Investigating the effect of ultrasonic consolidation on shape memory alloy fibres

This research was driven by the capability of the Ultrasonic Consolidation (UC) manufacturing process to create smart metal matrix composites for use within high value engineering sectors, such as aerospace. The UC process is a hybrid additive/subtractive manufacturing process that embeds fibres into metal matrices via the exploitation of a high plastic flow, low temperature phenomenon encountered at ultrasonic frequency mechanical vibrations. The research concerned an investigation of the use of the UC process for embedding Nickel-Titanium alloy (NiTi) shape memory alloy (SMA) fibres into Aluminium (Al) matrices which could potentially be used as vibration damping structures, stress state variable structures, as well as other future smart material applications. It was hypothesised that the fibre volume fraction within a UC matrix was limited due to a reduction in foil/foil bonding, caused by increased fibre numbers, as opposed to the total level of plastic flow of the matrix material being insufficient to accommodate the increased fibre numbers. This hypothesis was tested by increasing the NiTi SMA fibre volume fraction, within an Al 3003 (T0) metal matrix, beyond that of previous UC work. The metal matrix and the fibre matrix interface of these samples was then microscopically analysed and the overall UC sample integrity was tested via mechanical peel testing. It was found that a fibre volume fraction of ~9.8% volume (30 X Ø100 µm SMA fibres) was the maximum achievable using an Al 3003 (T0) 100 µm thick foil material and conventional UC fibre embedding. A revised hypothesis was postulated that the interlaminar structure created during UC was affected by the process parameters used. This interlaminar structure contained areas of un-bonded foil and the increase of UC process parameters would reduce this area of un-bonded foil. Areas of this interlaminar structure were also thought to have undergone grain refinement which would have created harder material areas within the structure. It was suggested that maximum plastic flow of the matrix had not been reached and thus the use of larger diameter NiTi SMA fibres were embedded to increase the effective SMA fibre volume fraction within Al 3003 (T0) UC samples. It was suggested that the embedding of SMA fibres via UC had an abrasive effect on the SMA fibres and the SMA fibres had an effect on the Al 3003 (T0) microstructure. It was further suggested that the activation of UC embedded SMA fibres would reduce the strength of the fibre/matrix interface and the matrix would impede the ability of the SMA fibres to contract causing a forceful interaction at the fibre to matrix interface, weakening the UC structure. The investigation to test the revised hypothesis was broken down into three sections of study. Study 1 was a methodology to determine the characteristics of the interlaminar surface created via UC and how this surface affected the nature of the consolidated sample. UC samples of Al 3003 (T0) were manufactured using a range of process parameters. The analysis involved optical microscopy to determine the UC weld density and the interlaminar surface; mechanical peel testing to quantify the interlaminar bond strength; white light interferometry to measure the interlaminar surface profile and microhardness measurements to determine the hardness of the interlaminar material. Study 2 was a methodology to allow the analysis of the microstructural and mechanical interactions at the fibre/matrix interface, post-UC. Al 3003 (T0) samples were manufactured via UC using a range of process parameters with various NiTi SMA fibre diameters embedded. The analysis involved using mechanical peel testing to determine the interlaminar bond strength; optical microscopy to determine the level of fibre encapsulation; scanning electron microscopy and focussed ion beam analysis to analyse the fibre and matrix grain structures and microscopic interactions. Study 3 was a methodology to investigate the fibre usage as would be expected from envisaged applications of an SMA containing metal matrix composite. Samples were manufactured using a range of UC process parameters with various SMA fibre diameters embedded and the embedded SMA fibres were subjected to different extension/contraction cycle numbers. The analysis involved using mechanical peel testing to determine the interlaminar bond strength; optical microscopy to determine the level of fibre encapsulation and the interlaminar effect of fibre activation; fibre pullout testing to measurement the strength of the fibre/matrix interaction and load rate testing of the activated SMA fibres to monitor performance. The interlaminar surface was found to affect the strength and density of interlaminar bonding during the UC process and the use of higher UC process parameters affected this interlaminar structure. Levels of un-bonded material were found within the interlaminar structure and these levels were found to decrease with increasing sonotrode amplitude and pressure with reducing speed. It was suggested that a specifically texture sonotrode could be developed to modify the interlaminar structure to the requirements of the intended sample application. The measurement of the interlaminar material hardness was unsuccessful and future work would likely require a different methodology to measuring this. The work identified a grain refining effect of the embedded SMA fibres on the Al 3003 (T0) matrix material, (grain sizes were reduced from ~15 µm to <1 µm within 20 µm of the SMA fibres), as well as localised damage caused by the UC process to the SMA fibres. The performance of the activated SMA fibres established that this damage did not prohibit the ability of the SMAs to function however the compressive nature of the Al 3003 (T0) matrix was identified as reducing the ability of the SMA fibres to contract. Additionally it was found that the activation of SMA fibres within an Al 3003 (T0) matrix resulted in a reduction of the fibre/matrix interface strength which allowed fibres to be pulled from the composite with greater ease (a loss of ~80% was encountered after a single activation and extension cycle). The use of larger SMA fibre diameters allowed for the fibre volume fraction to be increased however the activation of these SMA fibres had a delaminating effect on the Al 3003 (T0) structure due to the size of the radial expansion of the SMA fibre. The work furthered the understanding of the effect of UC on SMA fibres and highlighted the importance of the interlaminar surface in UC and that to increase the SMA fibre volume fraction to a useable level (25-50%) then an alternative fibre embedding method within UC is required. The fibre/matrix interface interactions during SMA activation have implications in the ability of UC SMA embedded smart metal matrix composites to function successfully due to weakening effects on fibre matrix interface strength and the ability to achieve SMA fibre activation within the metal matrix

