Development of new technologies for forming advanced high strength steel based fibre metal laminates for ultra high performance structures
File(s)
Author(s)
Ding, Zerong
Type
Thesis
Abstract
Fibre metal laminates (FMLs), composed of interlaced metal alloy and fibre-reinforced polymer (FRP) sheet layers, are advanced high-performance lightweight materials, offering substantial potential for contributing to a net-zero transportation sector. The success of FMLs in the aviation industry has sparked significant interest in their use for automobile structural components. However, manufacturing challenges hinder a wider application of FMLs, particularly ultra-high performance advanced high-strength steel (AHSS)-based FMLs. Attributing to the mismatch of forming temperature windows, existing AHSS-based FML components are produced in a multi-step process, resulting in long cycle time, high tool investment, and recyclability challenges due to adhesive usage.
This thesis presents a novel separate-heating, pre-cooling and one-shot forming technology to produce adhesive-free, ultra-high-performance AHSS-based FML components. Following the conceptual process design, hot stamping AHSS (22MnB5), and unidirectional carbon fibre-reinforced polyether-ether-ketone (UD CF/PEEK) are selected as material candidates, presenting the highest performance potential. Advanced in-situ experimental systems, including a hot press system and an integrated forming system, are developed, facilitating the subsequent research activities. The dominating deformation behaviours of CF/PEEK are characterised under potential forming conditions, based on which a set of constitutive models are developed, enabling the process simulation where the potential optimal forming temperature windows are identified. Forming trials are conducted, followed by a comprehensive evaluation on the as-formed components including appearance, bonding and delamination, and geometric accuracy. The successfully formed components demonstrate the feasibility of the proposed technology; in addition, the in-depth post-form evaluation provides a guidance to the tool design and optimal forming temperatures. Furthermore, a rapid, accurate stress-strain relationship prediction framework, generalisable to diverse FRPs at different forming temperatures, is developed, facilitating the expansion of this novel technology’s applicable material portfolio. This newly-developed, cost-effective, energy-efficient technology warrants a wider application of AHSS-based FMLs, contributing to a more sustainable automotive industry.
This thesis presents a novel separate-heating, pre-cooling and one-shot forming technology to produce adhesive-free, ultra-high-performance AHSS-based FML components. Following the conceptual process design, hot stamping AHSS (22MnB5), and unidirectional carbon fibre-reinforced polyether-ether-ketone (UD CF/PEEK) are selected as material candidates, presenting the highest performance potential. Advanced in-situ experimental systems, including a hot press system and an integrated forming system, are developed, facilitating the subsequent research activities. The dominating deformation behaviours of CF/PEEK are characterised under potential forming conditions, based on which a set of constitutive models are developed, enabling the process simulation where the potential optimal forming temperature windows are identified. Forming trials are conducted, followed by a comprehensive evaluation on the as-formed components including appearance, bonding and delamination, and geometric accuracy. The successfully formed components demonstrate the feasibility of the proposed technology; in addition, the in-depth post-form evaluation provides a guidance to the tool design and optimal forming temperatures. Furthermore, a rapid, accurate stress-strain relationship prediction framework, generalisable to diverse FRPs at different forming temperatures, is developed, facilitating the expansion of this novel technology’s applicable material portfolio. This newly-developed, cost-effective, energy-efficient technology warrants a wider application of AHSS-based FMLs, contributing to a more sustainable automotive industry.
Version
Open Access
Date Issued
2024-05-31
Date Awarded
2024-07-01
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Li, Nan
Lin, Jianguo
Sponsor
Imperial College London
Grant Number
N/A
Publisher Department
Dyson School of Design Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)