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Kheng Lim Goh

Newcastle University, School of Mechanical and Systems Engineering, Faculty Member

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Dr Goh is an Associate Professor at Newcastle University Singapore. His research aims to understand the physical properties of natural and synthetic materials and to use this understanding to engineer composite materials, as well as to repair damaged composite materials.He is the author of the book on 'Discontinuous -fibre reinforced composites: fundamentals of stress transfer and fracture mechanics', published by Springer (2017).

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Newcastle University

BTU Cottbus Senftenberg

Hassan M El-Dessouky

The University of Sheffield

University of Bath

Prakash Mangalgiri

Demitris Kotsabassidis

Universidade Candido Mendes

Norazean Shaari

Universiti Selangor

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Papers by Kheng Lim Goh

Experimental assessment of drilling-induced damage in impacted composite laminates for resin-injection repair: Influence of open/blind hole-hole interaction and orientation

by Wei Liang Lai and Kheng Lim Goh

Composite Structures, 2021

An experimental study of drilling-induced damage in barely visible impact damaged (BVID) carbon f... more An experimental study of drilling-induced damage in barely visible impact damaged (BVID) carbon fibre reinforced polymer (CFRP) laminates where small circular holes were intentionally drilled into the impacted zone as an intermediate step of the resin-injection repair process was described. In-plane compression testing was conducted to determine the mechanical properties of BVID specimens containing open/blind, single and binary holes. Binary-hole specimens at fixed distance apart were tested in parallel or normal to the applied uniaxial force. As expected, BVID specimens experienced significant diminution of property value (compared to pristine ones). No dependence of mechanical properties on hole-hole orientation was observed. Owing to the large hole-hole separation, this significantly mitigated the hole-hole interactions, even though the predicted stress concentration (around the holes) level was above the residual strength. Interestingly, single/binary-hole BVID laminates generated counter-intuitive laminate stiffening effects that the stiffness was significantly higher than that of undrilled BVID specimens.

Dataset on mechanical properties of damaged fibre composite laminates with drilled vent- holes for resin-injection repair procedure

by Wei Liang Lai and Kheng Lim Goh

This dataset comprises the mechanical properties of pristine and barely visible impact damaged (B... more This dataset comprises the mechanical properties of pristine and barely visible impact damaged (BVID) carbon fibre reinforced epoxy composite (CFRP) laminates. The mechanical dataset describes the compressive strength, compressive strain at fracture, strain energy density for resilience and strain energy density to fracture of the CFRP laminates with different number of vent holes (namely 4, 5 and 6) in the respective pristine and BVID states. The vent holes were created in the laminate to facilitate the resin-injection repair process. The mechanical properties were determined from in-plane compression test of the CFRP laminates. Structure-related dataset, namely infrared thermographs and ultrasonic C-scan images of BVID and other damage features induced by mechanical drilling, are included for completeness.

Cost-effective and efficient resin-injection device for repairing damaged composites

by Wei Liang Lai and Kheng Lim Goh

Traditionally, the main structural components of land transport vehicles, e.g. passenger vehicles... more Traditionally, the main structural components of land transport vehicles, e.g. passenger vehicles and trucks, have been made of metals such as steel and aluminium. As the number of vehicles increases on the road, global effort to reduce pollutant emission has put pressure on the vehicle manufacturers to design and manufacture fuel-efficient vehicles using strong and light-weight structures made of materials such as fibre-reinforced polymer composite (FRP) laminates. For instance, with regard to the new Volvo performance car, Polestar 1, a majority of the parts in the upper body, including doors, bonnet and boot lid, are made of carbon FRP (CFRP) laminates. Interestingly, this design not only provides for maximum stiffness and lightness, but reduces the weight of the upper body, lowers the vehicle’s centre of gravity that results in enhanced handling, performance and drivability.

Mechanical properties of low-velocity impact damaged carbon fibre reinforced polymer laminates: Effects of drilling holes for resin-injection repair

by Wei Liang Lai and Kheng Lim Goh

Barely visible impact damage Carbon fibre reinforced polymer composite Structural damage factor M... more Barely visible impact damage Carbon fibre reinforced polymer composite Structural damage factor Mechanical degradation index A B S T R A C T An important preparatory work of the resin-injection repair process for carbon fibre reinforced polymer laminates , damaged by low-velocity impact, involves drilling vent holes (VHs) and resin-injection holes (RHs). This paper reports the effects of the holes on the laminate mechanical integrity, by comparing the results of pristine and damaged laminates containing one RH in the presence of 4 to 6 VHs. Laminates were damaged by a quasi-static indentation method, followed by drilling. The VH-associated structural damage factor, λ, yielded no significant difference between pristine and damaged laminates. However, the RH-associated λ of damaged laminates was significantly higher than pristine ones. In-plane compression testing revealed that holes in damaged laminates reduced the resilience, fracture toughness, fracture strength and strain to fracture but no appreciable trend was observed with increasing number of VHs. The study indicates that RH exerted a greater influence than VH on the degradation of the mechanical properties.

Dataset on open/blind hole-hole interaction in barely visible impact damaged composite laminates

by Wei Liang Lai and Kheng Lim Goh

This dataset contains the mechanical properties and structural characteristics with images of the... more This dataset contains the mechanical properties and structural characteristics with images of the carbon fibre reinforced epoxy composite (CFRP) laminates with open/blind holes. The mechanical
dataset are the fracture strength, strain at fracture, strain energy density for resilience, strain energy density to fracture and stiffness of the CFRP laminates for dif- ferent setups (namely 1 hole, 2 holes parallel to applied load, and 2 holes normal to applied load) from pristine and barely visible impact damage (BVID) specimens, determine from in- plane compression test. The structural-related dataset include thermographs, images of BVID specimens, drilling-induced damage BVID specimens and video clips of crack propagation during in-plane compression testing.

