Ultrasonic Consolidation Process Research Articles

Predictive Thermal Modeling and Characterization of Ultrasonic Consolidation Process for Thermoplastic Composites

Abstract Ultrasonic consolidation (USC) of thermoplastic composites is a highly attractive and promising method to manufacture high-performance composites. This work focuses on USC of dry carbon fiber (CF) fabrics with high-temperature polyphenylene sulfide (PPS) films. Experimental trials to assess feasibility of the process are time-consuming. Consequently, a predictive thermal model would facilitate process parameters selection to reduce expensive trial-and-error approaches. This paper presents a 2D finite element model of samples under consolidation, incorporating equations for viscoelastic heating, matrix phase change, and material properties. Theoretical temperature profiles for nodes of interest were compared to the corresponding experimental temperature curves for various control parameters (i.e., weld time and vertical displacement of sonotrode) and showed good agreement during heating phase. It was found that welding time values below 1750 ms were insufficient to reach melting temperature, whereas weld times above 3000 ms led to the lowest average void content (2.43 ± 0.81%). More specifically, the time the material spent above melting temperature, i.e., residence time, was established as a parameter that could estimate cases resulting in better consolidation and lower void content (time above 2600 ms for void content below 2.5%). X-ray diffraction (XRD) characterization revealed that the USC process led to mostly amorphous PPS, due to the high cooling rates (70 °C/s to 108 °C/s). Overall, the thermal model and micro-structural outcomes confirmed the feasibility of the USC process for layered composites made from dry fabric and high-temperature thermoplastic films.

A novel ultrasonic consolidation method for rapid preparation of diamond/Cu composites

• An innovative method is proposed to design and manufacture diamond/Cu composites. • Diamond/Cu composites were fabricated via ultrasonic consolidation and resistance fast diffusion process. • The interfacial configuration of diamond/Cu composites was investigated. In this study, diamond/Cu composites were fabricated using ultrasonic consolidation and resistance rapid diffusion technology with Cr addition to improve the wettability between diamond and Cu martix, the interfacial configuration and thermal conductivity of diamond/Cu composites were also investigated. Excellent interfacial bonding between diamond and Cu matrix was achieved by surface metallization of diamond with Cr, and the formation of subgrain boundaries was observed in the Cr 7 C 3 and Cu matrix grains near the interface. The thermal conductivity of the composite prepared by this process reaches 421.314 W/m·K when diamond added mass at 1.34%, which is 12% higher than that of the Cu matrix.

Development of an analytical model for optimisation of the ultrasonic consolidation of composite prepreg

Mechanical properties of composite laminates are directly affected by the level of porosity of the part. Therefore, it is important to ensure that an adequate air debulking is provided during the manufacturing in order to obtain high quality products. The use of ultrasonic waves during the hand lay-up of prepreg layers can enhance this step. In a previous work we have demonstrated that this technique, named ultrasonic consolidation (UC), can lead to a large reduction in terms of manufacturing time and improvements of the Interlaminar Shear Strength (ILSS) of the final part. In this work, a model is proposed to analytically describe the influence of the ultrasonic stimulation on the air flux through the material and optimise the procedure, showing how the use of ultrasonic waves significantly increases the net air flow rate, particularly for small radius voids. The study provided some guidelines for the optimisation of the process parameters such as the frequency and location of the transducers. The efficiency of the method was experimentally validated by manufacturing several samples using UC debulking procedure with three exposition times (5-10-15 min). Microscope images showed a large decrement (up to 96%) of the voids projected area in samples section in comparison with reference. Flexural and Charpy impact properties were evaluated through mechanical tests, showing properties comparable to the reference samples, with improvements in terms of flexural modulus (up to 9%). Results from the analytical study and experimental tests indicate that the UC process is a reliable debulking procedure for the hand lay-up of prepreg that largely reduces manufacturing time and voids content, leading to improvements of the mechanical properties of the final part.

Predictive Thermal Modeling and Characterization of Ultrasonic Consolidation Process for Woven Thermoplastic Composites

Predictive Thermal Modeling and Characterization of Ultrasonic Consolidation Process for Woven Thermoplastic Composites

