title: Developing new multiscale models for the numerical simulation of Pultruded GFRP Structural Elements

authors: Abbaszadeh, Hadi

abstract: Pultruded Fibre-Reinforced Polymers (FRP) are innovative structural elements gaining popularity for various structural applications due to their unique properties, such as magnetic transparency and an excellent strength-to-weight ratio. These materials have been extensively studied through experimental and numerical methods to assess their performance as structural components. Accurately describing the micro- and macro-scale mechanical features of FRP elements necessitates complex computational models to predict their strength and investigate design parameters through numerical simulations. 

This research initially reviews the state-of-the-art in numerical modelling of structural fibre-reinforced polymeric elements, particularly pultruded Glass Fibre Reinforced Polymers (GFRP). It highlights their use as load-bearing structural elements and evaluates various numerical methods, including Finite Element Method (FEM), eXtended Finite Element Method (XFEM), Virtual Crack Closure Technique (VCCT), Cohesive Zone Modelling (CZM), Multiscale Reduced Order Modelling (ROM), and Random Lattice Modelling (RLM). Each method's distinctive features, challenges, and capabilities are discussed in detail. The aim is to assess the reliability of these numerical models for simulating FRP structural elements and provide recommendations for future research by discussing 160 references from the literature. 

In the next step, the experimental characterization of Pultruded GFRP materials evaluated. These composites exhibit remarkable strength, comparable or even superior to steel, and resistance to environmental effects. However, their strongly orthotropic behaviour and spatial variability in mechanical properties present challenges. Fibre orientation and distribution significantly affect the ultimate strength and stiffness of these materials. This work includes an experimental campaign on GFRP specimens in uniaxial tension and three-point bending, testing coupon specimens with fibre orientations of 0, 15, 45, and 90 degrees to characterize ultimate strength and failure modes. Detailed statistical measures of the strength values are presented, aiming to understand the variability in mechanical properties of commercially available profiles. 

In addition, the stiffness parameter was considered to investigate by analytical study comparing experimental results. Despite the promising properties of pultruded GFRP, their relatively low stiffness and strength in the direction orthogonal to the fibres limit their widespread adoption in civil engineering applications. This work investigates the mechanical behaviour of pultruded GFRP beams using analytical methods, presenting  experimental results from a small-scale campaign conducted by the researcher. These results validate the analytical model and compare the elastic stiffness concerning fibre orientation, providing insights into the potential and limitations of pultruded GFRP elements in structural applications. 

Finally, the last step of study demonstrates the inherent limitations of traditional lattice models and propose a new model to simulate the orthotropic materials` behaviours in different conditions. This section presents an innovative approach by using irregular lattice networks to simulate the elastic behaviour of orthotropic GFRP structural elements by Voronoi Cell Lattice Modelling (VCLM), focusing on different fibre-to-matrix elasticity ratios and fibre to load orientations. The proposed method first estimates the elastic properties for various fibre orientations and verifies the model against standard deformation cases and experimental data. Additionally, it compares numerical predictions to established theories like the Tsai-Hill criterion. Through sensitivity analysis, it explores how fibre-to-matrix ratios and Young’s modulus affect macroscopic Poisson’s ratio, offering new insights into stiffness effects on anisotropic material simulations.

text: Developing new multiscale models for the numerical simulation of Pultruded GFRP Structural Elements Pultruded Fibre-Reinforced Polymers (FRP) are innovative structural elements gaining popularity for various structural applications due to their unique properties, such as magnetic transparency and an excellent strength-to-weight ratio. These materials have been extensively studied through experimental and numerical methods to assess their performance as structural components. Accurately describing the micro- and macro-scale mechanical features of FRP elements necessitates complex computational models to predict their strength and investigate design parameters through numerical simulations. 

This research initially reviews the state-of-the-art in numerical modelling of structural fibre-reinforced polymeric elements, particularly pultruded Glass Fibre Reinforced Polymers (GFRP). It highlights their use as load-bearing structural elements and evaluates various numerical methods, including Finite Element Method (FEM), eXtended Finite Element Method (XFEM), Virtual Crack Closure Technique (VCCT), Cohesive Zone Modelling (CZM), Multiscale Reduced Order Modelling (ROM), and Random Lattice Modelling (RLM). Each method's distinctive features, challenges, and capabilities are discussed in detail. The aim is to assess the reliability of these numerical models for simulating FRP structural elements and provide recommendations for future research by discussing 160 references from the literature. 