A simple portable low-pressure healant-injection device for repairing damaged composite laminates

by Wei Liang Lai and Kheng Lim Goh

This article presents the outcomes of an undergraduate design-for-industry team-driven project to... more This article presents the outcomes of an undergraduate design-for-industry team-driven project to develop a portable low-pressure healant-injection device. The developed healant-injection device is intended to use for teaching purpose. The students practice some of the techniques of repairing damaged composite laminates, as part of an engineering composite-related course, which mainly covers the fundamentals and applications of composite laminates. The healant-injection device works by introducing resin into damaged site that can assist the healant to flow through the network of micro-cracks in a low-pressure environment. The device comprises three components: a chamber featuring a (rectangular box) cover made from acrylic that is intended to cover a damaged surface in a low-pressure environment, an injection unit and a vacuum pump unit. Only the vacuum chamber was designed from scratch by the team; the other components were sourced commercially. The repair of composite laminates can be performed using a low viscosity resin, which is made to flow through a hole on the roof of the chamber, assisted by the injection unit (fluid dispenser), from which the resin flows into the damaged (micro-cracks) site; the very low pressure environment (25-29 inHg) in the chamber facilitates the removal of air pockets in the cracks. The composite laminates featured in this project are carbon fibre reinforced composite laminates, which are of great interest to the aerospace industry. Testing and evaluation were carried out by the team to assess the performance of the healant-injection device using impacted carbon fibre

Resin-injection repair of barely visible impact damage on carbon fibre composite laminates

by Wei Liang Lai and Kheng Lim Goh

Carbon fibre reinforced polymer (CFRP) composites are heavily used in many industrial application... more Carbon fibre reinforced polymer (CFRP) composites are heavily used in many industrial application due to its excellent material properties. However, these materials are susceptible to damage in service. The types of impact damage can be classified based on high velocity impact which were caused by hails or bird strikes, or low velocity impact which were caused by tools dropped during maintenance [1]. The former results in visible damage to CFRP laminates and the latter results in barely visible impact damage (BVID). The BVID are hidden in the internal structure of the composites that affects the material capability to take up stress under loading by compression or bending. Therefore, it is important to address the BVID structure by repairing to restore the material structural integrity close to its pristine condition.
In this study, a systematic approach was employed to study how resin-injection repair method [2,3] could restore the mechanical integrity of the BVID CFRP laminates, the approaches are to (1) Create BVID using quasi-static indentation; (2) Evaluate BVID using non-destructive testing methods; (3) Investigate the effects of hole application in CFRP laminates of pristine and damaged states; (4) Investigate the mechanical and physical properties of epoxy with nanoparticles; (5) Perform resin-injection repair with and without vacuum-assisted resin-injection device (VARID) and (6) Evaluate the mechanical properties of CFRP in pristine, damaged and repaired state by in-plane compression test.

Electrospun chitosan/polyethylene-oxide (PEO)/halloysites (HAL) membranes for bone regeneration applications

Fabricating biomaterials that mimic the extracellular matrix (ECM) environment of human tissue wi... more Fabricating biomaterials that mimic the extracellular matrix (ECM) environment of human tissue with appropriate functional, biomechanical, and biocompatible properties remains a challenge. This research aims to fabricate chitosan/polyethylene-oxide (PEO) membranes reinforced with halloysite nanotubes (HAL) as potential scaffolds for bone regeneration applications through facile electrospinning method. Morphological study through FESEM and STEM imaging demonstrated the presence of HAL along the chitosan/PEO fiber matrix with average fiber diameter ranged from 72.07 ± 3.30 nm to 154.87 ± 6.77 nm. Furthermore, the membranes incorporated with up to 5 wt% HAL revealed to have a larger pore, which was suitable for bone regeneration applications. Moreover, the mechanical tests showed that the fabricated chitosan/PEO/HAL membranes exhibited appropriate tensile strength properties to support the growth of osteoblast cells. Thermal stability analysis showed an improved behavior with the addition of HAL to the chitosan/PEO membranes. In addition, the surface wettability of the chitosan/PEO membrane reinforced with 0-5 wt% of HAL ranged between 0 to 75 o , thus showed a hydrophilic nature appropriate for bone tissue regeneration. Besides, natural human osteoblast cell (NHOst) culturing demonstrated the cell adhesion and cell interaction with chitosan/PEO with 5 wt% HAL membrane through the attachment of matured NHOst and primary osteoblast cells on the membranes. Further in vitro analysis revealed that chitosan/PEO with 5 wt% HAL membranes increased the ALP activity by 2.5 times at the 14 days. In summary, the results obtained from this study demonstrated the potential of chitosan/PEO/HAL membranes for bone regeneration applications.

