Kim Yeow Tshai

Biaxial Characterisation of Materials for Thermoforming and Blow Moulding.

Abstract During free surface moulding processes such as thermoforming and blow moulding, heated polymer materials are subjected to rapid biaxial deformation as they are drawn into the shape of a mould. In the development of process simulations, it is therefore essential to be able to accurately measure and model this behaviour. Conventional uniaxial test methods are generally inadequate for this purpose and this has led to the development of specialised biaxial test rigs. In the present study, the results of several programmes of biaxial tests conducted at Queens University are presented and discussed. These have included tests on high impact polystyrene (HIPS), polypropylene (PP) and aPET, and the work has involved a wide variety of experimental conditions. In all cases, the results clearly demonstrate the unique characteristics of materials when subjected to biaxial deformation. PP draws the highest stresses and it is the most temperature-sensitive of the materials. aPET is initially easier to form but exhibits strain hardening at higher strains. This behaviour is increased with increasing strain rate but at very high strain rates, these effects are increasingly mollified by adiabatic heating. Both aPET and PP (to a lesser degree) draw much higher stresses in sequential stretching showing that this behaviour must be considered in process simulations. HIPS showed none of these effects and it is the easiest material to deform.

Hybrid Fibre Polylactide Acid Composite with Empty Fruit Bunch: Chopped Glass Strands

Hybrid polylactide acid (PLA) composites reinforced with palm empty fruit bunch (EFB) and chopped strand E-glass (GLS) fibres were investigated. The hybrid fibres PLA composite was prepared through solution casting followed by pelletisation and subsequent hot compression press into 1 mm thick specimen. Chloroform and dichloromethane were used as solvent and their effectiveness in dissolving PLA was reported. The overall fibre loading was kept constant at volume fraction, , of 20% while the ratio of EFB to GLS fibre was varied between of 0 : 20 to 20 : 0. The inclusion of GLS fibres improved the tensile and flexural performance of the hybrid composites, but increasing the glass fibre length from 3 to 6 mm has a negative effect on the mechanical properties of the hybrid composites. Moreover, the composites that were prepared using chloroform showed superior tensile and flexural properties compared to those prepared with dichloromethane.

Effect of Chitosan Loading on the Morphological, Thermal, and Mechanical Properties of Diglycidyl Ether of Bisphenol A/Hexamethylenediamine Epoxy System

The effect of chitosan filled diglycidyl ether of bisphenol A (DGEBA) epoxy system were investigated using the thermal, mechanical, and morphological properties. The mixing ratio of resin/hardener was kept constant while the chitosan of 1.0, 2.5, 5.0, 7.5, and 10 weight percentage (wt%) was incorporated into the system. The thermal stability and the transition behaviour of the chitosan filled epoxy system were analysed through a differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR) while atomic force microscope (AFM) and scanning electron microscopy (SEM) were used to investigate the morphology. It was observed that the additive tends to agglomerate, with the formation of clear phase separation, when the chitosan content increases above 5 wt%. At lower chitosan loading (2.5 wt% and below), relatively uniform dispersion of the additive can be achieved. The thermal stability of the system increases with chitosan loading while the mechanical tensile strength is compromised.

Manufacturing of Natural Fibre-Reinforced Polymer Composites by Solvent Casting Method

Globally increasing environmental concern of petroleum-based material leads to finding the alternative renewable natural sources. Natural fibre-based composite is gaining immense interest not only because of its positive environmental impact but also its economic advantages. One of the very first and simplest processing techniques that have been used for preparing natural fibre-reinforced polymer composites is solvent casting method. In practice, the major advantage of solvent casting is its ease of fabrication without the need of specialized equipment. There are several factors that may influence solvent casting method and hence, the performance of the overall polymer composites. The present chapter provides a comprehensive overview on the manufacturing of natural fibre-reinforced polymer composites by solvent casting method. It comprises information on the factors that influence the method and the properties of the natural fibre-reinforced polymer composites prepared by this method as well as the possible applications.

