS t-( U V

O

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o •« >o o eo o\ o\ i>«

o o o o CM cs cs fsi

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00 lA

lA in

• m • «n • CO

I o

in m • o <A • t» • in I o o • «

5

o

>-9

CO K

Id U

5e

CO Sf

Ml

+ 1 CMiHCM^S-vOOOm •* foovoc*^c^con c^^ ^.-It-lf-lrHr-lrH I-t lA- m in m in <n m m o o o o o o o

m o m o o m m

CM d «M CH< CM <N CM

O(J

Ed M

H H

\o o cjv ao CI »^ in

CM >* *0 r*.

^ <N| . SO

tn m <3- rv. fH

iao o to f** vo lA

CM in r) ^ CM <r

+1

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CM 00 m

<» »a- "So o o 00 00 00

<N|

i'

o o • o in • • «*

I I m in

<J- CO

1-1 O iH

•Ml

CO fJ O ^

vO 00 lA o o o o

CM CM CM CM

O moo . • • CO

CM CO CO I in

vO vO 00

c>j -» s»-

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-*CT\-*CTvvroor-r-~ m-a'O'Hinvovovo

Ix

in in m m m m o o o o o o

ooooooooo CMCMCMCMCSCSCMCMCM

m

O

I iH I I O mm

f». to CM CO «8- r- m v£> v£>

i

> w M Z

Cd U

9g

omooomor-

<N|i-ICs|CMCM<-lrMr-l

I I I I I I I I mommmomm

rHr^NS-mOOO»Ot-ltM

iHt-(nto«Ovoi>.r>»r>-

-<M|

O CM O CM •>» CO CM CM CM

CO

CM lA . o o o CM CN CM

m

r- m • o r- o m

• I o m o CM

o

CO

- IX o o o m m m

<M| - n

A'

vO

- IX -1

m o O m r~ • I CO CM CM I CM

Ml

I' -lA.

O O O O O

GO 00 OO OO 00

O O O

CM CM CM m o

O r~ m o

iH CM .H 1-1 t-l

1^ 00 O m m vo

>

0!B

vO o o ^ -a- m

?lm>9- o

ON

D

c

I m i-i m r-.

.-I m

I • m o O

00 O r» On

C

as c

•9
O

O > w M JZ a M Q PC < H

COm

CO omoo

si- oCM

CM

CO 00

m vO 00 00

00

m CO 00 r>.

m

iH iH iH iH iH

on in in

OOOOO o o o CM CM in m 00 00

iH rH tH rH iH rH iH m m O m « in m • • • CM • O o CM CO O CM 1 CM CM • 1 m 1 CM CM o o O o o • • • CM CM CM rH CM CM o o o o