Study of ultrasonically welded thermoplastic dowel-wood board assembly

• Ultrasonic welding is a fast joining of thermoplastic dowel-wood board assembly. • Density of wood board plays an important role in ultrasonic welding. • Dowel pulling force inversely proportional to the depth of the drilled hole. • Ultrasonic thermoplastic dowel welding is not suitable for wet wood boards. This study reports on an ultrasonic welding application for the assembly of a thermoplastic dowel and a wood board. Three types of medium density particleboards (MDP) and fiberboards (MDF) were used to indicate applicability of ultrasonic welding to fix a plastic wedge dowel into the wood boards: light-weight, standard, and heavy. Plastic wedge dowels made of resin nylon thermoplastic polyamide PA66 were used to compose ultrasonically welded wood boards’ joints. Ultrasonic welding is a joining technique without any additional substances, such as adhesives or solvents. It possesses local heating of only the joint area, short cycle times in the range of just a few seconds, and comparatively low cost-efficiency. During the ultrasonic consolidation process, energy generated from an ultrasonic transducer is transferred to the joint components (dowel – wood board) in the form of ultrasonic oscillation. The quality of the welded joint is mainly influenced by the density of the wood board, the quality of wood particles bonding, the depth and diameter of the drilled hole. The size of the contact area of the drilled hole (hole geometry, density and the size of hole walls) is also very important because the molten thermoplastic requires enough space to penetrate and settle to form a solid assembly.

Microstructure and mechanical properties of AI/Fe micro-laminated composites fabricated by ultrasonic consolidation

Ultrasonic consolidation technology is a new method for preparing high-performance laminate composite materials. This rapid consolidation additive manufacturing technology provides a new idea for the integration of complementary functional laminated composite structures. It has great potential for preparation of new generation of complex laminated composite parts, broadening the application field of laminated composite material, and means an advanced 3D additive manufacturing technology for materials and structures. In this paper, it is aimed at Al/carbon steel and Al/Fe laminated composites systems with low cost and multilayer structures, Al/carbon steel and Al/Fe laminated composite samples were consolidated by ultrasonic consolidation process. And the Al/carbon steel and Al/Fe interfacial bonding were studied by SEM and EDS. The hardness and tensile properties of laminated composites were tested by mechanical properties together with the fracture morphology of each interface was studied.

Microstructure and mechanical properties of amorphous strip/aluminum laminated composites fabricated by ultrasonic additive consolidation

Ultrasonic consolidation is a novel forming process for fabricating laminated composites with alternate stacking of tough layer and stiff layer to achieve the desired properties. Laminate composites stacking with Al foil and Fe-based amorphous strip were produced by ultrasonic consolidation. X-ray diffraction and microhardness measurements indicated that the respective structure of the individual layers was preserved together with excellent hardness and stiffness of the amorphous layer. Shear bands in the amorphous strip combined with thermodynamic stability measurements by differential scanning calorimeter (DSC) indicated that the plastic deformation of amorphous layer led to coordinated deformation and mechanical bonding during the ultrasonic consolidation process.

Thermo-mechanical finite element analysis of ultrasonic powder consolidation process

Ultrasonic welding is a solid-state joining process which uses ultrasonic vibration to join materials at relatively low temperatures. Ultrasonic powder consolidation is a derivative of the ultrasonic additive process which consolidates powder material into a dense solid block without melting. During ultrasonic powder consolidation process, metal powder under a compressive load is subjected to transverse ultrasonic vibrations resulting in a fully-dense consolidated product. While ultrasonic powder consolidation process is employed in a wide variety of manufacturing processes, bonding mechanism of powder particles during the consolidation process is not clearly understood. This study uses a coupled thermo-mechanical finite element analysis technique to understand the underlying bonding mechanism involved in ultrasonic powder consolidation process. The study also investigates the effect of critical process parameters including vibrational amplitude and base temperature on the stress, strain, and particle temperature distribution during this process. Based on the results of the simulation, a possible theory on the bonding mechanism involved in ultrasonic powder consolidation process is proposed. The outcomes of this study can be used to further the industrial applications of ultrasonic powder consolidation process as well as other ultrasonic welding based processes.

Experimental ultrasonic sub-surface consolidation of fiber bragg grating for sensorial materials

The paper investigates the ultrasonic consolidation process of fiber optics inside metals. It allows surface embedding of fiber Bragg grating to protect them from exposure to open environment. This particular process requests small amount of heat created at the contact interface to embed the fibers. FEM modeling and simulation of the process has been carried out prior to experiments to evaluate initial process parameters to trigger the experiments. The simulation matched the experimental results. Extensive experiments were carried out to understand the process of ultrasonic consolidation and the effect of its related parameters such as waves amplitude and welding time on the process with a selected host material e.g. aluminum. The ultrasonic frequency was kept constant throughout the tests. Coated fibers are easily embedded and more importantly protecting the fiber optics from an easy breakage while we observe a wavelength shift that should be updated when used for real measurements.

Power consumption and friction coefficient in the ultrasonic consolidation of aluminium alloys

Energy input and friction behaviour are two of the key phenomena related with the welding bond of ultrasonic consolidation (UC) process. In this study, the effects of welding parameters, such as the building height, travel speed, oscillation amplitude and applied force, on the power consumption of the horn and friction coefficient of the welding interface of UC are investigated for aluminium alloys 2024 and 7075. Multiple regression equations are developed to estimate the power consumption and friction coefficient using the welding parameters. A line-contact friction test is performed to examine the friction coefficient of UC under the various applied forces and preheating temperatures. The quantitative relationships among the welding parameters, friction coefficient and power consumption are derived.

