Fabric Parameter Effect on the Mechanical Properties of Woven Hemp Fabric Reinforced Composites as an Alternative to Wood Products

Research Article

Adv Res Text Eng. 2016; 1(1): 1004.

Fabric Parameter Effect on the Mechanical Properties of Woven Hemp Fabric Reinforced Composites as an Alternative to Wood Products

Misnon IM1,2, Islam MM¹*, Epaarachchi JA¹, Lau K-T³ and Wang H¹

¹Centre for Future Materials (CFM) and School of Mechanical and Electrical Engineering, Faculty of Health, Engineering and Sciences, University of Southern Queensland, Australia

²Faculty of Applied Sciences, University Teknologi MARA, Malaysia

³Swinburne University of Technology, Australia

*Corresponding author: Md Mainul Islam, Centre for Future Materials (CFM) and School of Mechanical and Electrical Engineering, Faculty of Health, Engineering and Sciences, University of Southern Queensland, Australia

Received: September 05, 2016; Accepted: October 25, 2016; Published: October 28, 2016

Abstract

Hemp is a common natural fibre which has reliable properties and is available in the forms of staple fibres, yarns and fabrics. However, less works were done by using woven hemp fabric in composite materials, especially for an alternative to wood products. In this work, woven hemp fabrics in different fabric layering orientations have been used to reinforce vinyl ester resin by employing hand lay-up method. The properties of hemp fabric were used to investigate how these properties can affect the physical and mechanical behaviour of the fabricated composites. The results show that fabric properties and layering orientations contribute to the tensile, flexural and impact properties of the composites. Based on the comparison to wood and engineered wood products’ properties, the mechanical properties of composites are found to be comparable. The comparison also shows that the woven hemp fabric reinforced vinyl ester can be an alternative for wood and engineered wood products in building industries especially in low-load bearing applications.

Keywords: Natural fibres composites; Hemp; Woven fabric; Mechanical properties; Wood products

Introduction

One of the big issues related to the environment is the uncontrolled and illegal timber logging and it has become more serious lately [1,2]. While in the building industry, it is reported by [3], United States Environmental Protection Agency (EPA) stated that 70.6 million tons of waste wood which is categorised as Municipal Solid Waste (MSW) and Construction and Demolition (C&D) debris were disposed in landfill in 2010. The waste woods is made up of softwood and hardwood which are used as building materials, furniture, pallets, container and crating, and a wide-range of consumer goods. Both issues, either the waste wood debris dumping in landfill or uncontrolled and illegal wood logging, are directly and/or indirectly giving an impact to the environment.

Thus, something needs to be done to solve or at least lessen the impact consequent upon the issues mentioned above. Bio-based composites have existed for quite sometimes and apparently the suitable nominee to be used in building industry since its current application is mainly for non-load bearing in many fields, especially in the automotive and building industries [4-8]. Bio-based materials have attracted considerable interest due to the worldwide awareness on the environmental issues such addressed as above [9-11]. The utilisation of natural fibre from plant in bio-based composites has led to the better environment and developing a more sustainable material cycle due to its lower price, global availability and complete data on its properties[7,8].

The main problem in utilising natural fibres is controlling over the fibre orientation and distribution thus the optimum mechanical properties are not efficiently utilised as reinforcement [12,13].

The availability and advancement in textile engineering as well as technology provide wide range of techniques to convert the natural fibres into yarn and then into fabric [14]. Utilisation of fibre in the form of textile fabric is more convenient considering their advantages on high strength, good fibre orientation and fibre distribution and more importantly easy to handle during composite fabrication [11,15]. Not all natural fibres can be converted into the woven fabric such as bagasse, kapok and kenaf. Only few fibres such as jute and hemp were long established in woven fabric and they possess good properties as reinforcement in composite materials [11,16].

