NBSIR 74-557

Non-Metallic Antenna-Support Materials

Second Annual Interim Report -

Nixon Halsey, Donald E. Marlowe and Leonard Mordfin

Engineering Mechanics Section

Mechanics Division

Institute for Basic Standards

National Bureau of Standards

Washington, D. C. 20234

June 1974

Interim Report for Period October 16, 1972 - October 15, 1973

Prepared for Air Force Materials Laboratory

Wright-Patterson Air Force Base

Ohio 45433

NBSIR 74-557

NON-METALLIC ANTENNA-SUPPORT MATERIALS

Second Annual Interim Report

Nixon Halsey, Donald E. Marlowe and Leonard Mordfin

Engineering Mechanics Section

Mechanics Division

Institute for Basic Standards

National Bureau of Standards

Washington, D. C. 20234

June 1974

Interim Report for Period October 16, 1972 - October 15, 1973

Prepared for Air Force Materials Laboratory

Wri^t-Patterson Air Force Base

Ohio ,45,433

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

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts. Director

CONTENTS

Page

1. INTRODUCTION 1

2. OPTIMIZATION OF THE MANUFACTURING PROCESS, 3

PART I 2.1 Process Parameters 4

2.2 Design of Experiment 10

2.3 Manufacture of Experimental Materials 12

2.4 Tests and Results 15

2.5 Analysis of Results 20

3. OPTIMIZATION OF THE MANUFACTURING PROCESS,

PART II

3.1 Experimental Materials 25

3.2 Test Results and Analysis 27

4. PLANS 33

5. REFERENCES 34

APPENDICES

A. Conversion Factors 3 5

B. Tensile Test Results, Runs 1-11 35

C. Stress-Rupture Test Results, Runs 1-11 35

i

NON-METALLIC ANTENNA-SUPPORT MATERIALS

Second Annual Interim Report

by

Nixon Halsey, Donald E, Marlowe and Leonard Mordfin

ABSTRACT

Thirteen samples of a pultruded, glass fiberreinforced-pol yester rod material were manufactured

using a different combination of the manufacturing

process parameters for each. These samples were tested

to evaluate the effects of nine different process

parameters on the properties and characteristics of

the rods. Elevated-temperature stress-rupture tests

under saturated humidity were used as an accelerated

measure of long-term weatherabil ity . The test results were somewhat inconsistent, but it appears that cer- tain process parameters, such as collimation and

ultrasonic agitation of the rovings during pultrusion,

were beneficial to both tensile strength and weatherability. Other parameters, such as pretensioning of the

rovings, were beneficial to weatherabil ity but detrimental to tensile strength. Additives to the resin

system were generally detrimental.

A high speed tension test method was developed

and it was found that the strength of the rod is

substantially greater under high loading rates.

An approximate relationship was observed between

transverse tensile strength and electrical breakdown

voltage. However, neither of these characteristics,

nor surface hardness, correlated with axial tensile

strength or weatherability.

Key Words: Composite materials; f iber-reinforcedplastic rod; gl ass-reinforced-polyester rod; guys,

antenna; processing parameters, pultrusion; pultrusion; reinforced plastic rod; stress rupture of FRP

rod; test methods, FRP rod; weatherability, FRP rod.

1 . INTRODUCTION

Glass-reinforced-plastic rod and rope materials constitute one of the

more interesting and valuable -- although lesser known -- products of

composite materials technology. These products are generally fabricated

1
from unidirectional glass fiber roving and a thermosetting plastic matrix

by a process called pultrusion. They are strong, lightweight, nonconduct

ing, corrosion resisting and comparatively inexpensive. This combination

of properties has led to the use of these products in a variety of applications where steel wire rope had previously been employed almost

exclusively. In terms of total volume, the largest application has been

in communications towers and arrays, wherein the use of non-metallic rod

and rope as guys and catenaries has permitted the elimination of the

large, expensive, ceramic insulators which are required when steel wire

rope is used.

As frequently happens when promising new products are developed, the

rod and rope were introduced into service before they were adequately

characterized and without the benefit of carefully compiled design data.

The result has been the occurrence of failures in several field installations. Fortunately, most applications have performed satisfactorily.

Some of the reported failures have involved arc tracking and flashover

damage, and burning, in intense electromagnetic fields. However, most of

the reported failures have been mechanical in nature and have occurred

after a period of service, ranging from months to years, during which

the materials have been under tension in a moist environment. With this

as a point of departure, the National Bureau of Standards embarked upon

a program to develop a new non-metallic f iber-reinforced-plastic rod or rope material which would exhibit superior mechanical properties and

greater resistance to moisture in the form of a hot, humid environment.

This program calls for the development to be accomplished through the

selection of potential improvements in the manufacturing process, the

reinforcing fibers and the matrix resin; the procurement of experimental

materials, which are manufactured in accordance with these potential

improvements; and the subsequent evaluation of these materials. The

evaluations are based primarily upon two types of mechanical tests:

tensile tests at normal and high rates of loading, and stress-rupture

tests at 160 o and 200 °F under saturated humidity conditions. The

results of the stress-rupture tests, when performed on a variety of

materials, are considered to be indicative of the relative weatherabilities of the materials.

This program, which was initiated October 16, 1971, is being carried

out in the Engineering Mechanics Section of NBS under the sponsorship

and with the financial assistance of the Air Force Materials Laboratory.

During the first year of activity on this program [1]

o six 30000-lbf-capacity creep testing machines

were designed for the stress-rupture tests.

These machines, which have since been assembled, will accommodate test specimens up to

nine feet long and are equipped with environmental chambers for use to 200 °F under saturated

humidity conditions.

o a study of industrial manufacturing capabilities

led to the selection of pultruded, glass-rein2
forced-polyester rod as the basic form of

material which will be upgraded in this

program.

o two new end fittings for glass-reinforcedplastic rod were developed in order that the

tensile strengths of these materials may be

accurately determined. These new fittings

have" been found to perform better, in this

application, than commercial end fittings.

o deficiencies in the physical characteristics of

existing glass-reinforced-polyester rod materials

were identified, and modifications to the manufacturing processes were proposed to overcome these

deficiencies. A subcontract was let for the manufacture of experimental glass-reinf orced-polyester

rods using the modified processes.

The second year of activity on this program was devoted primarily to

the manufacture and testing of these experimental materials, and to the

interpretation of the test results. This interim report describes the

progress made during the second year.

The U.S.A. is a signatory to the General Conference of Weights and

Measures which gave official status to the metric SI system of units in

1960, However, for simplicity, only U.S. customary units have been used

in this report. Conversion factors for these units are given in Appendix

A.

2. OPTIMIZATION OF THE MANUFACTURING PROCESS, PART I

The basic features of the manufacturing process for pultruded rod

have been reviewed Tlj. The process is quite complex, involving many

variable parameters. In this effort toward optimizing the process, a subcontract was let for the manufacture of thirteen different samples

of 1/2-in diameter rod using E-glass roving and an isophthalic polyester

resin matrix. (The characteristics of these two constituent materials

have been given [1].) Runs 1 through 11 were designed to examine the

effects of nine different process parameters using two values, or settings, of each parameter. On the basis of the subcontractor's experience plus the results obtained from a preliminary sample, which had been

manufactured and tested previously il], constant values were assigned to

three additional process parameters for the purposes of this study.

