Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | School of Fashion and Textiles | en_US |
| dc.contributor.advisor | Hu, Hong (SFT) | en_US |
| dc.contributor.advisor | Xu, Bingang (SFT) | en_US |
| dc.creator | Li, Keda | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/14532 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | en_US |
| dc.rights | All rights reserved | en_US |
| dc.title | Study of three-dimensional negative poisson’s ratio lattice structures with enhanced load bearing capacity | en_US |
| dcterms.abstract | Auxetic materials, defined by their negative Poisson’s ratio (NPR), exhibit lateral expansion under tensile loading and lateral contraction under compressive loading, resulting in enhanced energy absorption, indentation resistance, and stiffness. Among various auxetic configurations, lattice structures composed of periodic 2D or 3D unit cells have attracted growing interest due to their geometric tunability and lightweight nature. Their mechanical behavior depends on the deformation mode of the unit cells, typically classified as bending- or stretching-dominated, with the latter offering superior stiffness and structural efficiency for load-bearing applications. Recent efforts have focused on fabricating auxetic lattices using fibre-reinforced polymer composites, particularly carbon fibre-reinforced polymer (CFRP), which combines high specific stiffness with directional reinforcement capabilities. These properties make CFRP an attractive candidate for constructing 3D auxetic lattices with improved mechanical performance under both quasi-static and dynamic loading. This thesis presents a systematic study on the design, fabrication, mechanical characterization, and FE modeling of CFRP-based 3D auxetic lattice structures through three studies. | en_US |
| dcterms.abstract | The first study investigates a novel 3D hybrid auxetic lattice (HAL) structure, developed by combining re-entrant quadrilateral and double-arrowhead unit cells to achieve a stretch-dominated deformation mechanism. The structure is fabricated using an interlocking assembly approach with CFRP laminates, enabling precise control over both geometric complexity and material anisotropy. Quasi-static compression tests are performed to characterize the elastic properties, auxetic behavior, and deformation patterns using Instron 5982 universal testing machine, while FE simulations are employed via ABAQUS software to validate the experimental results and provide insight into stress distribution and failure initiation. A parametric analysis based on the Box–Behnken response surface methodology is conducted to investigate the influence of key geometric parameters (L/t0, t1/t0, t2/t0 and θ2) on structural stiffness and NPR. Multi-objective optimization is further applied to identify optimal configurations that enhance both load-bearing capacity and auxetic behavior. | en_US |
| dcterms.abstract | Building upon the quasi-static investigation, the second study examines the low-velocity impact performance of the same 3D HAL structure. Three configurations with varying strut thickness ratios (t1/t0) are fabricated using CFRP laminates and subjected to drop-weight impact tests at multiple energy levels to evaluate energy absorption and failure mechanisms. The structure maintains its NPR during impact and exhibits progressive deformation and damage evolution. Mechanical response, auxetic behavior, and failure patterns are systematically compared across configurations. Finite element simulations incorporating Hashin failure criteria are developed and validated against experimental data, offering insights into damage initiation, propagation, and post-impact integrity. The dominant failure modes include adhesive debonding, fibre breakage, and interlaminar delamination, all of which are strongly influenced by local stress concentrations and geometric design. Results show that increasing the strut thickness ratio effectively improves impact resistance and energy dissipation capacity. | en_US |
| dcterms.abstract | The third study investigates the second auxetic lattice structure proposed in this research, namely the 3D star-shaped anti-tetra-missing rib (S-ATMR) configuration. This structure incorporates star-shaped reinforcement trusses within a modified missing-rib framework to enhance nodal connectivity and promote a stretch-dominated deformation mechanism. The proposed structure is fabricated from CFRP laminates using an interlocking assembly method and subjected to quasi-static compression and low-velocity impact testing. The experimental results indicate that increasing the internal angle of the star-shaped units leads to improved stiffness and auxetic response. Under dynamic loading, the S-ATMR structure displays progressive collapse and effective energy absorption. FE simulations employing Hashin failure criteria capture the damage evolution with good agreement to experimental observations. Comparative analysis of the two loading conditions shows consistent deformation mechanisms, with impact loading inducing more severe damage and greater energy dissipation due to concentrated stresses at critical load bearing joints. | en_US |
| dcterms.abstract | This research advances the design, fabrication, and mechanical characterization of high-stiffness 3D auxetic lattice structures, contributing to their practical applicability in engineering contexts. A stretch-dominated design strategy is proposed to overcome the limitations of conventional auxetic lattices in stiffness and stability. A rapid, low-cost, and scalable fabrication method compatible with fiber-reinforced composites is developed to produce 3D auxetic lattices. Numerical models are established to evaluate equivalent elastic properties and to elucidate the stiffness tuning and auxetic deformation mechanisms of two distinct hybrid lattice designs. | en_US |
| dcterms.extent | xv, 127 pages : color illustrations | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 2026 | en_US |
| dcterms.educationalLevel | Ph.D. | en_US |
| dcterms.educationalLevel | All Doctorate | en_US |
| dcterms.accessRights | open access | en_US |
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