Polymer-metal Hybrid Structures Research Articles

MECHANICAL AND OPTICAL INVESTIGATION OF LASER WELDED STRUCTURAL STEEL - POLY(METHYL-METHACRYLATE) HYBRID JOINT STRUCTURES

Modern welding processes that can easily be automated (such as friction stir welding, laser welding and ultrasonic welding) are gaining popularity in joining metal-polymer hybrid structures. This field of science is intensively studied around the globe, as a dependable, productive joining method that directly produces structurally sound joints between a metal and a polymer structure could unleash unforeseen possibilities in the vehicle industry. In our experiments, we manufactured hybrid steel-poly(methyl-methacrylate) (PMMA) joints with laser welding, using the 2p design of experiment method. We measured the effect of cellulose reinforcing fibres (in varying weight percentages) on the transparency and weldability of the PMMA material and the effect of welding parameters on the mechanical properties of the joints. We also examined the vicinity of the welded seam with scanning electron microscopy.

Evaluation of Joint Formation and Mechanical Performance of the AA7075-T6/CFRP Spot Joints Produced by Frictional Heat.

The development of lightweight hybrid metal–polymer structures has recently attracted interest from the transportation industry. Nevertheless, the possibility of joining metals and polymers or composites is still a great challenge. Friction Spot Joining (FSpJ) is a prize-winning friction-based joining technique for metal–polymer hybrid structures. The technology is environment-friendly and comprises very short joining cycles (2 to 8 s). In the current work, aluminum alloy 7075-T6 and carbon-fiber-reinforced polyphenylene sulfide (CF-PPS) friction spot joints were produced and evaluated for the first time in the literature. The spot joints were investigated in terms of microstructure, mechanical performance under quasi-static loading and failure mechanisms. Macro- and micro-mechanical interlocking were identified as the main bonding mechanism, along with adhesion forces as a result of the reconsolidated polymer layer. Moreover, the influence of the joining force on the mechanical performance of the joints was addressed. Ultimate lap shear forces up to 4068 ± 184 N were achieved in this study. A mixture of adhesive–cohesive failure mode was identified, while cohesive failure was dominant. Finally, a qualitative comparison with other state-of-the-art joining technologies for hybrid structures demonstrated that the friction spot joints eventually exhibit superior/similar strength than/to concurrent technologies and shorter joining times.

Single-side resistance spot joining of polymer-metal hybrid structures

A new approach for resistance spot welding of hybrid polymer-metal components in overlap joint configuration is shown in this paper. The effect of welding current on the joining zone is demonstrated based on different process parameters. The results were transferred to a model concept of the joining zone geometry depending on current density and electrode arrangement. Furthermore, different surface conditions (corundum blasting, laser structuring) were applied and evaluated regarding mechanical properties.

Interfacial interaction and joining property of direct injection-molded polymer-metal hybrid structures: A molecular dynamics simulation study

Polymer-metal hybrid structures have been increasingly used to replace metallic components. Direct injection joining is one of the most promising technologies in fabricating polymer-metal hybrid structure. In this study, molecular dynamics method was used to study the interfacial interaction and joining property. Interfacial models with different surface structures on aluminum (Al) substrate were constructed. The influences of surface structure, non-bonded interaction strength, and pull-out force during the separation were systematically explored. Simulation results show that an obvious difference in polymer structure along z-axis is observed during the joining process. Influenced by the interfacial interaction, the atomic density is at its largest near the interface. As the separation continues, growing voids are observed near the interface. Polymer chains close to the Al substrate are greatly stretched, while the chains far away from the interface are relatively steady. Nevertheless, the changes in radius of gyration during the separation are much higher regardless of the substrate structures. The contact area mainly contributes to the interaction energy, whereas the mechanical interlocking formed in the undercut area contributes to the maximum inner force and work of separation. Moreover, the interfacial interaction is also affected by the non-bonded interaction strength and the pull-out force.

