17 research outputs found
Defects and uncertainties of adhesively bonded composite joints
© The Author(s) 2021. The increasing use of fibre reinforced polymer composite materials in a wide range of applications increases the use of similar and dissimilar joints. Traditional joining methods such as welding, mechanical fastening and riveting are challenging in composites due to their material properties, heterogeneous nature, and layup configuration. Adhesive bonding allows flexibility in materials selection and offers improved production efficiency from product design and manufacture to final assembly, enabling cost reduction. However, the performance of adhesively bonded composite structures cannot be fully verified by inspection and testing due to the unforeseen nature of defects and manufacturing uncertainties presented in this joining method. These uncertainties can manifest as kissing bonds, porosity and voids in the adhesive. As a result, the use of adhesively bonded joints is often constrained by conservative certification requirements, limiting the potential of composite materials in weight reduction, cost-saving, and performance. There is a need to identify these
uncertainties and understand their effect when designing these adhesively bonded joints. This article aims to report and categorise these uncertainties, offering the reader a reliable and inclusive source to conduct further research, such as the development of probabilistic reliability-based design optimisation, sensitivity analysis, defect detection methods and process development
Recommended from our members
Multi-scale reliability-based design optimisation framework for fibre-reinforced composite laminates
Purpose
The purpose of this study is to enable performing reliability-based design optimisation (RBDO) for a composite component while accounting for several multi-scale uncertainties using a large representative volume element (LRVE). This is achieved using an efficient finite element analysis (FEA)-based multi-scale reliability framework and sequential optimisation strategy.
Design/methodology/approach
An efficient FEA-based multi-scale reliability framework used in this study is extended and combined with a proposed sequential optimisation strategy to produce an efficient, flexible and accurate RBDO framework for fibre-reinforced composite laminate components. The proposed RBDO strategy is demonstrated by finding the optimum design solution for a composite component under the effect of multi-scale uncertainties while meeting a specific stiffness reliability requirement. Performing this using the double-loop approach is computationally expensive because of the number of uncertainties and function evaluations required to assess the reliability. Thus, a sequential optimisation concept is proposed, which starts by finding a deterministic optimum solution, then assesses the reliability and shifts the constraint limit to a safer region. This is repeated until the desired level of reliability is reached. This is followed by a final probabilistic optimisation to reduce the mass further and meet the desired level of stiffness reliability. In addition, the proposed framework uses several surrogate models to replace expensive FE function evaluations during optimisation and reliability analysis. The numerical example is also used to investigate the effect of using different sizes of LRVEs, compared with a single RVE. In future work, other problem-dependent surrogates such as Kriging will be used to allow predicting lower probability of failures with high accuracy.
Findings
The integration of the developed multi-scale reliability framework with the sequential RBDO optimisation strategy is proven computationally feasible, and it is shown that the use of LRVEs leads to less conservative designs compared with the use of single RVE, i.e. up to 3.5% weight reduction in the case of the 1 × 1 RVE optimised component. This is because the LRVE provides a representation of the spatial variability of uncertainties in a composite material while capturing a wider range of uncertainties at each iteration.
Originality/value
Fibre-reinforced composite laminate components designed using reliability and optimisation have been investigated before. Still, they have not previously been combined in a comprehensive multi-scale RBDO. Therefore, this study combines the probabilistic framework with an optimisation strategy to perform multi-scale RBDO and demonstrates its feasibility and efficiency for an fibre reinforced polymer component designUniversity of Aberdeen Elphinstone scholarship scheme
Recommended from our members
Investigating the post-yield behavior of mineralized bone fibril arrays using a 3D non-linear finite element unit-cell model
Data availability: Data will be made available on request.Copyright © 2023 The Authors. In this study, we propose a 3D non-linear finite element (FE) unit-cell model to investigate the post-yield behavior of mineralized collagen fibril arrays (FAY). We then compare the predictions of the model with recent micro-tensile and micropillar compression tests in both axial and transverse directions. The unit cell consists of mineralized collagen fibrils (MCFs) embedded in an extrafibrillar matrix (EFM), and the FE mesh is equipped with cohesive interactions and a custom plasticity model. The simulation results confirm that MCF plays a dominant role in load bearing prior to yielding under axial tensile loading. Damage was initiated via debonding in shear and progressive sliding at the MCF/EFM interface, and resulted in MCF pull-out until brittle failure. In transverse tensile loading, EFM carried most of the load in pre-yield deformation, and then mixed normal/shear debonding between MCF and EFM began to form, which eventually produced brittle delamination of the two phases. The loading/unloading FE analysis in compression along both axial and transverse directions demonstrated perfect plasticity without any reduction in elastic modulus, i.e., damage due to the interfaces as seen in micropillar compression. Beyond the brittle and ductile nature of the stress–strain curves, in tensile and compressive loading, the simulated post-yield behavior and failure mechanism are in good quantitative agreement with the experimental observations. Our rather simple but efficient unit-cell FE model can reproduce qualitatively and quantitatively the mechanical behavior of bone ECM under tensile and compressive loading along the two main orientations. The model's integration into higher length scales may be useful in describing the macroscopic post-yield and failure behavior of trabecular and cortical bone in greater detail.Swiss Government Excellence Scholarship, Grant/Award Number (2021.0686)