Christian and Billington [17] asserted that utilization of hemp composites can be used as an alternative material to replace some wood and engineered wood products. This can be achieved by taking advantages of hemp fibre in the form of fabric [18] utilised woven hemp fabric in their study by comparing two different kinds of weave structure (plain and twill structures) fabric to reinforce Poly Lactic Acid (PLA) resin. They found that the composite made of twill fabric has a better result than plain weave fabric in terms of mechanical, thermal and viscoelastic properties. However, both studies did not discuss in details on the attributes of fabric parameters in their works such as fabric density, yarn size, yarn crimp in fabric and fabric strength that might affect to their composite properties. Both studies only considered the fibre volume fraction and how this fibre fraction affects the mechanical properties of the composite in their works. In detail, Christian and Billington [17] mentioned about the yarn crimp. Nevertheless, there are no specific figures on the fabric yarn crimp. This is similar with the study of Song et al. [18] study, their idea to investigate the viscoelastic and thermal behaviour of the hemp fibre composite was good but they did not explain more on the yarn crimp role.

The properties of fabric are mainly dependent on how the fabric is designed [11,15] physically and mechanically, and these are the fabric density, yarn size, yarn crimp in fabric and fabric strength. These fabric properties will affect the behaviour of the fabricated composites. In the case of natural woven hemp fabric, less work is done on their utilization as a reinforcement material. Apart from the issues on considering woven hemp fabric properties above, less work was done on this woven hemp fabric composite, especially on the effect of different fabric stacking sequences in relation to its fabric properties.

Therefore, in this work, woven hemp fabric was used to fabricate bio-based composites employing hand lay-up method. The composites were fabricated in different fabric layer orientations in order to investigate the stacking sequence effect on the mechanical properties. The properties of fabric were determined and measured in order to study how these fabric parameters affect the physical properties and mechanical behaviour of composite fabricated. Some comparison to wood and engineered wood products was also done to see the suitability and readiness of woven hemp fabric reinforced vinyl ester to be used in building industry.

Materials and Methods

A commercial woven hemp fabric, with the product code, FSA10 was supplied by Hemp Wholesale Australia. According to the specifications given by the supplier, the fabrics were produced by 100% yarn hemp in both warp and weft. The yarns were converted from cleaned hemp fibre into yarn through spinning processes and the twist given was 430 twists per meter before it was woven into fabric in plain weave (taffeta) structure. Other than that, the supplier did not give much data. Therefore, further investigation was needed in order to characterize and renew the data of the hemp fabrics. Vinyl ester resin product code of SPV 1356 PROM THIX and the catalyst Methyl Ethyl Ketone Peroxide (MEKP), product code of NOROX 925H were supplied by Nuplex® Composite Industry (Australia).

Characterization of woven hemp fabric

Woven hemp fabric had been characterised employing several textile materials standard methods. These standard methods are commonly used in textile industry for characterization as well as product quality determination purposes. All the tests were performed under standard atmosphere, 21 ± 1°C and 65 ±2 % relative humidity and the fabric was opened from the roll to relax for 24 hours. Woven hemp fabrics are characterised for their thickness and fabric density or fabric count while their yarn was characterised for its yarn size and crimp (for warp and weft).

‘Fabric thickness’ was measured according to ASTM: D1777. Twenty (20) randomly selected locations were used to obtain the average value in order to make sure the precision. The thickness values were taken in millimetre (mm).ASTM: D3775 standard method was employed to determine ‘fabric density’ or ‘fabric count’. Woven hemp fabric was placed on a smooth surface and the number of warp and filling yarns were counted using a pick counter in a 2 cm length.

Yarn linear density was measured in accordance to ASTM: D1907. Yarn was unravelled from the fabric and then cut to 1 m length before it was weighed using a weighing balance. Ten specimens were measured and the average weight, w, in grams, was used for calculating the yarn linear density using Equation. (1).

