Characterization of Long‐Term Durability of Induction Welded Aluminum/Carbon Fiber Reinforced Polymer‐Joints

Abstract

Joining metal to carbon fiber reinforced polymer (CFRP) with a thermoplastic matrix is an essential contribution to lightweight construction since it offers new design possibilities: the design of hybrid structures. Hybrid structures can realize the optimized application of specific material qualities by enabling the substitution of single metal parts from metal structures with CFRP parts. An analysis of the aging behaviour of hybrid structures and the influence of different pretreatments on the aging behaviour are an essential step towards industrial application.Some results presented in the literature dealing with the aging behavior of metal/polymer joints include Guermazi et al. who researched the aging behavior of high density polyethylene coatings for pipeline applications with the conclusion that the aging affected is based on the diffusion of water molecules into the coating. [1] For the testing, the samples were immersed for six month in synthetic sea water and for reverence also in distilled water at a temperature of 70°C. The tensile strength, the tribological properties and the absorptions rate of the coating were analyzed. Nakache et al. conducted experiments on the aging of polymer/metal joints for submarine applications in sea water with cathodic protection and came to the conclusion that the delamination of the bond was caused by free radicals which were a product of reduced oxygen present in sea water. [2] The examined material was a polychloroprene with silica filler on a substrate of a copper-aluminum alloy. Both studies deal with complete submersion of the joints during the tests and during application. Therefore these results are only of limited comparability to this study. Other investigations which correlate to this study in a better way are: Hoikkanen et al. who tested the aging behavior of metal and ester based thermoplastic urethane (TPU) hybrid joints and compared different pre-treatments after accelerated aging. [3] The used pre-treatment methods for the substrate were electrolytic polishing with different parameters and etching. For the accelerated aging three different parameters were used: Isothermal aging (500 h at 85°C and ambient atmospheric conditions), isohume aging (500 h at 25°C and 85% relative humidity) and a combination of both (500 h at 85°C and 85% relative humidity). It was concluded that the mechanical properties of the joints are mainly dependent on the level of degradation of the TPU. Rahme et al. investigated the influence of humidity (distilled water) in the joining zone to the strength of the bonding. [4] For pre-treatment an acid was used based on 2% hexaflurotitanic acid in water and varied combinations of the additional components phosphoric acid, Manganese phosphate, Titanium and an organic phase (polyvinyl phenol modified with an amino group). It was discovered that the effects of the humidity are reversible just by drying the joints. De'Nève et al. conducted the aging behavior with torsional adhesive joints of bare and zinc electro-coated steel using a fill...

Durability of Metal-Composite Friction Spot Joints under Environmental Conditions

“…However, after one year both sets of joints retained more than 50% of their initial lap shear strength. These results are similar to those reported for the induction welding of the metal-composite joints after weathering conditions [24]. It can be argued that the moisture and humidity could penetrate slightly into the overlap area, deteriorating the bonding between the aluminum and composite, especially in the area of the consolidated molten PPS (known as AZ).…”

“…No information could be found in the literature regarding the influence of surface pre-treatments on the accelerated aging behavior of welding-based joining techniques. A few works have been published aiming at understanding the mechanical performance of metal-polymer hybrid joints under natural outside weathering [24,25]. Didi et al investigated the influence of different aluminum surface pre-treatments on the mechanical performance of AA5754/carbon-fiber-reinforced polyamide 66 (CF-PA66) induction welded joints after one year of weathering conditions [24].…”

“…A few works have been published aiming at understanding the mechanical performance of metal-polymer hybrid joints under natural outside weathering [24,25]. Didi et al investigated the influence of different aluminum surface pre-treatments on the mechanical performance of AA5754/carbon-fiber-reinforced polyamide 66 (CF-PA66) induction welded joints after one year of weathering conditions [24]. The authors reported that degreasing and corundum blasting resulted in a very low retained lap shear strength after 12 months.…”

Failure and fracture micro-mechanisms in metal-composite single lap joints produced by welding-based joining techniques

“…The influence of surface pre-treatments on the mechanical performance of the metalcomposite joints [21,[24][25][26], their durability [27,28] and fatigue performance [29] were also briefly reported in the literature. Despite the current knowledge on the physics of the processes and fundamental properties of welding-based metal-composite joints, there is still a lack of available information in the literature compared to the mature joining techniques such as adhesive bonding.…”

Joining of carbon fibres with aluminium structures – Processing and infiltration modelling

“…Consequently, a range of innovative joining techniques for combining fibres and metallic structures has been developed in the recent past. Ultrasonic welding, 2 friction lap joining 3 and induction welding 4 are used in practice today and demand the partial melting of the polymer matrix of a carbon reinforced polymer (CFRP). Energy required for melting is introduced in different ways depending on the heating process.…”