NBSIR 76-1079

Tensile Tests of Pultruded

Round Rods

Nixon Halsey and Leonard Mordfin

Engineering Mechanics Section

Mechanics Division

Institute for Basic Standards

National Bureau of Standards

Washington, D. C. 20234

April 1976

Final

Prepared for

American Society for Testing and Materials

Section D20. 18.02 on Reinforced Plastics Pultruded Shapes

NBSIR 76-1079

TENSILE TESTS OF PULTRUDED

ROUND RODS

Nixon Halsey and Leonard Mordfin

Engineering Mechanics Section

Mechanics Division

Institute for Basic Standards

National Bureau of Standards

Washington, D. C. 20234

April 1976

Prepared for

American Society for Testing and Materials

Section D20. 18.02 on Reinforced Plastics Pultruded Shapes

U.S. DEPARTMENT OF COMMERCE. Elliot L. Richardson, Secretary

Dr. Batty Ancfcer~Johneon. Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Acting Director

Final

TABLE OF CONTENTS

INTRODUCTION

SPECIMENS

TEST METHOD

3.1 End Fittings

3.2 Testing Procedure

TEST RESULTS

DISCUSSION

TENSILE TESTS OF PULTRUDED ROUND RODS

Nixon Halsey and Leonard Mordfin

ABSTRACT

The Engineering Mechanics Section of the National

Bureau of Standards (NBS) conducted sixty-seven tensile

tests on pultruded round rods as part of an ASTM interlaboratory testing program which was established to

assess and to compare various test methods which are

currently used by different testing organizations. The

test methods used by NBS are described and the test

results are given.

Key Words: Interlaboratory tests; plastics, glass fiberreinforced; pultrusions; reinforced plastics; round-robin

tests; tensile strength; tensile tests; test methods,

tensile; standards, voluntary.

1 . INTRODUCTION

As a necessary step toward the promulgation of voluntary product

specifications for pultrusions, ASTM Section D20. 18.02 on Reinforced

Plastics Pultruded Shapes has been pursuing the development of a standard tensile test method for round rod. A preliminary survey has revealed that there are almost as many different methods in use as there

are laboratories which conduct such tests. Therefore, in order to provide data which could be used to evaluate and compare these different

methods, an interlaboratory testing program was established.

The principal part of the program involved the voluntary participation of seven pultrusion manufacturers and nine testing organizations.

With few exceptions, each pultruder submitted samples of glass fiberreinforced-polyester rod in two preselected diameters, and each testing

organization conducted tensile tests on specimens of both diameters from

each manufacturer. Each testing organization was required to conduct

the tests using its own preferred method, to describe the method, and

to furnish the results of its tensile strength measurements.

By virtue of its unbiased position as neither a manufacturer nor

a large user of pultrusions, and its experience in test methods of this

kind, the Engineering Mechanics Section of NBS was invited to coordinate

the collection and distribution of the sample materials in order to maintain the anonymity of the pultruders, and also to participate in the program as one of the testing organizations.

This report presents a description of the methods used and the test

results obtained by the Engineering Mechanics Section.
2. SPECIMENS

Specimens were furnished in two nominal diameters, 1/2 in and

1/8 in (13 mm and 3 mm), each 36 in (0.91 m) long. Each specimen was

color coded on one end, a single color being used to designate all of

the specimens from each pultruder.