A Room‐Temperature High‐Conductivity Metal Printing Paradigm with Visible‐Light Projection Lithography

AbstractFabricating electronic devices require integrating metallic conductors and polymeric insulators in complex structures. Current metal‐patterning methods such as evaporation and laser sintering require vacuum, multistep processes, and high temperature during sintering or postannealing to achieve desirable electrical conductivity, which damages low‐temperature polymer substrates. Here reports a facile ecofriendly room‐temperature metal printing paradigm using visible‐light projection lithography. With a particle‐free reactive silver ink, photoinduced redox reaction occurs to form metallic silver within designed illuminated regions through a digital mask on substrate with insignificant temperature change (<4 °C). The patterns exhibit remarkably high conductivity achievable at room temperature (2.4 × 107 S m−1, ≈40% of bulk silver conductivity) after simple room‐temperature chemical annealing for 1–2 s. The finest silver trace produced reaches 15 µm. Neither extra thermal energy input nor physical mask is required for the entire fabrication process. Metal patterns were printed on various substrates, including polyethylene terephthalate, polydimethylsiloxane, polyimide, Scotch tape, print paper, Si wafer, glass coverslip, and polystyrene. By changing inks, this paradigm can be extended to print various metals and metal–polymer hybrid structures. This method greatly simplifies the metal‐patterning process and expands printability and substrate materials, showing huge potential in fabricating microelectronics with one system.

Huge Enhancement of Luminescence from a Coaxial-Like Heterostructure of Poly(3-methylthiophene) and Au.

Recently, the light-matter interaction at nanoscale has attracted great interest from physicists, chemists and material scientists, as it gives peculiar optical properties that couldn’t be observed at the bulk scale. The synthesis and characterization of organic-inorganic heterostructures forming quantum dots, nanowires or nanotubes provide opportunities to understand their photophysical mechanism and to apply optoelecronic devices. Herein, we report a huge enhanced luminescence in a coaxial-like heterostructured poly (3-methylthiophene) (P3MT) with Au. We electrochemically synthesized P3MT nanowires (NWs) on a nanoporous template, and sequentially deposited Au on the surface of P3MT NWs. The diameter of heterostructured P3MT/Au NWs was about 200 nm, where the cladding-shape Au were about 10 nm. The visible range absorbance, with two new absorption peaks of P3MT/Au NWs, was significantly increased compared with that of P3MT NWs. Accordingly, the photoluminescence (PL) of a P3MT/Au NW was enormously increased; up to 170 times compared to that of P3MT NWs. More interestingly, an unexpected enhancement of PL was observed from cross-junction point of P3MT/Au NWs. The abnormal PL properties of P3MT/Au NWs were attributed to the charge transfer and the surface plasmon resonance between the cladding-shape Au and the core-shape P3MT, which resulted in the enhanced quantum yield. This incites us to reconsider the light-matter interaction in polymer-metal hybrid structures applicable for high-performance optoelectronic devices.

Aluminum/polypropylene composites produced through injection molding

The contact angles of molten polypropylene on metals with different surface conditions were examined. A quantitative relation between the surface topography and mechanical strength as well as the optimum dimensional scope of the topography feature for achieving good mechanical performance was determined. High metal temperatures facilitated the filling of the surface features by the polymer melt. The interfacial strength between the metal surface and polymer was dramatically improved by increasing the metal temperature approximately to the heat-distortion temperature of polypropylene. The fracture mechanism of the polymer-metal hybrid structures as well as the correlation between the crystallinity of polypropylene near the interface and the bonding strength was examined. The β-crystals were found to have a significant effect on the mechanical performance of the polymer-metal hybrid structures.

AddJoining: A novel additive manufacturing approach for layered metal-polymer hybrid structures

A novel assembling technique based on additive manufacturing and materials joining principles has been introduced for layered metal-polymer hybrid structures. The AddJoining technique produces layered hybrid structures, using polymer 3D printing methods. The feasibility of the technique was demonstrated using fused deposition modeling for single-lap joint configuration. Microstructure and mechanical strength of the joints were studied using two combinations of materials; aluminum 2024-T3 with acrylonitrile butadiene styrene and aluminum 2024-T3 with alternate layers of polyamide-6 and carbon-fiber-reinforced polyamide-6. The latter reached an average ultimate lap-shear strength of 21.9 ± 1.1 MPa, showing 19% superior performance to the adhesively bonded joints. This exploratory investigation showed the potential of AddJoining to produce metal-polymer layered structures.

