Predicting Failure in Multi-Bolt Composite Joints Using Finite Element Analysis and Bearing-Bypass Diagrams

Abstract

Abstract.A three-dimensional finite element model of a three-bolt, single-lap composite joint is constructed using the non-linear finite element code MSC.Marc. The model is validated against an experiment where the load distribution in the joint is measured using instrumented bolts. Two different joint configurations are examined, one with neat-fit clearances at each bolt-hole and another with a 240 µm clearance at one hole with neat-fits at the others. Bearing and by-pass stresses are extracted from the model and used in conjunction with published bearing/by-pass diagrams to predict the failure load, mode and location for the joints. It is shown that the proposed model accurately predicts the failure behaviour of the joints, as determined from experiments on three-bolt joints loaded to failure. It is also shown that introducing a clearance into one hole significantly changes the failure sequence, but does not affect the ultimate failure load, mode or location. The proposed method demonstrates a simple approach to predicting damage in complex multi-bolt composite joints.

Study on Bearing Strength and Failure Modes of Single Bolted Joint Carbon/Epoxy Composite Materials

“…As the e/D ratio approaches 3.0, both parts of the specimen experience bearing failure, indicating the absence of tension failure (L1I). This result aligns with findings from prior investigations [ 69 , 70 , 71 , 72 , 73 , 74 ]. Alaattin Aktas reported that, while adjusting the e/D ratio from 1.0 to 5.0 with a fixed w/D ratio of 4.0 for CFRP plates, shear and bearing failures occurred together when the e/D ratio exceeded 5.0, suggesting a significantly conservative value compared to the e/D ratio of 2.0 presented in this study.…”

Bearing Strength and Failure Mechanisms of Riveted Woven Carbon Composite Joints

“…This phenomenon was related for two reasons: (1) there was a more extensive transverse section of the rivet to carry the load, and (2) a larger contact area was provided when the rivet diameter increased. McCarthy et al [3,6] reported that variations in the contact area (fastener composites) caused changes in the joint stiffness and ultimate bearing strength. Zhou et al [9] concluded that the geometric parameters (such as the w/D and edge-todiameter (E/D) ratios) should be appropriately chosen.…”

“…Mechanical joints for composites, whether by fasteners or rivets, are the only ones that aeronautics authorities have validated regarding the airworthiness certification process [1][2][3]. Riveted composites are currently used in last-generation aircraft, mostly for skin-stringer or skin-beam assemblies in primary structures (e.g., the wing, fuselage and stabilizer) [4] and secondary structures (e.g., flaps, rudder and ailerons) [5][6][7].…”

“…Riveted composite structures have been widely studied, principally focused on quantifying quasistatic lap shear failure loads [8][9][10][11]. Study cases have been prospected, from analyzing different width-to-diameter ratios (w/D) [6,10,11] and evaluating failure modes to comparing finite element analysis using cohesive and contact models [3,6,[9][10][11]. Inner riveted assembly variables, such as a hole's roughness, bolt preload, rivet pretension, hole-rivet clearance, the laminate stacking sequence and drilling damage, as well as laminate-fastener stresses, have been studied recently.…”