In the next step, the experimental characterization of Pultruded GFRP materials evaluated. These composites exhibit remarkable strength, comparable or even superior to steel, and resistance to environmental effects. However, their strongly orthotropic behaviour and spatial variability in mechanical properties present challenges. Fibre orientation and distribution significantly affect the ultimate strength and stiffness of these materials. This work includes an experimental campaign on GFRP specimens in uniaxial tension and three-point bending, testing coupon specimens with fibre orientations of 0, 15, 45, and 90 degrees to characterize ultimate strength and failure modes. Detailed statistical measures of the strength values are presented, aiming to understand the variability in mechanical properties of commercially available profiles. 

In addition, the stiffness parameter was considered to investigate by analytical study comparing experimental results. Despite the promising properties of pultruded GFRP, their relatively low stiffness and strength in the direction orthogonal to the fibres limit their widespread adoption in civil engineering applications. This work investigates the mechanical behaviour of pultruded GFRP beams using analytical methods, presenting  experimental results from a small-scale campaign conducted by the researcher. These results validate the analytical model and compare the elastic stiffness concerning fibre orientation, providing insights into the potential and limitations of pultruded GFRP elements in structural applications. 

Finally, the last step of study demonstrates the inherent limitations of traditional lattice models and propose a new model to simulate the orthotropic materials` behaviours in different conditions. This section presents an innovative approach by using irregular lattice networks to simulate the elastic behaviour of orthotropic GFRP structural elements by Voronoi Cell Lattice Modelling (VCLM), focusing on different fibre-to-matrix elasticity ratios and fibre to load orientations. The proposed method first estimates the elastic properties for various fibre orientations and verifies the model against standard deformation cases and experimental data. Additionally, it compares numerical predictions to established theories like the Tsai-Hill criterion. Through sensitivity analysis, it explores how fibre-to-matrix ratios and Young’s modulus affect macroscopic Poisson’s ratio, offering new insights into stiffness effects on anisotropic material simulations.

year: 2025

title: Selection of dispatching rules in simulation-based scheduling of flexible manufacturing

authors: Basnet, Chuda

subjects: flexible manufacturing systems

abstract: Discrete-event simulation has been proposed as a tool for the real-time selection of dispatching rules in the scheduling of flexible manufacturing systems (FMS). In this approach, a look-ahead simulation is used to predict the trajectory of the system under different dispatching rules. Then a rule is selected for use in the FMS, based on the performance criterion associated with each trajectory. However, this raises the issue of the criterion to be used for the selection of the rules. A simulation model of an FMS was used to test the effect of rule selection procedure on two performance measures. This simulator was run using four scheduling policies and the performance of the FMS was measured. The main finding of this research is that the use of global criteria gives better results than the use of local criteria.

text: Selection of dispatching rules in simulation-based scheduling of flexible manufacturing Discrete-event simulation has been proposed as a tool for the real-time selection of dispatching rules in the scheduling of flexible manufacturing systems (FMS). In this approach, a look-ahead simulation is used to predict the trajectory of the system under different dispatching rules. Then a rule is selected for use in the FMS, based on the performance criterion associated with each trajectory. However, this raises the issue of the criterion to be used for the selection of the rules. A simulation model of an FMS was used to test the effect of rule selection procedure on two performance measures. This simulator was run using four scheduling policies and the performance of the FMS was measured. The main finding of this research is that the use of global criteria gives better results than the use of local criteria.

year: 2011

title: One hundred years of Sylvia Ashton-Warner: An introduction.

authors: Middleton, Sue

subjects: Sylvia Ashton-Warner

abstract: A biography of Sylvia Ashton-Warner is presented. She was born on 17 December 1908 in New Zealand. She studied at the Auckland Teachers' Training College and taught in several native schools including Horoera Native School and Pipiriki Native School. Later she started writing, starting with "Teacher," a book about teaching schemes and followed by "Incense to Idols," "Bell Call," and "Greenstone." Also, her travels to various places are mentioned.

text: One hundred years of Sylvia Ashton-Warner: An introduction. A biography of Sylvia Ashton-Warner is presented. She was born on 17 December 1908 in New Zealand. She studied at the Auckland Teachers' Training College and taught in several native schools including Horoera Native School and Pipiriki Native School. Later she started writing, starting with "Teacher," a book about teaching schemes and followed by "Incense to Idols," "Bell Call," and "Greenstone." Also, her travels to various places are mentioned.

year: 2008