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Technical Paper

Extended Non-Destructive Testing of Composite Bonds

Composite materials are increasingly being used in the manufacturing of structural components in aeronautics industry. A consequent light-weight design of CFRP primary structures requires adhesive bonding as the optimum joining technique but is limited due to a lack of adequate quality assurance procedures. The successful implementation of a reliable quality assurance concept for adhesive bonding within manufacturing and in-service environments will provide the basis for increased use of lightweight composite materials for highly integrated aircraft structures thus minimizing rivet-based assembly. The expected weight saving for the fuselage airframe is remarkable and therefore the driver for research and development of key-enabling technologies. The performance of adhesive bonds mainly depends on the physico-chemical properties of adherend surfaces.
Technical Paper

Numerical and Experimental Investigation of the Mechanical Properties of Riveted Joints Considering the Installation Process

The riveting process in the aerospace industry underlies high requirements to achieve the expected manufacture quality. Process parameters, the choice of materials, and the joint configuration are some influencing factors that can affect the mechanical properties of riveted joints. These high requirements constitute challenges that drive manufacturers to a better understanding of the riveting process. The numerical study of the effect of the installation parameters on the mechanical properties of mechanically fastened joints is one tool to achieve this aim. Usually, three-dimensional finite element simulations of both installation process and mechanical loading of the joint in service must be performed to make detailed numerical predictions of the joint behavior. This paper aims at the reduction of the computational effort.
Technical Paper

Accuracy Analysis and Error Source Identification for Optimization of Robot Based Machining Systems for Aerospace Production

Strong market growth, upcoming global competition and the impact of customer-requirements in aerospace industry demand for more productive, flexible and cost-effective machining systems. Industrial robots have already demonstrated their advantages in smart and efficient production in a wide field of applications and industries. However, their use for machining of structural aircraft components is still obstructed by the disadvantage of low absolute accuracy and adverse reaction to process loads. This publication demonstrates and investigates different methods for performance assessment and optimization of robot-based machining systems. For conventional Cartesian CNC machining systems several methods and guidelines for performance assessment and error identification are available. Due to the attributes of a common 6-axis-robot serial kinematics these methods of decoupled and separated analysis fail, especially concerning optimization of the system.
Technical Paper

Real-Time Path Correction of an Industrial Robot for Adhesive Application on Composite Structures

Due to their unique and favorable properties as well as high strength to weight ratio, composite materials are finding increasing applications in automotive, aircraft and other vehicle manufacturing industries. High demand, production rates and increasing part complexity, together with design variations require fast, flexible and fully automated assembly techniques. In automotive and aircraft manufacturing, widely used bonding and sealing processes are automated using industrial robots due to their speed, flexibility and large working volume. However, there are limitations in achieving complete automation of these processes due to the inherent inaccuracies of the industrial robots, workpiece positioning and process tolerances. Currently, the robot programs are generated in CAD/CAM environment and are adjusted manually according to the actual workpiece.
Journal Article

Cracking Stopping in the Bondline of Adhesively Bonded Composite Adherents by Means of a Mechanical Fastener: Numerical and Experimental Investigation

The use of composite materials in aircraft manufactures increases more and more with the need of light weight and efficient airplanes. Combining composite materials with an appropriate joining method is one of the primordial ways of exploiting its light weight potential. Since the widely-established mechanical fastening, which originally, was developed for metallic materials, is not a suitable joining method for composite materials because of its low bearing strength, the adhesively bonding technology might be an appropriate alternative. However, adhesively bonding in the aircraft manufacturing, especially for joining of primary structures is liable to certification requirements, such as testing of every bond up to limit load before the operation begins or non-destructive testing of every bond before the operation begins as proof of the joint characteristics, which cannot be fulfilled with the current state of the art.
Journal Article

Numerical Investigation of the Rivet Installation in an Adhesively Bonded Joint and the Load Transfer in a Bolted/Bonded Hybrid Joint

Hybrid (bolted/bonded) joining is becoming one of the innovative joining processes for light weight structures in the transport industry, especially in the aerospace industry where weight reduction and high joining requirements are permanent challenges. Combining the adhesive bonding with the mechanical joining -riveting for instance- can lead to an enhancement of the properties of the joint compared to the wide established riveting, as a result of a synergistic load bearing interaction between the fastener and the adhesive bondline. The influence of the rivet installation process on a hybrid joint regarding the joint stress state, the change of the bondline thickness as well as its effects on the joint performance and load transfer are some of the factors that drive the users to a better understanding of the hybrid joining process.
Journal Article

Simulation of the Solid Rivet Installation Process

The riveting process with a solid rivet is one of the most applied joining processes in the aeronautic industry. New materials and new design requirements constitute challenges that drive the users to a better understanding of the installation process of riveted joints. Therefore, this study aims with the aid of FEM simulation to understand the phenomena occurring during the installation process and afterwards to predict the mechanical properties of the riveted joint depending on the installation parameters and characteristics of the adherends. The experimental installation process for the validation of the simulation model takes place in a fully automated C-frame riveting machine with all-electric drilling and riveting operations aptitude and continuous collection of process data. This paper deals with the simulation of the installation process. The simulation model consists of a solid rivet with universal head described by the standard EN6081 and aluminum (2024-T351) adherends.