Predicting Bearing Strength of Fiber Metal Laminates Via Progressive Failure Analysis

Abstract

Fiber metal laminates (FML), such as GLARE and CentrAL, can offer better structural performance compared to monolithic metal alloys for many aircraft components. Experiments show that the FML’s improve fatigue, residual strength, impact and corrosion resistance. Because of these enhanced capabilities, FML’s are finding their way into aircraft fuselage and wing sections. The next-generation super jumbo Airbus A380 selected GLARE for its fuselage sections. The fuselage sections are generally constructed using mechanical joints that contain rivets and bolts that contribute to the bearing strength issues. Bearing tests clearly show that bearing strength depends highly on the pin/fastener diameter and its distance from the edge. Numerically evaluating the bearing strength of coupons made from FML materials is difficult because of the combination of isotropic metallic layers with highly anisotropic composite layers. The complexity arises from the mixing of different material systems and the ability to track different failure mechanisms, such as such as net-tension, shear-out and bearing. A multi-stage progressive failure analysis, based on finite element analyses, was used to predict and validate the bolted joint structural performance under tension loading. Excellent correlation between test and prediction was observed.