Recommended from our members
Design against distortion for aerospace-grade additively manufactured parts - PADICTON
Collections: Brunel Composite CentreAdditive manufacturing (AM) is a computer-controlled 3D printing process with increasing demand in the aerospace sector. This manufacturing process offers the production of lighter components, design flexibility, reduced labour effort and material cost, as well as decreased waste generation compared with subtractive manufacturing. Additionally, AM can provide parts availability at the point of use, significantly improving the supply chain. However, producing advanced high-temperature AM thermoplastic components remains a challenging task as these require a high-temperature build chamber environment that is prone to producing parts with thermal stresses and warpage. PADICTON project aims to develop a tool capable of accurately and rapidly predicting and correcting such distortions, offering improved quality of the produced parts and minimising rejection rates. Creating this tool requires conducting a comprehensive mechanical and thermal characterisation campaign to optimise the print parameters and part geometry. In this study, the concept of the project and the findings of the initial mechanical and optical characterisation tests for two AM processes, namely fused deposition modelling and selective laser sintering, are presented and discussed.The authors would like to acknowledge the PADICTON partners, namely FDM Digital Solutions, e Xstream Engineering, part of Hexagon Manufacturing Intelligence, AMendate, as well as the Topic
Manager of the project, Airbus, for their assistance and encouragement towards the realisation of the
activities. In addition, the consortium would like to express its gratitude to EOS for their technical
support. Furthermore, the activities of PADICTON project have received funding from the Clean Sky 2
Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under
grant agreement number 86481
Recommended from our members
Graphene-based strain sensing in composites for structural and health monitoring applications
Copyright © 2022 The Author(s). Composite structures are attracting more interest due to their outstanding mechanical properties; thus, their inspection and health assessment are key items for their safe use. In this article we present a graphene-based sensor that evaluates the strain generated within a composite. A finite element model was developed to investigate the mechanism driving the graphene to act as a strain sensor. A prototype sensor was manufactured, using a commercially available graphene ink. The strain in composite samples was measured and the gauge factor identified by applying different load scenarios. The graphene sensor proved to be able to evaluate strain at various levels providing a gauge factor (exceeding 6) higher than commercially available strain gauges.Innovate UK for the project GRAPHOSITE “A Graphene Sensor for Defect Detection and Predictive Maintenance in Composite Materials” [grant number 104266]
Development of innovative automated solutions for the assembly of multifunctional thermoplastic composite fuselage
In this study, the development of innovative tooling and end-effector systems for the assembly of a multifunctional thermoplastic fuselage is presented. The increasing demand for cleaner and new aircraft requires utilising novel materials and technologies. Advanced thermoplastic composites provide an excellent material option thanks to their weldability, low density, low overall production cost, improved fracture toughness and recyclability. However, to fully appreciate their potentials, new manufacturing approaches and techniques are needed. Hence, this project develops three end-effector solutions to demonstrate the feasibility of assembling a full-scale multifunctional-integrated thermoplastic lower fuselage shell, including the integration of a fully equipped floor and cargo structure. The developed assembly solution comprises three individual yet well-integrated tooling systems that allow housing the skin and assembly; picking, placing and welding of the assembly parts, i.e. clips and stringers; and welding of frames and floor beam sub-assemblies. The process of developing these systems including the end-user requirements, technical challenges, tooling and end-effectors design and manufacturing process are detailed in this paper.This study is part of the TCTool project, which has received funding from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 865131. Project partners: GKN-Fokker Aerospace (Topic Manager), TWI Ltd., Andalusian Foundation for Aerospace Development – Advanced Center for Aerospace Technologies, Brunel University London (Brunel Composites Centre), London South Bank University, Acroflight Ltd., and Smart Advanced Manufacturing XL (SAM|XL)
Recommended from our members
Injection repair of advanced composites: a prospective method for delamination damage repair
Recommended from our members
Novel multi-zone self-heated composites tool for out-of-autoclave aerospace components manufacturing
© 2020 N. Jayasree et al. In this paper, a multi-zone self-heating composite tool is developed to manufacture out-of-autoclave complex and high-quality business jet lower wing stiffened composite panel. Autoclave manufacturing is regarded as a benchmark for manufacturing aerospace-grade composite parts. However, high accruing operational costs limit production rates thereby not being practical for smaller-scale companies. Therefore, significant work towards developing out-of-autoclave manufacturing is underway. In this study, a production line tool is developed with embedded heating fabric that controls temperature at the desired zones, replacing the need for autoclave cure. It investigates and identifies the optimal design parameters of the self-heating setup namely the placement of the heating fabric, zones, thermal management system, temperature distribution, heating rate and thermal performance using a thermal FEA model. The associated thermal characterisation of the tooling material and the part are measured for accurate simulation results. The design developed in this study will be used as production guideline for the actual tool.European Union’s Horizon 2020 research and innovation program, COMBUSS project [19], Clean Sky 2 Joint Undertaking grant agreement No 821297
Recommended from our members
A numerical anatomy-based modelling of bamboo microstructure
© 2021 Elsevier Ltd. All rights reserved. This is the accepted manuscript version of the article. The final version will be available online from Elsevier.Hungarian NKFIH; NRDI Fund TKP2020 IES; Stipendium Hungaricum scholarship schem