(Runs 12 and 13 will be discussed later.)

3
2.1 Process Parameters

2.1.1 Roving Preheat. Earlier studies have shown that the wetting of

the fibers by the resin might be improved by preheating the rovings to

drive off surface moisture before they enter the dip trough. This was

done, in this program, by passing the rovings through an oven prior to

entry into the dip trough. The oven is 54 in long and is capable of

continuous operation between 250 and 300 °F

2.1.2 Roving Twist. Glass roving is commercially available either

twisted or untwisted. The use of untwisted roving would conceivably

facilitate wetting and might also be conducive to achieving straight,

parallel fibers in the finished product. On the other hand, since

twisted rovings have less fuzz and catenary, these might, in fact,

result in better collimated fibers. Both twisted and untwisted rovings were used.

2.1.3 Roving End Count. Glass roving is also available in a wide range

of end counts (number of strands per roving). The pultrusion of a larger

number of rovings with a smaller end count could, perhaps, provide a more

uniform distribution of fibers throughout the cross section. At the same

time, the difficulties in achieving good collimation probably increase

with the number of rovings used. End counts of 30 and 60 were examined.

2.1.4 Roving Tension. It had been observed during the study of the

pultrusion process {1] that the fibers in pultruded rod are frequently

not straight but, rather, follow tortuous paths. This does not allow

the development of a uniform distribution of load among the fibers in a tensile application. In the present work, therefore, several samples were manufactured with the fibers pretensioned to straighten them. This was accomplished by passing the rovings over an S-bend, as shown in

Figure 1. Initially, the vertical separation of the two rods which form

the S-bend was 6 in and the horizontal separation was 4 in. Later, to

increase the tension, the vertical separation was reduced to 3 in and the

horizontal separation increased to 5 in. In addition, each roving was passed through an eyebolt, as shown in the figure. The individual eyebolts were rotated, as necessary, to approximately equalize the tension

in the various rovings.

2.1.5 Roving Collimation. In addition to being straight it is also

important that the rovings be alined parallel to the axis of the rod.

This was promoted by constraining the rovings to follow essentially

parallel paths through the dip trough. The rovings were passed through

a series of three polyethylene guide plates which were mounted in the

dip trough. Figure 2. Each plate contained holes -- one hole for each

roving -- arranged in a pattern of concentric circles. All of the holes were below the resin level in the trough, and the middle guide plate was set somewhat higher than the other two to introduce some tension

into the rovings. After passing through the third guide plate the

rovings followed an essentially horizontal path to the die, leaving the

dip trough through a 5/8-in orifice beneath the surface of the resin.

4


This apparatus is believed to reduce the inadvertent intertwining

of rovings, and to promote resin penetration by separating the mass of

rovings in the trough.

2.1.6 Immersion Length. The wetting of the fibers with the resin

could conceivably be improved by increasing the duration of the immersion

in the dip trough. This can be accomplished either by reducing the pulling speed of the rovings or by increasing the immersion length in the

dip trough. In this program pulling speed was maintained constant, as discussed below, and the effects of immersion time were examined by using

either a "standard" dip trough, which provides an immersion length of

approximately 23 in, or a long trough, for an immersion length of approximately 54 in.

2.1.7 Ultrasonic Agitation. Another approach to improving fiber wetout involves the use of ultrasonic excitation to agitate the fibers and

drive entrapped air from the rovings. In this program a 250-W ultrasonic exciter, which vibrates at 20000 Hz, was used in the manufacturing

process for several samples. The end of the ultrasonic horn, which has

a 3 1/2-in by 1/2- in rectangular cross section, was immersed in the dip

trough and placed in contact with the rovings near the point of their

emergence from the resin. The ultrasonic vibrations were damped out,

and the instrument rendered inoperative, if the horn was immersed to a depth exceeding about 1/16 in.

2.1.8 We tting Agent

Improved wet-out of the fibers was also sought

through the use of a wetting additive in the resin system. Poly (ecaprolac tone) or, simply, polycaprolac tone , was selected for this purpose

on the basis of its demonstrated ability to facilitate the dispersion of

glass particles in resins [2]. Polycaprolactone is a thermoplastic

polymer which is formed through the ring-opening reaction of e-caprolactone . It has the structure

where the subscript n depends on the molecular weight of the product.

It is commercially available in flake form and, according to the manufacturer, is readily compatible with styrene-unsaturated polyesters.

In concentrations of 5 to 10 percent it also imparts improved surface

properties to glass-reinforced plastics.

2.1.9 Resin System Formulation. On the basis of prior experience it was known that the resin system should have a dynamic viscosity in the

range of 11.5 to 13.0 poises for satisfactory pultrusion. This was accomplished by adding monostyrene to the iso'phthalic polyester resin.

The proportion of monostyrene had to be increased when the polycaprolactone wetting agent was used since the latter tends to raise the viscosity of the system. The resin system formulation, both with and without the wetting agent, is given in Table 1.

0

U n

7
Table 1. - Resin System Formulation, Runs 1-11

Without With

wetting wetting

agent agent

wt pet wt pet

Monostyrene 4.91 7.09

Peroxide catalyst 0.73 0.70

Die lubricant 0.92 0.86

Ultraviolet inhibitor 0.13 0.12

Wetting agent - 4.96

Isophthalie polyester resin Bal. Bal.

8
2.1.10 and 2.1.11 Curing Conditions. With a given resin system, attainment of a satisfactory cure is dependent upon two parameters: the pulling speed and the die temperature. From the results on a preliminary

sample |[ 1 ] a pulling speed of 12 in/min and a thermostat setting of

350 °F on the curing die were selected. These two processing parameters

were maintained for all of the pultrusion runs.

2.1.12 Post Curing. It has been found [1] that pultruded rods, in the

as-received condition, are not fully cured. At normal pultruding speeds

each increment of rod is exposed to the curing die for a very short time

and it is not possible to effect a complete cure in this interval. Although cure undoubtedly proceeds to completion under ambient conditions

over a period of months, the addition of a post cure to the manufacturing

process would provide the benefits of a complete cure frcan the outset.

These benefits may include enhanced weather resistance as well as increased

strength. This parameter was examined by adding a post cure (16h at 275 °F)

to the manufacturing process for one sample.

9
2.2 Design of Experiment

Nine of the variable process parameters were examined in two values,

or settings, of each. For example, the effects of roving end count were investigated by manufacturing some rod samples with 30-end roving and

others with 60-end roving. For most of the parameters, however, the

two values, or settings, consisted of a "yes" or "on" condition and a "no" or "off" condition. Thus, the effects of ultrasonic agitation were investigated by manufacturing some rod samples with agitation (the "yes"

setting) and others without agitation (the "no" setting). The nine parameters and their settings were:

Roving preheat (yes, no)

Roving twist (yes, no)

Roving end count (60, 30)

Roving tension (yes, no)

Roving collimation (yes, no)

Immersion length (long, standard)

Ultrasonic agitation (yes, no)

- Wetting agent (yes, no)

Post curing (yes, no)

Three other process parameters (resin viscosity, pulling speed, die

temperature) were kept constant.