Natural fiber-reinforced polymer composites: application in marine environments

s0010 3.1 Introduction p0010 Composite materials can be developed by incorporating various reinfo... more s0010 3.1 Introduction p0010 Composite materials can be developed by incorporating various reinforcements, such as fibers and particulates, into the polymer matrix, whether they are synthetic or biodegradable types. With the correct selection, these composite materials can be found to be suitable for various applications, such as marine applications, which resist the various chemical attacks. As we already aware, seawater composition changes with respect to the location-this can be because of the watercourses which ultimately carry eroded materials and agricultural runoff into the sea. As per Kester et al. [1], the composition of 1 kg of seawater consists of around 19.4 g Cl 2 , 10.8 g Na 1 , 2.7 g SO 4 22 , 1.3 g Mg 21 , 0.4 g Ca 21 , 0.4 g K 1 , 0.1 g HCO 3 2 , 0.1 g Br 2 , and other chemicals (at lower levels). As per the given composition of seawater , it has been observed that the salt water environment is found to be corrosive to most engineering metals and, in addition, marine animals, for example, naval ship-worm (Teredo navalis), and gribble (Limnoriidae), can result in rapid decay of wood. p0015 The utilization of composite materials and their structures in marine industries is growing, as in other industries. For example, sandwich composite panels having glass or carbon skins with a polymeric core have been found to be one of the most used advanced composites for the development of entire hulls and structures of marine craft. It has been noticed that the composite materials and their structures show various advantages/benefits as compared to the conventional metallic materials , for example [2]: u0010 • Light in weight; u0015 • Good corrosion resistance; u0020 • Nonmagnetic structure; u0025 • Lower acoustic and thermal signatures; and u0030 • High blast resistance. p0045 It has been observed that the seawater environment generally consists of combinations of various parameters. Some of the primary parameters are: Biomass, Biopolymer-Based Materials and Bioenergy.

Rahman 2019 Cost effective and efficient resin injection device for repairing damaged composites

Traditionally, the main structural components of land transport vehicles, e.g. passenger vehicles... more Traditionally, the main structural components of land transport vehicles, e.g. passenger vehicles and trucks, have been made of metals such as steel and aluminium. As the number of vehicles increases on the road, global effort to reduce pollutant emission has put pressure on the vehicle manufacturers to design and manufacture fuel-efficient vehicles using strong and light-weight structures made of materials such as fibre-reinforced polymer composite (FRP) laminates . For instance, with regard to the new Volvo performance car, Polestar 1, a majority of the parts in the upper body, including doors, bonnet and boot lid, are made of carbon FRP (CFRP) laminates . Interestingly, this design not only provides for maximum stiffness and lightness, but reduces the weight of the upper body, lowers the vehicle's centre of gravity that results in enhanced handling, performance and drivability .

Mechanical properties of low-velocity impact damaged carbon fibre reinforced polymer laminates: Effects of drilling holes for resin-injection repair

Barely visible impact damage Carbon fibre reinforced polymer composite Structural damage factor M... more Barely visible impact damage Carbon fibre reinforced polymer composite Structural damage factor Mechanical degradation index A B S T R A C T An important preparatory work of the resin-injection repair process for carbon fibre reinforced polymer laminates , damaged by low-velocity impact, involves drilling vent holes (VHs) and resin-injection holes (RHs). This paper reports the effects of the holes on the laminate mechanical integrity, by comparing the results of pristine and damaged laminates containing one RH in the presence of 4 to 6 VHs. Laminates were damaged by a quasi-static indentation method, followed by drilling. The VH-associated structural damage factor, λ, yielded no significant difference between pristine and damaged laminates. However, the RH-associated λ of damaged laminates was significantly higher than pristine ones. In-plane compression testing revealed that holes in damaged laminates reduced the resilience, fracture toughness, fracture strength and strain to fracture but no appreciable trend was observed with increasing number of VHs. The study indicates that RH exerted a greater influence than VH on the degradation of the mechanical properties.

Hossain 2020Chap Unidirectionally aligned electrospun nanofibres

Dataset on mechanical properties of damaged fibre composite laminates with drilled vent- holes for resin-injection repair procedure

This dataset comprises the mechanical properties of pristine and barely visible impact damaged (B... more This dataset comprises the mechanical properties of pristine and barely visible impact damaged (BVID) carbon fibre reinforced epoxy composite (CFRP) laminates. The mechanical dataset describes the compressive strength, compressive strain at fracture, strain energy density for resilience and strain energy density to fracture of the CFRP laminates with different number of vent holes (namely 4, 5 and 6) in the respective pristine and BVID states. The vent holes were created in the laminate to facilitate the resin-injection repair process. The mechanical properties were determined from in-plane compression test of the CFRP laminates. Structure-related dataset, namely infrared thermographs and ultrasonic C-scan images of BVID and other damage features induced by mechanical drilling, are included for completeness.

Annamalai 2020 The rise of short fibres 2

Currently, a lot of attention is focused on composite laminates made from continuous carbon fibre... more Currently, a lot of attention is focused on composite laminates made from continuous carbon fibre reinforced plastics. On the other hand, there is also renewed interest in using carbon fibre fragments for producing new reinforced plastic laminates partly because of advancement in technology for recovering the fibres (in fragmented forms) from the recycling of used plastic laminates. Additionally, short fibres also find applications in repair. For instance, damaged areas in reinforced-plastic laminates are replaced by a similar plastic reinforced by fibres, known as stepped/patch or scarf, specially tailored to the size of the damage site. What is the performance of short fibres derived from recycling? How do the size-tailored fibres enhance the mechanical integrity of the repaired laminates? Here, we take a fresh look at the basic concepts of short fibre reinforced plastics to make sense of these practical issues.

Woodhead Publishing Series in Composites Science and Engineering Interfaces in Particle and Fibre Reinforced Composites Current Perspectives on Polymer, Ceramic, Metal and Extracellular Matrices

Mechanical testing of glutaraldehyde cross-linked mitral valves. Part one: In vitro mechanical behaviour

The aim of this study was to perform an initial assessment, in vitro, of the feasibility of using... more The aim of this study was to perform an initial assessment, in vitro, of the feasibility of using a glutaraldehyde cross-linked porcine mitral valve to retain acute functionality, focusing on assessing mitral regurgitation. Six porcine hearts were tested using an in vitro simulator. Testing was repeated following cross-linking of mitral valves; where cross-linking was achieved by placing them in a glutaraldehyde solution. The simulator enabled systolic pressure on the ventricular side of the valve to be mimicked. Following testing, mitral valve leaflets underwent Scanning Electron Microscopy of the ventri-cular surface of both the anterior and posterior leaflets (1 cm 2 samples). The peak pressure withstood by cross-linked valves was significantly lower than for untreated valves (108 mmHg cf. 128 mmHg for untreated valves; p \ 0.05). The peak pressure was typically reached 0.5 s later than for the untreated valve. While both cross-linked and untreated valves exhibited endothelium denudation, the unfixed valve had less endothelial loss. Glutaraldehyde cross-linking of porcine mitral valves may be of potential value in assessing improved bioprosthetic mitral valve replacements. However, a more immobile valve exhibiting endothelial denudation (i.e. sclerosis) was a possible concerns identified following in vitro acute assessment.

