Papers by Keyword: Adhesive Bonding

Abstract: Adhesive bonding is increasingly used in lightweight structural applications, though its effectiveness for carbon fiber reinforced polymers is often limited by low surface energy. This study investigates the concurrent effect of infrared laser surface texturing and resin pre-coating on the mechanical performance of carbon fiber-reinforced polymer single-lap joints. Using a CO₂ laser system, micro-dimples were generated on the substrate to promote mechanical interlocking, while various concentrations of an epoxy resin (5 wt%, 10 wt%, and 20 wt%) were applied as precoating to enhance surface wetting and interfacial continuity. To validate the experimental findings, a numerical investigation was performed using a Cohesive Zone Model implemented within a finite element framework. This model utilized a bilinear traction-separation law and a quadratic delamination criterion to predict the progressive debonding and failure of the interface. Experimental results indicate that the 10 wt% resin pre-coating concentration provides the highest lap shear strength.

Abstract: This study explores the application of Polycarbosilane (PCS) as an intermediate adhesive bonding technique for 4H-SiC substrates aiming to overcome the challenges of producing high-quality and cost-effective substrates for high-power electronics. Thin layers of PCS mixed with m-xylene and AIBN (azobisisobutyronitrile) were deposited onto 4H-SiC substrates via a spin coating. For demonstration purposes, these coated 4H-SiC substrates were then bonded with another 4H-SiC substrate. A defect-free, high-temperature stable bond is facilitated by annealing at high temperatures. Effusion measurements were conducted to characterise the PCS thin films and examine the organic-inorganic transitions and the resulting outgassing at high temperatures. SEM analysis confirmed the uniformity of the bonded layer. These results demonstrate PCS’s potential in high-temperature applications and will stimulate further research exploring doped SiC bonding layers and their electrical properties.

Abstract: A structural composite material is obtained by incorporating continuous and strong fibres in a polymer matrix. Such a design leads to materials with exceptional mechanical properties over a very small density. This family of composite materials can be extended further by combining special designs of composite sub-parts, like in honeycomb structures. Thanks to their performances, these composites are increasingly used in a range of applications mainly in the energy, construction, automotive and aerospace sectors. However, it is very difficult to dismantle composite materials in multi-material structures for recycling purposes; currently, they are mainly incinerated to produce energy. The present paper proposes adding “smart chemical additives” during composite manufacturing and assembly, which will facilitate both the separation of multi-material structures into single blocks, and the separation of composite sub-parts into raw materials. This innovative “debonding on-demand” function provides a significant incentive to using composite materials in a circular economy, i.e. promoting the repair, reuse and recycling of these materials.

Abstract: In the last decades, structural adhesives have found an increasing use owing to the fact that they, compared to traditional techniques like bolting and riveting, allow more uniform stress in the joint without drilling the parts of the assembly. Moreover, the quality of a bonded joint is strongly linked to the surface treatment used for the adherends. Recently, many studies showed the opportunity to use a CO₂ laser for enhancing the mechanical properties of bonded joints in FRP. Nowadays, to optimize their process parameters and texturing represent a necessary step for the growth in this technology. In this work, a numerical study of the effect of laser texturing on end notched flexure (ENF) joints realized in CFRP has been developed. In particular, it is possible to design of the laser texturing for optimizing the mechanical response of bonded joints.

Abstract: The surface condition of carbon fibre reinforced plastic (CFRP) substrates is decisive to obtain high bond strength and lifetime of adhesively bonded parts. Those surfaces were adjusted in terms of their microscopic topography by means of peel plies and release foils. The subsequent surface treatment via atmospheric pressure plasma jet or vacuum blasting allowed the modification of the microscopic roughness as well as the surface chemistry. Those configuration were assessed using surface analytic methods as well as quasi-static and cyclic fracture tests on single lap shear specimens. The microscopic surface roughness, if at all, only showed a small influence on the bond strength. Despite release agent residues, fracture was found within the fiber-matrix interface, which caused difficulties in evaluating the effect of surface pretreatments on the adhesion strength. Fatigue tests revealed a lifetime reduction of uneven microscopic rough surfaces, which was assigned to stress concentrations at the tip of asperities. The crack propagation was accelerated in case of release agent residues. If surfaces were free of contaminations, no differences between microscopically smooth and slightly structured surfaces were found. Overall, fatigue testing on single lap shear specimens showed an increased sensitivity with regard to the assessment of surface morphology.