Eleven samples of rod were manufactured. Table 2 gives the selected

settings of the nine variable process parameters for each of Runs 1 throu

11. This scheme permits the effects of each of three parameters (preheat

collimation, post curing) to be examined by comparing the properties of

two samples, which had been manufactured such that all of the process

parameters were the same for both except the parameter being studied.

Thus, for example, the process parameters for Runs 1 and 2 were nominally

identical except that the roving was preheated in Run 2 while in Run 1 it was not.

The remaining six variable parameters (twist, end count, tension,

immersion length, ultrasonics, wetting agent) were investigated more extensively using eight rod samples. The parameter settings for these

eight manufacturing runs were designed, by Dr. G. M. Jouris of the

Mathematics Department at the Westinghouse Research Laboratories, such

that each of the six variable parameters occurs four times at its high

or "yes" setting and four times at its low or "no" setting. The other

three variable parameters (preheat, collimation, post curing) were kept

constant throughout these eight manufacturing runs. This method permits

samples from all eight runs to be used in making a decision about each of

the six variable parameters being studied. A large difference between

the average value of a given rod property at the high setting, and the

average value of that property at the low setting, indicates that the

variable parameter is important to that property. Conversely, a negligible difference suggests that the property is essentially independent

of the variable parameter.

10
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11
Examination of Table 2 shows which samples must be compared in order

to evaluate the effects of each variable process parameter. This information is summarized in Table 3.

2.3 Manufacture of Experimental Materials

Eleven samples of 1/2-in diameter glass-reinf orced-polyes ter rod were manufactured in accordance with the process parameter settings given

in Table 2. Some of the operating conditions for these manufacturing runs are given in Table 4 and discussed below.

2.3.1 Number of Rovings

The number of rovings used in the manufacture

of each sample was not arbitrary but was determined by the amount of glass

needed to produce good quality rod under the preselected processing conditions. The use of tension, for example, made it necessary to increase the

number of rovings to properly fill out the die. The glass contents in

the finished samples were measured by the manufacturer and are reported

in Table 4. Note that for a given glass content twice as many 30-end

rovings are required as 60-end rovings.

2.3.2 Ultrasonic Loading. The ultrasonic generator was operated at the

minimum power level required to maintain loading of the ultrasonic horn

without stalling. When tension was used on the glass roving, increased

power was required to keep the horn operating.

2.3.3 Resin Temperature. Use of ultrasonic agitation caused the temperature of the resin in the dip trough to rise, resulting in partial polymerization of the resin. This problem was serious when the standard

iiranersion length was used rather than the long immersion length since,

in the latter case, the energy could be dissipated to a greater volume of

resin. In Run 9, for example, which employed the standard immersion

length, the increased resin temperature made it necessary to remove 2-

to 3-oz chunks of gelled resin, from the vicinity of the horn, at 15-

to 20-min intervals. Small resin additions were, therefore, frequently

required in order to maintain the proper resin level, and this helped to

control the temperature rise.

The higher power levels required for ultrasonic agitation, when

roving tension was used, increased the heating problem. In Run 7, when

ultrasonic agitation was used in conjunction with roving tension and a standard immersion length, the problem became most severe and the dip

trough had to be cooled externally. This was only partially successful,

and it was necessary to discontinue this run after only about 60 ft of

rod had been pultruded.

A certain amount of resin heating was found to be desirable when

the wetting agent was used since it tended to separate from the resin

solution at temperatures below about 77 °F. Consequently, infrared lamps

mounted beneath the dip trough were employed when ultrasonic agitation

was not being used.

12
Table 3. - Evaluation of the Variable Process Parameters

To evaluate

the effect

of:

Preheat

Collimation

Post Cure

Twis t

End Count

Tension

Immersion Length

Ultrasonics

Wetting Agent

Compare

these runs

(high or "yes" setting)

the average rod properties from

^ i these runs jwith|^

(low or "no" setting)

2

10

11

2, 3, 4, 5

2, 3, 6, 7

4, 5, 6, 7

3, 5, 6, 8

3, 5, 7, 9

3, 4, 7, 8

1

2

2

6, 7, 8, 9

4, 5, 8, 9

2, 3, 8, 9

2, 4, 7, 9

2, 4, 6, 8

2, 5, 6, 9

13
Table 4. - Operating Conditions for Manufacture of Runs 1 through 11

Run

No.

No. of

rovings

Glass

content

Ambient

relative

humidity

Ultrasonic S-bend , . Resin

1 J- (a) loading spacing temperature

wt pet percent W in

1

2

3

4

5

6

7

8'

9

10

11

22

22

22

46

49

23

23

44

44

23

22

70.8

70. 7

71.9

73.8

76.2

73.4

73.8

71.9

70.6

73. 7

70. 7

30-31

30-31

36-38

16-18

20-23

22-25

18-21

24

22-25

25

27-28

200-225

238-250

250

150-175

(4,6)

(4,6)

(5,3)

(5,3)

(b)

(b)

82-100

81-86

84-93

74-79

108-118

77-81

68-106

(b)

(b)

(a)

(x,y) means x inches horizontal spacing, y inches vertical spacing.

(b)

Not measured, approximately ambient.

14
2.4 Tests and Results

Some of the more important product characteristics and mechanical

properties of the rods, from Runs 1 through 11, were evaluated by means

of the following tests:

Hardness tests.

Diametral compression tests (to measure approximate

transverse tensile strength)

Electrical breakdown tests (to obtain a relative

indication of the degree of fiber wetting)

Tensile tests.

High-speed tensile tests.

Stress-rupture tests at 160 "^F and saturated h-anidity.

Stress-rupture tests at 200 and saturated humidity.

The test methods that were used for all of these tests, except the highspeed tensile tests, were described earlier [1,.

2.4.1 Product Characteristics. The average results of the tests to

determine the surface hardness, the transverse tensile strength and the

breakdown voltage, for each of Runs 1 through 11, are given in Table 5,

2.4.2 Tensile Breaking Load. Forty-one tensile tests were performed on rod specimens from Runs 1 through 11. These were carried out at room temperature using a crosshead speed of 0.75 in/min.

The test results are given in Appendix B and the average breaking loads

are summarized in Table 6.

2.4.3 High-Speed Tensile Tests. These tests were carried out at room

temperature in a 50000- Ibf- capac ity , closed loop, elec trohydraulic testing machine i3j. Special adapters were designed and fabricated to enable

H3M end fittings [lj4j to be used in this machine. A calibrated load cell

in series with the test specimen was used to measure load, and the loadtime trace for each test was recorded with a calibrated storage oscilloscope. See Figure 3. The crosshead speed in these tests was measured

using an LVDT extensometer and was found to be approximately 300 in/min.

In the first three high-speed tensile tests that were performed the

failures appeared to initiate in an end fitting. Because of the viscoelastic nature of the C2W3 potting compound (which is normally used with

H3M end fittings) it was surmised that the high loading rates were causing

the potting compound to behave like a stiff material. Consequently, a new potting compound, C1W2, was formulated, which is more flexible than

C2W3 . Nevertheless, failure in most of the high-speed tensile tests

appeared to initiate in an end fitting.

