A nanometre-scale fibre-to-matrix interface characterization of an ultrasonically consolidated metal matrix composite

Future ‘smart’ structures have the potential to revolutionize many engineering applications. One of the possible methods for creating smart structures is through the use of shape memory alloy (SMA) fibres embedded into metal matrices. Ultrasonic consolidation (UC) allows the embedding of SMAs into metal matrices while retaining the SMA's intrinsic recoverable deformation property. In this work, NiTi SMA fibres were successfully embedded into an Al 3003 (0) matrix via the UC layer manufacturing process. Initially the plastic flow of the Al matrix and the degree of fibre encapsulation were observed using optical microscopy. Then microstructural grain and sub-grain size variation of the Al 3003 (0) matrix at the fibre–matrix interface, and the nature of the fibre–matrix bonding mechanism, were studied via the use of focused ion beam (FIB) cross-sectioning, FIB imaging, scanning electron microscopy, and mechanical peel testing. The results show that the inclusion of the NiTi SMA fibres had a significant effect on the surrounding Al matrix microstructure during the UC process. Additionally, the fibre–matrix bonding mechanism appeared to be mechanical entrapment with the SMA surface showing signs of fatigue from the UC embedding process

Ultrasonic additive manufacturing research at Loughborough University

Ultrasonic Additive Manufacturing (UAM) has been subject to research and investigation at Loughborough University since 2001. In recent years, three particular areas of significant focus have been: • The influence of pre-process material texture on interlaminar bonding. • Secure fibre positioning through laser machined channels. • Freeform electrical circuitry integration. This paper details the key findings and a number of conclusions from these work areas. The results of this work have led to the further research and developmental applications for the UAM technology

3D printing with moondust

Purpose – The purpose of this paper is to investigate the effect of the main process parameters of Laser Melting (LM) type Additive Manufacturing (AM) on multi layered structures manufactured from JSC-1A Lunar regolith (Moondust) simulant powder. Design/methodology/approach – Laser diffraction technology was used to analyse and confirm the simulant powder material particle sizes and distribution. Geometrical shapes were then manufactured on a Realizer SLM™ 100 using the simulant powder. The laser-processed samples were analysed via Scanning Electron Microscopy (SEM) to evaluate surface and internal morphologies, Energy-dispersive X-ray Spectroscopy (EDS) to analyse the chemical composition after processing and the samples were mechanically investigated via Vickers micro-hardness testing. Findings – A combination of process parameters resulting in an energy density value of 1.011 J/mm2 allowed the successful production of components directly from Lunar regolith simulant. An internal relative porosity of 40.8 %, material hardness of 670 ± 11 HV and a dimensional accuracy of 99.8 % were observed in the fabricated samples. Originality/value – This research paper is investigating the novel application of a Powder Bed Fusion AM process category as a potential on-site manufacturing approach for manufacturing structures/components out of Lunar regolith (Moondust). It was shown that this AM process category has the capability to directly manufacture multi-layered parts out of Lunar regolith, which has potential applicability to future moon colonization

Ultrasonic additive manufacturing - a hybrid production process for novel functional products

Ultrasonic Additive Manufacturing (UAM), or Ultrasonic Consolidation as it is also referred, is a hybrid form of manufacture, primarily for metal components. The unique nature of the process permits extremely novel functionality to be realised such as multi-material structures with embedded componentry. UAM has been subject to research and investigation at Loughborough University since 2001. This paper introduces UAM then details a number of key findings in a number of areas that have been of particular focus at Loughborough in recent years. These include; the influence of pre-process material texture on interlaminar bonding, secure fibre positioning through laser machined channels, and freeform electrical circuitry integration

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

Field repair and replacement part fabrication of military components using ultrasonic consolidation cold metal deposition