The effect of ultrasonic excitation on the electrical properties and microstructure of printed electronic conductive inks

Ultrasonic Additive Manufacturing (UAM) is an advanced manufacturing technique, which enables the embedding of electronic components and interconnections within solid aluminium structures, due to the low temperature encountered during material bonding. In this study, the effects of ultrasonic excitation, caused by the UAM process, on the electrical properties and the microstructure of thermally cured screen printed silver conductive inks were investigated. The electrical resistance and the dimensions of the samples were measured and compared before and after the ultrasonic excitation. The microstructure of excited and unexcited samples was examined using combined Focused Ion Beam and Scanning Electron Microscopy (FIB/SEM) and optical microscopy. The results showed an increase in the resistivity of the silver tracks after the ultrasonic excitation, which was correlated with a change in the microstructure: the size of the silver particles increased after the excitation, suggesting that inter-particle bonding has occurred. The study also highlighted issues with short circuiting between the conductive tracks and the aluminium substrate, which were attributed to the properties of the insulating layer and the inherent roughness of the UAM substrate. However, the reduction in conductivity and observed short circuiting were sufficiently small and rare, which leads to the conclusion that printed conductive tracks can function as interconnects in conjunction with UAM, for the fabrication of novel smart metal components

Additive manufacturing using extra-terrestrial multi-component ceramic materials

Powder Bed Fusion (PBF) based Additive Manufacturing (AM) is a category of advanced manufacturing technologies that can fabricate three-dimensional assets directly from CAD data, on a successive layer-by-layer strategy by using thermal energy from a laser source, to irradiate and fuse particles on a powder bed. The aim of this research was to investigate the application of this advanced manufacturing technique to laser process ceramic multicomponent materials into 3D layered structures. These ceramic materials matched those found on the Lunar and/or Martian surface. These indigenous extra-terrestrial materials could potentially be used for manufacturing physical assets onsite (i.e. off World) on future planetary exploration missions and could cover a range of potential applications including infrastructure, radiation shielding, thermal storage, etc. JSC-1A Lunar and JSC-Mars-1A Martian soil simulants, mimicking the mineralogical and basic properties of these planetary indigenous materials were used for the purpose of this study and processed with commercially available laser additive manufacturing equipment. The results of the laser processing were investigated and quantified through mechanical hardness testing, optical and scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). The research resulted in the identification of a range of parameters that resulted in the successful manufacture of three-dimensional components from Lunar and Martian ceramic multicomponent simulant materials. The feasibility of using thermal based additive manufacturing with multi-component ceramic materials has therefore been established which represents a potential solution to off-world bulk structure manufacture due to there being no requirement for additional materials and resources other than the manufacturing equipment to be shipped off-world