Influence of process parameters on bond properties of Al laminated structure produced by ultrasonic consolidation

Purpose The purpose of this paper is to investigate the influence of key parameters on the bond strength and failure modes of laminated structures made of different aluminum alloys (i.e. Al 2024 and Al 7075) via the ultrasonic consolidation (UC) process. Design/methodology/approach The UC is used to fabricate laminated structures with various parameters. The push-pin tests were performed on the specimens of different materials and parameters, and the force and displacement were recorded during the tests. The peak punch force was used to represent the bond quality of the laminated structure, and the curves of force versus displacement were used to study the failure modes of the structures. Findings It is found that the lower normal force, the larger vibration amplitude and the lower travel speed can result in stronger bonding. Three different failure modes are observed in the tests, due to the different relations between the toughness of interface and raw materials. The process parameters have influence on the interface toughness of a laminated structure, which further leads to different failure modes. Originality/value The overall mechanical properties of a laminated structure highly depend on the bond quality between laminated layers. The push-pin test can easily and effectively evaluate the bond quality of the laminated structure. This paper not only focuses on the bond strength evaluation, but also analyzes the different failure modes of laminated structures made of different aluminum alloys, which can give an opportunity to optimize the parameters for different materials.

Mechanical properties and microstructure of Al/Al laminated structure produced via ultrasonic consolidation process

Mechanical properties of a 2024 aluminium alloy laminated structure produced by the ultrasonic consolidation were investigated. In comparison with the monolithic aluminium alloy, the existence of laminated structure gave different fatigue and fracture mechanisms that associated with the layer interfaces. The Al/Al laminated specimens had the lower tensile strength but much higher fracture toughness than the monolithic Al specimens due to the exit of interface delaminations around the crack tip. The fatigue life of the laminated specimens was comparable to that of the monolithic Al specimens, though the initiation and propagation of the crack in the laminated specimens depended strongly on the microstructure of each material. The interface between layers could arrest the fatigue crack and impede the further propagation.

Towards understanding of ultrasonic consolidation process with “process map”

Purpose – The purpose of this paper is to identify the key parameters that control the bonding formation of foils by the ultrasonic consolidation (UC) process and to build the correlations among process operating conditions and key control parameters through the concept of “process map”. Design/methodology/approach – The concept of “process map” is proposed based on the diffusion bonding mechanism for the UC process, and numerical simulations have been applied to the UC process to predict peak temperature and plastic strain at the contact interface by considering a wide range of process operating conditions. Findings – This map reveals that the formation of bonding among foils by the UC process requires a good match between temperature and plastic deformation at the contact interface. This limits the process operating window to a narrow region in the strain – temperature coordinate system. Originality/value – This work has identified the underlying mechanism for bonding formation and the key control parameters of the UC process. The concept of “process map” for the UC process was developed, which allows the process optimization through two critical process control parameters of temperature and plastic strain at the contact interface instead of five operating conditions.

Energy and bond strength development during ultrasonic consolidation

A process model was developed that couples the effects of the three adjustable ultrasonic consolidation (UC) process parameters (amplitude, force and speed) into a single term – thermal weld energy due to frictional and volumetric heat generation. Infrared thermography was used to evaluate weld energy during UC and a relationship was established between weld energy and the peel strength of ultrasonically consolidated aluminum. An optimum processing widow was identified for bonding Al 1100-0 and Al 3003-H14 based on UC processing temperature and weld time. Bonding occurred well below the material melting temperatures, confirming that thermal softening in the bulk of the material or melting are not the bonding mechanisms and that bonding takes place in the solid-state.

In-situ scanning electron microscopy studies of small fatigue crack growth in ultrasonic consolidation bonded aluminum 2024 laminated structure

This work used in-situ scanning electron microscopy method to investigate the small fatigue crack behavior of the aluminum alloy 2024 laminated structure produced by ultrasonic consolidation process. The influence of local microstructure on the crack propagation of the laminates after different heat treatments (T4 and T62) has been compared and discussed. It was found that both the precipitations and the interfaces of the layers could retard crack growth and alter the growth direction, and the effect of interfaces was much stronger. Due to the higher ratio of the toughness to bond strength, the barrier effect of the interfaces on impeding the fatigue crack growth in specimens after the T4 heat treatment was more evident.

