Experimental Data on Single-Bolt Joints in Quasi-Isotropic Graphite/Polyimide Laminates.

The results of an experimental program to determine the bolted-joint strength and failure modes of graphitepolyimide laminates are presented. Sixteen-ply, quasi- isotropic laminates of Celion 6000PMR-15 and Celion 6000LARC-160 with a fiber orientation of O459O-45sub 2S were evaluated. Tensile and open-hole specimens were tested at room temperature to establish laminate tensile strength and net tensile strength at an unloaded bolt hole. Double-lap joint specimens with a single 4.83-mm 0.19-in. diameter bolt torqued to 1.7 N-m 15 lbf-in. were tested in tension at temperatures of 116 K -250 F, 297 K 75 F, and 589 K 600 F. The joint ratios of wd specimen width to hole diameter and ed edge distance to hole diameter were varied from 4 to 6 and from 2 to 4, respectively. The effect of joint geometry and temperature on failure mode and joint stresses are shown. Joint stresses calculated at maximum load for each joint geometry and test temperature are reported. Five failure modes were observed for the double-lap joint specimens. For all joint ratios tested, net-tension, bearing, and shear-out stresses decreased with increasing temperature from 116 K -250 F to 589 K 600 F. Joint strength in net tension, bearing, and shear-out at 116 K -250 F, 297 K 75 F, and 589 K 600 F are given for the Celion 6000PMR-15 and Celion 6000LARC-160 laminates.