00o00

00

PL4 o

sr

CO

00mo

CO vo

ON oCM

m

rHin

rH o

CMm om

rH

CMI m

CMo00o

CM

in

CMo

COOCM

(0

CO

(Uco

•H

4J

0)>

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CO

(U

cd

(U

39
Table 2.2.5 Comparison of Polyester Adhesive Bond Strength With and

Without Laboratory AgingV

GROUP B

(1.0-2.0 mm)-'^

GROUP C

(2.0-3.0 mm)-/

GROUP D

(3.0-5.0 mm)-/

1/

2/

TEMP

MAY T HAn

W/0 AGING

MAY T OAn

W. AGING

TT3CT

TEMP

MAY THAn

W/0 AGING

MAY THAn

W. AGING TEMP

MAA LUAU

W/0 AGING

MAA LUAU

W. AGING

°F lbs lbs °F lbs lbs °F lbs lbs

73 263 247 73 203 181 73 163 158

105 162 186 105 134 152 105 104 104

120 156 132 120 118 130

150 115 96 150 67 81

180 76 62 180 62 67

Aged by ASTM C481 method

— Range of adhesive thickness

40
Table 2.2.6A Effect of Loading Rate on Polyester Adhesive

Bond Strength

GROUP A (<1 nim)-/

SPECIMEN AfflESIVE TEST TIME TO MAX

NUMBER THICKNESS TEMP FAILURE LOAD

nun op min lbs

159 0.75 120 0.4 • 220

160 0.25-0.75 120 0.4 242

188 0.50 120 0.4 230

Tv" — 9 71 ^/

l^X - LOX) —

150 0.5-0.75 120 3.6 192

1 n T 151 0.5-1.0 120 3.6 176 r~ _ -1 QA\ 2/

153 0.3-1.5 120 32.4 120 JL M V/ 154 0.5-0.75 120 27!6 137

(x = 129}—

178 0. 75-1.0 _1_ 180*J w 0 4 92

190 0.5 180 0.4 87

(x = 90)-/

162 0.75 180 2.6 67

165 0.5-0.75 180 2.8 70

(x = 69)-/

173 0.75-1.0 180 25.6 53

—/ Range of polyester adhesive thickness —/ X is the mean value

41
Table 2.2.6B Effect of Loading Rate on Polyester Adhesive

Bond Strength

GROUP B (1.0-2.0 iTim)i/

1 IMc lU MAX

NUMBER THICKNESS TEMP FAILURE LOAD

mm op min lbs

oee laDie Z .L.O 120 0.4 (x = 150)-'

114 1.5-2.5 120 3.1 84

116 1.5-2.0 120 3.0 94

l^x — oy J

121 1.5 120 25.8 78

128 1.5 120 24.8 67

132 1.5-2.0 120 26.4 78

Ty" = 74^ ^/

I A — / t 1 —

See Table 2 .2.3 150 0.4 Cx = 115ll/

152 00

155 1.0-1.5 150 3.0 66 — 2/

(x = 76)-'

156 1.0-2.0 150 29.0 56

158 0.75-1.25 150 29.4 70

163 0.5-1.5 150 24.4 50

(x = 59)—

See Table 2 2 3 xou /DJ —

164 1.25 180 2.2 55

167 1.0-1.75 180 2.2 60

168 1.0-1.25 180 2.4 49

(x = 55)i/

169 1.25 180 21.4 45

171 0.5-2.0 180 19.6 46

(x = 46)-/

— Range of polyester adhesive thickness —/ X is the mean value

42
I

Table 2.2.6C Effect of Loading Rate on Polyester Adhesive

Bond Strength

GROUP C (2.0-3.0 ram)-/

SPECIMEN ADHESIVE TEST TIME TO MAX

NUMBER THICKNESS TEMP FAILURE LOAD

nim op rain lbs

See Table 2.2.3 105 0.4 - 2/

(x = 134) --^

120 2.0 105 1.9 95

122 2.0 105 2.0 85

[X = yuj—

123 2.0 105 ly . i

1 n Q IUd

124 2.5 105 14.8 52

See Table 2.2.3 120 0.4 (x = 118)—

130 2.5-3.0 120 3.4 62

131 2.0 120 3.2 56

134 2.5-3.0 120 3.4 70

133 2.5-3.5 120 4.0 62

(x = 63)-/

125 2.0 120 39.8 81

126 2.0 120 27.2 70

127 2.5-3.0 120 27.6 36

(x = 62)-/

— • Range of polyester adhesive thickness

2/ — — X is the mean value

43
rH

•H

cdo

4-)

5-

T3O

•H

+->

CO

t/5

(Au

X!

00 o o LO o o (NI CSI o CD • • • o r-. o o o tsi (Ni (M LO

(NI

A

A

(U (D u 5h I—

i-H •H •H oo nJ • • M-l oo Q Q

Pi (=! oo O LO X! • * to oo o o • • 52

t/) /—

• • to (NI C (A o o LO o S 3

•"^f 00 UT) •HO . -HO o o o O LO • • u xi U o o o LO LO !—

1—

CD (D • • • o o I—

p,o P^o o o o to (/) o tn o o o • o LO o LO o • • (NI to (NI to o rg 00 (NJ VO t--~ LO o f-1 o o O to vO o •> (1) O O o o o (NI (NJ LO oo +-> • • . • • (NI m O O O o o o 1-H l-t (NI ni a <D

US US US in f=! •H •H

XII SLZ at at -6 -6 -6 -6 Q

T*dl ar Ma Ma MajYia Ma

App bO

a

H •S •H Oj

p +->

M +->

OOO

(/) (/) tn

CD <U (U H H H

Dead Dead Dead o o o o o LO LO o vO LO to (NJ iH

44
T

6 in. -t

8 ft.

FRP LAMINATE

ROOF/CEILING ASSEMBLYFRP LAMINATE

EXTERIOR WALL5/8 in. PLYWOOD SUB-FLOORING

2x4 Plate =1-1/2" x 3-1/2"

2x8 Joi«t =1-1/2" X 7-1/4"

-2X4 PLATE

SPRAYED

-TEXTURED

COATING

2X4 PLATE

3/4in.TRIM

2X8(g)l6"o.c

FLOOR JOISTS

Fig. 1.2.1 Typical section for the FRP laminate housing system.