Influence of the interlayer film thickness on the mechanical performance of AA2024-T3/CF-PPS hybrid joints produced by friction spot joining

Friction Spot Joining (FSpJ) is an innovative friction-based joining technique for metal-polymer hybrid structures. Friction spot joints of aluminium alloy 2024-T3 and carbon fibre-reinforced poly(phenylene sulphide) composite laminate (CF-PPS) were produced with an additional PPS film interlayer. Two different film thicknesses were investigated in this study: 100 and 500 μm. Lap shear testing demonstrated that the joints produced with 100-μm film (2093 ± 180 N) were stronger than the joints with 500 μm (708 ± 69 N). Additionally, the fracture surface analysis revealed a larger bonding area for the joints with 100-μm film (53 ± 2 mm2) as compared to the joints with 500-μm film (40 ± 1 mm2). Considering the low thermal conductivity of PPS, the thinnest film is more likely to soften by the frictional heat during the joining process. Hence, the low viscosity of the molten PPS favours the wettability of the parts’ surfaces. Microstructural analyses proved that the metallic nub formation and the interdiffusion of PPS chains between film and composite matrix are also favoured for thinner film use. Thus, superior adhesion between the partners is achieved. Therefore, it was concluded that the addition of the thinnest film interlayer leads to stronger joints.

Friction riveting (‘FricRiveting’) of 6056 T6 aluminium alloy and polyamide 6: influence of rotational speed on the formation of the anchoring zone and on mechanical performance

Metal-polymer hybrid structures can be used as an alternative solution for reducing weight and fuel consumption in the transport industry, which aims to minimise the emission of harmful gases that have a greenhouse effect. Friction riveting is a relatively new technique for joining metal-polymer hybrid structures. The process is based on the generation of frictional heat between the components, resulting in the plastic deformation of the end of the metal rivet, which is anchored inside the polymer component. This study assessed the technical feasibility of joining AA 6056 T6 and PA6, focusing on the influence of the rotational speed of the rivet on the mechanical performance of the joints. The maximum temperature reached during the process increased with the rotational speed, from 291 ± 6 °C with 10,000 rev/min to 375 ± 5 °C with 15,000 rev/min. The use of higher rotational speeds led to the tip of the rivet undergoing plastic deformation during the friction phase. This produced mechanically stronger joints, because the metal rivet was anchored more securely in the polymer block. The AA 6056 T6-PA6 joints perform well in terms of tensile strength, reaching 85% of the tensile strength of the metal rivet. We therefore confirmed that it is possible to join AA 6056 T6 and PA6 using the technique of friction riveting, and that rotational speed directly affects the tensile strength of the joints.

Investigating the suitability of roughness parameters to assess the bond strength of polymer-metal hybrid structures with mechanical adhesion

Abstract The joining of distinct incompatible materials, like metals and polymers or fiber-reinforced polymers, is gaining in importance, especially for lightweight applications. Here, it is advantageous if the materials can be joined during the manufacturing of the hybrid component. Besides conventional technologies, like over-molding or the use of adhesive bonds, the use of micro structures is a promising approach for in-mold assembly. However, the characterization of these micro structures to assess the bond strength is difficult, especially for a load perpendicular to the joining surface. This paper deals with the assessment of the bond strength of polymer-metal hybrid structures with micro-structured metal inserts by the use of roughness parameters. The micro structures were produced by electrochemical treatments.

Joining of Incompatible Polymer Combinations by Form Fit Using the Vibration Welding Process

The production of components consisting of various polymer types by welding is severely restricted and only possible for bonding compatible materials with melting points in a close range. Several modifications, such as the cross-linking of one joining partner, allow for circumventing the restrictions regarding the melting points but do not help in joining bonding incompatible materials. Investigations of dissimilar material combinations, especially from polymer-metal hybrid structures, show a high potential of connections based on form fits. Within the scope of this paper, the possibility of joining incompatible polymer combinations, such as polyamide 66 and high-density polyethylene, by micro form fit using the vibration welding process is analyzed. For this purpose, the generated bonding strength of the test specimen was determined by shear tests. Furthermore, the undercuts of the generated prestructures and the resulting bond of the test specimen were examined microscopically by computer-tomography. These investigations depict the high potential of joining incompatible polymer combinations by form fit in the vibration welding using prestructuring to generate undercuts.

