Aidah Jumahat

Compressive behaviour of nanoclay modified aerospace grade epoxy polymer

Abstract The effect of nanoclay on the compressive response of an aerospace grade epoxy polymer was studied. The resin was modified with montmorillonite clay type nanomer I.30, and compressive tests were performed on the optimised specimen geometry. A series of nanocomposite with 1–5 wt-% nanoclay content was fabricated using mechanical stirring and three-roll mill methods. The degree of dispersion of the clay nanoplatelets was examined using TEM. Static uniaxial compression tests were conducted. The compressive stress–strain curves showed that the presence of nanoclay improved the compressive strength and stiffness, promoted higher plastic hardening behaviour after yielding and enhanced the fracture toughness (area under σ–ϵ curve) of the epoxy polymer. The fracture surfaces of the broken specimens were observed using SEM with the aim to identify critical failure mechanisms that contributed to the polymer toughening. Rule of mixtures, Halpin–Tsai and modified Halpin–Tsai models were employed to estimate the compressive modulus of the clay–epoxy nanocomposite system.

The Influence of Alumina Filler on Impact Properties of Short Glass Fiber Reinforced Epoxy

mpact resistance is one of the main consideration in measuring service life, liability and safety of polymer composite structures or products. Impact resistance of a composite material can be measured in terms of energy absorption, depth of penetration and total impact time. In this study, the influence of alumina Al2O3 on impact properties of short glass fiber reinforced polymer was investigated. The drop weight impact tests were performed in accordance to ASTM D7136 standard using Dynatup impact tester. Based on the results, the incorporation of micronsize alumina filler enhanced the energy absorbed during crushing, reduced the depth of penetration of the impactor and expanded the total impact time hence improved the impact properties of the composites.

Mechanical Properties of Kevlar Reinforcement in Kenaf Composites

The development of high-performance materials made from natural resources are increasing worldwide in recent years. Natural fibres offer both cost savings and reduction in density when compared to Kevlar fibres. However, the strength of natural fibres is not as great as Kevlar. The following preliminary research investigated the use of Kevlar fibres in kenaf composites as a possible to improve the impact properties. The impact properties of Kevlar reinforced in kenaf composites was studied by using DYNATUP 9250 drop weight machine. According to the standard ASTM D638 Kevlar fibres in different weight percentage of 10,15,20 and 25 wt% were reinforced with kenaf/epoxy composites by using hand lay-up combined with cold-press method. It is clearly observed that the impact strength and hardness were increased with the addition of weight percentage of woven Kevlar in the kenaf composites. The highest energy was recorded at 12.76 J by hybrid composite in combination of 2Kevlar/Kenaf/2Kevlar. The microstructure observation of impacted hybrid samples indicated that the delamination area was increased with the increasing of the impact energy.

Flexural response of nanoclay-modified epoxy polymers

Abstract Epoxy resin is one of the most common polymer matrices, used in a wide range of applications. Cured epoxy exhibits brittle behaviour and low fracture toughness when subjected to mechanical loadings. The aim of this work was to study the effect of nanoclay on the flexural stress-strain response and flexural properties of Epikote 828 and aerospace grade-Cycom 977 polymers. Three-point bending tests were conducted on two polymer nanocomposite systems which contained 1-5 wt-% montmorillonite nanoclays. The white clay powder used in this study had a mean dry particle size of 8-10 μm before the mechanical stirring or milling process was performed. It was found that the slope of the stress-strain curves increased with increasing nanoclay content. This indicates that nanoclay enhanced the flexural modulus of the epoxy. The results showed that the degree of reinforcement depends on the degree of nanoparticles dispersion in the epoxy.

Fabrication and characterisation of carbon fibre reinforced polymer rods with aluminium foam core

Abstract Carbon fibre reinforced polymer composites are high-performance materials that have become the dominant advanced composite materials used for aerospace, automobile, sporting goods and other applications owing to their high strength, high modulus and low density. In this study, a new fabrication technique of aluminium foam was employed where NaCl was used as the space holder and argon gas was injected into the aluminium molten metal. The NaCl particles were then removed by dissolution process. The aluminium foam specimens were then wrapped with carbon fibre pre-preg and cured in a vacuum oven. The compressive properties such as compressive strength, elastic modulus and failure strain were obtained from the analysis of stress-strain curves. The results showed that carbon fibre reinforced polymer composite tubes with aluminium foam core exhibited higher compressive strength and elastic modulus compared with neat aluminium foam rods and neat carbon fibre reinforced polymer rods.