45
FACING

SHEET

LAMINATE

CORRUGATED

CORE LAMINATE

NOTCH A (TYPE I)

POLYESTER

ADHESIVE

2.1 Adhesive bond specimen with notch type 1.

46
j/ariable

« k

FACING

SHEET —

LAMINATE

T

r

r

CORRUGATED

CORE LAMINATE

NOTCH A (TYPE 2

)

POLYESTER

ADHESIVE

1/2"

Fig. 2.2.2 Adhesive bond specimen with notch type 2.

47


I 50
51
•H

Pi o o o o o o o in o tf> o ro oj CM — —

san *avon aannivd

52

54


Fig. 2.3.3 Test setup for racking test No. 3. ^7
58

Fig. 2.3.6 Load vs. displacement for racking test No. 1.

60

1000 1—

900 —

800

700

^ 600

<

o

_J

o

z

o

<

a:

500 -

400

300

200 -

100 -

I®

RESIDUAL

MAXIMUM L0AD = I0I0 lb/ft

D) UNDER LOAD

©—I

RACKING TEST no.

2

® = NET DRIFT

0.1000 0.2000 0.3000

DISPLACEMENT, in

Fig. 2.3.8 Load vs. displacement for racking test No. 2.

62
63
DISPLACEMENT, in

ig. 2.3.10 Load vs. displacement for racking test No. 3.

64
RACKING LOAD, lb/ft

(D = EXTENSION

© = CONTRACTION

o = UNDER LOAD • = RESIDUAL

(GAGE LENGTHS= 118.25")

[

PnTTTT

RACKING TEST no.2

-0.1000 -00500

(CONTRACTION)

0 -H 00500

DEFORMATION, in (EXTENSION) ^

2.3.12 Load vs. diagonal deformation for racking test No. 2.

65
RACKING LOAD, lb/ft

(D = EXTENSION

(C) = CONTRACTION

(GAGE LENGTHS = 118.25)

RACKING TEST no

MAXIMUM L0AD = 800 lb/ft

100

-00500 0 -•-0.0500

DEFORMATION, in (CONTRACTION) (EXTENSION) -

Fig. 2.3.11 Load vs. diagonal deformation for racking test No. 1 66
RACKING LOAD, lb/ft

-0.0500 0 + 0.0500

DEFORMATION, in (CONTRACTION) (EXTENSION)

Fig. 2.3.13 Load vs. diagonal deformation for racking test No. 3.

67

69
Fig. 2.3.16 Failure in short-term compressive test No. 2. 70
3000 1—

2700 -

MAXIMUM L0AD = 6240 lb/ft

COMPRESSION TEST no.l O = UNDER LOAD • = RESIDUAL

0 0.0100 0.0200 0.0300 0.0400 0.0500

SHORTENING IN 8-ft.,in

Fig. 2.3.17 Load vs. shortening for compressive test No. 1.

71
2400

2100

I I— •

1800

1500

1200

900

600 —

MAXIMUM LOAD = 5925 lb/ft

J

I

I

/

/

/

/

J

300 7

0 1

COMPRESSION TEST no.2

O = UNDER LOAD • = RESIDUAL

1

0.0100 0.0200 0.0300 0.0400 0.0500 0.0600

SHORTENING IN 8-ft, in

Fig. 2.3.18 Load vs. shortening for compressive test No. 2.

72
3000r2700

2400

2100

1800

1500

1200

900<

•I 600 •

I

I•

I 300 i o

MAXIMUM L0AD = 6240 lb/ft

COMPRESSION TEST no. O = UNDER LOAD • = RESIDUAL

0.0100 0.0200 0.0300 O0400 0.0500

LATERAL DEFLECTION, in

0.0600

Fig. 2.3.19 Load vs. lateral deflection for compressive test No. 1.

73
2400 1—

2100

<

3

>

CO

C/)

LlI or

Q.

oO

1800

1500

1200

900

MAXIMUM L0AD = 5925 lb/ft

o

Io

J

/

I

I ^ ; /

600 H • O

'/

/

300

0

•o

//

— w

/

1

COMPRESSION TEST no. 2

O = UNDER LOAD

• = RESIDUAL

\ \ J

0.0100 0.0200 0.0300 0.0400 0.0500

LATERAL DEFLECTION, In

Fig. 2.3.20 Load vs. lateral deflection for compressive test No. 2.

