Aluminum Adherends Research Articles

Numerical Evaluation of Hydroformed Tubular Adhesive Joints under Tensile Loads

Adhesive joints are widespread in the aerospace, aeronautics, and automotive industries. When compared to conventional mechanical joints, adhesive joints involve a smaller number of components, reduce the final weight of the structure, enable joining dissimilar materials, and resist the applied loadings with a more uniform stress state distribution compared to conventional joining methods. Hydroformed tubular adhesive joints are a suitable solution to join tubes with identical cross-sections, i.e., tubes with the same dimensions, although this solution is seldom addressed in the literature regarding implementation feasibility. This work aims to numerically analyze, by cohesive zone modelling (CZM), hydroformed tubular adhesive joints between aluminum adherends subjected to tensile loads, considering the variation of material parameters (type of adhesive) and geometrical parameters. Initially, a validation of the proposed CZM approach is carried out against experimental data. Next, the aim is to numerically evaluate the tensile characteristics of the joints, measured by the maximum load (Pm) and energy of rupture (ER), considering the main geometrical parameters (outer tube diameter of the non-hydroformed adherend or dENHA, overlap length or LO, tube thickness or tAd, and joggle angle or q). CZM validation was successfully performed. The numerical study determined that the optimal geometry uses the adhesive Araldite® AV138, higher dENHA and LO highly benefit the joint behavior, tAd has a moderate effect, and q has negligible influence on the results.

Effect of surface treatment of aluminum adherends on capacitance and strength of adhesively bonded joints

Effect of surface treatment of aluminum adherends on capacitance and strength of adhesively bonded joints

Sikahyflex-Epoxy Mixed Adhesive’s Effect on the Aluminum-Composite Joint’s Shear Tensile Strength for the Automotive Industry

The automotive industry sector encounters challenges in the construction of connections between different materials. Hence, a breakthrough is needed in the automotive industry in manufacturing connections between different wall panel materials. Mixed adhesive materials for different materials are required and represent an innovation in the manufacturing process for joints of different materials due to the need for stiff and slightly ductile adhesives. This research aims to analyze the effect of using a sikahyflex-epoxy mixture adhesive in aluminum-composite joints on the shear tensile strength of the joints for the automotive industry. This research serves as an innovation in dissimilar material connection systems by developing the use of mixed adhesives and cocofiber aluminum-composite adherend materials with environmentally friendly and corrosion-resistant properties. The research material used aluminum 5083-cocofiber composite. The adherend surface was roughened employing sandpaper of #60, #80, and #150. The adhesive used the addition of sikahyflex adhesive to the epoxy adhesive with additional variations of 10%, 20%, 30%, and 40% sikahyflex. Connections between different materials with the single lap joint type refer to ASTM D1002. The roughness test results yielded the best roughness grade #150 on the surface of the aluminum adherend and coco fiber composite. The shear tensile test results by adding 40% sikahyflex adhesive, 0.4 mm adhesive thickness, and #150 sandpapering resulted in a 20% increase in shear tensile strength in the single lap joint of 2.51 N/mm2. The surface roughness enhanced the adhesive bond strength between mechanical interlocking adhesives and adherend. Meanwhile, the failure modes observed in macro observations included thin-layer cohesive failure, cohesive failure, two-stage failure, and stock-break failure modes. The SEM observation revealed that in the initial propagation of microcracking and voids, which mark the initial onset of adhesive failure, tearing took place, leading to a failure mode in the aluminum-composite coco fiber single overlap joint.

The reduction of stress concentrations in adhesive joints with the use of curved aluminum adherends

The study proposes a novel concept of a curved single lap joint (SLJ) with non- uniform adhesive thickness to reduce stress concentrations near overlap edges. Experimental and numerical methodologies investigate this joint using two adhesives: Araldite 2015-1 and AV138. Numerical models in ABAQUS predict cohesive failure in the adhesive layer. The curved configuration doesn’t significantly enhance strength in SLJ using ductile adhesives, but for brittle ones, strength increased by 131% due to sensitivity to peak stresses. In conclusion, the curved SLJ effectively reduces stress concentrations and the effectiveness of this concept is linked to the ductility of the adhesive used.

