Evaluation of Bonding Parameters on Random Fatigue Life of Bonded Aluminum Joints

Eighteen adhesively bonded aluminum coupons were tested on a vibration shaker at room temperature to determine the effects of varying the adhesive type/thickness, primer, and adherend surface preparation on their random bending fatigue life. Most of the fatigue failures occurred within 10 super(6) to 10 super(7) cycles, all at 900 microstrain. While neither the primer thickness nor the surface treatment seemed to influence the overall results, the coupons with thicker adhesive had a noticeably shorter fatigue life. Fractographic analyses of the failed adhesive surfaces showed the locus of fracture for all coupons was predominantly within the adhesive. The nitrile phenolic adhesive demonstrated a better fatigue resistance than the nitrile epoxy.