74
30001-

2700

2400 —

2100 -

1800 -

- 1500 -

<O

^ 1200 -

CO

a:

a.o

o

900 -

600 -

300

100 200 300 400 500 600

SURFACE COMPRESSIVE STRAIN, 10'^ In/in

Fig. 2.3.21 Load vs. average surface strain for compressive test No. 1.

75
Long-term compressive load test with flat -bottom support.

76
Fig. 2.3.23 Long-term compressive load test with eccentric -bottcm support.


80


.I(±)

GAP —

(BOTH ENDS)

.REACTION BEAM ^

\-2-LVDTs

END SUPPORT ASSEMBLY \

77ZZ/////////////////// /\/ ///////

/

I [-*- 4 1/2" Wall (Typ) (^Span

t ROCKER I h" ^11'- 7 1/2"

AIR BAGS

-3' -8" —

SECT A-A

DETAIL

A .l" Thick FRP LAMINATE FAQNG

B POLYESTER ADHESIVE

C .05" Thick FRP LAMINATE

CORRUGATED CORE

D SAME AS "b"

E SAME AS "a"

Fig. 2.4.4 Schematic of test setup for short-term flexural test on roof panel.

83


86
ir-7i/2"

B

J

1 1 1 1 1 1 1 . II 1 1 1 1 1 1 -5

|-€

1/ }1 B-^J J

/

STEEL

ROCKER

STEELROLLER

DEFLECTION 6A6E

SEE DETAIL

1

32"

1 N

5.3/4

SECT. B-B

^^"^—

DRY SAND

POLYESTER

ADHESIVE

WOOD RETAINING SLATS

FRP LAMINATE

Fig. 2.4.8 Schematic of long-term (creep) sustained load test setup.

87
g

I-o

iij

LlI Q

2

CDQ

(VI

O

o

o

g . O 10

"S ^

rH 0

4H rH

TO 0) n +-) •H fH

> <D

(NI

•H

isd 'avon i/MdOJiNn

88
o

I-o

UJ

UJ

o

o

o

o

c

o

O

•P

•H

+-> U

(J p

I—I 0)

M-l T-H 0 m

(D

•H >H E O

• t/) in> 0

• H

isd *avon waodiNfi

89

= ORM NBS-n4A <l.7i) U.S. DEPT. OF COMM. 1. PUIUJCATION OR RHPORT NO. 2. (lov't Accession

Rial innRAPHir data No- SHEET NBSIR 73-188

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Structural Tests on Housing Coinponents of Glass Fiber

Reinforced Polyester Larriijiate

5. Publication Date

6. Performing Organization Code

7. AUTHOR(s) J jY.REiaiARD; W.E.GREENE, JR; L.E. CATTANEO;

L.W. MASTERS '

8. Performing Organization

NBSIR 73-188

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/ iask/Work Unit No. 460 0430

11. Contract/Grant No.

T AA—H — 1 ft — lCi

12. Sponsoring Organization Name and Address

Office of Researcli ^ Teclmology

Department of Housing and Urban Development

Washington, D.C. 20410.

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

I''

bibliography or literature survey, mention it here.) This report describes a series of structural evaluation tests performed on housing

components made with a glass fiber reinforced polyester (FRP) laminate. The conponents

tested were: (1) the FRP laminate used for the facings and the corrugated core of the basic panel; (2) the adhesive bond between tiie facing and core; (3) typical

wall panels; and (4) typical roof panels. Test data include: (1) the effect of

tenperature and moisture on the tensile and compressive strength of the FRP

laminate; (2) the effect of tenperature, accelerated aging and sustained loads on the

tensile shear strength of the facing- to-core polyester adliesive bond; (3) the short-

! term strength of the wall paiiels under compressive and in-plane shear loading; (4)

\ the long-term strength of the wall panels under sustained compressive loading; and

(5) the short-term and long-term performance of the roof panels under flexural

loading.

i 17. KEY WORDS (Alphabetical order, separated by semicolons) Adliesive bond ; aging; conposites ; coiTipression;

I flexure; glass fiber; housing system; innovations; laminate; Operation

1 Breakthrough ; racking; reinforced plastics; reinforced polyester; sustained loading;

1 18. AVAILABILITY STATEMENT tensile shear.

li

r,

|j ^

UNLLMITED.

i FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE

11 TO NTIS.

19. SECURi n' CLASS

(THIS REPORT)

UNCLASSIFIED

2L NO. OF PAGES

20. SECURin' CLASS

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UNCLASSIFIED

22. Price

' , _ USCOMM-DC 66244. P7t