Characterization of Bending Strength in Similar and Dissimilar Carbon-Fiber-Reinforced Polymer/Aluminum Single-Lap Adhesive Joints

In recent years, the adhesive bonding method has gained increased attention, especially in the automotive industry, for constructing efficient body structures from dissimilar and lightweight materials such as aluminum and polymeric composites. Adhesively bonded automotive structures endure complicated loading conditions, including tensile and bending loading, during their service lives. To the best of the authors’ knowledge, there is no published work on the assessment of bending strength in single-lap adhesive joints (SLJs) when considering dissimilar adherends under three-point bending. In this study, three-point bend experiments were carried on the bending strength and the failure mechanisms of dissimilar SLJs made of carbon-fiber-reinforced polymer (CFRP) and aluminum substrates bonded with Araldite 2015 adhesive. Additional experiments were conducted individually on similar SLJs, including aluminum/aluminum and CFRP/CFRP, to investigate and compare the effects of adherend material type on the bending strength and failure behavior of SLJs. The results indicate that a CFRP/CFRP single-lap adhesive joint exhibits significantly higher joint strength in comparison to an aluminum/aluminum single-lap adhesive joint under three-point bending. The strength of dissimilar CFRP/aluminum single-lap joints usually falls between that of an aluminum/aluminum and that of a CFRP/CFRP single-lap adhesive joint. When the CFRP adherend is situated at the bottom of the joint in three-point bending, it imparts significantly greater joint strength and deformation compared to situations where the aluminum adherend is placed at the bottom.

Parametric cohesive zone analysis of bi-adhesive single-step joints

The industry has advanced in replacing traditional joining methods, such as screwing/riveting and welding, especially the aeronautical and automotive industries, which have adopted the adhesive bonding method. This method has the advantages of simplifying the process, improving performance in terms of fatigue load, and improving the union between dissimilar materials. In addition, the development of computational numerical methods, with greater precision, has contributed to the dimensioning of joints, as well as the prediction of the resistance of these joints, which has contributed to more reliable simulations of different adhesive bonding solutions and their industrial implementation. Different modifications to the conventional designs are addressed in the literature to achieve the best results, including geometrical and material modifications. In the present research, the strength of single-step single-adhesive joints and bi-adhesive joints (BAJ) manufactured with AW 6082-T651 aluminium adherends is experimentally and numerically studied for different overlap lengths (LO). Three commercial adhesives were studied, from brittle to ductile, along with different adhesive combinations in the BAJ technique. The experimental work was mainly used for numerical model validation. The numerical analysis took advantage of triangular cohesive zone models (CZM) and included the study of peel and shear stresses, strength, and energy to failure. It was possible to validate the CZM accuracy by comparison with the experimental data. The analysis carried out showed that the BAJ technique did not reveal significant increases in strength compared to single-adhesive joints. However, when damage tolerance and dissipated energy are analysed, a noticeable increase in performance is observed, especially in joints with larger LO.

Enhanced mechanical interlocking of adhesive-bonded joints via tailored serrated patterns manufactured with laser ablation

ABSTRACT Laser ablation is currently used as an effective alternative to mechanical or chemical surface pre-treatments for adhesive-bonded joints due to benefits in terms of adherend surface morphology and surface free energy. Several works have seen production of micro-scale textures on both metallic and polymeric substrates via 3D printing, while others have sought to modify the macroscopic topography by generating serrated profiles on adherends prior to joint assembly. In this work, laser ablation has been used to create micro-scale tooth-like interlocking features forming structured patterns with complementary profiles on aluminium adherends of single lap joints. In a first set of experiments, laser processing parameters were varied while an optical profiler was used to quantify the geometry of induced ablation craters and lines while assessing the distribution of re-melt in and around the exposed region. Subsequently, an ablation strategy was developed to achieve specific interlocking features. Finally, different symmetrical and asymmetrical patterns were generated for each pair of coupled adherends while differentiating the orientation of features with respect to the load direction. The results confirm the critical role that laser ablation plays in strengthening adhesive bonded-joints, with interlocking features providing additional benefits depending on the structure type and load direction.