In all, nineteen high-speed tensile tests were carried out on rod

specimens from Runs 1 through 11. The results of these tests are given

in Table 7, The free lengths of all specimens were 27 or 28 in and,

except as noted, all failures appeared to have initiated in an end fitting.

15
Table 5. - Average Product Characteristics, Runs 1-11

Rockwell

Run hardness

No. (Scale E )

1 53 1300 22

2 51 1300 22

3 24 2200 43

4

' 34 1400 23

5 . 53 1600 29

6 56 1700 25

7 44 1900 35

8 42 2000 45

9 47 1200 19

10 47 1200 20

11 62 1800 22

Transverse

tensile Breakdown

strength voltage

2 Ibf/in kV

16
Table 6. - Average Breaking Loads, Runs 1-11

Run No . , Average breaking load

Ibf

1 29000

2 29100

3 27100

4 22500

5 23000

6 24700

7 26200

8 25900

9 28000

10 . 30400

11 29600

17
Figure 3 - Storage oscilloscope used in high-speed tensile tests, showing a typical trace of load (ordinate) vs time (abscissa)
Table 7. - Results of High-Speed Tensile Tests, Runs 1-11

Run

No.

Specimen

No.

Potting

compound

Average

diameter

Average

density

Average

_weight

Maximum

load Notes

m Ib/in^ lb/ft Ibf

RlPcSC

RlPc7B

C2W3

C1W2

0.5021

.5013

0.0687

.0691

0.163

.164 36000

2 R2Pc7C C2W3 .5008

2 R2Pc5D C1W2 .5023

3 R3PclC C1W2 .4954

3 R3Pc5A C1W2 .4960

4 R4Pc6A C1W2 .4964

4 R4Pc6B C1W2 .4964

5 R5APc2B C1W2 .4977

6 R6Pc6A C1W2 .4951

6 R6Pc6C C1W2 .4951

6 R6Pc9A C1W2 .4966

8 RBPcllA C1W2 .4947

9 R9Pc5A C1W2 .4959

10 R10Pc4C C2W3 .4967

10 R10Pc3C C1W2 .4956

10 R10Pc6A C1W2 .4960

10 R10Pc6B C1W2 .4960

11 RllPc2A C1W2 .5002

.0691 .163 34700

.0688 .164 33200

.0696 .161 33500

.0695 .161 37000

.0702 .164 29000

.0702 .164 28500

.0697 .163 32500

.0714 .165 38100 b

.0714 .165 17000 c .0710 .165 35000

.0699 .161 34000

.0697 .161 36000

.0706 .164 - a .0709 .164 - a .0708 .164 15000 c .0708 .164 34000

.0691 .163 32500

Notes

a. Maximum load not measured.

b. Failure appeared to have initiated in the free length.

c. Specimen pulled out of an end fitting.

19
2.4.4 Stress-Rupture Tests. Eighty-three stress-rupture tests were carried out on rod specimens from Runs 1 through II under saturated

humidity conditions. Thirty-eight of these tests were performed at

160 °F and forty-five at 200 °F. The original intent of the tests was

to study the rupture strength of each sample of material, at each temperature, over the time range from 1 to 1000 h. It was soon realized,

however, due to scatter in the test results and to the occasional occur- rence of long-term failures which initiated in the end fittings, that

far more tests would be required to characterize the rupture strengths

than had been planned. Some trade-offs were effected by conducting fewer

tests on samples which exhibited low rupture strengths so that additional

tests could be conducted on the other samples. In particular, no tests were carried out at loads less than 10000 Ibf because 1/2- in rods with

rupture loads below this are clearly not competitive with commercially

available products.

The results of the stress-rupture tests are given in Appendix C.

These results show several interesting features. If the data are plotted

on semi- log coordinates (see, for example, Fig. 4) the slope of the curve

of load vs log time-to-rupture becomes increasingly negative with increasing time. This is contrary to the behavior of most structural materials.

Also, there was no clear distinction between the stress-rupture properties

at 160 °F and those at 200 °F. Certain samples of material appeared to

be stronger at 200 °F than at 160 °F while in some cases (see, for example.

Fig. 5) the rupture curves appear to intersect.

These anomalies make it difficult to rank the eleven samples in

terms of their s tress- rup ture strengths. Nevertheless, such a ranking

would be very helpful in assessing the effects of the various processing

parameters. Accordingly, the 100-h rupture load was arbitrarily selected

as the characteristic which would be used for comparing the anticipated

weatherabilities of the samples. Values of the 100-h rupture loads were derived by interpolating -- and, in some cases, extrapolating -- the test

data. In so doing, considerable judgement had to be exercised regarding

the shapes of the rupture curves between data points. The derived values

are given in Table 8 and must be regarded as estimates at best; the table

is provided solely to enable the most general comparisons to be made

between the rupture strengths of different samples.

2.5 Analysis of Results

The effects of the nine variable process parameters, on the properties

of the rods, were calculated by applying the evaluation procedures (Table

3) to the average tensile breaking load values (Table 6) and to the average

estimated rupture load values (Table 8). The results of these evaluations

are given in Table 9.

It may be seen that four of the process parameters appear to be

beneficial to both the tensile strength and the rupture strength, namely,

collimation and ultrasonic agitation of the rovings , increased end count,

and post cure of the rod. Two of the process parameters are detrimental

to the strength properties, namely, increased immersion length and the

20
<

o

10-

8-

I

ai I 10 100

TIME TO RUPTURE, h

1000

Figure 4 - Stress-rupture properties of rod from Run 1 at 200 °F under

saturated humidity.

21
0.1 I 10 100 1000

TIME TO RUPTURE, h

Figure 5 - Stress-rupture properties of rod from Run 2 under saturated

humidity.

22
Table 8. - Estimated Stress-Rupture Loads, Runs 1-11

Run Tensile load to produce rupture in lOOh at

No. 160 °F 200 °F average

Ibf Ibf Ibf

1 10500 13000 11250

2 11700 10000 10850

3 9900 9500 9700

4 9000 9300 9150

5 12300 11500 11900

6 11900 11500 11700

7 11500 9800 10650

8 4000 3000 3500

9 10700 9000 9850

10 11600 11600 11600

11 12000 13000 12500

23
Table 9. - Effects of the Variable Process Parameters on Rod Properties, Runs 1-11

Incremental effect on

Parameter

tensile breaking

load

Ibf

100-h rupture

load

Ibf

Preheat + 100

Collimation +1300

Post cure + 500

Twist - 800

End count +1900

Tension -3400

Immersion length -1300

Ultrasonics + 500

Wetting agent - 800

- 400

+ 800

+1600

+1500

+2100

+2400

- 900

+1700

-2800

24
wetting agent additive. The detrimental effect of increased immersion

length is particularly puzzling; an explanation is not immediately

apparent. The effect of preheating the rovings was found to be relatively insignificant. The use of twisted rovings, and the application

of added tension in the rovings during pultrusion, were both found to be

beneficial to the rupture strength but detrimental to the tensile strength.