Micro Palm and Kenaf Fibers Reinforced PLA Composite: Effect of Volume Fraction on Tensile Strength

Extensive environmental concern associated with the disposal of solid plastic wastes has stirred tremendous interest in the production and use of sustainable biodegradable polymers. Among the vast variety of available materials, Polylactic Acid (PLA) standout as the most commercially viable mass produced resin to date. However, its low thermal and mechanical stability, excessive brittleness, and relatively higher cost have led to numerous research efforts in producing biodegradable polymer composite filled with natural organic fibers. This paper describes the preparation and the mechanical characteristics of a compression molded biodegradable composite made entirely of renewable raw materials. The composites were reinforced with pulverized palm, kenaf and alkali (1M NaOH:fiber in ratio 2:1) treated kenaf fibers, at a fiber mass proportion of 20 to 60% blended PLA and processed in a custom-built compression mold. SEM microscan revealed that the kenaf fiber has a mean diameter of 40μm, length 1236.6μm, and aspect ratio of 31 while the measured values for palm fiber was 58.7μm, 1041.2μm, and 17.7, respectively. All resulting composites showed significant enhancement in tensile strength. At 20, 40 and 60% fiber loading, the palm/PLA composite recorded tensile strength increment of 46.9, 47.8 and 36.6%, respectively. For the kenaf/PLA composite, greatest improvement was achieved at 40% fiber loading with alkali treated kenaf, with approximately 54% higher than the neat PLA while only 12.6% was recorded for the non-treated kenaf/PLA composite, signifying that the surface modification greatly improved fiber-matrix adhesion. SEM observations on the fracture surface showed similar findings. Compared to commercially available palm/Polypropylene (palm/PP) composite at 50% fiber loading, our measured tensile strength for the PLA composite loaded with 40% alkali treated kenaf fiber was still about 20% lower. Further enhancement in the mechanical characteristic of the kenaf/PLA composite is required to push for its wider utilization in the polymer industry.

Burst strength of carbon fibre reinforced polyethylene strip pipeline repair system – a numerical and experimental approach

Oil and gas pipelines are susceptible to various forms of damage where repair mechanisms have since been developed for rehabilitation. Once installed, structural health monitoring often incurs excessive costs and defects rectification of the repaired pipeline becomes a major challenge. Finite element analysis (FEA) provides a rapid route to predict the behaviour of the rehabilitated pipelines under prescribed in-service conditions. In this paper, burst strength of a commercially available composite sleeve repair system, Helicoid Epoxy Sleeve (HES)™, which combines the use of carbon fibre strip and epoxy grout as reinforcement to damaged pipe, was investigated through experimental and numerical approaches. Design standards for subsea pipelines are used in the calculation of design pressure and burst pressure. In the experimental setup, API 5L X52 steel pipe was machined with 50% metal loss defect in wall thickness to simulate external corrosion. Results from design calculations, experimental and FEA showed good correlation with margin less than 10%.

Finite element analysis of combined static loadings on offshore pipe riser repaired with fibre-reinforced composite laminates

The stress–strain response of an offshore pipe riser subjected to combined internal pressure, tension and bending is studied. Finite element analysis was used to study three conditions of pipe riser – uncorroded, corroded and corroded and repaired with designated laminate orientation of carbon/epoxy or E-glass/epoxy fibre-reinforced composite. The behaviour of the pipe riser (grade API 5L X60 steel) was studied using Ramberg–Osgood model. Two composites laminate systems, a pre-cured prepreg (grade AS4 3501-6 carbon/epoxy) and a wet-layup filament-wounded composite (grade Gevetex LY556/HT917/DY063 E-glass/epoxy), were characterised. Design conditions were determined via a limit analysis known as the double-elastic slope method. The results showed that under combined hoop, tensile and bending loads, the riser tends to approach failure at a much lower strain compared with each of these loads being applied individually. The limiting design factor of the composite repair system was due to excessive tensile strain experienced in a bent riser while the compressive stress caused by reversing the bending load occurred well within the linear-elastic region. With respect to the types of composite repair system, carbon fibre displayed a much better strength rehabilitation over glass fibre. In the aspect of laminate orientation, off-axis plies [90°/ ± 30°]s and [90°/ ± 45°/0°]s laminates were found capable of restoring the strength of the corroded riser and provide superior reinforcement in both hoop and axial directions.