Calculation of the moisture diffusion coefficient at the adhesive interface of double cantilever beam specimens by studying the fracture surfaces

Adhesives used in aircrafts degrade because of moisture. To understand the fractures at the adhesive interface, moisture diffusion coefficients must be estimated, which is challenging and has not yet been reported. In this study, we prepared double cantilever beam specimens using an aluminum adherend and epoxy adhesives, immersed them in a hot bath, and observed the resultant fracture surfaces. The distance of moisture penetration at the interface was estimated from the fracture morphology, and the diffusion coefficient for moisture penetration into the adhesive was measured using a bulk immersion test. Both these values were used to determine the moisture diffusion coefficient at the adhesive interface, which was ∼3 times higher than that of the bulk. The relationship between immersion temperature and moisture diffusion coefficient of the adhesive interface adhered to the Arrhenius equation, as same as that of bulk.

Numerical bond assessment of carbon-epoxy stepped-lap joints

With the main purpose of obtaining lightweight and durable structures, bonding techniques have improved significantly in several industries. Depending on the type of structure, joining different components with different materials may require different joint geometries, which may perform better or worse. Still, only the bond performance of a very limited number of joint geometries is well known. A lack of knowledge, for instance, about the debonding process of one and two-step joints persists, especially for the latter. The present work intends to mitigate this gap by studying the debonding processes of one and two-step joints made with CFRP and aluminium adherends. To that end, implicit and explicit numerical methods (finite and distinct element methods, respectively), were applied to study different joint geometries and identify which one shows the best bond performance when subjected to a monotonic load consistent with pure fracture mode II. Based on the bond stresses obtained within the interface of the joints, the debonding propagations of the one and two-step joints are analyzed thoroughly. In the case of the one-step bonded joints, the results revealed that when the ratio between the axial stiffness of the adherends is r = 1.0 the load capacity of these joint configurations is maximized. With two-step joints, the load capacity is very sensitive to the relationship between the axial stiffness on the left (ra) and right-hand side (rb). Based on 162 different numerical simulations, the results also suggest that the load capacities of the two-step joint configurations can be maximized when the axial stiffness ra and rb of the joint are equal to 1/3 and 3.0, respectively.

Mechanical response of adhesive and hybrid joints containing novel additive manufacturing adherends

The paper presents a novel concept of purely adhesive and hybrid joints fabrication with the application of Additive Manufacturing (AM) technology. 5 different models of metal-polymer single lap joints (SLJ) were manufactured using VHB (Very High Bonding) 5925 double-sided tape and experimentally tested. To reduce the SLJ eccentricity during the tensile loading an appropriate chamfering of the polymer part shape was proposed by applying the AM technology. The Zortax M300 printer was used to produce the polymer adherends and “dog bone” type specimens, which allowed the determination of tensile strength, which value was 6.62 MPa. The effectiveness of the joints was assessed by the maximum force values, the absorption energy, and the repeatability of the results for each model. The highest force of 400.4 N was obtained for the single-lap reference model. Finally, hybrid joints were produced by the application of double-sided tape and mechanical connectors, like tenons placed in the 3D printed polymer part and mortises situated in the aluminium adherends. This new joining technique allowed for an increase in maximum force to a value of 832.5 N.

Application of an Eco-Friendly Adhesive and Electrochemical Nanostructuring for Joining of Aluminum A1050 Plates

In adhesive joints used in several industrial applications, the adherends' bonding is made using an adhesive, which is usually an epoxy resin. However, since these adhesives are derived from petroleum fractions, they are harmful to the environment, due to the pollutants produced both during their manufacture and subsequent use. Thus, in recent years, effective steps have been made to replace these adhesives with ecological (green) ones. The present work focuses on the study of aluminum A1050 joints bonded with a green adhesive; the study also involves the electrochemical anodization method applied to adherends for nano-functionalization. The nanostructured aluminum adherends allow the formation of an expanded surface area for adhesion, compared to the non-anodized adherends. For comparison reasons, two different adhesives (Araldite LY1564 and Green Super Sap) were used. In addition, for the same reasons, both anodized and non-anodized aluminum adherends were joined with both types of adhesives. The lap joints were subsequently tested under both shear-tension and three-point bending conditions. The major findings were that aluminum A1050 anodization in all cases resulted in shear strength enhancement of the joints, while joints with both aluminum anodized and non-anodized adherends and bonded with the eco-friendly adhesive showed a superior shear behavior as compared to the respective joints bonded with Araldite adhesive.

