|
Six different designs
of polystrene shims were submitted for an evaluation of compressive properties.
The tests were conducted in accordance with ASTM D 695. Flat rectangular
samples were prepared from sections of molded parts where the surface
exhibited the greatest degree of regularity and therefore afforded good
overall contact with the compression platens over the entire part.
Stress levels of 25-40% were used to ensure that the material went through
the yeild point. This is clearly identified in the graphs as the inflection
point between the proportional region and the area of decreased slope.
The program identifies the stress at strain levels of 5% and 10%. The
yield and endpoint can be identifed visually with the cursor and are included
in the summary of average values given below.
Summary
of Compressive Test Results
|
Sample
|
Stress
@5%
(psi)
|
Stress
@
10% (psi)
|
Yield
Stress
(psi)
|
Strain
@ End
(20%) (psi)
|
Modulus
(psi)
|
|
Small
Black
|
4428
|
5529
|
4127
|
7079
|
88,680
|
|
Large
Black
|
6448
|
7777
|
6358
|
8804
|
148,760
|
|
Small
Blue
|
5954
|
9528
|
7487
|
11201
|
148,970
|
|
Large
Blue
|
6296
|
8865
|
7386
|
10780
|
163,430
|
|
Small
Red
|
7549
|
9088
|
7444
|
10720
|
176,440
|
|
Large
Red
|
7118
|
10017
|
8246
|
12089
|
197,920
|
No obvious pattern
of properties as a function of color, wall thickness, or foaming agent
could be determined from this data. However, it is apparent that all of
the products have yield stresses well in excess of 2000 psi.
|