Friction Spot Joining of aluminum alloy 2024-T3 and carbon-fiber-reinforced poly(phenylene sulfide) laminate with additional PPS film interlayer: Microstructure, mechanical strength and failure mechanisms

Abstract Friction Spot Joining is an innovative friction-based joining technique for metal–polymer hybrid structures. In this work, aluminum alloy 2024-T3 and CF-PPS friction-spot joints were produced with additional PPS film interlayer. The joints were investigated in terms of the microstructure, mechanical performance under quasi-static loading and failure mechanisms. Macro- and micro-mechanical interlocking as well as adhesion forces were identified to dictate bonding mechanisms in the FSp joint with film interlayer. The ultimate lap shear force of the joints (2700 ± 115 N up to 3070 ± 165 N) were 20%–55% higher than the corresponding joints without interlayer, due to the larger bonding area, better load distribution and improved micro-mechanical interlocking. The failure analysis of the joints revealed a mixture of adhesive-cohesive failure, whereas cohesive failure was dominant.

Influência da Espessura do Filme Polimérico Intermediário na Resistência Mecânica de Juntas Híbridas de Alumínio 2024-T3 e CF-PPS Produzidas por União Pontual por Fricção

Resumo A União Pontual por Fricção (FSpJ) é uma técnica inovadora para união de estruturas híbridas metal-polímero e baseia-se na geração de calor por fricção. Juntas de alumínio 2024-T3 e compósito laminado de poli(sulfeto de fenileno) com fibra de carbono (CF-PPS) foram produzidas com filme intermediário de PPS. Duas espessuras de filme foram investigadas: 100 e 500 µm. Ensaios de cisalhamento sob tração demonstraram que as juntas com filmes de 100 µm são mais resistentes (2093 ± 180 N) em relação às juntas com filme de 500 µm (708 ± 69 N). Adicionalmente, as superfícies de fratura das juntas revelaram áreas de união maiores para as juntas com filmes de 100 µm (53 ± 2 contra 40 ± 1 mm2). Para o filme mais fino, a extensão do amolecimento devido ao calor friccional é maior. Consequentemente, a baixa viscosidade atingida com a fusão do polímero favorece a molhabilidade das superfícies dos componentes da junta pelo PPS amolecido, resultando em melhor adesão entre as partes. Ademais, análises microestruturais demonstraram que a formação do cerne metálico e a interdifusão das moléculas de PPS entre compósito e filme também são favorecidas. Portanto, concluiu-se que a adição do filme mais fino produziu juntas mais resistentes.

On the feasibility of a friction-based staking joining method for polymer–metal hybrid structures

The increased use of hybrid structures to reduce weight currently faces the limitations of traditional joining methods. Consequently there is a niche for development of new joining techniques, which can reduce or overcome some of the existing limitations. This paper presents for the first time the new Friction-based Injection Clinching Joining technique (F-ICJ), describing the microstructure and changes in local properties of joints between polyetherimide (PEI) and aluminum alloy 6082-T6. A shear layer around the rotating tool composes a polymer thermomechanically affected zone (PTMAZ), which presents pores as a result of evolution of gaseous products. The PTMAZ shows decreases of 8% to 12% in local strength compared to the base material, as measured by microhardness. Ultimate forces of 1419±43N in lap shear and 430±44N in cross tensile were achieved for F-ICJ joints. These levels are similar to ultrasonic staking joints of the same material combination, but the hollow design of F-ICJ stakes accounts for improved strength-to-weight ratio (18% in lap shear, 21% in cross tensile). Although the F-ICJ process currently requires longer cycles (7.5s) than state-of-the-art ultrasonic staking (2.8–2.9s), generated results indicate that the F-ICJ process is a competitive staking joining method with potential for improvement.