Six Sigma in IT Processes, IT Services and IT Products: A Fact or a Fad? Six Sigma beyond Manufacturing in IT Processes, IT Services and IT Products

Quality is key for any organization to survive, compete and move forward in todays increasingly competitive business environment. Quality is determined by the product users, clients or customers, not by society in general. The aim is not to eliminate mistakes or defect completely, but to minimize the occurrence of defects/mistakes a company can manage and handle. A suitable and flexible quality improvement initiative can help companies formalize a systematic well-rounded approach covering top management all the way to the operations level in handling day-to-day tasks. Six Sigma is one of the upcoming methodologies gaining popularity amongst IT and non-IT organizations. Six Sigma is no longer a methodology solely for the manufacturing sector. An increase of Six Sigma adoption and implementation into the field of IT project management for medium-to-large scale organizations is observed. Nevertheless, the purpose of this paper is to create a general overview and raise awareness among IT organizations and IT specialists (especially in the region of South-East Asia) regarding the feasibility and possibility of adopting and implementing Six Sigma into the field of IT in the three IT business areas: IT Processes, IT Services and IT Products, not limiting to a single sub-trade of IT related businesses.

Finite Element Modelling of Composite Repair in Offshore Pipe Riser

The effects of coupled internal pressure and external tension on corroded offshore pipe riser repaired with a designated laminate orientation of carbon/epoxy (C/E) and E-glass/epoxy (EG/E) fibre reinforced composite (FRC) was evaluated. The steel riser (API 5L X60) was characterised through Ramberg-Osgood model while input data of the composites were extracted from those used as benchmark for analysis in the first world-wide failure exercise (WWFE) [1, 2]. It was found that the C/E composite provides superiority over the EG/E and laminates with a dedicated orientation is capable of enhancing the performance of risers subjected to the coupled loadings.

Effects of organophosphorus and mineral based flame retardants on combustibility and mechanical performances of natural fiber reinforced composites

Purpose The study aimed to investigate epoxy composites reinforced with mechanical performances, thermal decomposition and ignitibility of natural fiber (NF) and doped with 5 wt.% of varying flame-retardant (FR) compounds. The incorporation of ammonium polyphosphate (APP) and zinc borate (ZB) showed improvement in modulus and elongation to break compared to the empty fruit bunch-filled epoxy (control). However, slightly lower tensile and impact strengths were recorded in all FR-containing composites. Design/methodology/approach Among the FR-loaded specimens, enhancement in flexural property was observed in composites with APP, whereas the addition of ZB and alumina trihydrate (ATH) resulted in the reduction of flexural strength. Thermogravimetric analysis results indicated that the introduction of APP and ATH negatively impacted the thermal degradation temperature (Td) of the NF-filled composites. Greater mass residue with FR-filled composites, where increment was in the range from 32-80 per cent compared to the control, was observed, with the greatest being the ZB-containing formulation. Vertical Bunsen burner experiment revealed that the addition of ZB and APP led to a zero dripping flame system, whereas such a phenomenon was absent in both the control and NF composites loaded with ATH. The bomb calorimeter results revealed that addition of NF into neat epoxy significantly enhanced the FR behavior of the composite, and the gross heat of combustion was greatly reduced when FRs were incorporated into the control sample. Findings Results from the current study concluded that non-halogenated FRs including APP, ZB and ATH were able to enhance the fire retardancy of EFB epoxy composite without significantly deteriorate the mechanical behaviors. Originality/value It can be shown from scanning electron microscopy micrographs that the fabrication technique produced composites with good interfacial adhesion between NF and epoxy matrix, and homogenous distribution of FRs were achieved.