Data presented in Appendix C also indicate that the stress-rupture

strength under saturated humidity conditions is significantly greater at

room temperature than at 160 or 200 °F . This tends to support the use of

the elevated- temperature rupture tests as accelerated measures of longterm weatherability

No meaningful correlation was found between the tensile breaking

load values and the 100-h rupture load values. Similarly, there is no apparent correlation between either of these two quantities and any of

the product characteristics given in Table 5. On the other hand, there

does appear to be some correlation between transverse tensile strength

and breakdown voltage, as shown in Figure 6. The degree of correlation

is too poor, however, to be of much practical value.

Comparison of the tensile breaking loads (Table 6) with the results

of the high-speed tensile tests (Table 7) shows that the maximum loads are significantly greater at high loading rates than at normal testing

speeds. This suggests that special provisions need not be made for high

loading rates in the design of glass-reinf orced-plas tic antenna-support

systems and, also, that breaking strength data for glass-reinforcedplastic rod products are not entirely meaningful unless accompanied by

information regarding the speed of loading,

3. OPTIMIZATION OF THE MANUFACTURING PROCESS, PART II

3.1 Experimental Materials

The processing conditions for Run 12 were selected with the intention of optimizing the long-term weatherability of the rod. Using the

stress-rupture strength under conditions of elevated temperature and

saturated humidity as the laboratory index of long-tera weatherability.

Table 9 indicates, in principle, what . the processing conditions should

be. In practice, this optimum combination of the variable processing

parameters could not be employed with the available manufacturing facilities. Specifically, the special equipment required to introduce collimation is not readily compatible with the special equipment required to

introduce added tension in the rovings. Also, the collimating equipment

constrains the rovings to a path which is too far below the resin surface

in the dip trough to permit the ultrasonic horn to be used. In addition,

as described earlier, attempts to use ultrasonic agitation in combination

with added tension in the rovings introduces overheating problems, particularly when the s tandard- length dip trough is used. Accordingly, the

following values of the nine variable processing parameters were selected

25
60

>

Id

<

IO

>

o

o

<

a:CD

40

30

20

10

8

ORUNS l-M

+ RUNS 12,13

3X id

TRANSVERSE TENSILE STRENGTH, Ibf/ifi?

Figure 6 - Electrical breakdown voltage vs transverse tensile strength.

•

26
for Run 12. These represent a compromise between the ideal combination,

as indicated by the results given in Table 9, and the limitations of the

available manufacturing facilities.

Wetting agent:" no

The three constant processing parameters (resin viscosity, pulling speed

and die temperature) were unchanged from those used in Runs 1 through 11,

and the resin system formulation was the same as that used for those

earlier samples which did not employ the wetting agent.

The singular lack of success which was achieved with the wetting

agent in Runs 1 through 11 led to a decision to use Run 13 to evaluate

the benefits of adding a coupling agent, rather than a wetting agent, to

the resin system. The coupling agent selected for this purpose is a conmercially available, cationic methacrylate functional silane having

typical properties as shown in Table 10. The settings of the other

process parameters for Run 13 were the same as those listed above for

Run 12. The resin system formulations for the two runs are given in

Table 11 and the operating conditions are given in Table 12.

The samples from Runs 12 and 13 were subjected to the same types of

tests as had been used for Runs 1 through 11. The results of these tests

are given in Tables 13, 14, 15, and 16, and the relationship between

transverse tensile strength and electrical breakdown voltage is shown in

Figure 6,

Unfortunately, the rods were somewhat bowed as received from the

manufacturer, presumably because they had been inadequately supported

during the post-curing operation. This caused longitudinal splitting,

or delamination, to develop in the tensile tests (Table 14) prior to

total failure. It is felt that this splitting promoted the initiation

of premature failures in the end fittings. Nevertheless, the maximum

loads attained with the Run 12 specimens are not far removed from the

calculated breaking load for this run, which is 26100 Ibf.* Comparison

of the breaking loads for Run 13 with those for Run 12 shows that the

coupling agent additive in Run 13 was ineffective, at best, insofar as

the tensile breaking load is concerned.

* This calculation is straightforward. Starting, for example, with

the breaking load for Run 1 (Table 6), the breaking load for Run 12

is found by algebraically adding to this value the breaking load

increments for tension and post cure (Table 9).

Roving preheat: no Roving twist: yes

Roving end count: 60

Roving tension: yes

Immersion length: std

Ultrasonic agitation: no Collimation: no Post cure: yes

3.2 Test Results and Analysis

27
Table 10. - Typical Properties of Silane Coupling Agent

Percent solids: 50.

Solvents: Mostly diaceto:

Color: Amber brown.

Refractive index at 77 °F: 1.457.

Specific gravity at 77 °F: 1.06.

Viscosity at 77 °F: 0.74 poises.

Flash point, open cup: 130 °F.

Suitable diluents: Alcohols, wate

(a) According to the manufacturer.

Table 11. - Resin System Formulation, Runs 12 and 13

Run 12 Run 13

wt pet wt pet

Monostyrene 4.91 4.89

Peroxide catalyst 0.73 0.74

Die lubricant 0.92 0.93

Ultraviolet inhibitor 0.13 0.13

Coupling agent - 0.30

Isophthalic polyester resin Bal. Bal.

28
Table 12.- Operating Conditions for Manufacture of Runs 12 and 13

Ambient

relative

humidity

Run

No.

12

13

(a)

(b)

No. of

rovings

2A

24

See Table 4.

Ambient

Glass

content

wt pet

-75.4

75.6

percent

37-39

39-40

S-bend

spacing

in

(5 3)

(5,3)

Resin

temperatu

(b)

(b)

Table 13.- Average Product Characteristics, Runs 12 and 13

Rockwell Transverse

Run hardness tensile Breakdown

No

(Scale E) strength voltage

Ibf/in^ kV

12 67 1600 22

13 60 1400 15

29
Table 14.- Results of Tensile Tests, Runs 12 and 13

Run

No.

Specimen

No.

Average

d i ame t e r Average

densi ty

Average

we i ght

Maximum

load Notes

in Ib/in^ lb/ft Ibf

12 R12Pcl6 0.4983 0.0720 0.168 23750 a

12 R12Pcl7 .4967 .0721 .168 25750 b

12 R12Pcl8 .4990 .0715 .168 24250 a

12 R12Pc2A .4970 .0723 . 168 26750 a, c

12 R12Pc2B .4970 .0723 .168 24700 a, c

13 R13PC16 .4990 .0715 .168 23950 a

13 R13Pcl7 .4981 .0718 . 168 25000 a

13 R13Pcl8 .4972 .0721 .168 24400 a

13 ; Rl3Pc2B .4970 .0721 .168 25250 a, c

13 Rl3Pc2G .4970 .0721 .168 23 750 a, c

Notes:

a. Failed in end fitting following delamination.

b. Failed in free length following delamination,

c. Free length, 23 to 26 in.

30
Table 15. - Results of High-Speed Tensile Tests, Runs 12 and 13

Run Specimen Potting Average Average Average Maximum

No. No. compound diameter density weight load

in Ib/in^ lb/ft Ibf

12 Rl2Pc9A C1W2 0.4968 0.0721 0.168 32600

12 R12Pcl5A C1W2 .4984 .0718 .168 34500

13 R13Pc6A C1W2 .4966 .0728 .169 33000

31
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32
In the high-speed tensile tests (Table 15) the failures also appeared

to have initiated in the end fittings. However, just as with Runs 1 through 11, the breaking loads in the high-speed tests are significantly

greater than those achieved in the conventional tensile tests.

