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Friction-based Injection Clinching Joining (F-ICJ) is a new advanced staking joining technology for lightweight hybrid structures. This PhD work was devised to understand the fundamental scientific and engineering aspects of F-ICJ. The joint formation mechanisms, process-related changes in the joined materials, and quasi-static mechanical behavior...
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... 38. Reptation theory, t0 < t1 < t2 < Tr (the tube renewal time)[148] Over time, in the process of self-diffusion along its contour, the chain gradually disentangles from the original tube to find itself in a new environment, like in a new tube, as illustrated inFigure 1.38. To describe the movement of the polymer, the Rouse model [141] is considered. ...
... 39. Interdiffusion of chains across an interface[148] ...
Additive manufacturing is attractive because it allows to reduce significantly the development and industrialization phases of part design. Among the promising technologies for thermoplastic parts, the SLS (Selective Laser Sintering) process stands out because of its ability to produce geometries with low dimensional tolerances. This process is based on the displacement of a laser beam that interacts with the powder bed. The attractiveness of additive manufacturing counterbalances, however, with the choice of currently available materials: these are mainly polyamides. Polyaryletherketones (PAEK) suitable to SLS process are still rare on the market and expensive. In this work, various powders have been characterized to deeper understand the properties necessary for their use in SLS and to define their processability temperature window. The absence of suitable PEEK powder led us to develop a new material by blending PEEK with an amorphous thermoplastic, polyethersulfone (PESU). The initially immiscible blends have been compatibilized in order to improve their mechanical properties and to delay their crystallization on cooling. During manufacturing, many process parameters control the melting of the powder, and thus the properties of the parts and their dimensional accuracy. Thus, a statistical analysis of the response of the parameters was led by a design of experiments to extract the most influential parameters. The parametric study, done with the polyamide powder, was carried out by varying five parameters and by looking at their influence on five groups of responses relating to the physical, mechanical and thermal properties as well as to the printing duration of the parts. The design of experiments made it possible to establish the mathematical models of the response surfaces linking the responses to factors and their interactions. These statistical models were used to define an optimal set of parameters. Finally, a combined experimental and numerical simulation approach was conducted to estimate the influence of each laser pass on the degree of crystallinity and the mechanical properties of each layer. The results show that the heating due to the successive laser passes cover a thickness equivalent to 14 deposited layers. However, only the 4 upper layers are significantly thermally affected by the laser pass on a powder layer and thus show an evolution of their degree of crystallinity.
... Friction-based Injection Clinching Joining (F-ICJ) has been recently explored as an alternative advanced staking process for new lightweight structures by Abibe et al. [17][18][19]. Typical staked structures use joints in the most common configurations of rosette, dome, or hollow stakes ( Figure 1a) [20]. ...
... The tool retreats and the F-ICJ joint is created. The fundamentals of the F-ICJ process have been described in [18] and [19]. Joints are formed by providing frictional heat to a polymeric stud, which flows within a shear layer around the tool to create a stake. ...
... For processing conditions see Table 1. Adapted from [19]. ...
This work presents a comprehensive study on the effects of the Friction-based Injection Clinching Joining (F-ICJ) process on the microstructure and local properties of the stake head. The manuscript evaluates the consequences on the quasi-static mechanical performance of hybrid joints of amorphous polyetherimide (PEI) with aluminium AA6082. Through an overlay of microhardness map on a cross-polarized transmitted-light optical microscopy (CP-TLOM) image, two lower-strength microstructural zones in the PEI stake head were observed: a plastically-deformed zone (PDZ) and a thermo-mechanically-affected zone (PTMAZ). When compared to the base material, PDZ and PTMAZ have a reduction of 12%–16% and 8%–12%, respectively, in local mechanical properties. The reduced local strength was associated with distinct volumes of loosely packed PEI chains with unsteady chain conformation and thus larger free volume in the affected regions. The mechanical strength reduction is reversible through physical aging by thermal annealing the joints, which additionally shows that process-induced thermomechanical degradation of PEI by chain scission, as evidenced by size exclusion chromatography (SEC) analysis, does not appear to affect local mechanical strength. An evaluation of typical loading regimes of staked joints in lap shear (average ultimate force of 1419 ± 43 N) and cross tensile (average ultimate force of 430 ± 44 N) testing indicates that the process-induced changes of PEI do not compromise the global mechanical performance of such a structure. These findings provide a better understanding of the relationships between processing, microstructure, and properties for further F-ICJ process optimization.
... Tous jouent un rôle dans l'apport d'énergie en entrée et par-là influencent le comportement et la distribution de la zone affectée thermo-mécaniquement durant les différentes phases de l'opération. Cette technologie issue des travaux de thèse de A.B. Abibe[85] est récente et a fait notamment l'objet d'un brevet (US20070124912 A1). ...
Ces travaux de thèse portent sur la question de l'assemblage multi-matériaux polymère-acier. Dans un environnement automobile grande série, le rivetage auto-poinçonneur est le procédé d'assemblage proposé qui permet de répondre à la problématique industrielle. Dans un premier temps, la faisabilité de la technique i été étudiée en recherchant l'influence de la vitesse de rivetage et de l'effort serre-flan sur les caractéristiques géométriques du joint riveté et sur la tenue mécanique. Ainsi, il se révèle que l'augmentation de la vitesse de rivetage a un effet favorable: l'effort à la rupture en traction pure augmente de +10% en accord avec l'augmentation de l'ancrage mécanique. Par contre, l'augmentation de l'effort serre-flan a un effet défavorable : l'effort à la rupture en traction pure et en traction-cisaillement diminue de -6.6%. Par la suite, un modèle numérique 2D axisymétrique a été mis au point dans le but de simuler l'opération de rivetage. Les propriétés mécaniques effectives du matériau composite sont estimées par une méthode d'homogénéisation tandis que le comportement mécanique du matériau acier par un modèle élasto-plastique endommageable. Comparée à la coupe transversale issue d'un essai expérimental, la simulation effectuée sous Abaqus 6.10- 1® démontre être capable de correctement prédire la déformée en particulier pour la valeur d'ancrage mécanique. Enfin, un modèle numérique 30 a été développé et permet de simuler des chargements destructifs et asymétriques. L'effort à rupture et les déformées macroscopiques estimées sont en bon accord avec les résultats expérimentaux, grâce notamment à la prise en compte de l'endommagement local de la couche composite.
In recent years, 2D and 3D imaging has become a standard tool for scientific and industrial applications in materials science. Imaging at second- and third-generation synchrotron radiation (SR) facilities makes use of the low divergence and high intensity of the source to record parallel 2D projections of samples using monochromatic X-rays. Employing the high-intensity sources at neutron facilities and the highly brilliant and collimated X-ray sources at second and third-generation SR facilities, specialized contrast techniques were developed. Complementary access to both the techniques, neutron tomography, and SR tomography, allows the development of new techniques and will give new insight in the 3D behavior of samples especially in materials science. Exploiting the source characteristics of the new third-generation SR facility PETRA III at DESY will allow extending the spatial resolution into the nanometer regime. The standardization of the different imaging techniques will allow for optimal investigations of samples consisting of low-absorbing and absorbing components.