Additive manufacturing of physical assets by using ceramic multicomponent extra-terrestrial materials

Powder Bed Fusion (PBF) is a range of advanced manufacturing technologies that can fabricate three-dimensional assets directly from CAD data, on a successive layer-by-layer strategy by using thermal energy, typically from a laser source, to irradiate and fuse particles within a powder bed.The aim of this paper was to investigate the application of this advanced manufacturing technique to process ceramic multicomponent materials into 3D layered structures. The materials used matched those found on the Lunar and Martian surfaces. The indigenous extra-terrestrial Lunar and Martian materials could potentially be used for manufacturing physical assets onsite (i.e., off-world) on future planetary exploration missions and could cover a range of potential applications including: infrastructure, radiation shielding, thermal storage, etc.Two different simulants of the mineralogical and basic properties of Lunar and Martian indigenous materials were used for the purpose of this study and processed with commercially available laser additive manufacturing equipment. The results of the laser processing were investigated and quantified through mechanical hardness testing, optical and scanning electron microscopy, X-ray fluorescence spectroscopy, thermo-gravimetric analysis, spectrometry, and finally X-ray diffraction.The research resulted in the identification of a range of process parameters that resulted in the successful manufacture of three-dimensional components from Lunar and Martian ceramic multicomponent simulant materials. The feasibility of using thermal based additive manufacturing with multi-component ceramic materials has therefore been established, which represents a potential solution to off-world bulk structure manufacture for future human space exploration

Assessing extraterrestrial regolith material simulants for in-situ resource utilization based 3D printing

This research paper investigates the suitability of ceramic multicomponent materials, which are found on the Martian and Lunar surfaces, for 3D printing (aka Additive Manufacturing) of solid structures. 3D printing is a promising solution as part of the cutting edge field of future in‐situ space manufacturing applications. 3D printing of physical assets from simulated Martian and Lunar regolith was successfully performed during this work by utilising laser‐based powder bed fusion equipment. Extensive evaluation of the raw regolith simulants was conducted via Optical and Electron Microscopy (SEM), Visible‐Near Infrared/Infrared (Vis‐NIR/IR) Spectroscopy and thermal characterisation via Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). The analysis results led to the characterisation of key properties of these multicomponent ceramic materials with regards to their processability via powder bed fusion 3D printing. The Lunar and Martian simulant regolith analogues demonstrated spectral absorbance values of up to 92% within the Vis‐NIR spectra. Thermal analysis demonstrated that these materials respond very differently to laser processing, with a high volatility (30% weight change) for the Martian analogue as opposed to its less volatile Lunar counterpart (<1% weight change). Results also showed a range of multiple thermal occurrences associated with melting, glass transition and crystallisation reactions. The morphological features of the powder particles are identified as contributing to densification limitations for powder bed fusion processing. This investigation has shown that – provided that the simulants are good matches for the actual regoliths – the lunar material is a viable candidate material for powder bed fusion 3D printing, whereas Martian regolith is not

Embedding of printed electronic interconnections in additively manufactured metal components

Ultrasonic Additive Manufacturing (UAM) is an advanced hybrid manufacturing technology, which enables the embedding of electronic components and interconnections within solid metal structures, due to the low temperature/high plastic flow encountered during ultrasonic bonding. The UAM process is based on the ultrasonic metal welding of thin metal foils in a layer-by-layer fashion. This work summarises the recent advances made towards the integration of UAM with printed electronics and other advanced manufacturing technologies for the encapsulation of conductive tracks between the interfaces of the welded foils. Two different approaches were followed: Screen printing was utilized in the first approach, for the deposition of an insulating polymer layer and silver-loaded conductive adhesive tracks on the surface of an aluminium substrate prepared with UAM. In the second approach, the aluminium foils were surface modified prior to welding, in order to selectively create an insulating ceramic layer directly onto the foil surface. These modified foils were bonded using UAM and a syringe system was used for the dispensing of the silver conductive tracks. The effectiveness and advantages of each of these two methodologies are illustrated and commented upon. The results of this ongoing research project are promising and showcase the successful integration of advanced manufacturing technologies for the fabrication of intricate metal structural electronic components