Some delamination due to bowing was also experienced in the stressrupture tests (Table 16) but the conclusion is nevertheless clear that

the coupling agent additive in Run 13 was detrimental to the stressrupture strength.

The average 100-h rupture load for Run 12, interpolated czid estimated

from the data in Table 16, is approximately 12300 Ibf. This is considerably

less than the calculated value (from Tables 8 and 9) of 15300 Ibf. It is,

however, approximately equal to the 100-h rupture load for Run 11 (12500 Ibf)

which was the highest of all. It may be that this is about the limit of

the improvement that can be attained in the rupture load through modification of the manufacturing process parameters.

4 . PLANS

The third and final year of effort on this program will be devoted

primarily to improvements in non-metallic antenna-support rods that can

be achieved through variation of the constituent materials. Experimental

rods with different resin and fiber materials will be manufactured and

tested

* * *

The authors gratefully acknowledge the valuable contributions of

Mr. Oscar 0. Owens and Mr. Raymond G. Russell of the Engineering Mechanics

Section, NBS, and of Dr. Fred A. Yeoman, Mr. John S, Hudock and Mrs. Donna

K. Nowakowski of the Westinghouse Electric Corporation.

33
5. REFERENCES

1. Marlowe, D, E., Halsey, N., Mitchell, R, A. and Mordfin,

L,, Non-Metallic Antenna- Support Materials, First Annual

Interim Report, NBSIR 73-233 (April 1973).

2. Lundberg, R. D., Koleske, J. V. and Walter, E. R., Dispersing Aids for Particulate Solids, Canadian Patent No. 866261

(Mar 16, 1971).

3. Chwirut, D. J. (Coordinator), Research and Testing Facilities of the Engineering Mechanics Section, National Bureau

^ of Standards, Washington, D. C, NBS Spec Publ 370 (1973).

4. Mitchell, R. A., WooUey, R. M. and Halsey, N.: High-Strength

End Fittings for FRP Rod and Rope, J. Engineering Mechanics

Div. ASCE 100, EM4, pp 687-706. (Aug 1974).

5. Halsey, N. , Mitchell, R. A. and Mordfin, L., Evaluation of

GRP Rod and Rope Materials and Associated End Fittings,

NBSIR 73-129 (Dec 1972).

34
APPENDIX A. CONVERSION FACTORS

Factors for converting U. S. customary units to the International

System of Units (SI) may be found in ASTM Standard Metric Practice Guide

(ASTM Designation E380-70) . Copies are available from the American

Society for Testing and Materials, 1916 Race Street, Philadelphia,

Pennsylvania 19103. Conversion factors for units used in this paper

are given in Table A.l.

The results of forty-one tensile tests on rod specimens from Runs

1 through 11 are given in Table B.l. Except as otherwise noted, each

specimen was fitted with H3M end fittings using cruciform wedges and

C2W3 potting compound [1,4], and had a free length between 52 and 62 in.

Also given in Table B.l is the average breaking load for each run. In

general, this was calculated by averaging the maximum loads that were attained with specimens that failed in their free lengths. However,

this procedure could not be applied to the results from Runs 3 and 7 because, in these cases, failures in the free lengths were not obtained.

Run 3 was one of the runs which utilized the wetting agent, which is a very effective low-profile additive, and this, together with a long

immersion time and ultrasonic agitation, produced a rod with an extremely

slick outer surface which could not be adequately gripped. Four tensile

tests resulted in four pullouts. The average breaking load of Run 3 is,

therefore, only estimated on the basis of the highest maximum load attained.

Two tensile tests on rod specimens from Run 7 resulted in failures

which apparently initiated in an end fitting. The shortage of material

from Run 7 precluded additional testing and the average tensile strength

of this run is also estimated on the basis of the limited data obtained.

In calculating the average tensile strength for Run 10, the results

of two tests, which had culminated in pullouts, were included in the

average since the maximum loads in these two tests exceeded that obtained

with one specimen which had failed in its free length.

The results of eighty- three rupture tests on rod specimens from

Runs 1 through 11 are given in Tables C.l and C.2. Each specimen was fitted with Type R/P commercial end fittings [5] using cruciform wedges

and C2W3 potting compound [1]. Except as otherwise noted, each specimen

failed in its free length within the temperature-humidity chamber.

In addition, one specimen from Run 10 was tested at room temperature

and saturated humidity under a load of 12000 Ibf. This test was discontinued after 2255 h without any indication of impending failure. The

data for this specimen are as follows:

APPENDIX B. TENSILE TEST RESULTS, RUNS 1-11

APPENDIX C. STRESS -RUPTURE TEST RESULTS, RUNS 1-11

Specimen No. Rl0Pc7A

Diameter, 0.4960 in.

Density, 0.0708 lb/in

Weight, 0.164 lb/ft.

35
Table A.I.- Conversion Factors

U. S. customary

Quantity unit SI unit Conversion factor

Force pound-force (Ibf) newton (N) 1 Ibf = 4.448 N

Length inch (in)

foot (ft)

centimeter (cm)

meter (m)

1

1

in = 2.54 cm

ft = 0.3048 m

Mass (weight) ounce (oz)

pound (lb)

pound (lb)

gram (g)

gram (g)

kilogram (kg)

1

1

1

oz = 28.35

g

lb = 453.6

g

lb = 0.4536 kg

Temperature degree Fahrenheit (°F)

degree Celsius

(°C)

°C = (5/9) (°F - 32)

Density Ib/in"^ 1 lh/±n^ = 27.68 g/cm

Speed in/min m/s 1

-4

in/min = 4.233x10

Stress Ibf/in^ N/m 1 Ibf/in^ = 6895 N/m^

Viscosity,

dynamic

poise (P) N •s/m 1

2 P = 0.1 N-s/m

Weight per

unit length

lb /ft kg/m 1 lb/ft = 1.488 kg/m

36
Table B.l. - Results of Tensile Tests, Runs 1-11

Run

No.

Specimen

No.