Cost-effective microvalve-assisted bioprinter for tissue engineering

There are numerous commercial bioprinters based on the most prevalent bioprinting method of extru... more There are numerous commercial bioprinters based on the most prevalent bioprinting method of extrusion. Despite the popularity of these bioprinters, other technologies like droplet-based or drop-on-demand systems are rapidly gaining traction. These alternate methods exhibit advantages in terms of cost, reliability and adaptability to a broader spectrum of cell types. This paper describes the development and validation of a cost-effective, droplet-based, microvalve assisted bioprinter. The mean and the coefficient of variation values are reported for cell numbers dispensed via three modes: manual pipetting (mode 1), bioprinting without the aid of a cell mixer (mode 2) and bioprinting with the aid of a cell mixer (mode 3). Consistent and reproducible results were obtained when cells were dispensed with a mixer maintaining the cells in a homogenous suspension. The printer was assessed for positional accuracy, variability in cell numbers and post-print viability for a range of cell types. This report demonstrates that it is feasible to custom design a cost effective, microvalve based printer to suit specific cell types for a range of tissue engineering applications.

Panjwani 2019CHAP 9 In GOH 2019 Interfaces in particle and fibre reinforced composites

A facile method for processing lignin reinforced chitosan biopolymer microfibres: optimising the fibre mechanical properties through lignin type and concentration

A chitosan biopolymer microfibre-reinforced by lignin-has been processed by a wet-spinning method... more A chitosan biopolymer microfibre-reinforced by lignin-has been processed by a wet-spinning method. To optimise the fibre mechanical and structural properties two types of lignin, with molecular weights 28 000 g mol −1 and 60 000 g mol −1 , were examined and the chitosan fibre was blended with the respective lignin type at 1, 3, 5, 7 and 8 wt% lignin concentrations. The main effects of lignin type and concentration, as well as the interaction between the two parameters, on the fibre tensile stiffness, extensibility, strength and toughness were evaluated using the two-factor analysis of variance. Significant variations in the respective mechanical properties were observed with varying lignin concentrations (P<0.05). The magnitude of the respective mechanical properties is low at 1 wt% but peaks at 3 wt% before decreasing steadily with increasing lignin concentration. Except for extensibility, significant variations in the strength and toughness were observed with respect to lignin type (P<0.05); variations in the stiffness were masked by interactions between lignin type and concentration. These results were related to the dispersion of lignin in the fibre and the nature of the bonds between lignin and chitosan, based on findings from scanning electron microscopy and Fourier transform infrared spectroscopy. This new method for the fabrication of chitosan biopolymer microfibre is inexpensive and versatile and could lend itself to the production of high performance biocomposite structures.

The equilibrium and fixed-bed study of malachite green adsorption on chitosan hydrogels

Chitosan hydrogel beads were prepared by a precipitation process, on which Q1 the adsorption of M... more Chitosan hydrogel beads were prepared by a precipitation process, on which Q1 the adsorption of Malachite Green (MG) oxalate was investigated under various conditions. It was found that adsorption equilibrium was most sensitive to the pH value at pH <8 while fixed bed breakthrough kinetics presented asymmetric s-shaped profiles which could not be adequately described by conventional models such as Adams-Bohart and Yoon-Nelson models. The possible reasons were discussed and an improved model was proposed to better describe the changes in mass transfer mechanisms during adsorption.

Experimental assessment of drilling-induced damage in impacted composite laminates for resin-injection repair: Influence of open/blind hole-hole interaction and orientation

by Wei Liang Lai and Kheng Lim Goh

Composite Structures, 2021

An experimental study of drilling-induced damage in barely visible impact damaged (BVID) carbon f... more An experimental study of drilling-induced damage in barely visible impact damaged (BVID) carbon fibre reinforced polymer (CFRP) laminates where small circular holes were intentionally drilled into the impacted zone as an intermediate step of the resin-injection repair process was described. In-plane compression testing was conducted to determine the mechanical properties of BVID specimens containing open/blind, single and binary holes. Binary-hole specimens at fixed distance apart were tested in parallel or normal to the applied uniaxial force. As expected, BVID specimens experienced significant diminution of property value (compared to pristine ones). No dependence of mechanical properties on hole-hole orientation was observed. Owing to the large hole-hole separation, this significantly mitigated the hole-hole interactions, even though the predicted stress concentration (around the holes) level was above the residual strength. Interestingly, single/binary-hole BVID laminates generated counter-intuitive laminate stiffening effects that the stiffness was significantly higher than that of undrilled BVID specimens.

Dataset on mechanical properties of damaged fibre composite laminates with drilled vent- holes for resin-injection repair procedure

by Wei Liang Lai and Kheng Lim Goh

This dataset comprises the mechanical properties of pristine and barely visible impact damaged (B... more This dataset comprises the mechanical properties of pristine and barely visible impact damaged (BVID) carbon fibre reinforced epoxy composite (CFRP) laminates. The mechanical dataset describes the compressive strength, compressive strain at fracture, strain energy density for resilience and strain energy density to fracture of the CFRP laminates with different number of vent holes (namely 4, 5 and 6) in the respective pristine and BVID states. The vent holes were created in the laminate to facilitate the resin-injection repair process. The mechanical properties were determined from in-plane compression test of the CFRP laminates. Structure-related dataset, namely infrared thermographs and ultrasonic C-scan images of BVID and other damage features induced by mechanical drilling, are included for completeness.

