Predictive modelling and experimental measurement of composite forming behaviour

Optimised design of textile composite structures based on computer simulation techniques requires an understanding of the deformation behaviour during forming of 3-dimensional double-curvature components. Purely predictive material models are highly desirable to facilitate an optimised design scheme and to significantly reduce time and cost at the design stage, such as experimental characterisation. In-plane shear and out-of-plane bending are usually thought to be the key forming mechanisms. Therefore, this thesis is concerned with studies of the shear and bending behaviour by experimental characterisation and theoretical modelling. Micromechanical interaction between fibre and matrix offers fundamental understanding of deformation mechanisms at the micro-scale level, leading to development of composite viscosity models, as input to shear and bending models. The composite viscosity models were developed based on rheological behaviour during movement of fibres, and validation was performed using experimental results collected from the literature. A novel characterisation method for measuring the bending behaviour, by means of a large-displacement buckling test, was attempted due to some significant advantages over other methods. Development of a bending model was also undertaken for unidirectional composites but experimental validation suggests further study may be required for woven composites. The shear behaviour was characterised using a picture frame test for viscous polymer composites. To obtain reliable experimental data, some efforts of improving the characterisation method were made. The experimental results were then used to validate a shear model, suggesting that further improvement is required, in terms of weave patterns, rate and temperature dependence

Predictive modelling and experimental measurement of composite forming behaviour

Optimised design of textile composite structures based on computer simulation techniques requires an understanding of the deformation behaviour during forming of 3-dimensional double-curvature components. Purely predictive material models are highly desirable to facilitate an optimised design scheme and to significantly reduce time and cost at the design stage, such as experimental characterisation. In-plane shear and out-of-plane bending are usually thought to be the key forming mechanisms. Therefore, this thesis is concerned with studies of the shear and bending behaviour by experimental characterisation and theoretical modelling. Micromechanical interaction between fibre and matrix offers fundamental understanding of deformation mechanisms at the micro-scale level, leading to development of composite viscosity models, as input to shear and bending models. The composite viscosity models were developed based on rheological behaviour during movement of fibres, and validation was performed using experimental results collected from the literature. A novel characterisation method for measuring the bending behaviour, by means of a large-displacement buckling test, was attempted due to some significant advantages over other methods. Development of a bending model was also undertaken for unidirectional composites but experimental validation suggests further study may be required for woven composites. The shear behaviour was characterised using a picture frame test for viscous polymer composites. To obtain reliable experimental data, some efforts of improving the characterisation method were made. The experimental results were then used to validate a shear model, suggesting that further improvement is required, in terms of weave patterns, rate and temperature dependence

Predictive modelling and experimental measurement of composite forming behaviour

Optimised design of textile composite structures based on computer simulation techniques requires an understanding of the deformation behaviour during forming of 3-dimensional double-curvature components. Purely predictive material models are highly desirable to facilitate an optimised design scheme and to significantly reduce time and cost at the design stage, such as experimental characterisation. In-plane shear and out-of-plane bending are usually thought to be the key forming mechanisms. Therefore, this thesis is concerned with studies of the shear and bending behaviour by experimental characterisation and theoretical modelling. Micromechanical interaction between fibre and matrix offers fundamental understanding of deformation mechanisms at the micro-scale level, leading to development of composite viscosity models, as input to shear and bending models. The composite viscosity models were developed based on rheological behaviour during movement of fibres, and validation was performed using experimental results collected from the literature. A novel characterisation method for measuring the bending behaviour, by means of a large-displacement buckling test, was attempted due to some significant advantages over other methods. Development of a bending model was also undertaken for unidirectional composites but experimental validation suggests further study may be required for woven composites. The shear behaviour was characterised using a picture frame test for viscous polymer composites. To obtain reliable experimental data, some efforts of improving the characterisation method were made. The experimental results were then used to validate a shear model, suggesting that further improvement is required, in terms of weave patterns, rate and temperature dependence

PSN-PC: A Novel Antimicrobial and Anti-Biofilm Peptide from the Skin Secretion of Phyllomedusa-camba with Cytotoxicity on Human Lung Cancer Cell

Peptides derived from amphibian skin secretion are promising drug prototypes for combating widespread infection. In this study, a novel peptide belonging to the phylloseptin family of antimicrobial peptides was isolated from the skin secretion of the Phyllomedusa camba, namely phylloseptin-PC (PSN-PC). The biosynthetic precursor was obtained by molecular cloning and the mature peptide sequence was confirmed through tandem mass spectrometry (MS/MS) fragmentation sequencing in the skin secretion. The synthetic replicate exhibited a broad spectrum antimicrobial activity against Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans at concentrations of 2, 2, 8, 32 and 2 µM, respectively. It also showed the capability of eliminating S. aureus biofilm with a minimal biofilm eradication concentration of 8 µM. The haemolysis of this peptide was not significant at low concentrations but had a considerable increase at high concentrations. Additionally, this peptide showed an anti-proliferation effect on the non-small cell lung cancer cell line (NCI-H157), with low cytotoxicity on the human microvascular endothelial cell line (HMEC-1). The discovery of the novel peptide may provide useful clues for new drug discoveries

Investigation of cleaning effect for airport runway lamps by using baking soda powder

In order to ensure the bright effect of airport navigation lights, dry powder cleaning technology was adopted in this paper to improve the efficiency of removing sticky dirt on the lamp surface. The atomization scheme by mixing dry powder with water was designed through deliberately selecting the appropriate injection nozzle structure to reduce impact of powder pollution on the environment. Both simulation analysis and experimental testing showed that the overall cleaning effect and the atomization scheme were feasible, which reduce the dust pollution by more than 90%

A predictive approach to simulating the forming of viscous textile composite sheet

A commercial Finite Element (FE) code is used to simulate the forming of a thermoplastic viscous textile composite sheet. The main success of this work is in combining two distinct models. The first is a rate and temperature dependent unit cell energy model, designed to predict the shear force - shear angle - shear rate response of viscous textile composites. The second is a non-orthogonal rate-independent constitutive model that has been implemented previously in the code. Both models are reviewed briefly and the method of combining these models in the code is described. Preliminary results of Picture Frame test simulations together with complex forming simulations are presented and discussed

Properties and ceramic transformation of Si–Zr–O–C precursor ceramics with porous structure

The preparation of ceramic materials with complex porous structures through photopolymerization-based 3D printing requires the development of stable and printable slurries. In this study, zirconium acetylacetonate was incorporated into the thiol vinyl organosilicon prepolymer to create a photosensitive Si–Zr–O–C slurry. Regarding the natural bone structures and the Tyson polygon principle, a gradient pore structure was designed and then printed using a digital light processing 3D printer. After printing, the effects of sintering temperatures on the phase composition and structure of Si–Zr–O–C ceramics were systematically investigated. Subsequently, a comparative analysis of structure and properties was performed on sintered samples with different zirconium acetylacetonate contents. The results revealed that the sample containing 30 wt. % zirconium acetylacetonate exhibited a higher compressive strength of 9.70 ± 0.28 MPa and a lower room temperature thermal conductivity of 0.528 W m−1 K−1. This study confirmed the significant potential of using 3D printing technology to prepare Si–Zr–O–C precursor ceramics with a porous structure