Page 8 - Automotive Aerospace

Designing for Safety

An understanding of the material fatigue properties under a variety of materials in order to replace them before fracture occurs.
environments and situations provides important indicators at the Therefore, understanding the fatigue properties of materials is
design stage. Predicting the fatigue life of materials allows the important to ensure a long aircraft life, maintain passenger safety, and
establishment of maintenance plans for periodic replacement of parts guarantee reliable flying.
subjected to stress and for regular inspections to detect fine cracks in

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Fatigue Strength Testing of Composite Materials
ASTM D 3479/D 3479M-96
Constant-Load Amplitude Tension-Tension Fatigue Testing of CFRP
This jig can be used for the constant-load amplitude tension-tension fatigue testing in the direction of
the fibers in CFRP unidirectional reinforced materials or textile-reinforced materials stacked in layers.
Front-opening hydraulic grips offer superior ease-of-operation and high accuracy for tensile and
compression testing across a wide test-force range.

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Front-opening hydraulic grips
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Fatigue Strength Evaluation of GFRP
For aircraft materials such as composites that have been in use for many years, great weight is placed
on impact resistance and fatigue strength according to the environment in which they were used.
As an example, we performed fatigue testing on GFRP and then plotted the resulting S-N curve to show
the relationship between the maximum load stress among the six stress standards (one sample per
standard) and the number of cycles to sample fracture. Internal observations reveal that glass fibers
inside the sample that had no particular orientation before fatigue testing began to align somewhat in
the direction of loading after one million load cycles, and were uniformly aligned vertically just before
fracture.

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Grips
Sample Held in Manual Grips for Flat Samples
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S-N Curve for GFRP
Repeated maximum stress (MPa) Direction
Direction of loading
of loading
Start of fatigue testing After one million load cycles Before fracture
Number of cycles to fracture
Internal X-Ray Images of GFRP
Fatigue Test Results
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