Abstract: Hot stamping of high strength steel parts is an established way to realize today ́s structural lightweight components in car bodies through sheet thickness reduction. The steel typically used for hot stamping is a boron-manganese 22MnB5 steel reaching up to 1,900 MPa in strength. New boron-manganese alloys achieving higher strength are expected to be developed, generating challenges for the manufacturing process by means of formability. Thus, a further reduction of steel thickness resulting in lighter components is not expected. Hybrid lightweight design approaches aim at weight reduction by reducing steel thickness and applying fiber-reinforced plastics (FRP) to regain structural stiffness and strength. The use of residual heat remaining from the hot stamping process allows to activate adhesives to bond FRP to hot stamped steel. The performances of adhesive bonds depend strongly on surface characteristics. To avoid scaling and decarburization during the heating process several coatings for hot stamped steels are used forming intermetallic layers through heat treatment. The most common coating in today’s automotive application is an Al-Si coating. Thus, the overall performance of the adhesive bonded hot stamped metal polymer hybrid is not only depending on adhesives performance but also strongly on the hot stamped steel’s coating performance. In this paper, the characteristics of hot stamped steel 22MnB5 Al-Si coating are investigated with regard to adhesion performance. Therefore, hot stamped specimens are manufactured under realistic industrial conditions investigating the influence of furnace temperature and dwell time on the overall coating and intermetallic layers of Al-Si coating. The specimens are investigated with respect to Al-Si coating thickness, lap shear strength of hybrid specimen and tensile strength of hot stamped steel demonstrating the dependency of the overall hybrid specimen performance from the coating performance.

Abstract: Ultrasonic inspection using b-scan (brightness scan) and its application for discontinuity and flaws detection were investigated. Brightness scan is one of the ultrasonic technique’s branches, it provides thorough image of the material which undergone inspection via density of the material where then depicted in different colour in conjunction with the acoustic impedance of the phase gone through by the sound wave. The sound wave generated with a piezoelectric transducer was propagated through aluminum wafer samples and were identified by the b-scan system. Its ability to detect flaw at certain depth which was introduced manually been examined. Experimental results show different brightness characteristic, depending on the adhesive treatments, type of material and medium when the waves pass through in each sample. Brightness scan system was proven to be reliable non-destructive testing method in ultrasonic for inspection of structural bonded materials.

Abstract: Innovative lightweight structures realized by employing assembly injection molding bears high potential. Using assembly injection molding, complex shaped hybrid structures can be manufactured in a precise and fast processing step. Though, especially the interface quality of a hybrid joint is a crucial factor, which determines the overall quality of such lightweight structures. High bonding strength values were achieved between aluminum and multiple polymeric materials with double-lap joints manufactured by employing assembly injection molding. Thereby, the influence of aluminum surface pre-treatments as well as intrinsic adhesion modifications of the polymeric materials were investigated.

Abstract: Adhesive bonding is a suitable joining technique for composite materials. The thick adherents shear’ tests (TASTs) are common joint-specimen tests performed to determine the adhesive shear properties. This paper presents the results of numerical modelling of several TAST specimen configurations. The numerical models were conceived considering the adherents made of fiber reinforced polymer (FRP) strips and bonded with an epoxy type adhesive. The adhesive layer thickness has varied as 1 mm, 2 mm and 3 mm, while the overlap length has been increased from 50 mm to 70 mm and 100 mm, respectively. Unidirectional tensile load of 500 N, 1000 N and 2000 N are applied and the stress-strain distributions are investigated. The results are presented in terms of total deformation, equivalent stress (von-Mises) and equivalent strain (von-Mises).

Abstract: The recent trend in automotive industry is characterized by the replacement of existing metal materials with composite ones or the combination of both for lightweight parts. This study 1) created single lap joint specimens of SPCC used for automobile frame and four adhesives; epoxy, urethane, acrylic, mixed (urethane and acrylic) and rivets to bind dissimilar materials of CFRP necessary for weight lightening, and 2) performed a tensile shear test on adhesive bonding versus adhesive bonding with rivets. In summary, this study investigated on the bonding performance of different specimens: bonding strength, shapes of the failure surface, and the effect of rivets on bond strength.