3. TEST METHOD

3.1 End Fittings

The NBS H3M experimental end fitting, Figure 1, was used for all

of the 1/2- in (13-mm) diameter specimens. In order to mount this fitting on a rod, the inside surface of the fitting was first coated with

an epoxy-release agent. The rod was then passed through the fitting

and a cruciform wedge, Figure 2, was driven into the end of the rod,

concentrically, dividing the end into four quarters and wedging the

quarters apart. The periphery of the rod, where it emerged from the

fitting, was then built up with tape to provide a seal. The cavity in

the fitting was then filled with the potting compound, which was subsequently cured for approximately two hours at 163 °F (74 °C) using

infrared lamps

The potting compound used for all of the specimens consisted of

two parts of epoxy resin adhesive C-4 and three parts of activator W,

both available from Armstrong Products Company, Warsaw, Indiana.*

In contrast to the situation with 1/2-in (13-mm) diameter rods,

the Engineering Mechanics Section has relatively little experience in

the testing of 1/8- in (3-mm) diameter rods. H3M end fittings were not

available for rods of this size. Several potting heads for synthetic

rope (No. 9901, Reliable Electric Company, Franklin Park, Illinois) were

on hand, however, and these were used as much as possible. The procedure

for mounting these on the rod specimens was essentially the same as that des

cribed above for the H3M end fittings, except that cruciform wedges were

not used. Instead, the end of the rod was quartered with a saw and the

quarters were wedged apart by threading a wood screw into the rod end.

*Certain commercial equipment and materials are identified in this

report in order to adequately specify the experimental procedure. In

no case does such identification imply recommendation or endorsement by

the National Bureau of Standards, nor does it imply that the material

or equipment is necessarily the best available for the purpose.

2
Unfortunately, the quantity of these potting heads which was available for this work was inadequate, and a simple shear- type end fitting

was devised for use in most of the tests on 1/8- in (3-mm) diameter rod.

This consisted of a 12-in (300-mm) length of steel pipe having an inside

diameter of 5/8 in (16 mm) and a wall thickness of 0.10 in (2.5 mm). The

end of the pipe was sealed with a plastic plug, the rod was inserted concentrically, and the cavity was filled with the potting compound which

was then cured.

3.2 Testing Procedure

The 1/2-in (13-mm) diameter specimens were tested in a 400 000-lbf

(1.8-MN) capacity screw-powered testing machine using the 80 000 lbf

(360-kN) loading range. The H3M end fittings were gripped in the machine's

wedge-type jaws and the specimens were loaded to failure, in tension, at a controlled crosshead speed of 0.2 in/min (0.08 mm/s).

The jaws in this machine could not properly accommodate the end fittings on the 1/8-in (3-mm) diameter specimens, so these specimens were

tested in a 60 000-lbf (270-kN) capacity hydraulic-powered testing machine

using the 2400-lbf (11-kN) loading range. The pipe fittings were gripped

in the machine's wedge- type jaws while the Reliable fittings were gripped

through a thimble-and-eye attachment which provided a reasonably good measure of self-alinement. This testing machine is not equipped for controlled

crosshead speeds so these specimens were loaded to failure at a constant

loading rate of 1500 lbf /min (110 N/s)

4. TEST RESULTS

For each test the maximum load was recorded, and the apparent manner

in which failure initiated was observed. The test results are given in

Table 1, in which the failure modes are classified into three categories:

(a) failures which appeared to have initiated in, or adjacent to, an end

fitting; (b) failures which appeared to have initiated in the free lengths

of the specimens, i.e., at a location apart from the fittings; and (c)

failures which resulted from the specimens pulling out of the end fittings.

5. DISCUSSION

The test results presented herein will be used, together with the

results obtained by the other participating testing organizations, to assess and compare the different test methods. Presumably, statistical

analyses will be employed. In doing so it must be borne in mind that the

numerical results by themselves can be misleading; the meaning of each numerical

value should be considered in the context of the failure mode with which it is

associated.

3
The failure modes obtained in the tests were classified into three

categories, each of which has a different significance. When a tensile

failure initiates in the free length of a specimen, i.e., at a location

removed from the end fittings, the measured strength is by definition

the strength of the rod tested. If the failure initiates in or adjacent

to an end fitting, the measured strength value may or may not be close

to the strength of the rod. Without further data it is impossible to

tell whether or not the strength reductions imposed by the fitting were

severe. If the rod simply pulls out of an end fitting, without exhibiting significant damage elsewhere, it is probable that the strength of

the rod was not approached. Several examples using the data in Table 1

will serve to illustrate these remarks.