Fibre Misalignment Measurement of Nanomodified-Unidirectional Carbon Fibre Laminates

This paper investigates the effect of nanosilica on the fibre waviness or misalignment angle distribution of carbon fibre reinforced polymer composite unidirectional laminates. The quality of the laminates was evaluated using image analyzer technique. The polished specimens were examined using Polyvar B-met optical microscope and analysed using KSRUN ZEISS software. The effect of 3, 7 and 13 vol.% nanosilica on the fibre misalignment angle distribution was determined. The results showed that, the fabricated laminates have average fibre volume fraction Vf of 42%, low fibre waviness distribution (average φo = 2.5o) and less than 1% void content. This implies that the fabrication technique, which was employed in the current work, successfully produced good quality laminates. The presence of nanosilica results in a narrow fibre angle distribution in the HTS40/828 laminate.

Fracture Toughness of Nanomodified-Epoxy Systems

The effect of nanosilica, multiwalled carbon nanotubes (MWCNT) and montmorillonite (MMT) nanoclay on critical stress intensity factor and critical energy release rate of Epikote 828 epoxy polymer was studied. Fracture toughness tests were conducted on three types of nanocomposites which contain 5-25 wt% nanosilica, 0.5-1 wt% MWCNT and 1-5 wt% MMT nanoclay. The compact tension specimens of 9 mm initial crack length were fabricated and tested in tension. It was found that, the load at crack growth initiation FQfor all nanomodified polymer systems was higher than that of the neat epoxy. Hence, the presence of nanosilica, carbon nanotubes and nanoclay improves the critical stress intensity factor and critical energy release rate of the polymer. For the nanoclay-modified epoxy system, the degree of enhancement depends on the morphology of the nanocomposites. At high nanoclay content (> 3 wt%), a detrimental effect on the fracture toughness was observed. This is due to a weak nanomer/epoxy interfaces in a highly intercalated structure nanocomposite.

Thermogravimetry analysis of nanosilica-filled epoxy polymer

Abstract Thermogravimetry is one of the most well-known thermal analysis techniques. It is used to determine thermal properties or thermal degradation characteristics of solid polymers under controlled heating conditions. The aim of this work is to study the effect of nanosilica on thermal degradation behaviour and maximum degradation temperature of the Epikote 828 epoxy system using the thermogravimetry analysis (TGA) technique. In addition, TGA was also used to measure the weight fraction of constituents in pure polymer and nanocomposite systems. The nanocomposite samples, which contain 5, 13 and 25 wt-% nanosilica, were prepared using DGEBA-type epoxy, anhydride-type hardener and 20 nm silica nanospheres. TGA profiles were plotted at three different heating conditions. The results showed that the maximum degradation temperature of the nanocomposites samples was higher than that of the neat system. This means that the inclusion of nanosilica enhance thermal stability of the epoxy polymer.

Effect of Alkaline Treatment on Tensile and Impact Strength of Kenaf/Kevlar Hybrid Composites

This study is about the hybrid composite which used the woven Kevlar, long Kenaf fibre, and unsaturated polyester as the matrix. It focused on the mechanical characterization and properties of hybrid composite. The hybrid composites were fabricated by treated and untreated kenaf fibre and Kevlar as reinforcement in unsaturated polyester matrix using hand lay-up process. Effect of 6wt% of sodium hydroxide (NaOH) on the hybrid composites were analyzed using X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) analysis. The tensile and impact performance of the samples were tested according to the standard ASTM D3039 and ASTM D3763, respectively. Based on scanning electron micrograph (SEM) morphological examination, it revealed that the interfacial adhesion between the fibre surface and polymer matrix were improved. The results proved that the alkaline treatment can help to improve the mechanical properties compared to the untreated kenaf fibre.

The Compressive Properties of Kevlar/Kenaf Hybrid Composites

Natural fibres are aimed to replace or at least to reduce the dependence of the industrial sector against low degradability of raw material. Hence, this study is performed to investigate the effect of stacking sequence and fibre orientation on the compressive properties of Kevlar/kenaf hybrid composites. Previous study suggested that treated kenaf fibres improved the fibre’s properties. Therefore, kenaf fibres was treated with NaOH of 6% concentration for 12 hours before rinsed and dried to be used in this study. The stacking sequence was varied for different weight percentage of woven Kevlar from 0 wt% to 23 wt%, while the kenaf fibres were arranged at 0° and 90° orientation, respectively. The compressive properties of the Kevlar/kenaf fibre hybrid composites were investigated using Instron Universal Testing Machine (ASTM standard D3410M). Stereo-zoom was used to identify the fibre orientation and the bonding between the fibres and matrix. For stacking sequence, the study showed that the arrangement of kenaf fibres on the middle part, “sandwiched” between Kevlar on the outer part, gave the best compressive performance. The sample in 0° orientation exhibited better compressive strength and modulus than 90° orientation. The outcome of this research has shown significant increase of compressive strength with the addition of kenaf fibre replacing the Kevlar.