Hom Nath Dhakal

Development of flax/carbon fibre hybrid composites for enhanced properties

Uni-directional (UD) and cross-ply (CP) cellulosic flax fibre epoxy composites were produced by hybridising UD carbon fibre prepreg onto flax system. A compression moulding technique was used to produce both flax and carbon/flax hybridised laminates. The effect of carbon fibre hybridisation on the water absorption behaviour, thermal and mechanical properties of both UD and CP flax specimens were investigated by means of water absorption, tensile, thermogravemetric analysis and flexural testing. The results showed that water absorption behaviour of hybrid samples are markedly improved compared to those without hybridisation. Similarly, the thermal stability, tensile and flexural properties of the hybrid composites are significantly improved in comparison with UD and CP flax composites without hybridisation. The experimental results suggest that cellulosic flax fibre reinforcement contributed to improve the toughness properties by promoting crack propagation whereas the carbon fibre contributed in improving thermal stability, water absorption behaviour and the overall strength and the stiffness of the hybrid composites.

Effects of water immersion ageing on the mechanical properties of flax and jute fibre biocomposites evaluated by nanoindentation and flexural testing

Flax and jute fibres are inexpensive and easily available bast fibres and they are extensively used as reinforcement in polymer matrix composites. However, due to their susceptibility to moisture absorption, their application is restricted to non-structural interior products. In this study, flax- and jute fibre-reinforced bioresin-based epoxy biocomposites were fabricated using hand lay-up method and their nanoindentation and flexural properties were investigated. In order to study the effects of water absorption on the nanoindentation and flexural properties, the biocomposites were subjected to water immersion tests by immersing specimens in a de-ionised water bath at 25℃ for a period of 961 h. The nanoindentation behaviour and flexural properties of water-immersed specimens were evaluated and compared alongside with dry specimens. The percentage of moisture uptake and diffusion coefficient (D) was recorded higher for jute-reinforced specimens compared with flax. The flexural properties for both types of specimens were found to decrease with increase in percentage moisture uptake. Comparison of flexural strength and flexural modulus between flax dry and flax wet biocomposites showed that wet samples lost almost 40% of strength and 69% of modulus compared with dry flax samples. The jute wet samples lost 60% of strength and 80% of modulus compared with dry samples. The nanohardness value decreased from 0.207 to 0.135 GPa for dry flax sample after immersion in water.

Lean readiness level within Kuwaiti manufacturing industries

Purpose – The purpose of this paper is to develop a measurement framework to evaluate the lean readiness level (LRL) and lean systems (LS) within Kuwaiti small and medium‐sized manufacturing industries (K‐SMMIs). A measurement framework which encompasses the quality practices related to LS (processes; planning and control; human resources; top management and leadership; customer relations; and supplier relations) is used to assess the quality practices in K‐SMMIs and determine whether they have the foundation to implement LS.Design/methodology/approach – The authors conducted a comprehensive literature review, semi‐structured interviews with 27 senior managers, and a quantitative survey administered to 50 K‐SMMIs. The responses were entered into SPSS software to conduct a reliability test and independent sample t‐test.Findings – The results indicate that current quality practices within K‐SMMIs are not very supportive towards LS. Many factors are revealed to affect K‐SMMIs with respect to LS, including la...

Lean “Leadership People Process Outcome” (LPPO) implementation model

Purpose – The purpose of this paper is to present the Lean “Leadership People Process Outcome” (LPPO) implementation model. Design/methodology/approach – The model is developed from existing models through literature review and its success from use in lean implementation is reported in case studies. Findings – The LPPO model is a Lean implementation model that is flexible and easily adaptable. It is system based, people driven, customer centred, with measurable outcome and a drive for continuous improvement. Research limitations/implications – This work is based on existing literature and case studies. Practical implications – The paper would be of interest to Lean practitioners as the model developed is system generic and easily adaptable. Originality/value – The LPPO model presented in this paper has been newly developed and the successful application is seen in the case studies.

