Numerical and experimental studies of multi-ply woven carbon fibre prepreg forming process

Woven carbon fibre prepreg is being increasingly used in high-performance aerospace and automotive applications, primarily because of its superior mechanical properties and formability. A wide range of forming simulation options are available for predicting material deformation during the prepreg forming process, particularly change in fibre orientation. Development of a robust validated simulation model requires comprehensive material characterisation and reliable experimental validation techniques. This paper presents experimental and numerical methods for studying the fibre orientation in multi-ply woven carbon fibre prepreg forming process, using a double-dome geometry. The numerical study is performed using the commercial forming simulation software PAM-FORM and the material input data are generated from a comprehensive experimental material characterisation. Two experimental validation methods are adopted for fibre shear angle measurement: an optical method for measuring only the surface plies, and a novel CT scan method for measuring both the surface plies and the internal plies. The simulation results are compared against the experimental results in terms of fibre shear angle and the formation of wrinkles to assess the validity of the model

X-Ray tomography study on porosity and particle size distribution in In Situ Al-4.5Cu-5TiB2 Semisolid rolled composites

X-ray computed tomography (XCT) was used for three-dimensional (3D) visualization of the internal microstructure and quantification of the porosity and second-phase particles in Al-4.5Cu-5TiB2 composites prepared by an in situ liquid metallurgy casting route. The as-cast composites were subjected to hot rolling and mushy-state rolling for deagglomeration and to achieve a uniform distribution of CuAl2-TiB2 particle clusters. Qualitative results obtained by scanning electron microscopy (SEM) and quantitative results obtained by XCT both showed that mushy-state rolling as well as hot rolling resulted in fragmentation and a homogeneous distribution of the CuAl2-TiB2 particle clusters, with the mushy-state-rolled composite exhibiting the highest number of smaller-size particles. The porosity was increased in both rolling conditions through debonding of particles due to the compressive force during solid-state deformation along with the quick solidification of the solute-rich liquid during mushy-state rolling. These results show that application of secondary processes such as hot-rolling and mushy-state rolling can help to achieve a relatively more uniform particle distribution in Al-4.5Cu-5TiB2 in situ composite

A metrological inspection method using micro-CT for the analysis of drilled holes in CFRP and titanium stacks

This paper demonstrates a novel method that combines X-ray computed tomography (CT) and image processing for investigating two materials with significantly different densities. CT is increasingly used in industrial applications of inspecting materials and defects. The limitations of the system and data reconstruction are continuously researched so as to improve the quality of the results. One of the most common issues in CT is beam hardening, frequently experienced in multi-material scanning. The materials examined to demonstrate the method are carbon fibre reinforced polymers (CFRP) and titanium alloy Ti6Al4V, often used in combination in industry to optimise the weight to strength ratio. The assembly of the materials is usually achieved by bolting and riveting, which requires drilling through the two materials together. The machining of these materials is difficult due to their higher specific properties and as a result tool wear is always an issue. CFRPs properties depend on the nature, orientation and bond of the fibres and as a result drilling affects their service life. The results of the method ensure the quality of the drilled holes by measuring the variation of the maximum diameter, circularity, positioning of the hole and an examining the entrance delamination and exit burrs by image processing

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)

Computed tomography metrological examination of additive manufactured acetabular hip prosthesis cups

Additive manufacturing (AM) is uniquely suitable for healthcare applications due to its design flexibility and cost effectiveness for creating complex geometries. Successful arthroplasty requires integration of the prosthetic implant with the bone to replace the damaged joint. Bone-mimetic biomaterials are utilised due to their mechanical properties and porous structure that allows bone ingrowth and implant fixation. The predictability of predetermined interconnected porous structures produced by AM ensures the required shape, size and properties that are suitable for tissue ingrowth and prevention of the implant loosening. The quality of the manufacturing process needs to be established before the utilisation of the parts in healthcare. This paper demonstrates a novel examination method of acetabular hip prosthesis cups based on X-ray computed tomography (CT) and image processing. The method was developed based on an innovative hip prosthesis acetabular cup prototype with a prescribed non-uniform lattice structure forming struts over the surface, with the interconnected porosity encouraging bone adhesion. This non-destructive, non-contact examination method can provide information of the interconnectivity of the porous structure, the standard deviation of the size of the pores and struts, the local thickness of the lattice structure in its size and spatial distribution. In particular, this leads to easier identification of weak regions that could inhibit a successful bond with the bone

The spontaneous emulsification of entrained inclusions during casting of high aluminum steels