Cost-effective and efficient resin-injection device for repairing damaged composites

by Wei Liang Lai and Kheng Lim Goh

Traditionally, the main structural components of land transport vehicles, e.g. passenger vehicles... more Traditionally, the main structural components of land transport vehicles, e.g. passenger vehicles and trucks, have been made of metals such as steel and aluminium. As the number of vehicles increases on the road, global effort to reduce pollutant emission has put pressure on the vehicle manufacturers to design and manufacture fuel-efficient vehicles using strong and light-weight structures made of materials such as fibre-reinforced polymer composite (FRP) laminates. For instance, with regard to the new Volvo performance car, Polestar 1, a majority of the parts in the upper body, including doors, bonnet and boot lid, are made of carbon FRP (CFRP) laminates. Interestingly, this design not only provides for maximum stiffness and lightness, but reduces the weight of the upper body, lowers the vehicle’s centre of gravity that results in enhanced handling, performance and drivability.

Mechanical properties of low-velocity impact damaged carbon fibre reinforced polymer laminates: Effects of drilling holes for resin-injection repair

by Wei Liang Lai and Kheng Lim Goh

Barely visible impact damage Carbon fibre reinforced polymer composite Structural damage factor M... more Barely visible impact damage Carbon fibre reinforced polymer composite Structural damage factor Mechanical degradation index A B S T R A C T An important preparatory work of the resin-injection repair process for carbon fibre reinforced polymer laminates , damaged by low-velocity impact, involves drilling vent holes (VHs) and resin-injection holes (RHs). This paper reports the effects of the holes on the laminate mechanical integrity, by comparing the results of pristine and damaged laminates containing one RH in the presence of 4 to 6 VHs. Laminates were damaged by a quasi-static indentation method, followed by drilling. The VH-associated structural damage factor, λ, yielded no significant difference between pristine and damaged laminates. However, the RH-associated λ of damaged laminates was significantly higher than pristine ones. In-plane compression testing revealed that holes in damaged laminates reduced the resilience, fracture toughness, fracture strength and strain to fracture but no appreciable trend was observed with increasing number of VHs. The study indicates that RH exerted a greater influence than VH on the degradation of the mechanical properties.

Dataset on open/blind hole-hole interaction in barely visible impact damaged composite laminates

by Wei Liang Lai and Kheng Lim Goh

This dataset contains the mechanical properties and structural characteristics with images of the... more This dataset contains the mechanical properties and structural characteristics with images of the carbon fibre reinforced epoxy composite (CFRP) laminates with open/blind holes. The mechanical
dataset are the fracture strength, strain at fracture, strain energy density for resilience, strain energy density to fracture and stiffness of the CFRP laminates for dif- ferent setups (namely 1 hole, 2 holes parallel to applied load, and 2 holes normal to applied load) from pristine and barely visible impact damage (BVID) specimens, determine from in- plane compression test. The structural-related dataset include thermographs, images of BVID specimens, drilling-induced damage BVID specimens and video clips of crack propagation during in-plane compression testing.

A simple portable low-pressure healant-injection device for repairing damaged composite laminates

by Wei Liang Lai and Kheng Lim Goh

This article presents the outcomes of an undergraduate design-for-industry team-driven project to... more This article presents the outcomes of an undergraduate design-for-industry team-driven project to develop a portable low-pressure healant-injection device. The developed healant-injection device is intended to use for teaching purpose. The students practice some of the techniques of repairing damaged composite laminates, as part of an engineering composite-related course, which mainly covers the fundamentals and applications of composite laminates. The healant-injection device works by introducing resin into damaged site that can assist the healant to flow through the network of micro-cracks in a low-pressure environment. The device comprises three components: a chamber featuring a (rectangular box) cover made from acrylic that is intended to cover a damaged surface in a low-pressure environment, an injection unit and a vacuum pump unit. Only the vacuum chamber was designed from scratch by the team; the other components were sourced commercially. The repair of composite laminates can be performed using a low viscosity resin, which is made to flow through a hole on the roof of the chamber, assisted by the injection unit (fluid dispenser), from which the resin flows into the damaged (micro-cracks) site; the very low pressure environment (25-29 inHg) in the chamber facilitates the removal of air pockets in the cracks. The composite laminates featured in this project are carbon fibre reinforced composite laminates, which are of great interest to the aerospace industry. Testing and evaluation were carried out by the team to assess the performance of the healant-injection device using impacted carbon fibre

Resin-injection repair of barely visible impact damage on carbon fibre composite laminates

by Wei Liang Lai and Kheng Lim Goh

Carbon fibre reinforced polymer (CFRP) composites are heavily used in many industrial application... more Carbon fibre reinforced polymer (CFRP) composites are heavily used in many industrial application due to its excellent material properties. However, these materials are susceptible to damage in service. The types of impact damage can be classified based on high velocity impact which were caused by hails or bird strikes, or low velocity impact which were caused by tools dropped during maintenance [1]. The former results in visible damage to CFRP laminates and the latter results in barely visible impact damage (BVID). The BVID are hidden in the internal structure of the composites that affects the material capability to take up stress under loading by compression or bending. Therefore, it is important to address the BVID structure by repairing to restore the material structural integrity close to its pristine condition.
In this study, a systematic approach was employed to study how resin-injection repair method [2,3] could restore the mechanical integrity of the BVID CFRP laminates, the approaches are to (1) Create BVID using quasi-static indentation; (2) Evaluate BVID using non-destructive testing methods; (3) Investigate the effects of hole application in CFRP laminates of pristine and damaged states; (4) Investigate the mechanical and physical properties of epoxy with nanoparticles; (5) Perform resin-injection repair with and without vacuum-assisted resin-injection device (VARID) and (6) Evaluate the mechanical properties of CFRP in pristine, damaged and repaired state by in-plane compression test.