Timely repair and replacement of military components without degrading material properties offers tremendous opportunities for cost and schedule savings on a number of military platforms. Effective field-based additive manufacturing repair approaches have proven difficult to develop, as conventional additive metal deposition technologies typically include a molten phase transformation and controlled inert deposition environments. The molten stage of laser and electron beam based additive processes unfortunately results in large dimensional and microstructural changes to the component being repaired or re-fabricated. As a result, high residual stresses and unpredictable ductility profiles in the repair area, or the re-fabricated part, make the final product unsafe for redeployment. Specifically, the heat affected zone associated with traditional deposition-based repair methods can produce a low strength, non-homogenous region at the joint; these changes in the materials properties of the repaired parts are detrimental to the fatigue life, and are a major concern where cyclic loading is experienced. The use of solid state high power Ultrasonic Consolidation (UC) technologies avoids the liquid-solid transition complexity and creates a predictable “cold” bond. This method then allows for strong, homogenous structures to be manufactured and repaired in the field and opens the door for the use of high strength repair material that may reduce the frequency of future failure itself. In addition, UC further offers the opportunity to provide enhanced functionality and ruggedness to a component either during repair or from original manufacture by allowing the embedding of passive and functional elements into the new fabricated component or feature

Solid-state additive manufacturing for metallized optical fiber integration

The formation of smart, Metal Matrix Composite (MMC) structures through the use of solid-state Ultrasonic Additive Manufacturing (UAM) is currently hindered by the fragility of uncoated optical fibers under the required processing conditions. In this work, optical fibers equipped with metallic coatings were fully integrated into solid Aluminum matrices using processing parameter levels not previously possible. The mechanical performance of the resulting manufactured composite structure, as well as the functionality of the integrated fibers, was tested. Optical microscopy, Scanning Electron Microscopy (SEM) and Focused Ion Beam (FIB) analysis were used to characterize the interlaminar and fiber/matrix interfaces whilst mechanical peel testing was used to quantify bond strength. Via the integration of metallized optical fibers it was possible to increase the bond density by 20–22%, increase the composite mechanical strength by 12–29% and create a solid state bond between the metal matrix and fiber coating; whilst maintaining full fiber functionality

Exploring the mechanical strength of additively manufactured metal structures with embedded electrical materials

Ultrasonic Additive Manufacturing (UAM) enables the integration of a wide variety of components into solid metal matrices due to the process induced high degree of metal matrix plastic flow at low bulk temperatures. Exploitation of this phenomenon allows the fabrication of previously unobtainable novel engineered metal matrix components. The feasibility of directly embedding electrical materials within UAM metal matrices was investigated in this work. Three different dielectric materials were embedded into UAM fabricated aluminium metal-matrices with, research derived, optimal processing parameters. The effect of the dielectric material hardness on the final metal matrix mechanical strength after UAM processing was investigated systematically via mechanical peel testing and microscopy. It was found that when the Knoop hardness of the dielectric film was increased from 12.1 HK/0.01 kg to 27.3 HK/0.01 kg, the mechanical peel testing and linear weld density of the bond interface were enhanced by 15% and 16%, respectively, at UAM parameters of 1600 N weld force, 25 µm sonotrode amplitude, and 20 mm/s welding speed. This work uniquely identified that the mechanical strength of dielectric containing UAM metal matrices improved with increasing dielectric material hardness. It was therefore concluded that any UAM metal matrix mechanical strength degradation due to dielectric embedding could be restricted by employing a dielectric material with a suitable hardness (larger than 20 HK/0.01 kg). This result is of great interest and a vital step for realising electronic containing multifunctional smart metal composites for future industrial applications

Fiber laser induced surface modification/manipulation of an ultrasonically consolidated metal matrix

Ultrasonic Consolidation (UC) is a manufacturing technique based on the ultrasonic joining of a sequence of metal foils. It has been shown to be a suitable method for fiber embedment into metal matrices. However, integration of high volume fractions of fibers requires a method for accurate positioning and secure placement to maintain fiber layouts within the matrices. This paper investigates the use of a fiber laser for microchannel creation in UC samples to allow such fiber layout patterns. A secondary goal, to possibly reduce plastic flow requirements in future embedding processes, is addressed by manipulating the melt generated by the laser to form a shoulder on either side of the channel. The authors studied the influence of laser power, traverse speed and assist gas pressure on the channel formation in aluminium alloy UC samples. It was found that multiple laser passes allowed accurate melt distribution and channel geometry in the micrometre range. An assist gas aided the manipulation of the melted material