Betrouwbaarheid van hyperelastische lijmverbindingen - Experimentele en numerieke studie van productiefouten en spreiding van materiaaleigenschappen

Many modern designs combine different materials in highly dynamic environments. Traditional joining methods such as screws or rivets may provide some solutions, but introduce point loads and cannot seal gaps between components. Adhesive bonding alleviates these challenges. Traditional stiff adhesives are sufficiently understood to be used in critical applications, but cannot sustain large deformations. By contrast, hyperelastic adhesives are less well understood but can accommodate large deformations when applied with sufficient bondline thickness. Their low modulus enables large relative displacements, while the large adhesive volume contributes to vibration damping. This large required volume introduces challenges for joint manufacturing, as it can lead to geometric and material variability, reducing the reliability of the bonded structure. This study focuses on the initial reliability of joints bonded with hyperelastic adhesives, combining experimental and numerical methods to identify material and bonding defects. This results in a qualitative evaluation of important parameters in the bonding process. This research considers the commercially available single component (1K) moisture-curing modified siloxane polymer (MS polymer) adhesive TEC7 by Novatech. The main objectives of this research are to provide insight into the mechanics of bonding with hyperelastic adhesives, and to study the variability of bonded joints and identify the sources of this variability. Achieving these objectives requires a thorough investigation of the ability of commercial finite element analysis (FEA) tools to model the mechanical behaviour of such bonded joints, including the effects of practical manufacturing tolerances and defects. This involves the development of a modelling pipeline capable of predicting joint behaviour based on simple, repeatable, and low-cost experiments on the bulk adhesive. These objectives are approached from several angles. An initial literature study provides insight into the mechanics of bonding with moisture curing 1K adhesives, identifying potential sources of variability due to environmental effects or joint design choices. A thorough material modelling study demonstrates the ability of FEA tools to accurately represent the bulk adhesive when using an appropriate hyperelastic material model. Experiments on bonded butt joint coupons show the large variability of completed joints. Bondline thickness and joint eccentricity are identified as the dominant parameters governing joint stiffness, strength and allowable elongation. The effect of eccentricity can be alleviated by suitable manufacturing jigs. Fracture surface analysis indicates predominantly cohesive failure of the adhesive. However, the presence of voids in the adhesive layer adversely affects the bond reliability, reducing its strength and stiffness. Numerical experiments with nominal and replicated coupons capture these observed trends, confirming the suitability of the modelling approach, and its ability to qualitatively predict the effects of manufacturing tolerances and defects on the mechanical behaviour of bonded joints. This work demonstrates that a combined experimental and numerical approach provides insight into the initial reliability of bonded joints using hyperelastic adhesives. The qualitative effects of manufacturing tolerances and defects are demonstrated through both experimental and numerical results. Together, these findings form a framework that supports reliability-oriented design of hyperelastic bonded joints, integrating FEA tools with experimental investigation.