Mold slag entrainment during the continuous casting process presents a late stage source of non-metallic inclusions (NMI) with a high likelihood of ending up in the final product. The reaction between the entrained slag phase and surrounding liquid steel in the continuous casting mold affects the inclusion morphology and properties. However, there is a lack of information on the kinetics of the NMI-steel reaction. A novel approach, utilizing controlled synthetic inclusion/metal samples, has been developed to study the reactions between free inclusion-slag droplets and steel. The technique combines High-Temperature Confocal Scanning Laser Microscopy (HT-CSLM), X-ray Computed Tomography (XCT) and advanced electron microscopy techniques offering rapid controlled heating performance and extensive characterization of the samples. This method offers the ability to observe the size, shape and composition of an unconstrained reacting inclusion and to investigate the interface between the materials with respect to reaction time. This study interrogates a low aluminum steel (0.04 wt pct) and a high aluminum steel (1 wt pct) in contact with an inclusion-slag phase with a starting composition aligned to a typical mold slag. It was found that the reaction between silica and aluminum across the interface of the two phases provided a driving force for spontaneous emulsification to occur. Products of such emulsification will have a significant effect on the inclusion size distribution and potentially the prevalence of inclusion retention in molten steels solidifying in the continuous caster (for example if emulsified buoyancy forces are reduced to near zero) and hence in the subsequent solid product

Looking Deeper into the Galaxy (Note 7)

Li-ion cell designs, component integrity, and manufacturing processes all have critical influence on the safety of Li-ion batteries. Any internal defective features that induce a short circuit, can trigger a thermal runaway: a cascade of reactions, leading to a device fire. As consumer device manufacturers push aggressively for increased battery energy, instances of field failure are increasingly reported. Notably, Samsung made a press release in 2017 following a total product recall of their Galaxy Note 7 mobile phone, confirming speculation that the events were attributable to the battery and its mode of manufacture. Recent incidences of battery swelling on the new iPhone 8 have been reported in the media, and the techniques and lessons reported herein may have future relevance. Here we look deeper into the key components of one of these cells and confirm evidence of cracking of electrode material in tightly folded areas, combined with a delamination of surface coating on the separator, which itself is an unusually thin monolayer. We report microstructural information about the electrodes, battery welding attributes, and thermal mapping of the battery whilst operational. The findings present a deeper insight into the battery’s component microstructures than previously disseminated. This points to the most probable combination of events and highlights the impact of design features, whilst providing structural considerations most likely to have led to the reported incidences relating to this phone

Non-destructive examination of additive manufactured acetabular hip prosthesis cups

The application of Additive Manufacturing (AM) in medicine is extensive with the production of anatomical models, endoprosthetics, surgical guides, implants and scaffold implants. This is due to its design flexibility and cost effectiveness when geometrical complexity is required. Total hip arthroplasty is a common surgical procedure with a prevalence increase of 0.72% in 20 years that it is expected to grow faster in the next decades. The work presented demonstrates a novel non-destructive, non-contact examination method utilising X-ray Computed Tomography (XCT) and image processing. This method examines an AM bone-mimetic structure that enhances bone ingrowth and implant fixation of acetabular hip prosthesis cups. The results of the image processing analysis include information on the interconnectivity of the bone-mimetic structure, local thickness and spatial distribution

The application of x-ray computed tomography in aerospace industry : innovation report

In the 2015 report of ‘The aerospace industry: statistics and policy’, UK Government presents the aerospace industry as “phenomenal success story” with “tremendous opportunities for growth” (Rhodes, et al., 2015). The success of this sector depends on high efficiency and productivity levels while maintaining quality and satisfying market demands which request aircraft to stay safely in service for longer with reduced maintenance budgets. One of the strategic objectives of the aerospace companies is continuous improvement of the technologies and engineering capabilities. X-ray Computed Tomography (CT) is a growing Non-Destructive Evaluation (NDE) method with various applications in several sectors of industry. CT collects numerous radiographs that are then reconstructed to create a 3D model of the examined object. The results demonstrate the outer and inner structure of the part including any defects, altered densities and hidden constructions in the case of Additive Layer Manufacturing (ALM) parts. Product development in the aerospace industry is a challenging task with significant risks that are handled by complex processes for quality control. The product development steps in this industry follow the products from concept to manufacturing and from service to disposal. This project examines the capabilities and limitations of CT in order to identify potential applications in this sector by considering all of the stages of development. Several case studies demonstrate its application in the research and development phase of composite design and machining selection as well as in the production phase with metrological and non-destructive evaluation applications. Finally, the application of CT in failure investigations and forensic examinations, close to the end of the life and disposal of the product was also considered. The results of these investigations demonstrate the possibilities of this technology as well as its limitations and led the sponsoring company to purchase a digital radiography system with CT capabilities. The presented investigations answer the research question of ‘How can CT be applicable in aerospace industry?’ by identifying the product development phases where CT is applicable. The developed innovative methods provide CT inspections and measurements while reducing human error. They identify the capabilities and limitations of this technology and develop improved scanning methods and standard operating procedures. This report summarises the results of these investigations that clearly demonstrate the potential applications of this technology as well as their limitations while it also introduces and demonstrates innovative methods to overcome these limitations. The innovation of this project is in the novel methods that allow this technology to be used in this industrial sector and provide the required results that are unobtainable with other NDT methods