Example 1 . All of the 1/2-in (13-mm) black-coded rods failed in

or adjacent to an end fitting. As such, it is impossible to determine

whether or not the strengths of the rods were approached. In the tests

of the 1/2-in (13-mm) orange-coded rods, on the other hand, three specimens

failed in or near a fitting while two failed in their free lengths. Yet,

all of the measured strength values were close to one another. In this

case, therefore, it is apparent that the strengths of the rods were, indeed, approached even in those tests which culminated in an end-fitting

failure.

Example 2 . Five 1/8-in (3-mm) black-coded rods were tested with

the shear-type fittings and one with the Reliable end fittings. The

measured strength values for the five specimens tested with pipe fittings were close to one another, despite the fact that three of these

failed in their free lengths while two failed in or near one of the

fittings. It is clear, therefore, that the strength of the rod was

closely approached even in those tests in which end-fitting failures

were obtained. The sixth specimen failed in one of its Reliable fittings at a somewhat lower load than the others. By itself, there would

be no way of knowing whether or not the strength of the material was approached in this test. However, by comparison with the results of the

other five tests it becomes apparent that the strength of the rod was

not approached in the sixth test and that the pipe fitting was more effective than the Reliable fitting for this material in this application.

Example 3 . Five tests of 1/8-in (3-mm) blue-coded rods were performed with pipe fittings and one with Reliable fittings. The five tests

with pipe fittings all culminated in pullout failures. The sixth specimen failed in one of its Reliable fittings at a substantially higher load.

It is clear that the strength of the rod was not approached with the pipe

fittings and that the Reliable fitting was more suitable for this material

in this application. However, there is no way of knowing if the strength

of the rod was approached even with the Reliable fittings.

4
Example 4 . Five tests of 1/8-in (3-mm) green-coded rods were performed with pipe fittings and four with Reliable fittings. All of the

tests with pipe fittings culminated in pullout failures. Two of the

specimens tested with Reliable fittings failed in their free lengths and

two in or near one of the fittings. The measured strength values in the

latter four tests were generally greater than those obtained with the

pipe fittings and were all reasonably close to one another. In this case

it is not only clear that the Reliable fitting was preferable to the pipe

for this material , but also that the strength of the rod was approached

even when the specimens failed in or near one of their Reliable fittings.

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All dimensions in inches (1 in = 25.4 mm)
NBS-114A (REV. 7-73)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

NBSIR 76-1079

2. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

TENSILE TESTS OF PULTRUDED ROUND RODS

5. Publication Date

a r 1 1 Ci 1 C April iy/o

6. Performing Organization Code

7. AUTHOR(S)

Nixon Halsey and Leonard Mordfin

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 2130141

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Same as Item 9

13. Type of Report & Period

Covered

Final, 12/75-3/76

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

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

bibliography or literature survey, mention it here.)

The Engineering Mechanics Section of the National Bureau of Standards (NBS)

conducted sixty-seven tensile tests on pultruded round rods as part of an ASTM

interlaboratory testing program which was established to assess and to compare

various test methods which are currently used by different testing organizations.

The test methods used by NBS are described and the test results are given.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Interlaboratory tests; plastics, glass fiber-reinforced; pultrusions; reinforced

plastics; round-robin tests; tensile strength; tensile tests; test methods,

tensile; standards, voluntary.

18. AVAILABILITY [ ] Unlimited

fy] For Official Distribution. Do Not Release to NTIS

1 1 Order From Sup. of Doc, U.S. Government Printing Office

Washington, D.C. 20402. SD Cat. No. CI 3

1 ! Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS

(THIS REPORT)

UNCL ASSIFIED

21. NO. OF PAGES

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

22. Price

USCOMM-DC 29042-P74

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