Effect of Specimen Thickness on the Long-Life Fatigue Performance of a Randomly-Oriented Continuous-Strand Glass-Mat-Reinforced Polypropylene Composite
Little RE
(Received 0 0; accepted 0 0)

Abstract
This paper summarizes an experimental study of how three specimen thicknesses—⅛, 3/16, and ¼ in. (3.18, 4.76, and 6.35 mm)—affect the long-life fatigue performance of a thermoplastic composite material with 40% randomly-oriented continuous-strand glass in a polypropylene matrix (Azdel). Axial-load and four-point-bending fatigue tests were conducted to compare (1) the respective median logarithmic fatigue lives for a common alternating stress amplitude and (2) the respective estimated median fatigue strengths at 10⁷ stress cycles. Both the median logarithmic fatigue life and the median fatigue strength decreased markedly when the specimen thickness was increased from ⅛ to 3/16 in. (from 3.18 to 4.76 mm). However, in each case, no further decrease was statistically evident when the specimen thickness was increased from 3/16 to ¼ in. (from 4.76 to 6.35 mm).

Keywords:
Azdel, composite material, long-life fatigue behavior, median fatigue strength, optimal test methods, statistical analysis of variance, thickness effect, up-and-down test method

ASTM International is a member of CrossRef.
Author Little RE Title Effect of Specimen Thickness on the Long-Life Fatigue Performance of a Randomly-Oriented Continuous-Strand Glass-Mat-Reinforced Polypropylene Composite Symposium , Committee: on