HOKIESAT COMPOSITE PANEL COUPON SHEAR TEST PLAN
AA22901-DOC008-1
Written by: Ann Bergquist
Test performed by: Ann Bergquist, Craig Stevens
Date: 7 August, 2001
Table of Contents
1.0 Introduction
1.1 Scope
1.2 Component description
2.0 Testing equipment
2.1 Test facility
2.2 Test components
3.0 Safety
3.1 Machine safety
4.0 Quality assurance
5.0 Procedure
5.1 Test preparation
5.2 Test setup
5.3 Test sequence
6.0 Appendix of figures
6.1 Figure 1
6.2 Figure 2
6.3 Figure 3
6.4 Figure 4
1.0
Introduction
1.1
Scope
The shear test is performed to determine the apparent shear strength of the 2216
epoxy bond used on the six HokieSat composite panels. Twenty coupons
prepared according to ASTM Standard D 1002-94 during composite panel
fabrication are tested. The test also ensures that the quality of the epoxy bond
application, including surface preparation, bond thickness and cure time, is
adequate. Each of the twenty coupons are clamped on both ends and pulled apart
until fracture. The load at which fracture occurs is recorded to determine the
shear strength of each bond. It should be noted that environmental changes under
which the panels will be subjected, including thermal vacuum testing, may induce
internal stresses that effect the strength of the adhesive. This test is meant only as
a guideline.
1.2
Component description
1.2.1
Test specimens are made according to the ASTM Standard D
1002-94. The specimens are made out of aluminum plates 6 x 6
(+/- 0.125) inches 1/8” thick. Pairs of specimens are bonded
together with ½” (+/- 0.010”) overlap. Each bonded pair
corresponds to one or two composite side panels and is bonded
using the same 2216 gray epoxy mix and at the same time as its
corresponding composite panel.
1.2.2
Test coupons are prepared according to the ASTM Standard D
1002-94. Each bonded pair is cut into 6 1” (+/- 0.0625”) wide
individual test coupons. The end strips are marked during testing
and eventually discarded.
2.0
Testing equipment
2.1
Test facility
2.1.1
This test is performed in the Materials Testing Laboratory, room
127 Norris Hall. The supervisor in this lab is Robert Simonds.
2.2
Test components
2.2.1
Loading Apparatus – to load the structure, and Instron 4468
Universal Testing Machine, as shown in Figure 3, is used. This
machine has a horizontal bar that is accurately traversed up and
down under digital control by means of two large jackscrews. The
machine has one clamp mounted on its base and one clamp
mounted on the traverse bar to hold the two ends of each coupon.
This machine uses a 10 kip load cell.
2.2.2
Data Collection Software – Lab View data plotter is used for data
collection in all six tests. The software outputs the load at which
fracture occurs.
3.0
Safety
3.1
Machine safety
Keep hands away from the testing machine while the test is in progress to
avoid harm. The people performing the test should stand a safe distance
away from the coupons while they are being sheared to avoid being hit by
aluminum shards as the coupon breaks. Protective glasses should be worn
during all tests.
4.0
Quality assurance
All specimens are prepared according to the ASTM Standard D 1002-94. Flight
hardware is not used in this test.
5.0
Procedure
The shear test is performed by clamping each coupon and applying a tensile force
coinciding with its minor axis. The computer records loads and displacements for
the duration of each test.
5.1
Test preparation
5.1.1
Cut the 6” plates into 1” coupons………………………..____
5.1.2
Ensure that the proper clamps are mounted to the testing
machine…………………………………………………..____
5.2
Test setup
5.2.1
Loading apparatus setup
5.2.1.1
Attach the ends of the coupon to the clamps on the
testing machine so that the outer 1” of each end are in
contact with the jaws…………………………____
5.2.2
Computer setup
5.2.2.1
Bring up the Lab View software on the
screen…………………………………………____
5.2.2.2
Set the plotter program so that it is ready to take
data…………………………………………..____
5.3
Test sequence
5.3.1
Press the up arrow on the testing machine to begin the loading
process (load should be applied at the rate of 80 to 100 kg/cm2 of
the shear area per minute, a traverse speed of 1.3 mm (0.05in) per
minute……………………………………………………____
5.3.2
Press the stop button on the test machine when the coupon
fractures……………………………………………….…____
5.3.3
Save the data recorded by the Lab View software to a network
file………………………………………………………..____
6.0
Appendix of figures
Figure 1: Front view of test coupon
Figure 2: Side view of test coupon showing overlap bond close-up
Figure 3: Instron 4468 Universal Testing Machine with coupon ready for test
Figure 4: Coupon in tension