Low-cost resin infusion mould tooling for carbon fibre composites manufacture

This article describes the research to date carried out under the BAE Systems/Engineering and Physical Sciences Research Council (EPSRC)-funded programme ‘Flapless Aerial Vehicle Integrated Interdisciplinary Research’ (FLAVIIR), aimed at developing innovative technologies for the low-cost manufacture of next-generation Unmanned Aerial Vehicles. The aim of the researchers in FLAVIIR was to develop low-cost innovative tooling technologies to enable the affordable manufacture of complex composite aerospace structures. The advances in tooling technology were achieved through the application of rapid prototyping, tooling and manufacture technologies to provide rapidly configured and reconfigurable tool concepts, for low-cost resin infusion moulding. This article introduces three tooling innovations: reconfigurable tooling concept, variable cavity tooling, and porous cavity tooling

Generalized dilaton-Maxwell cosmic string and wall solutions

The class of static solutions found by Gibbons and Wells for dilaton-electrodynamics in flat spacetime, which describe nontopological strings and walls that trap magnetic flux, is extended to a class of dynamical solutions supporting arbitrarily large, nondissipative traveling waves, using techniques previously applied to global and local topological defects. These solutions can then be used in conjunction with S-duality to obtain more general solitonic solutions for various axidilaton-Maxwell theories. As an example, a set of dynamical solutions is found for axion, dilaton, and Maxwell fields in low energy heterotic string theory using the SL(2,R) invariance of the equations of motion.Comment: 11 pages; to appear in Phys.Lett.

Polyorganosiloxanes as electronic device encapsulants

Heat curable polysiloxane inorganic - organic hybrid materials, prepared from the hydrolysis and condensation of chloro - or alkoxysilanes, have been investigated as possible electric device encapsulants. Preparation - structure - property relationships have been determined for a simple difunctional system prepared by the direct hydrolysis of chlorosilanes. The system cyclisation was found to be highly dependent upon the system concentration, and most sensitive at low dilution. Due to the dilution associated with the addition of an aqueous base, even a solventless preparation was found to result in a large cyclic content, a result independent of the organic nature of the precursor employed. The copolymerisation of inorganic monofunctional end - blocking units with difunctional species was found to be beneficial in reducing the level of cyclisation within the system. However, high levels of end blocker with unreactive organic functionalities are to be avoided as the resulting high levels of oligomeric species are deleterious to the material's thermal and dielectric properties. The introduction of thermally reactive organics at much higher levels are possible without property degradation although high levels of reactive groups such as vinyl (-CHCH2) or allyl (CH2CH=CH2) are deleterious to the hermetic properties of the material. Introduction of tri - and tetrafunctional inorganic units into the difunctional systems, to prepare inorganically cross - linked materials, was easily achievable by the cohydrolysis of the precursors. The inorganic cross - linking afforded control over the system viscosity which was found to be particularly sensitive to the distribution of the di - and trifunctional species throughout the network, which in turn was a function of both the preparation pH and temperature. Useable materials were obtained for T group levels of less than 20%. Levels up to 50% were possible for more homogeneous T group distributions. Interpenetrating networks employing short and long chain components were successfully prepared. Their mechanical properties were assessed and correlated to their composition and structure. The role of the inorganic cross - links was found to be a larger determinant of the mechanical properties than the inorganic network. Extreme values of Young's moduli of 288kPa and 16.6 MPa were obtained for low and high vinyl containing materials respectively. Their dielectric properties were comparable to conventional encapsulation materials, with E' and tanS being in the range 3.36±O.06 to 3.9±O.1 and O.OOl±O.OO5 to 0.0370±O.OOO2 respectively. A number of IPN materials exposed to environmental testing (85°C I 85% RH), all afforded protection over the entire l000hrs test period, with no failure resulting from sample limitations

Real-time rheological monitoring with the smart stirrer

This paper presents an approach for wireless real-time measurements of dynamic viscosity in the range of 50-1000 mPa·s utilising a laboratory hotplate in conjunction with the Smart Stirrer device. The Smart Stirrer, an innovative tool resembling a conventional magnetic stirrer enhanced with embedded System-on-Chip (SoC) Bluetooth Low Energy (BLE) module, inertial measurement unit (IMU) and magnetometer sensors, serving as a platform for viscosity monitoring. The principle of measurement based on the interaction between the magnetic field of the hotplate’s magnet and the Smart Stirrer’s internal magnets, with variations in a liquid viscosity impacting the rotational dynamics of the Stirrer and measured by the sensors. The paper details the experimental setup, data acquisition, and analysis procedures, demonstrating the capability of the system to accurately and non-invasively measure the viscosity of various liquid solutions in real-time. The method addresses the practical limitations of existing methods and offers a integrative approach for monitoring in-situ rheological properties in laboratory settings. It stands out for its simplicity, ease of integration, and potential for broader applications, making it a valuable tool in various fields requiring fluid property measurements

