• Version
• 131 Downloads
• 1.95 MB File Size
• 1 File Count
• December 2, 2016 Create Date
• December 2, 2016 Last Updated

National Advisory Committee for Aeronautics, Technical Notes - Impact Strength and Flexural Properties of Laminated Plastics at High and Low Temperatures

The Izod-impact strengths and flexural properties of sev—
eral types of plastic laminates, which are either in use or
have potential application in aircraft structures and part3,
were determined at different temperatures in the range of
~70° to 200°.F.

The materials investigated were unsaturated-polyester
laminates reinforced with glass fabric and phenolic laminates
reinforced with asbestos fabric. high—strength paper, rayon
fabric, and cotton fabric. Both high—pressure and low—pressure
types of cotton-fabric phenolic laminates_were_included.

The impact strength of specimens tested flatwise at 77° F
was 4 to 7 foot—pounds per inch of notch for all at; laminates
except the glass fabric and rayon fabric laminates. These two
materials had impact strengths of Bl and 17 foot—pounds,
respectively, at 77° F. The high— strength-paper, rayon— —fabric,
and asbestos~ fabric phenolic laminates showed small changes in
impact strength between -70° and 200° F. Cottonnfabric pheno—
lic laminates showed pronounced decreases in impact s_trength
at the low temperature and small changes between 776 and 200°
F. The glass- -fabric unsaturated-polyester laminates had in—
creased impact strengths at the low temperature.

The flexural strengths and moduli of elasticity of all
the materials increased with change in the test temperature
from 77° to ~70° F. Under exposure to a 200° F temperature,
all materials except the asbestos-fabric laminate lost 30 to
40 percent of their flexural strength at 77° F and the moduli
of elasticity of all the materials, except the asbestos—fabric
and one cotton-cloth phenolic laminate, decreased about 20
percent.

Tests made at room temperature after heating the materi-
als at 2000 F for 24 hours indicate that prolonged heating
with consequent loss of moisture content and further cure of
the resin may offset the effect of high temperature alone. In
flexural tests made at 150° F and 90 percent relative humidity
tw0 laminates showed considerable loss in strength.