Volume 25, Issue 5 (September 1997)
Effect of Specimen Thickness on the Long-Life Fatigue Performance of a Randomly-Oriented Continuous-Strand Glass-Mat-Reinforced Polypropylene Composite
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).