Recent advances in twist drill design for composite machining: A critical review

In the field of composite technology, inefficient and poor designs of twist drills contribute immensely to the challenges facing drilling of composite materials. An attempt to report some of the drill design methods and their inherent challenges confronting composite machining necessitates the writing of this article. A critical review has been conducted to offer a clear understanding of the current advances in the field of mechanical drilling of composite materials, focusing on geometry, material and parametric tool designs. The inter-dependable effects of thrust force, cutting speed, feed rate, cutting force and torque on drill design are similarly reviewed. This article also reveals other associated issues facing composite drilling including delamination, surface roughness, rapid tool wear and drill breakage. Well-designed drill geometry and good knowledge of drilling parameters afford the producers of polycrystalline diamond, carbide and high-speed steel tooling materials better opportunity of developing a drill that will minimise delamination of the reinforced composites and tool wear and produce a high-quality surface. Twist drill manufacturers and users will benefit from this article as they seek to have well-designed and improved drills.

Water Absorption Behavior, Mechanical and Thermal Properties of Vinyl Ester Matrix Nanocomposites Based on Layered Silicate

The water absorption behavior, mechanical and thermal properties of vinyl ester matrix nanocomposites based on layered silicate were investigated. To characterize interlaminar structure of the nanocomposites, XRD, SEM, EDS, and TEM were performed. The mechanical and thermal properties of neat sample were improved by the incorporation of layered silicate. The improvement of the water repellence behavior was observed for the nanocomposites. The hardness and elastic moduli after water absorption was reduced due to the effect of water molecules entering into the polymer chains. However, the higher amount of clay reinforcement led to less reduction in hardness since the barrier properties.

The use of hemp fibres as reinforcements in composites

The use of hemp fibres as reinforcement in composite materials has received increasing attention by both academia and industry because of their unlimited availability, lower density and much higher specific strength than conventional fibres such as carbon and glass, and the fact that they are renewable. This chapter is concerned with the evaluation of the key fibre properties, cultivation and quality issues, surface modification and its effect on the properties as well as the applications of hemp fibre-reinforced composite materials.

Study on T-bolt and pin-loaded bearing strengths and damage accumulation in E-glass/epoxy blade applications:

In this paper, the ultimate bearing strengths of pin-loaded double shear and T-bolt loaded connections were studied in thick composites, where the diameter of the pin equates to the thickness of the laminate. These bearing strengths were obtained for E-glass/epoxy laminates of [(±45, 03)n ,±45] and a Vf of 54%. It is found that the values for ultimate bearing failure and first non-linearity of pin-loaded connections should be reduced by 25% and 38%, respectively, when applied to T-Bolt connections. The failure modes prior to ultimate failure were primarily dominated by fibre matrix shear-out and delamination. As far as laminates with specific reinforcement architecture and a large percentage of reinforcement orientated to the load axis are concerned, the long-term service life of T-bolt connections may be impacted due to the visible onset of damage at a similar level to that accepted by Germanischer Lloyd for load introduction zones.

Low Velocity Impact and Creep-Strain Behaviour of Vinyl Ester Matrix Nanocomposites Based on Layered Silicate

The impact properties of neat vinyl ester and the nanocomposites were performed using a low velocity impact testing. The addition of layered silicate into the polymer matrix shows that an optimum range of nanoclay reinforcement in the vinyl ester matrix can produce enhanced load bearing and energy absorption capability compared to the neat matrix. In addition, the amount of microvoids in the nanocomposites structure influences the overall properties. Likewise, the influence of the clay addition into the neat polymer on the creep relaxation behaviour at 25°C and 60°C was studied. In both cases, the presence of the layered silicate remarkably improved the creep behaviour. The improvement of these properties can be assigned to the stiff fillers and the configurational linkage between the polymer and the layered silicate which are supported by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterisations by showing a distinct change in surface morphology associated with improved impact toughness and creep response.

Moisture measurement and effects on properties of marine composites

Natural fibre composites have recently attracted a great deal of attention by the marine industry due to their many attractive benefits for structural applications. Beneficial properties include; high strength-to-weight ratio, sustainable characteristics and low cost. These materials unfortunately are highly susceptible to moisture ingress which can lead to inferior thermo-mechanical properties and structural failure. These failure routes may be diverse and difficult to detect therefore adequate material selection, processing, and testing is paramount in achieving a long lasting functional marine structure. This chapter focuses on the investigation of these imparted moisture related attributes and their influence on properties.