Average

diameter

Average

density

"ibTinJ

Average

weight

Maximum

load Notes

in lb/ft Ibf

RlPcSB

RlPc3B

RlPc6B

RlPcSA

Average

0.5021

.5016

-.5023

.5021

0.0687

.0688

.0686

.0687

0.163

.163

.163

.163

29450

29000

28600

25300

29000

..aa

aa,b

2 R2Pc5B .5023 .0688 .164 28700 a

2 R2Pc7B .5008 .0691 .163 20550 c

2 R2PclA .5017 .0689 .163 26550 d

2 R2PclB .5017 .0689 .163 29450 a

2 R2Pc4B .5065 .0676 .163 7150 c , e

2 Average 29100

3 R3PclA .4954 .0696 .161 24650 C

3 R3Pc2A .4959 .0694 .161 11850 c

3 R3Pc2A .4959 .0694 .161 25250 c(_ , fJ. 3 R3Pc4A .4960 .0694 .161 27050 c 3 Average 27100 g

4 R4Pc3B .4956 .0709 .164 22950 a

4 R4Pc4A 4957 0708 1 64 9^ Don CL 4 R4Pc8A .4954 .0710 .164 20000 d

4 R4Pc8B .4954 .0710 .164 10300 c 4 R4Pc8C .4954 .0710 .164 23550 a

4 Average 22500

5 R5APc4A .4950 .0732 .169 23150 a

5 R5APc1B .4960 .0729 .169 22800 a

5 R5APclA .4960 .0729 .169 18500 d

5 Average 23000

6 R6Pc2B .4960 .0714 .166 20700 a

6 R6Pc2A .4960 .0714 .166 25450 a

6 R6Pc2C .4960 .0714 .166 28000 a

6 Average 24700

7 R7PclA .4946 .0712 .164 25750 d

7 R7PclB .4946 .0712 .164 26150 d

7 Average 26200 g

8 RSPclA .4957 .0697 .161 25400 a

8 R8Pc2A .4953 .0698 .161 26750 a

8 R8Pc3A .4957 .0697 .161 25700 a

8 Average 25900

37

Continued
Table B.l. - (continued)

Run

No.

Specimen

No.

Average

diameter

Average

density

Average Maxi mum

1 OrlH in lb/in3 XL; 1 h //fJ_ ^L XD L

9 R9PclA 0.4949 0.699 0.161 27800 a

Q 1 fii . xox ZOX 9R1 "^0 JU a

Q RQP<- T

is.yr c jfi • JX .xox ZOO 9 A A JU^O u

Q rive: L d^fc: zouuu 98000

RIvX1 OPr VJF L. Xri 1 A H 7 U -L 0708 . X O H "^0700 JU / uu n

R 1 nP(- 9 A • H 7 U -J 0707 C

10 RlOPc3A .4956 .0709 .164 31400 a 10 RlOPcAA .4968 .0706 .164 28400 a^l

xu KXUr CoA . H 7DD . 0707 U / U / . XDh 1 AA TjX/1 9 jU"^O n,x

xu R 1 HP r> 7 A . ^^OU . 070R U / Uo . XDh 1 <^ A ZD9<^ XUU 1 OO a } D xu rive: I cl^c jUHUU "^OAOO

11 RllPc5 .5001 .0696 .164 28000 c 11 RllPclA .5008 .0699 .165 28150 a 11 RllPc7B .5008 .0699 .165 30950 a 11 Average 29600

Notes

a. Failed in the free length.

b. Exposed to stress-rupture conditions prior to tensile test. (See Appendi

C.) Free length, 62 or 63 in. Result not included in the average.

c. Pulled out of end fitting. Result not included in the average.

d. Failure appeared to have initiated in an end fitting. Result not included

the average

e. End fittings potted with C1W2 compound. Free length, 47 in.

f. Same specimen as above, retested with Mod 4 end fittings.

g. Estimated •

h. Pulled out of end fitting. Result included in the average.

i. Free length, 48 to 51 in.

38
Table C .1. - Results of Stress-Rupture Tests at 200 °F, Runs 1-11

Run Specimen Average Average Average Time to

No. No. diameter density weight Load rupture Not

in Ib/in ib/ r t Ibr n

1 RlPc6C 0.5023 0.0686 0.163 14000 0.5

11 RlFc4A . 5U10 .Od92 . ±54 1 A AAA i4U00 O A 3.9

1 RlPclOA 1 0 A A A 13000 114 .

a

1 RlPc3A . 5016 . 06oo 1 £.1

. lb J

1 O AAA 12000 CCA 550

1

n 1 Ti — O A RlPcoA . 5021 O "7 .06B/ . lb J 10000 b

2 R2Pc5C .5023 .0688 .164 14000 22.2

2 R2PclOA .5007 . 06oo . 163 13000 47.6

2 R2Pc4A . 5065 A ^1 "7 ^. 06 /6 . lb 3 12000 37 .

2 R2PclOB .5007 .0688 .163 11000 76.9

2 R2Pc6B .5013 .0705 .167 10000 92.8

3 R3PclB .4954 .0696 .161 11000 2.6

3 R3Pc4B . 4960 .0694 .161 10000 16.5 c 3 KJr C/B . 4959 . 0694 . Ibl 1 AAAA 10000 OA ^

/, KAr c /A .4953 A'7An . u/uy . ib4 1 1 AAA A O 0. 3 D /. D « "7 "D K4r c / D . u /uy . ±d4 1 AAAA o. 3

5 R5APc8 .4982 .0725 .170 12000 27.9

cJ K_)Ar COA . 4y /U A 7 0 ^

. U /ZD . iby IIUUU O 1 A

c

c3 RjAPcoA /OTA .49/0 A "7 O ^ .0/26 . Ib9 llOOU 424

d

rJ RjAPcoB /. n "7 r\

. 49/0 A *7 O ^ .0/26 . Ib9 T T AAA 11000 172 .

5 R5APc3A .4973 .0725 .169 10000 180.4

O RoPcoB . 4962 .U/11 . 1d3 n OAAA 13000 4 .

c.0 RoPc9 . 4966 . 0710 . 165 12000 C" "7 / 57.4 e

6 R6Pc5A .4961 .0712 .165 11000 114.4 f

6 R6PclA .4957 .0712 .165 10000 169.6

7 R7Pcl .4945 .0714 .164 12000 0.8

7 R7Pc3A .4950 .0711 .164 11000 73.0 f

"7/ K/PcZA . 4950 A *7 1 1

. 0711 . 164 1 AAAA 10000 66 .

QO KoPC jB . 4y J / A^ n T

. Oo9 / . 161 1 1 AA A 11000 A AO 0. 08

8 R8PclB .4957 .0697 .161 10000 0.2

9 R9Pc1B .4949 .0699 .161 13000 0.05

9 R9Pc2B .4958 .0695 .161 12000 2.2

9 R9Pc9B .4958 .0696 .161 11000 26.5

Continued

39
Table C.l. - Results of Stress-Rupture Tests at 200 °F, Runs 1-11

(Continued)

Run Specimen Average Average Average Time to

No. No. diameter density weight Load rupture Notes

in lb /in lb/ft Ibf h

9 R9Pc3B 0 . 4951 0.0697 0.161 10000 13.3

9 R9Pcl0A " — 10000 20.0 a

10 R10Pc3B . 4956 .0709 .164 13000 2.0

10 R10Pc2B . 4965 .0707 .164 12000 28.4

10 R10Pc4B . 4968 .0706 .164 11000 450. h

11 RllPcl3A .5010 .0692 .164 14000 0.3

11 RllPc4A .4998 .0694 .163 13000 168.

11 RllPcllA .5017 .0688 .163 12000 25.6 e 11 RllPcl9A .5009 .0690 .163 11000 0.00 c 11 RllPc20A .5012 .0690 .163 11000 214.5

11 RllPc9A .5015 .0687 .163 11000 293.3 e 11 RllPcl5 .5023 .0687 .163 10000 67.7

11 RllPc3 .5004 .0692 .163 10000 123.4 i

Notes

a. Diameter, weight and density not measured.

b. Test discontinued after lOOOh without failure.

c. Specimen pulled out of end fitting.

d. Same as specimen above. Ends repotted. Sustained 402. 8h additional

before failure.

e. Failure initiated at or in end fitting.

f. Test interrupted by 3-day power outage during which load was maintained but temperature and humidity decreased to ambient.