E-Manufacturing for product improvement at Red Bull technology

In Formula 1 racing, there is a strong motive for reducing component weight and thereby improving efficiency. This paper demonstrates the advantages e-Manufacturing brings to the production of hydraulic components. The DMLS production technique would enable weight reductions to be attained by its geometric design freedom coupled with this material’s attributes. The use of EOS Titanium Ti64 material for hydraulic components has been assessed by a hydraulic soak test at 25 MPa and no significant losses or failure occurred. The benefits to the efficiency of hydraulic flow have been measured using Particle Image Velocimetry (PIV) and the use of DMLS designed geometry has improved flow characteristics by 250% over that of the currently used techniques of manufacturing channels and bores

Stereolithography for 3D photoelasticity

Recently, the use of photoelasticity has become more widespread due to the development of digital methods of fringe analysis [1] that allow a significant reduction in the time taken to achieve a stress map for any given model, particularly when only fractional fringe orders are displayed. However, in order for the full potential of the photoelastic method to be realised, a technique for rapidly producing complex 3-dimensional photoelastic models must be developed. Stereolithography is one so-called ‘rapid-prototype’ method that works by building a laminar model from a tank of photo-curing resin. A perforated metal plate is submerged in the liquid resin to a depth of typically around 0.1mm. A laser then traces the shape of the first layer of the component onto the plate, curing a thin layer of the resin. The plate is lowered by 0.1mm, and a further layer of resin cured by the laser. By this method, complex structures may be ‘laid-up’ in a matter of hours. Previous studies concerned with the use of stereolithography for the production of photoelastic models [2] have noted that unacceptable levels of residual birefringence and stress have remained in the photoelastic model even after conventional annealing methods. Thus the use of such methods has been limited. If the stereolithographic method were developed for photoelasticity, one possible area of interest would be the design and analysis of orthopedic implants. This paper outlines a series of studies looking at the requirements of photoelastic materials for three-dimensional stress analysis

Additive manufacture of 3D auxetic structures by laser powder bed fusion — design influence on manufacturing accuracy and mechanical properties

The mechanical response of steel auxetic structures manufactured using laser-powder bed fusion was explored. The level of control exerted by the key design parameters of vertical strut length (H), re-entrant strut length (L), strut thickness (t) and re-entrant angle (ϴ) on the mechanical response was examined through a design of experiment approach with ANOVA statistical analysis methods applied. The elastic modulus in directions normal to (Ex) and parallel to (Ey) the vertical strut was found to be primarily dependent upon t and L, respectively, whereas yield strength in both test directions (σx and σy) was strongly dependent on t and L. A large variation in modulus was found between the two test directions (Ex / Ey – 1.02 ± 0.07 GPa/ 4.4 ± 0.1 GPa), whereas, yield strength showed little anisotropy (σx / σy–45 ± 6 MPa/ 45 ± 9 MPa). Poisson’s ratio parallel to the vertical strut varied considerably with geometry but not in a direction normal to the vertical strut. Deformation mechanisms were found to be different of compression in the x and y directions, being a combination of stretching of the vertical strut; compression, bending and hinging of the re-entrant strut (x); and vertical strut compression and re-entrant strut stretching and bending (y)

Design & manufacture of a high-performance bicycle crank by additive manufacturing

A new practical workflow for the laser Powder Bed Fusion (PBF) process, incorporating topological design, mechanical simulation, manufacture, and validation by computed tomography is presented, uniquely applied to a consumer product (crank for a high-performance racing bicycle), an approach that is tangible and adoptable by industry. The lightweight crank design was realised using topology optimisation software, developing an optimal design iteratively from a simple primitive within a design space and with the addition of load boundary conditions (obtained from prior biomechanical crank force–angle models) and constraints. Parametric design modification was necessary to meet the Design for Additive Manufacturing (DfAM)considerations for PBF to reduce build time, material usage, and post-processing labour. Static testing proved performance close to current market leaders with the PBF manufactured crank found to be stiffer than the benchmark design (static load deflection of 7.0±0.5 mm c.f. 7.67mm for a Shimano crank at a competitive mass (155g vs. 175g). Dynamic mechanical performance proved inadequate, with failure at 2495±125cycles; the failure mechanism was consistent in both its form and location. This research is valuable and novel as it demonstrates a complete work flow from design, manufacture, post-treatment, and validation of a highly loaded PBF manufactured consumer component, offering practitioners a validated approach to the application of PBF for components with application outside of the accepted sectors (aerospace, biomedical, autosports, space, and power generation)

Monitoring chemistry in situ with the Smart Stirrer a magnetic stirrer bar with an integrated process monitoring system

Inspired by the miniaturisation and efficiency of the sensors for telemetry, we have developed a device that provides the functionalities of laboratory magnetic stirring and integrated multi-sensor monitoring of various chemical reaction parameters. The device, called Smart Stirrer, when immersed in a solution, can in situ monitor physical properties of the chemical reaction such as the temperature, conductivity, visible spectrum, opaqueness, stirring rate, and viscosity. This data is transmitted real-time over a wireless connection to an external system, such as a PC or smartphone. The flexible open-source software architecture allows effortless programming of the operation parameters of the Smart Stirrer in accordance with the end-user needs. The concept of the Smart Stirrer device with an integrated process monitoring system has been demonstrated in a series of experiments showing its capability for many hours of continuous telemetry with fine accuracy and a high data rate. Such a device can be used in conventional research laboratories, industrial production lines, flow reactors, and others where it can log the state of the process to ensure repeatability and operational consistency