Influence of the Arrangement of Mechanical Fasteners on the Static Strength and Fatigue Life of Hybrid Joints.

Andrzej Komorek,Jan Godzimirski,Michał Jasztal,Marek Rośkowicz,Jarosław Gąsior

doi:10.3390/ma13235308

Andrzej Komorek, Jan Godzimirski + Show 3 more

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https://doi.org/10.3390/ma13235308

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Abstract

This paper presents the results of experimental research and numerical calculations regarding the static strength and fatigue life of hybrid joints. In the experiments, specimens built as single-lap adhesive–mechanical joints (hybrid joints) were tested. In a two-stage process of the failure of the hybrid joints, the adhesive joint was damaged first. Therefore, it was assumed that the assembly of fasteners closer to the edge of the overlap (beyond the ranges recommended for mechanical joints) limits the negative impact of the peeling phenomenon on the strength and performance properties of hybrid joints. The specimens used in the experiments were prepared from composite elements (i.e., carbon fiber-reinforced polymer (CFRP)), as well as from the aluminum alloy 2024T4. Because the detection of fatigue damage in composite materials is a complex problem, computed tomography was used to evaluate the degradation of the composite material. Experimental and numerical comparative analyses of the static strength and fatigue life of hybrid joints with adhesive and mechanical joints confirmed the assumptions made.

Highlights

The pursuit of aviation transport constructors, especially of aircraft, to lower the weight has led to the replacement of a very large number of designed metal components with composite elements.Composite structures are joined in three different ways—by using mechanical joints [1,2], by means of an adhesive [3], or by a combination of these two methods [4,5].Hybrid joints are a combination of adhesive joints and mechanical fasteners.Those joints build a structural node and are often simpler and cheaper to realize than other traditional joining methods [6]
The aim of the numerical calculations was to test the hypothesis that the distribution of mechanical connectors in hybrid joints affects the normal stresses in the adhesive layer, causing it to peel, and impacting the strength of joints and their durability
Values occurred at the holes, whilemaps at the in edges the overlap, highest valuesThe of maximum values of shear stress occurred at the holes, while at the edges of the overlap, the highest maximum principal stress and normal stress perpendicular to the adhesive layer were noted—these values of maximum stress andoccurring normal stress the adhesive layer stress were are a measure of the principal peel phenomenon in thisperpendicular type of joint. to

Summary

Introduction

Hybrid joints are a combination of adhesive joints and mechanical fasteners (e.g., rivets and bolts). Those joints build a structural node and are often simpler and cheaper to realize than other traditional joining methods [6]. Due to the increasing use of polymer composite materials in aircraft or in cars, the performance of this type of joint, as well as their mechanical properties, including the load capacity and fatigue life, are taken into consideration [9,10]. The load capacity and fatigue life of hybrid joints depend on several construction, technological, and material parameters, including the type of joint and the adhesives and rivets used [11,12,13]. Rivets in this type of joint limit an Materials 2020, 13, 5308; doi:10.3390/ma13235308 www.mdpi.com/journal/materials

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