Electrospun chitosan/polyethylene-oxide (PEO)/halloysites (HAL) membranes for bone regeneration applications

Fabricating biomaterials that mimic the extracellular matrix (ECM) environment of human tissue wi... more Fabricating biomaterials that mimic the extracellular matrix (ECM) environment of human tissue with appropriate functional, biomechanical, and biocompatible properties remains a challenge. This research aims to fabricate chitosan/polyethylene-oxide (PEO) membranes reinforced with halloysite nanotubes (HAL) as potential scaffolds for bone regeneration applications through facile electrospinning method. Morphological study through FESEM and STEM imaging demonstrated the presence of HAL along the chitosan/PEO fiber matrix with average fiber diameter ranged from 72.07 ± 3.30 nm to 154.87 ± 6.77 nm. Furthermore, the membranes incorporated with up to 5 wt% HAL revealed to have a larger pore, which was suitable for bone regeneration applications. Moreover, the mechanical tests showed that the fabricated chitosan/PEO/HAL membranes exhibited appropriate tensile strength properties to support the growth of osteoblast cells. Thermal stability analysis showed an improved behavior with the addition of HAL to the chitosan/PEO membranes. In addition, the surface wettability of the chitosan/PEO membrane reinforced with 0-5 wt% of HAL ranged between 0 to 75 o , thus showed a hydrophilic nature appropriate for bone tissue regeneration. Besides, natural human osteoblast cell (NHOst) culturing demonstrated the cell adhesion and cell interaction with chitosan/PEO with 5 wt% HAL membrane through the attachment of matured NHOst and primary osteoblast cells on the membranes. Further in vitro analysis revealed that chitosan/PEO with 5 wt% HAL membranes increased the ALP activity by 2.5 times at the 14 days. In summary, the results obtained from this study demonstrated the potential of chitosan/PEO/HAL membranes for bone regeneration applications.

Natural fiber-reinforced polymer composites: application in marine environments

s0010 3.1 Introduction p0010 Composite materials can be developed by incorporating various reinfo... more s0010 3.1 Introduction p0010 Composite materials can be developed by incorporating various reinforcements, such as fibers and particulates, into the polymer matrix, whether they are synthetic or biodegradable types. With the correct selection, these composite materials can be found to be suitable for various applications, such as marine applications, which resist the various chemical attacks. As we already aware, seawater composition changes with respect to the location-this can be because of the watercourses which ultimately carry eroded materials and agricultural runoff into the sea. As per Kester et al. [1], the composition of 1 kg of seawater consists of around 19.4 g Cl 2 , 10.8 g Na 1 , 2.7 g SO 4 22 , 1.3 g Mg 21 , 0.4 g Ca 21 , 0.4 g K 1 , 0.1 g HCO 3 2 , 0.1 g Br 2 , and other chemicals (at lower levels). As per the given composition of seawater , it has been observed that the salt water environment is found to be corrosive to most engineering metals and, in addition, marine animals, for example, naval ship-worm (Teredo navalis), and gribble (Limnoriidae), can result in rapid decay of wood. p0015 The utilization of composite materials and their structures in marine industries is growing, as in other industries. For example, sandwich composite panels having glass or carbon skins with a polymeric core have been found to be one of the most used advanced composites for the development of entire hulls and structures of marine craft. It has been noticed that the composite materials and their structures show various advantages/benefits as compared to the conventional metallic materials , for example [2]: u0010 • Light in weight; u0015 • Good corrosion resistance; u0020 • Nonmagnetic structure; u0025 • Lower acoustic and thermal signatures; and u0030 • High blast resistance. p0045 It has been observed that the seawater environment generally consists of combinations of various parameters. Some of the primary parameters are: Biomass, Biopolymer-Based Materials and Bioenergy.

Rahman 2019 Cost effective and efficient resin injection device for repairing damaged composites

Traditionally, the main structural components of land transport vehicles, e.g. passenger vehicles... more Traditionally, the main structural components of land transport vehicles, e.g. passenger vehicles and trucks, have been made of metals such as steel and aluminium. As the number of vehicles increases on the road, global effort to reduce pollutant emission has put pressure on the vehicle manufacturers to design and manufacture fuel-efficient vehicles using strong and light-weight structures made of materials such as fibre-reinforced polymer composite (FRP) laminates . For instance, with regard to the new Volvo performance car, Polestar 1, a majority of the parts in the upper body, including doors, bonnet and boot lid, are made of carbon FRP (CFRP) laminates . Interestingly, this design not only provides for maximum stiffness and lightness, but reduces the weight of the upper body, lowers the vehicle's centre of gravity that results in enhanced handling, performance and drivability .

Mechanical properties of low-velocity impact damaged carbon fibre reinforced polymer laminates: Effects of drilling holes for resin-injection repair

Barely visible impact damage Carbon fibre reinforced polymer composite Structural damage factor M... more Barely visible impact damage Carbon fibre reinforced polymer composite Structural damage factor Mechanical degradation index A B S T R A C T An important preparatory work of the resin-injection repair process for carbon fibre reinforced polymer laminates , damaged by low-velocity impact, involves drilling vent holes (VHs) and resin-injection holes (RHs). This paper reports the effects of the holes on the laminate mechanical integrity, by comparing the results of pristine and damaged laminates containing one RH in the presence of 4 to 6 VHs. Laminates were damaged by a quasi-static indentation method, followed by drilling. The VH-associated structural damage factor, λ, yielded no significant difference between pristine and damaged laminates. However, the RH-associated λ of damaged laminates was significantly higher than pristine ones. In-plane compression testing revealed that holes in damaged laminates reduced the resilience, fracture toughness, fracture strength and strain to fracture but no appreciable trend was observed with increasing number of VHs. The study indicates that RH exerted a greater influence than VH on the degradation of the mechanical properties.