Investigation on the transitional micromechanical response of hybrid composite adhesive joints by a novel adaptive DEM model

This work developed a discrete element model to adaptively capture the transitional micromechanical response and failure mode of adhesive joints with dissimilar adherend materials and different configurations. Especially, the development of the model only requires one-time calibration. Loctite EA 9497 epoxy adhesive, aluminium (AL) and polyphthalamide (PPA) were selected to make different types of hybrid adhesive joints for the lab tests. The modelling applicability in simulating Mode I, Mode II cohesive failure and adhesive, mixed failure modes was subsequently validated with the experimental data. The validation shows that the proposed model can accurately capture the observed failure modes and joint performances. It is followed by investigating the ability to adaptively obtain the variation of fracture energies with different adhesive thicknesses. The results agree well with the current reports on the growth trend of fracture energies which see a rise till the thickness reaching 0.8 mm and subsequently decline to a plateau. Finally, key factors including the adhesive thickness, lap length were selected to perform a parametric study to investigate their influences on the failure mechanism and micromechanical response of hybrid joints. It is found that a thickness range of 0.1–0.3 mm is adequate to obtain satisfactory joint strength whilst thicker adhesive over 0.6 mm will decrease the joint strength. This is due to that a thinner adhesive layer can facilitate its cohesive fractures and thus fully use the resistance of adhesive. A range of lap length from 6 mm to 12.5 mm was found to have a higher efficiency of improving the joint strength when AL adherend was used.

The effect of hygrothermal aging on the adhesion performance of nanomaterial reinforced aluminium adhesive joints

Adhesive joints are subjected to various environmental factors such as humidity and temperature, depending on their use in industrial applications. It is important to examine and improve the performance of adhesive joints formed with polymeric adhesives, which are known to be sensitive to humidity and temperature parameters, under these conditions. For this reason, in this study, FPL-etched AA7075-T6 aluminium adherends bonded with nonreinforced and BNNP (boron nitride nanopowder), ANP (alumina nanopowder) and MWCNT (multiwalled carbon nanotubes) reinforced epoxy adhesive as a single lap adhesive joint. Thereafter, performance of the adhesive joints that exposed hygrothermal aging conditions of 1, 2, 4 and 6 weeks at 100% relative humidity (RH) and 60 °C were investigated. Glass transition temperature (Tg) values of nonreinforced and reinforced epoxy adhesives before and after hygrothermal aging were determined by DSC (Differential Scanning Calorimeter) analyses. Depending on the nanomaterial types, the tendency of the adhesive joints to water uptake was determined and compared with nonreinforced adhesive joints. When the shear strength findings were investigated, it was defined that the adhesive joints reached almost saturation after 2 weeks of hygrothermal aging. In addition, the most effective nanomaterial type against hygrothermal aging was determined as MWCNT. After 2 weeks hygrothermal aged, the shear strength decreases of MWCNT reinforced adhesive joints were 21.77% and 16.97% less than BNNP and ANP reinforced adhesive joints, respectively. Although the adhesive deteriorates chemically after hygrothermal aging, its adhesion performance improved with the physical benefits of nanomaterials. However, ANP, which is cheaper in terms of price/shear strength performance in long-term aging times, showed similar results with MWCNT. In addition, fracture mechanisms were examined in more detail with SEM (Scanning Electron Microscope) analyses before and after aging, and the effects of hygrothermal aging on the adhesive joints were determined.

Effect of Temperature and Al2O3 NanoFiller on the Stress Field of CFRP/Al Adhesively Bonded Single-Lap Joints

In this paper, the effect of aluminum oxide, Al2O3, nanoparticles’ inclusion into Epocast 50-Al/946 epoxy adhesive at different temperatures, subjected to quasi-static tensile loading, is numerically investigated. The single-lap adhesive joint with two different types of material adherends (composite fiber-reinforced polymer (CFRP) and aluminum (Al) 5083 adherends) and adhesive Epocast 50-A1/hardener 946 were modeled in ABAQUS/CAE. A numerical methodology was proposed to analyze the effect on peel stress and shear stress by adding Al2O3 nanoparticles into the neat adhesive at 25 °C, 50 °C, and 75 °C temperatures at four different locations of the adhesive regions: the interface of the adhesive and aluminum adherend (location A), the middle plane of the adhesive region (location B), the middle longer edge (along the length of the adhesive, location C), and the middle shorter edge (along the width of the adhesive, location D). The results showed that adding nanoparticles into the neat adhesive improves joint strength at room and elevated temperatures. High peel and shear stresses were recorded near both edges of the locations (A, B, C, and D). For location A, adding nanofillers into the adhesive resulted in the reduction in peak peel stress by 1.3% for 25 °C; however, it increased by 2.7% and 10.7% for 50 °C and 75 °C temperatures, respectively. Furthermore, the peak shear stress observed a considerable reduction of 19.6% for 25 °C, but it increased by 7.7% and 8.7% for 50 °C and 75 °C temperatures, respectively, for location A. The same trend was also observed for other locations (i.e., B, C, and D). This signified that adding aluminum oxide nanoparticles in the adhesive resulted in increased stiffness at higher temperatures and increased ductility of the joint, as compared to the joint with neat adhesives at room temperature. Moreover, it was observed that locations A and B were more vulnerable to damage initiation, as the peak of stresses lay near the edges, indicating that the crack initiation would take place close to the edges and propagate towards the center, leading to ultimate failure.