Modelling of ultrasonic consolidation using a dislocation density based finite element framework

A dislocation density based constitutive model has been developed and implemented into a crystal plasticity quasi-static finite element framework. This approach captures the evolution of dislocations and grain fragmentation at the bonding interface when boundary conditions pertaining to the Ultrasonic Consolidation process (UC) are prescribed. The model is initially calibrated using experimental data from published refereed literature for simple shear deformation of a single crystal pure aluminum and uniaxial tension of a polycrystalline Aluminum 3003-H18 alloy. The model has then been extended to predict the results of an Al 3003- H18 alloy undergoing UC. Good agreement between the experimental and simulated results has been observed for the evolution of linear weld density and embrittlement due to grain substructure evolution. For computational time efficiencies, a novel time homogenisation approach has been followed which significantly reduces the computational overhead.

A thermomechanical crystal plasticity constitutive model for ultrasonic consolidation

We present a micromechanics-based thermomechanical constitutive model to simulate the ultrasonic consolidation process. Model parameters are calibrated using an inverse modeling approach. A comparison of the simulated response and experimental results for uniaxial tests validate and verify the appropriateness of the proposed model. Moreover, simulation results of polycrystalline aluminum using the identified crystal plasticity based material parameters are compared qualitatively with the electron back scattering diffraction (EBSD) results reported in the literature. The validated constitutive model is then used to simulate the ultrasonic consolidation process at sub-micron scale where an effort is exerted to quantify the underlying micromechanisms involved during the ultrasonic consolidation process.

Ultrasonic Consolidation and Ignition Characteristics of Thermite Composites

The fabrication and characterization of metal‐based energetic composite materials are currently being examined for a range of new applications. A newly developed ultrasonic consolidation process is used for the synthesis of Al/Fe2O3 and Al/Cu2O compacts over a wide range of powder ratios at room temperature. Powder consolidation was achieved by a multistep procedure involving simultaneous application of pressure and ultrasonic vibrations. The observed reaction characteristics of the composites are similar to those of previously reported thermite compacts prepared by a traditional powder metallurgy method.

Finite element analysis of ultrasonic insertion of SiC fibre in aluminium alloy 6061

In this work, a computational framework has been proposed to successfully simulate the fibre embedding using ultrasonic consolidation process. The main components of the proposed computational approach are a developed constitutive model and a friction model which are especially suitable for the condition of ultrasonic process. The effect of different process parameters, such as velocity of sonotrode, displacement amplitude of ultrasonic vibration and applied loads are studied. The presented work especially focuses on the quality of the developed weld and the fibre coverage due to the plastic flow around the fibre. The areas of maximum plastic flow predicted by the simulation are confirmed by the EBSD microstructural studies.

Dislocation Density-Based Finite Element Method Modeling of Ultrasonic Consolidation

A dislocation density based constitutive model has been developed and implemented into a crystal plasticity quasi‐static finite element framework. This approach captures the statistical evolution of dislocation structures and grain fragmentation at the bonding interface when sufficient boundary conditions pertaining to the Ultrasonic Consolidation process are prescribed. Hardening is incorporated using statistically stored and geometrically necessary dislocation densities (SSDs and GNDs), which are dislocation analogs of isotropic and kinematic hardening respectively. The GND considers strain‐gradient and thus renders the model size‐dependent. The model is calibrated using experimental data from published refereed literature and then validated for the Aluminum 3003 alloy. Introduction As a direct result of ongoing research efforts in ultrasonic consolidation (UC) worldwide [1], it has become apparent that a new approach to modeling of UC bonding is needed. A model which provides a better understanding of the effects of process parameter changes on grain refinement, plastic deformation and bonding during UC will better enable researchers to predict which materials will bond, how the mechanical properties of UC-produced parts can be improved, and how to better design the next generation of UC equipment. The continuum properties of parts made using UC are strongly dependent upon the micromechanics of the bonded interface [1]. Interfacial-scale microstructures can be studied fundamentally using electron microscopy [1] and can be used to correlate atomic and mesoscopic mechanisms of deformation to their continuum counterparts. A dislocation density-based crystal plasticity Finite Element Model (FEM) can capture the statistical distribution of dislocations, partials and various deformation mechanisms at the bonding interface as inputs to predict macroscopic deformation profiles as a function of energy input characteristics. These input characteristics are a function of the process parameters used in a UC machine, namely vibration amplitude, normal force, ultrasonic frequency, welding speed, sonotrode geometry and temperature. Problem Formulation It has been shown that material sheets subjected to UC undergo inhomogeneous plastic deformation through their thickness [1]. Classical continuum plasticity theories do not fully explain this phenomenon [2]. Therefore, a study of strain localization and grain refinement at the material interfaces during UC bonding is required. The following steps lead to the calculation of these localized strains and their effects. Large Deformation Quasi-Static Crystal Plasticity Description The deformation map in space and time is described by the total deformation gradient tensor F (Figure 1). Applying the Kroner-Lee assumption, F is decomposed into elastic Fe and plastic gradient Fp tensors using multiplicative operator theory