Hossain 2020Chap Unidirectionally aligned electrospun nanofibres

Dataset on mechanical properties of damaged fibre composite laminates with drilled vent- holes for resin-injection repair procedure

This dataset comprises the mechanical properties of pristine and barely visible impact damaged (B... more This dataset comprises the mechanical properties of pristine and barely visible impact damaged (BVID) carbon fibre reinforced epoxy composite (CFRP) laminates. The mechanical dataset describes the compressive strength, compressive strain at fracture, strain energy density for resilience and strain energy density to fracture of the CFRP laminates with different number of vent holes (namely 4, 5 and 6) in the respective pristine and BVID states. The vent holes were created in the laminate to facilitate the resin-injection repair process. The mechanical properties were determined from in-plane compression test of the CFRP laminates. Structure-related dataset, namely infrared thermographs and ultrasonic C-scan images of BVID and other damage features induced by mechanical drilling, are included for completeness.

Annamalai 2020 The rise of short fibres 2

Currently, a lot of attention is focused on composite laminates made from continuous carbon fibre... more Currently, a lot of attention is focused on composite laminates made from continuous carbon fibre reinforced plastics. On the other hand, there is also renewed interest in using carbon fibre fragments for producing new reinforced plastic laminates partly because of advancement in technology for recovering the fibres (in fragmented forms) from the recycling of used plastic laminates. Additionally, short fibres also find applications in repair. For instance, damaged areas in reinforced-plastic laminates are replaced by a similar plastic reinforced by fibres, known as stepped/patch or scarf, specially tailored to the size of the damage site. What is the performance of short fibres derived from recycling? How do the size-tailored fibres enhance the mechanical integrity of the repaired laminates? Here, we take a fresh look at the basic concepts of short fibre reinforced plastics to make sense of these practical issues.

Woodhead Publishing Series in Composites Science and Engineering Interfaces in Particle and Fibre Reinforced Composites Current Perspectives on Polymer, Ceramic, Metal and Extracellular Matrices

Mechanical testing of glutaraldehyde cross-linked mitral valves. Part one: In vitro mechanical behaviour

The aim of this study was to perform an initial assessment, in vitro, of the feasibility of using... more The aim of this study was to perform an initial assessment, in vitro, of the feasibility of using a glutaraldehyde cross-linked porcine mitral valve to retain acute functionality, focusing on assessing mitral regurgitation. Six porcine hearts were tested using an in vitro simulator. Testing was repeated following cross-linking of mitral valves; where cross-linking was achieved by placing them in a glutaraldehyde solution. The simulator enabled systolic pressure on the ventricular side of the valve to be mimicked. Following testing, mitral valve leaflets underwent Scanning Electron Microscopy of the ventri-cular surface of both the anterior and posterior leaflets (1 cm 2 samples). The peak pressure withstood by cross-linked valves was significantly lower than for untreated valves (108 mmHg cf. 128 mmHg for untreated valves; p \ 0.05). The peak pressure was typically reached 0.5 s later than for the untreated valve. While both cross-linked and untreated valves exhibited endothelium denudation, the unfixed valve had less endothelial loss. Glutaraldehyde cross-linking of porcine mitral valves may be of potential value in assessing improved bioprosthetic mitral valve replacements. However, a more immobile valve exhibiting endothelial denudation (i.e. sclerosis) was a possible concerns identified following in vitro acute assessment.

Cost-effective microvalve-assisted bioprinter for tissue engineering

There are numerous commercial bioprinters based on the most prevalent bioprinting method of extru... more There are numerous commercial bioprinters based on the most prevalent bioprinting method of extrusion. Despite the popularity of these bioprinters, other technologies like droplet-based or drop-on-demand systems are rapidly gaining traction. These alternate methods exhibit advantages in terms of cost, reliability and adaptability to a broader spectrum of cell types. This paper describes the development and validation of a cost-effective, droplet-based, microvalve assisted bioprinter. The mean and the coefficient of variation values are reported for cell numbers dispensed via three modes: manual pipetting (mode 1), bioprinting without the aid of a cell mixer (mode 2) and bioprinting with the aid of a cell mixer (mode 3). Consistent and reproducible results were obtained when cells were dispensed with a mixer maintaining the cells in a homogenous suspension. The printer was assessed for positional accuracy, variability in cell numbers and post-print viability for a range of cell types. This report demonstrates that it is feasible to custom design a cost effective, microvalve based printer to suit specific cell types for a range of tissue engineering applications.

Panjwani 2019CHAP 9 In GOH 2019 Interfaces in particle and fibre reinforced composites

A facile method for processing lignin reinforced chitosan biopolymer microfibres: optimising the fibre mechanical properties through lignin type and concentration

A chitosan biopolymer microfibre-reinforced by lignin-has been processed by a wet-spinning method... more A chitosan biopolymer microfibre-reinforced by lignin-has been processed by a wet-spinning method. To optimise the fibre mechanical and structural properties two types of lignin, with molecular weights 28 000 g mol −1 and 60 000 g mol −1 , were examined and the chitosan fibre was blended with the respective lignin type at 1, 3, 5, 7 and 8 wt% lignin concentrations. The main effects of lignin type and concentration, as well as the interaction between the two parameters, on the fibre tensile stiffness, extensibility, strength and toughness were evaluated using the two-factor analysis of variance. Significant variations in the respective mechanical properties were observed with varying lignin concentrations (P<0.05). The magnitude of the respective mechanical properties is low at 1 wt% but peaks at 3 wt% before decreasing steadily with increasing lignin concentration. Except for extensibility, significant variations in the strength and toughness were observed with respect to lignin type (P<0.05); variations in the stiffness were masked by interactions between lignin type and concentration. These results were related to the dispersion of lignin in the fibre and the nature of the bonds between lignin and chitosan, based on findings from scanning electron microscopy and Fourier transform infrared spectroscopy. This new method for the fabrication of chitosan biopolymer microfibre is inexpensive and versatile and could lend itself to the production of high performance biocomposite structures.