Insights into the micromechanical response of adhesive joint with stochastic surface micro-roughness

Micro-roughness at adhesion surface yields significant influences on the structural behaviour of adhesive joints. Investigations into the micromechanical mechanism are extremely limited. This works developed a novel particle-based model of joints with stochastic microstructural features of roughness, which can capture refined multi-scale responses as first of this kind. Aluminium adherends with mechanical surface treatments were firstly scanned using 3D laser scanning microscope. The statistical features and reconstruction method of micro-roughness profiles were determined. Single lap shear tests on joints made of epoxy adhesive (Loctite EA 9497) and treated aluminium adherends were performed to provide testing data and observations on failure modes. The refined numerical models were subsequently developed to examine the influences of the actual micro-roughness on the micromechanical behaviors and failure mechanism. The mechanical interlocking, mitigation on crack propagation due to the irregular roughness were investigated. It is followed by introducing the reconstructed roughness of various magnitudes and further numerically examining the micromechanical responses by key stochastic parameters such as root mean square roughness and correlation length. The results indicate that the mechanical interlocking contribute more to enhancing the joint strength than the increase of adhesion area by micro-roughness. A rougher surface in either horizontal or vertical directions does not exhibit a consistent improvement of joint strength, which also depends on the threshold of roughness and the surface skewness triggering the transition of failure modes.

Evaluation of strength and performance for a single lap bonded joint by insertion of structural elements in adhesive

The present study aims to validate bond strength of SLJs with dissimilar adherends such as CFRP and Aluminum. Aluminum adherend was considered for surface treatment using Resin pre-coating (RPC) and NaOH for SLJs, as well as mixing structural elements (ZnO tetrapods) within the adhesive. Young-Laplace measurement technique was used to determine the contact angle for specimens with different surface treatments. Nondestructive testing (NDT) methods like ultrasonic testing(UT) and X-ray radiography were used to determine the defects of the SLJs. The strength of the bond was assessed using flexural and tensile test equipment in UTM. Improved bonding performance was observed in terms of maximum load and shear strength of RPC surface treated specimens when compared to surface specimens without treatment. The structural elements mixed into adhesive showed improved bonding performance in terms of flexural strength. A numerical simulation model was developed for validating the results. The morphological studies of de-bonded joints to analyze the bonding mechanism in each group of specimens with maximum load bearing were done.

Numerical evaluation of tensile-loaded tubular scarf adhesive joints

Tubular adhesive joints are widely employed when joining tubes and rods. The loads to which these joints are subjected may be axial or torsional. When loaded in the axial direction, cylindrical joints present stress concentrations in the adhesive layer, as is the case of lap joints. To improve the joint strength in the axial direction, the cross-section of the tubes can be chamfered to produce a scarf tubular joint. The geometrical variations produced by machining the chamfers increase the overall bonding area, leading to higher joint strength. This study aims to compare the tensile performance of tubular scarf joints (TSJ) with aluminium (AW6082-T651) adherends, considering the variation of the scarf angle (α) from 45° to 3.43°; the joints were bonded with a moderately ductile adhesive, the Araldite® 2015. Firstly, through the comparison of experimental tests and numerical analysis of tubular lap joints (TLJ), the cohesive zone model (CZM) technique and respective cohesive parameters were validated. A CZM analysis was then performed on the TSJ to analyse peel (σy) and shear stresses (τxy) in the adhesive layer. Damage and joint strength analyses were also carried out, as well as the study of the dissipated energy for the different joint configurations. The CZM technique was validated, and the numerical analysed showed a major α effect, with benefits for smaller α, and improved stress distributions over TLJ.