3D printing with extraterrestrial materials

Additive manufacturing and its related powder bed fusion process category, consists of a group of key enabling technologies that allow the fabrication of various structures (...continues)

Selectively anodised aluminium foils as an insulating layer for embedding electronic circuitry in a metal matrix via ultrasonic additive manufacturing

Ultrasonic Additive Manufacturing (UAM) is a hybrid Additive Manufacturing (AM) process that involves layer-by-layer ultrasonic welding of metal foils and periodic machining to achieve the desired shape. Prior investigative research has demonstrated the potential of UAM for the embedding of electronic circuits inside a metal matrix. In this paper, a new approach for the fabrication of an insulating layer between an aluminium (Al) matrix and embedded electronic interconnections is presented. First, an Anodic Aluminium Oxide (AAO) layer is selectively grown onto the surface of Al foils prior to bonding. The pre-treated foils are then welded onto a UAM fabricated aluminium substrate. The bonding step can be repeated for the full encapsulation of the electronic interconnections or components. This ceramic AAO insulating layer provides several advantages over the alternative organic materials used in previous works

Ultrasonic additive manufacturing as a form-then-bond process for embedding electronic circuitry into a metal matrix

Ultrasonic Additive Manufacturing (UAM) is a hybrid manufacturing process that involves the layer-by-layer ultrasonic welding of metal foils in the solid state with periodic CNC machining to achieve the desired 3D shape. UAM enables the fabrication of metal smart structures, because it allows the embedding of various components into the metal matrix, due to the high degree of plastic metal flow and the relatively low temperatures encountered during the layer bonding process. To further the embedding capabilities of UAM, in this paper we examine the ultrasonic welding of aluminium foils with features machined prior to bonding. These pre-machined features can be stacked layer-by-layer to create pockets for the accommodation of fragile components, such as electronic circuitry, prior to encapsulation. This manufacturing approach transforms UAM into a “form-then-bond” process. By studying the deformation of aluminium foils during UAM, a statistical model was developed that allowed the prediction of the final location, dimensions and tolerances of pre-machined features for a set of UAM process parameters. The predictive power of the model was demonstrated by designing a cavity to accommodate an electronic component (i.e. a surface mount resistor) prior to its encapsulation within the metal matrix. We also further emphasised the importance of the tensioning force in the UAM process. The current work paves the way for the creation of a novel system for the fabrication of three-dimensional electronic circuits embedded into an additively manufactured complex metal composite

Additively manufactured lab-on-chip devices

3D printing of microfluidics is in its infancy but it is already demonstrating game-changing potential. The technology offers new capabilities in highly complex geometries that can be designed and printed to high resolutions in many iterations. At Loughborough University our goal is to create smart complex 3D printed bespoke reactors that can adhere to a variety of industrial applications. This work is highly interdisciplinary and is spearheaded by a cross-campus collaborative expert group from Manufacturing and Chemical Engineering, Biology and Chemistry. The presented work was based on the production of a variety of flow reactor Lab-on-Chip (LOC) devices, each possessing unique capabilities in regards to both sensing and particle manipulation techniques. Multiple applications are covered such as the embedding of metal coated optical fibres and electronics within a metal matrix for inline sensing capabilities; the manufacture of high pressure and high temperature metal matrix LOC devices for application in supercritical fluid chemistry and hostile sampling; and the design and optimisation of magnetic particle continuous flow separators. The results are demonstrated for all three of the above mentioned applications and the outcomes, to date, of the individual projects will be concluded with the expected further work