Effect of Hole Arrangement on Failure Mechanism of Multiple-Hole Fiber Metal Laminate under On-Axis and Off-Axis Loading

Abstract

Mechanical joints are commonly required in structures made of fiber metal laminate (FML), which pose a threat due to multi-site stress concentrations at rivet or bolt holes. Thus, for a reasonably designed FML joint, it is essential to characterize the failure mechanism of multiple-hole FML; however, little information about this has been found in open literature. In the present work, influences of hole arrangement and loading strategy (on-axis or off-axis) on the failure mechanism of multiple-hole FML were investigated, by performing finite element analyses and energy dissipation analyses with elastoplastic progressive damage models that took curing stress into account. Six types of specimens with holes arranged in parallel and staggered forms were designed, whose geometrical parameters were in strict accordance with those specified for composites joints. It indicated that the stress distribution, gross/net notched strength, critical fracture path, and damage evaluation process were only slightly influenced by the hole number and hole arrangement. On the other hand, they were strongly influenced by the loading strategy, due to the transition of failure domination. Results presented here can provide evidence for introducing design regulations of composite joints into the more hybrid FML, and for reasonably determining its multiple-hole strength merely based on the sing-hole specimen.

Mechanical behavior of fiber-glass plastic with hole pattern using digital image correlation and acoustic emission methods

“…However, due to the anisotropic and brittle nature of materials in composites, bolt-induced stresses are redistributed differently, affecting the assumed limit states. In structures where composite components are bolted together [3][4][5], it is often necessary to introduce multi-start holes, it is necessary to perform parametric analysis of stresses taking into account multiple variations of hole configuration [6][7][8][9][10]. The importance of finite element mesh selection in modeling composites with stress concentrators is discussed in study [11], where models with different degrees of sampling are studied and the results of which model are closest to the experimental data are identified.…”