Experimental Study of Single-Lap, Hybrid Joints, Made of 3D Printed Polymer and Aluminium Adherends.

This paper presents the results of an experimental study into single-lap joints. One part of the joint was made as a 3D printed polymer and had cylindrical tenons, while the other part was made of an aluminium flat bar having mortises whose diameter and distribution corresponded to the polymer tenons. In addition to the mechanical joint, a layer of double-sided VHB (Very High Bond) adhesive tape was also placed in the lap, thus creating a hybrid joint. In total, 80 specimens were made, which were divided into four groups: A—specimens with one tenon of different diameters, B—specimens with different number of tenons of the same diameter, C—specimens characterised by multi-stage operation and R—reference specimens, connected only by double-sided adhesive tape. The joints were subjected to uniaxial tensile tests. The force–displacement characteristics obtained and the energy required, up to the point of the failure of the joints, have been analysed in this paper. The four and six-stage joints designed can significantly increase the safety of the structures in which they will be used.

Water absorption mechanism and mechanical performance of adhesively joint aluminum alloy with GNP reinforced epoxy

This work investigates the effects of Graphene Nanoplatelets (GNP) reinforcement to water absorption behavior and mechanical properties of adhesively joint aluminum. 1.0 wt% GNP was incorporated into epoxy adhesive to joint aluminum adherend subjected to various immersion periods (10–60 days) for investigating its effect on water uptake, water absorption rate and shear strength. When compared to pristine adhesive, GNP reinforced epoxy exhibit two distinct trends with regard to water uptake and water absorption rate; i) at lower immersion period (10–40 days), increased water uptake and water absorption rate is observed where highest increment recorded are 99.9% and 98.2% respectively at 10 days immersion period, while ii) at longer immersion period (50–60 days) reduced water uptake and water absorption rate is observed where lowest value recorded are 18.4% and 17.9% respectively, at 60 days immersion period. When compared to pristine epoxy, regardless of immersion periods, GNP reinforced specimens have more or less demonstrated retention/deterred joining performance. In this work, it is noted that all fractured specimens with GNP reinforcement demonstrate the combination of both cohesive and adhesive fracture.

Influence of high-temperature and high-humidity aging on the material and adhesive properties of addition curing silicone adhesives

Silicones are commonly used as sealants when high-performance materials are required due to harsh environmental conditions. To ensure a proper sealing function, the buildup of adhesion to the adherends is a prerequisite that is often addressed by the addition of adhesion promoters. However, the investigation of the fundamental adhesion mechanisms of silicones has been widely neglected. This work focuses on adhesive bond properties with aluminum adherends without the usage of adhesion promoters. The influence of high-temperature and high-humidity aging on the adhesive bond and material properties is examined. For this purpose, we formulated an addition curing silicone adhesive with a known composition. Aging took place for up to 56 d at different temperatures ranging from room temperature to 150 °C. In addition, we examined the influence of moisture by applying high-humidity conditions (85 °C/85% relative humidity). Changes in bulk material properties were characterized by stress at break, strain at break, Shore A hardness and swelling degree. Moreover, Fourier-transform infrared (FTIR) spectroscopy provided information about the chemical processes. The adhesive properties were determined using lap-shear joints. At high-temperature aging, the strain at break decreases while the hardness of the bulk material increases. A lower degree of swelling suggests an increasing cross-linking density. At the same time, lap-shear strengths increase and cohesive fracture patterns indicate a substantial buildup of adhesion. The samples aged under high-humidity conditions show a more complicated behavior. The increase in cross-linking density proceeds slower compared to high-temperature conditions (130 °C and 150 °C) but reaches higher values after 56 d. Lap-shear strengths tend to be lower compared to high-temperature storage and are accompanied by a significant amount of adhesive failure. FTIR spectroscopy reveals reactions of the residual hydrosiloxane groups of the cross-linking agent. However, these reactions are insufficient to fully explain the observed behavior. Therefore, reactions of the siloxane backbone are suggested. Although no specific adhesion promoters were used, high-temperature conditions enabled a substantial adhesion buildup of addition curing silicones on aluminum adherends under dry conditions. In contrast, humid conditions disturb adhesion buildup and are rather unfavorable for adhesion.