Stress distribution of secondary bending in single-lap bolted joints with dissimilar joining plates and plate types

Single-lap joints are an important class of bolted joint in the aerospace and civil engineering sectors. This type of joint is preferred as it can reduce weight and hence help to optimize fuel efficiency. However, bolted single-lap joints exhibit secondary bending due to eccentricity of the applied loads. Flexural of plates during tensile loading alters the contact regions in the single-lap joint significantly, resulting in more non-linear behaviour and a stress gradient across the plate thickness. 3-D bolted single-lap joint were modelled in ABAQUS CAE incorporating the effect of the bolt tension from application of a tightening torque. Current 3-D model used elastic properties based on smeared-out properties, the effect of joint construction is considered further by examining the stress in a composite-composite joint and comparing with a composite-steel joint. In a related investigation the effect of varying composite thickness in the composite-steel joints is also studied

Improvement of adhesive-bonded structural joints

Investigation is described of methods for obtaining uniform shear stress distribution in adhesives used in double-lap bonded joints. Design rules for reducing adhesive peak shear stresses are listed. Test results of an analysis of straight-lap joint design and stepped-lap joint design are given

High temperature epoxycarborane adhesives Final report

Carborane adhesive bonding properties and lap shear strength of metal to metal joint

The Alternating Surface Segmented Lap Joint: a Design for Thin Highly Loaded Joints

The combination of thin airfoil sections and high aerodynamic loads on many wind tunnel models presents a major problem for attachment of flap elements. Conventional methods of attaching fixed control elements such as lap and tongue-in-groove joints are not rigid enough to provide surface continuity required in high Reynolds number research. For the extreme cases, the solution has been to fabricate separate wings for each flap setting with the flap element being and integral part of the wing. Here an attractive solution to this problem, the alternating surface segmented lap joint, is discussed. This joint provides increased rigidity and lower stress levels than conventional joints. Additionally, attachment fastener loading is low and the joint can be designed to accommodate high shear levels due to bending without the use of dowel pins

Mechanical properties of a lap joint under uniform clamping pressure

Equations were derived for the load deflection relations, the energy dissipation per cycle, and the instantaneous rate of dissipation for a lap joint idealized as two overlapping plates clamped together under a uniform clamping pressure

Design, fabrication and test of graphite/polyimide composite joints and attachments for advanced aerospace vehicles

Bonded and bolted designs are presented for each of four major attachment types. Prepreg processing problems are discussed and quality control data are given for lots 2W4604, 2W4632 and 2W4643. Preliminary design allowables test results for tension tests and compression tests of laminates are included. The final small specimen test matrix is defined and the configuration of symmetric step-lap joint specimens are shown. Finite element modeling studies of a double lap joint were performed to evaluate the number of elements required through the adhesive thickness to assess effects of various joint parameters on stress distributions. Results of finite element analyses assessing the effect of an adhesive fillet on the stress distribution in a double lap joint are examined

Use of two-dimensional transmission photoelastic models to study stresses in double-lap bolted joints

The stress distribution in two hole connectors in a double lap joint configuration was studied. The following steps are described: (1) fabrication of photoelastic models of double lap double hole joints designed to determine the stresses in the inner lap; (2) assessment of the effects of joint geometry on the stresses in the inner lap; and (3) quantification of differences in the stresses near the two holes. The two holes were on the centerline of the joint and the joints were loaded in tension, parallel to the centerline. Acrylic slip fit pins through the holes served as fasteners. Two dimensional transmission photoelastic models were fabricated by using transparent acrylic outer laps and a photoelastic model material for the inner laps. It is concluded that the photoelastic fringe patterns which are visible when the models are loaded are due almost entirely to stresses in the inner lap

Hybrid (bolted/bonded) joints applied to aeronautic parts : analytical one-dimensional models of a single-lap joint

The load transfer in hybrid (bolted/bonded) single-lap joint is complex due to the association of two different transfer modes (discrete and continuous) through elements with different stiffness. Analytical methods exist for these two different modes, when considered separately. In this paper two one-dimensional elastic analytical models are presented for the determination of the load transfer in single lap configuration. The first one is developed by using the integration of the local equilibrium equations. From this first method an elastic-plastic approach is presented. The second one uses the Finite Element Method, introducing a new element called “bonded-bar”. These models are robust, easy to use and provide the same results. They allow to analyze the load transfer and to evaluate different geometric and mechanical parameters’ influence. Thus they represent the first step for the design of a hybrid joint able to replace its bolted equivalent used on aircraft

Experimental investigation of woven fabric cfrp bolted joints: parametric study

Present paper comprises a wide ranging experimental study of mechanically fastened woven CFRP using double-lap joint (DLJ) configurations. Details of the bolted joint materials and its configurations are given. This is followed by an account of the sample preparation process and a description of the range of joint types and variables investigated. Mechanical testing set-up and test method are then described. Experimental results relating to damage observations and ultimate strength are then presented. This is followed by discussion on the relationships between the bearing stress at failure and the hole size of specimens, the level of clamp-up and different joint type