Effect of Tensile Mean Stresses on Fatigue Properties of Plastic Laminates Reinforced with Unwoven Glass Fibers

摘要

Fatigue curves are presented for plastic laminates reinforced with layers of unwoven 'E' glass filaments in a matrix of epoxy type resin and subjected to various alternating stress amplitudes superimposed on constant mean tensile loads. The S-N curves were determined by axially loading specimens that had alternate layers of glass at 0 degrees, =5 degrees, =10 degrees, and =15 degrees to the principal axis. Curves were also determined for three special constructions of unwoven glass laminates in which: (1) 71.4 percent of the fibers were parallel to the principal axis, (2) 85.2 percent were parallel, and (3) all layers were parallel with each layer supported by a 'carrier' of 2-mil glass fabric. All experiments were conducted on unnotched specimens, at 900 cycles per minute, and in an atmosphere maintained at 73F. and 50 percent relative humidity. Loads were applied parallel to the principal axis. (Author)