Additive manufacturing lattices for enhanced dynamic performance
File(s)
Author(s)
Jameekornkul, Piyapat
Type
Thesis
Abstract
Lattices enable lightweight structures with tailored mechanical response and high energy absorption. However, their behaviour in the intermediate strain-rate regime remains weakly characterised and inconsistently interpreted, limiting adoption in impact applications demanding efficient energy absorption. This thesis addresses this gap by consolidating multi-scale design principles linking material composition and lattice architecture to failure mechanisms, to enhance dynamic performance.
Herein, a systematic dynamic characterisation of graded lattices within the intermediate strain-rate regime is established. Results show cell-size and density grading alter collapse sequencing and crack initiation, increasing energy absorption by >15% relative to the ungraded baseline. When reinforced with short carbon fibres, absorbed energy increases nearly fourfold through fibre–matrix interfacial dissipation mechanisms absent in isotropic lattices. While energy dissipation is enhanced, stiffness and strength remain governed by the dominant deformation mode and relative density, confirming the applicability of power-law scaling under dynamic regime. Lattice-scale strain-rate sensitivity is analytically corroborated, demonstrating that dynamic strengthening arises from both constituent material behaviour and lattice architecture.
Despite superior stiffness-to-weight efficiency, plate-based lattices exhibit localised instability under impact, motivating plate modification. The proposed sinusoidal modification mitigates abrupt buckling, stabilises deformation progression, and produces a smoother stress–strain response with improved impact reusability. Its effectiveness is influenced by plate orientation relative to the loading direction, resulting in distinct performance enhancements between BCC and FCC configurations.
Failure control is further explored through two bio-inspired interfacial designs: (i) interpenetrating composite lattices, which enhance strength and recoverability under impact through phase-constrained deformation and interfacial load transfer, and (ii) a Bouligand-inspired continuous-fibre honeycomb, which stabilises shear response and promotes damage delocalisation. Across both, interfacial bond quality dictates dynamic performance.
By elucidating the governing mechanisms that regulate collapse, instability, and interfacial dissipation across multiple length scales, this thesis provides practical guidelines for engineering lightweight structures capable of resilient impact performance.
Herein, a systematic dynamic characterisation of graded lattices within the intermediate strain-rate regime is established. Results show cell-size and density grading alter collapse sequencing and crack initiation, increasing energy absorption by >15% relative to the ungraded baseline. When reinforced with short carbon fibres, absorbed energy increases nearly fourfold through fibre–matrix interfacial dissipation mechanisms absent in isotropic lattices. While energy dissipation is enhanced, stiffness and strength remain governed by the dominant deformation mode and relative density, confirming the applicability of power-law scaling under dynamic regime. Lattice-scale strain-rate sensitivity is analytically corroborated, demonstrating that dynamic strengthening arises from both constituent material behaviour and lattice architecture.
Despite superior stiffness-to-weight efficiency, plate-based lattices exhibit localised instability under impact, motivating plate modification. The proposed sinusoidal modification mitigates abrupt buckling, stabilises deformation progression, and produces a smoother stress–strain response with improved impact reusability. Its effectiveness is influenced by plate orientation relative to the loading direction, resulting in distinct performance enhancements between BCC and FCC configurations.
Failure control is further explored through two bio-inspired interfacial designs: (i) interpenetrating composite lattices, which enhance strength and recoverability under impact through phase-constrained deformation and interfacial load transfer, and (ii) a Bouligand-inspired continuous-fibre honeycomb, which stabilises shear response and promotes damage delocalisation. Across both, interfacial bond quality dictates dynamic performance.
By elucidating the governing mechanisms that regulate collapse, instability, and interfacial dissipation across multiple length scales, this thesis provides practical guidelines for engineering lightweight structures capable of resilient impact performance.
Version
Open Access
Date Issued
2025-10-31
Date Awarded
2026-04-01
Copyright Statement
Attribution-Non Commercial-No Derivatives 4.0 International Licence (CC BY-NC-ND)
Advisor
Panesar, Ajit
Publisher Department
Department of Aeronautics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)