Rebitagem por Fricção (“FricRiveting”) de Liga de Alumínio 6056 T6 e Poliamida 6: Influência da Velocidade de Rotação na Formação da Zona de Ancoragem e no Desempenho Mecânico

Resumo O uso de estruturas híbridas metal-polímero é uma alternativa para a redução de peso e de consumo de combustível na indústria de transporte que visa minimizar a emissão de gases nocivos ao efeito estufa. A Rebitagem por Fricção (‘Friction Riveting) é uma técnica relativamente nova para união de estruturas híbridas metal-polímero. O processo baseia-se na geração de calor friccional entre os componentes resultando na deformação plástica da extremidade do rebite metálico, que é ancorado dentro do componente polimérico. O presente estudo avaliou a viabilidade técnica da união de AA 6056 T6 e PA6, com foco na influência da velocidade de rotação do rebite no desempenho mecânico das juntas. A máxima temperatura atingida no processo aumentou com o acréscimo na velocidade de rotação, de 291 ± 6°C com 10000 rev/min para 375 ± 5°C com 15000 rev/min. A utilização de maiores valores de velocidade de rotação causou a deformação plástica da ponta do rebite durante a fase de fricção. Isso levou a juntas mecanicamente mais resistentes, devido à maior ancoragem do rebite metálico na placa polimérica. As juntas de AA 6056 T6-PA6 apresentaram bom desempenho de resistência à tração atingindo 85% da resistência à tração do rebite metálico. Portanto, verificou-se que é possível unir AA 6056 T6 e PA6 pela técnica de rebitagem por fricção e que a velocidade de rotação influencia diretamente a resistência à tração das juntas.

Combining mechanical interlocking, force fit and direct adhesion in polymer–metal-hybrid structures – Evaluation of the deformation and damage behavior

The joint of long fiber reinforced thermoplastic polymer–metal-hybrid structures is evaluated. For this the deformation and damage behavior of joints combining mechanical interlocking, force fit and direct adhesion is determined experimentally. Results show that each joining mechanism results in a specific deformation and damage behavior. Experimental results also show that the behavior of the combination is dependent on the interaction of the single joining mechanisms. With finite element simulations the deformation and damage behavior of joints with combined mechanism has been evaluated beyond the tested configurations. It is demonstrated how the developed simulation tool can be used to support the selection of the best joint configurations.

Experimental investigations and modeling of the melting layer in polymer-metal hybrid structures

The melting layer in thermal joining of polymer-metal hybrid joints is analyzed according to process management and microstructure. These results were transferred to spot joints for describing the material behavior and the resulting joining zone. This leads to a generally valid model concept for laser-based polymer-metal joining.

Friction Spot Joining of aluminum AA2024/carbon-fiber reinforced poly(phenylene sulfide) composite single lap joints: Microstructure and mechanical performance

Friction Spot Joining is a promising alternative joining technology for polymer–metal hybrid structures. In this work, the feasibility of Friction Spot Joining of aluminum AA2024-T3 (bare and alclad)/carbon-fiber reinforced poly(phenylene sulfide) is reported. The process temperature and the microstructure of the joints were investigated. Lap shear tensile strength as high as 27MPa was achieved by using aluminum bare specimens. Sand blasting was also performed as an effective mechanical surface pre-treatment on aluminum surfaces, which resulted in higher surface roughness and accordingly improved mechanical performance for the selected conditions. In addition, the alclad specimens exhibited promising mechanical performance (lap shear strength of up to 43MPa) that justifies further investigations. Finally, the bonding and failure mechanisms of the joints are briefly discussed.

Polymer-Metal Hybrid Structures Based on Polydiphenylamine and Co Nanoparticles

Polymer-metal hybrid structures based on polydiphenylamine (PDPhA) with Co nanoparticles homogeneously distributed in polymer matrix have been prepared for the first time. In situ synthesis of Co/PDPhA hybrid structure is carried out during condensation of diphenylamine crystalline oligomers in the presence of Co acetate (Co(CH3COO)2 4H2O) under the conditions of IR-irradiation. As a result, polymer chain growth occurs and hydrogen molecules are eliminated. Reduction of Co2+ up to Coo takes place under IR-irradiation with participation of hydrogen. The structure, content and morphology of obtained hybrid materials were characterized by Fourier-transform IR-spectroscopy, X-ray powder diffraction patterns, atomic-absorptive spectroscopy and transmission electron microscopy (TEM). Co nanoparticles appeared to exist in -Co and -Co modifications. Their relationship depends on IR-light intensity and time treatment. Co nanoparticles dimensions fall inside the limits of 2 < d < 8nm as it is indicated from TEM microphotographs. Magnetic properties of Co/PDPhA were investigated and superparamagnetic behavior was proved. Thermal properties of nanocomposites were evaluated by thermogravimetric analysis and excellent thermal stability was shown.