The equilibrium and fixed-bed study of malachite green adsorption on chitosan hydrogels

Chitosan hydrogel beads were prepared by a precipitation process, on which Q1 the adsorption of M... more Chitosan hydrogel beads were prepared by a precipitation process, on which Q1 the adsorption of Malachite Green (MG) oxalate was investigated under various conditions. It was found that adsorption equilibrium was most sensitive to the pH value at pH <8 while fixed bed breakthrough kinetics presented asymmetric s-shaped profiles which could not be adequately described by conventional models such as Adams-Bohart and Yoon-Nelson models. The possible reasons were discussed and an improved model was proposed to better describe the changes in mass transfer mechanisms during adsorption.

Current understanding of interfacial stress transfer mechanisms in connective tissue 20

Collagen fibrils, the tiny numerous slender fibrillar particles that are embedded in extracellula... more Collagen fibrils, the tiny numerous slender fibrillar particles that are embedded in extracellular matrix of soft connective tissues such as tendons and ligaments, provide mechanical reinforcement to the tissue during physiological activity and also functions to resist forces that attempt to break the tissue apart. The mechanics of reinforcement underpins stress transfer at the collagen fibril/PG matrix interface in connective tissue involving the following key aspects.
• A plastic stress transfer mechanism, described by a model of a plastic PG matrix shear- sliding over an elastic collagen fibril, when the tissue is subjected to an external applied load
• No consensus has yet to be established for the nature of the bridges linking the adjacent fibrils, particularly the molecular interactions at the fibril/PG matrix interface that contribute to the mechanical response of the tissue. It is instructive that nanotube network and particles in the fibre-fibre matrix in engineering fibre reinforced composites have demonstrated that
they can enhance the mechanical properties of the composites.
• Simultaneous micromechanical/microscopy testing of tendon fascicles has enabled valuable
insights to be drawn concerning the interaction of the hydrated PG-rich matrix and the discontinuous collagen fibrils, pointing to the importance of interfibrillar shear as underpin- ning the fascicle mechanical response to external loading.

The Other Connective Tissue: Echinoderm Ligaments and Membranes as Decellularized Bioscaffold for Tissue Engineering

This chapter examines the sea urchin ligament as a potential decellular-ized bioscaffold by discu... more This chapter examines the sea urchin ligament as a potential decellular-ized bioscaffold by discussing the significance of collagen fibrils, which are highly-paralleled slender structures embedded in the hydrated proteoglycan-rich (PG) extra-cellular matrix (ECM) of tendons, for reinforcing the soft connective tissue. The discussion is presented in two parts as follows. Part one examines the role of collagen fibrils for providing structural support for the tissue, in the context of the structure of the collagen fibril, and mechanics of stress transfer in the tissue. Part two will review the potential clinical applications of the decellularized bioscaffold, related to tissue implants for repair and regeneration.

Current understanding of interfacial stress transfer mechanisms in connective tissue 20

Fibre reinforcement in fibre composite materials: effects of fibre shape

by Kheng Lim Goh and Kheng Goh

The aim of this project was to investigate the effects of fibre shape on its ability to reinforce... more The aim of this project was to investigate the effects of fibre shape on its ability to reinforce a fibre composite material. Analytical and finite element (FE) models of an axisymmetric fibre composite material were developed and used to achieve this aim. Fibres of cylindrical shape, ellipsoidal shape, with paraboloidal ends and with conical ends were considered: fibre geometry was further characterised by an axial ratio, q. The scope of this study covered elastic and plastic load transfer processes.

Resin-injection repair of barely visible impact damage on carbon fibre composite laminates

by Wei Liang Lai and Kheng Lim Goh

22nd International Conference on Composite Materials, 2019

Carbon fibre reinforced polymer (CFRP) composites are heavily used in many industrial application... more Carbon fibre reinforced polymer (CFRP) composites are heavily used in many industrial application due to its excellent material properties. However, these materials are susceptible to damage in service. The types of impact damage can be classified based on high velocity impact which were caused by hails or bird strikes, or low velocity impact which were caused by tools dropped during maintenance [1]. The former results in visible damage to CFRP laminates and the latter results in barely visible impact damage (BVID). The BVID are hidden in the internal structure of the composites that affects the material capability to take up stress under loading by compression or bending. Therefore, it is important to address the BVID structure by repairing to restore the material structural integrity close to its pristine condition.
In this study, a systematic approach was employed to study how resin-injection repair method [2,3] could restore the mechanical integrity of the BVID CFRP laminates, the approaches are to (1) Create BVID using quasi-static indentation; (2) Evaluate BVID using non-destructive testing methods; (3) Investigate the effects of hole application in CFRP laminates of pristine and damaged states; (4) Investigate the mechanical and physical properties of epoxy with nanoparticles; (5) Perform resin-injection repair with and without vacuum-assisted resin-injection device (VARID) and (6) Evaluate the mechanical properties of CFRP in pristine, damaged and repaired state by in-plane compression test.