This intei^al not included in time to rupture.

g. +7.5h; timer failed to function properly.

h. +25h; timer failed to function properly.

i. +12. 2h; timer failed to function properly.

40
Table C.2. - Results of Stress-Rupture Tests at 160 °F, Runs 1-11

Run Specimen Average Average Average Time to

No. No. diameter density weight Load rupture Not

in Ib/in^ lb/ft Ibf h

1 RlPclA

-

0.5001 0.0694 0.164 13000 0.6

1 RlPc2B .5002 .0694 . 164 12000 5.1

1 RlPc2A .5002 .0694 . 164 11000 148.1

1 RlPclB .5001 .0694 . 164 10000 83.4

1 RlPc4B .5010 .0692 . 164 10000 229.2

1 RlPc7A .5013 .0691 .164 10000 270.7 a

2 R2Pc8 . 5010 .0691 . 163 13000 0.2

2 R2Pc2 .5001 .0692 .163 13000 0.8

2 R2Pc6A .5013 .0705 .167 12000 49,4

2 R2Pc3A .5008 .0701 .166 11000 362.

2 R2Pc3B .5008 .0701 .166 10000 480.

3 R3Pc9A .4954 .0697 . 161 10000 0.7

3 R3Pc3A 10000 4.6 b

4 R4?c9 .4959 .0709 .164 10000 2.3

5 R5APc5 .4977 .0724 . 169 13000 3.3

5 R5APc8B . 4982 .0725 . 170 12000 167. c

5 R5APc2A .4977 .0697 .163 11000 780. d

5 R5APc3B .4973 .0725 .169 10000 444.

6 R6Pc8A .4962 .0711 • 165 13000 6.2

6 R6Pc6B .4951 .0714 .165 12000 80.8

6 R6Pc5B .4961 .0712 .165 11000 540.

6 R6PclB .4957 .0712 .165 10000 599

7 R7Pc4 .4954 .0710 .164 12000 2.0 e

7 R7Pc3B .4950 .0711 .164 11000 114.4 f

7 R7Pc2B .4950 .0711 .164 10000 418.

8 R8Pc2B .4953 .0698 .161 10000 0.5

9 R9Pc8B .4851 .0698 .161 11000 0.07

9 R9Pc8A .4951 .0698 .161 11000 0.5

9 R9PclOB 10000 847. b

Continued

41
Table C.2. - Results of Stress-Rupture Tests at 160 "F, Runs 1-11

(Continued)

Run Specimen Average Average Average Time to

No. No. diameter density weight Load rupture Note:

- - in Ib/in^ lb/ft Ibf h

10 RlOPcS 0.4966 0.0707 0. 164 12000 2.0

10 R10Pc6A .4960 .0708 . 164 12000 46.7 g

10 RlOPc5A .4967 .0706 .164 11000 241.5

10 R10Pc5B .4967 .0706 .164 10000 411.

11 RllPcSA .5008 .0691 .163 13000 22.9

11 RllPcl7 .5009 .0690 .163 12000 94.7

11 RllPclS .5008 .0696 .165 11000 145.5

11 RllPcl2 . 5007 . 0693 . 164 10000 509

f

11 RllPc6 .5019 .0688 .163 10000 600. f

Notes

a. +9 . 5h; timer failed to function properly.

b. Diameter, weight and density not measured.

c. +7.5h; timer failed to function properly.

d. Test interrupted by 3-day power outage during which load was maintained

but temperature and humidity decreased to ambient. This interval

not included in time to rupture.

e. Failure initiated at surface blemish on specimen.

f. Failure initiated at or in end fitting.

g. Specimen pulled out of end fitting.

42
NBS-114A (REV 7-731

U'^- Ut"'- \J v_ W " BIBLIOGRAPHIC DATA

SHEET

I. I'l HLK .\ 1 Iv)i\ KH\ Ki t ' )K 1 NBSIR 74-557

2. Ciov 't Acccssuin

No.

3. Recipient's Aiccssion No.

4. Ti l l-l- AM) SI H 11 I

NON-METALLIC ANTENNA-SUPPORT MATERIALS

Second Annual Interim Report

5. Publication Date June 1974

nW* 1 f*Cllv'linillK r i i\r m tnn \\J\ir ^tAIII/lal n 'i r\ t t a t 1(111 1 1 1 r\ \^ i tii f

713.04

7. Al'TllOR(Si

Nivon H;il.t;py, non^ld K. Marlnwp and Lpnn;ird Mordfin._ _

8. Performing Organ. Report No. NBSIR 74-557

9. PLRKORMIN'C.'ORGAMZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Projcct/Task/Work Unit No. 9130441

11. Contract/Grant No.

D.O. F33615-72-M-5000

12* Sponsoring Org jnization N^mc and Complete Add res s (Street, City , Stste , IP

Air Force Materials Laboratory

Wright-Patterson Air Force Base, Ohio 45433

13. Type of Report & Period Covered Interim

lO/lfi/7? - in/Ti/73

14. oponsoring Agency Code

AFML (MXE)

15. SUPPLEMENTARY NOTES

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

bibliography or literature survey, mention it here.)

Thirteen samples of a pultruded, glass f iber-reinforced-polyester rod material were

manufactured using a different combination of the manufacturing process parameters for

each. These samples were tested to evaluate the effects of nine different process

parameters on the properties and characteristics of the rods. Elevated-temperature

stress-rupture tests under saturated humidity were used as an accelerated measure of

long-term weatherability. The test results were somewhat inconsistent, but it appears

that certain process parameters, such as collimation and ultrasonic agitation of the

rovings during pultrusion, were beneficial to both tensile strength and weatherability.

Other parameters, such as pretensioning of the rovings, were beneficial to weatherability but detrimental to tensile strength. Additives to the resin system were

generally detrimental.

A high speed tension test method was developed and it was found that the strength

of the rod is substantially greater under high loading rates.

An approximate relationship was observed between transverse tensile strength and

electrical breakdown voltage. However, neither of these characteristics, nor surface

hardness, correlated with axial tensile strength or weatherability.

17. KEY UORDS (six to five/ve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons

Composite materials; f iber-reinforced-plastic rod; glass-reinforced-polyester rod; guys,

antenna; processing parameters, pultrusion; pultrusion; reinforced plastic rod; stress

rupture of FRP rod; test methods, FRP rod; weatherability, FRF rod.

18. AVAILABILITY

^

Unlimited

[ l"or Official Distribution. Do Not Release to NTIS

_ Order From Sup. of Doc, U.S. Government Printini; Office Washington, D.C. 20-102, SD C.k. No. (1 ^

[ Order I"rorn N.uional Icchnical Inform.uion Service (NTIS)

"^prin^.-ticlil, Viru-inia 22l'^l

19. SECURITY CLASS

(THIS REPORT)

UNCL ASSIFIED

20. SE( URITY CLASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF PAGES

61

22. Price

USCOMM-DC 29042-P74