Yarnsize( tex ),N= w×k l    (1) [email protected]@[email protected]@+=feaaguart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=xfr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaaeaaaaaaaaa8qacaWGzbGaamyyaiaadkhacaWGUbGaam4CaiaadMgacaWG6bGaamyzamaabmaapaqaa8qacaWG0bGaamyzaiaadIhaaiaawIcacaGLPaaacaGGSaGaamOtaiabg2da9maalaaapaqaa8qacaWG3bGaey41aqRaam4A[email protected][email protected]

Where l is the length of yarn in meter and k is the constant which equals 1000 m/g for tex.

ASTM: D3883 was used to measure yarn crimp. Parallel lines were marked in the warp direction 20 cm apart (this is the distance of the yarn in the fabric, Y1 = 20 cm). A cut of 30 cm was made along the filling yarn, which crossed the parallel lines. Several yarns from one edge were unravelled. The next ten (10) yarns were carefully unravelled for measurement. Each yarn was pulled taut without exerting extreme force and the extended length between the two marks was measured as Y2. The yarn crimp, C, is calculated as shown below in Equation. (2).

Yarncrimp(%),C= Y 2 Y 1 Y 1 ×100    (2) [email protected]@[email protected]@+=feaaguart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=xfr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaaeaaaaaaaaa8qacaWGzbGaamyyaiaadkhacaWGUbGaam4yaiaadkhacaWGPbGaamyBaiaadchacaGGOaGaaiyjaiaacMcacaGGSaGaam4qaiabg2da9maalaaapaqaa8qacaWGzbWdamaaBaaaleaapeGaaGOmaaWdaeqaaOWdbiabgkHiTiaadMfapaWaaSbaaSqaa8qacaaIXaaapaqabaaakeaapeGaamywa8aadaWgaaWcbaWdbiaaigdaa8aabeaaaaGcpeGaey41aqRaaGyma[email protected][email protected]

The density of the hemp fibres was determined by Multipycnometer MVP D160E. Helium gas was used as a displacement medium. The helium was added to the fibres under vacuum conditions to ensure that all interior air cavities in the submerged fibres (e.g. the fibre lumen) were filled with helium. The data reported are the average and standard deviation of 3 measurements.

The aerial density or fabric weight, W, can be measured precisely using Equation. (3) [19,20].

Fabricweight( g m 2 ),W= N 1 ( 1+ C 1 ) P 1 + N 2 ( 1+ C 2 ) P 2      (3) [email protected]@[email protected]@+=feaaguart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=xfr=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[email protected][email protected]

Where N is the yarn size calculated from Equation. (1), C is the yarn crimp percentage calculated from Equation. (2) while subscripts 1 and 2 refer to warp and weft yarn respectively. P is the yarn spacing in mm which can be calculated from Equation. (4) [20].

Yarnspacing( mm ), P n = t d      (4) [email protected]@[email protected]@+=feaaguart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=xfr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaaeaaaaaaaaa8qacaWGzbGaamyyaiaadkhacaWGUbGaam4CaiaadchacaWGHbGaam4yaiaadMgacaWGUbGaam4zamaabmaapaqaa8qacaWGTbGaamyBaaGaayjkaiaawMcaaiaacYcacaWGqbWdamaaBaaaleaapeGaamOBaaWdaeqaaOWdbiabg2da9maalaaapaqaa8qacaWG0baapaqaa8qacaW[email protected][email protected]

Where subscript n = 1 or 2 which refer to warp or weft yarn, t is the constant value of length for certain fabric density which is equal to 20 mm and d is the respective fabric density.

Total fabric cover factor (K) was measured using Equation. (5) and this K value is the ratio on how big the area is covered by the yarns [20].

Totalfabriccover,K= C 1 + C 2 C 1 C 2     (5) [email protected]@[email protected]@+=feaaguart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=xfr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaaeaaaaaaaaa8qacaWGubGaam4BaiaadshacaWGHbGaamiBaiaadAgacaWGHbGaamOyaiaadkhacaWGPbGaam4yaiaadogacaWGVbGaamODaiaadwgacaWGYbGaaiilaiaadUeacqGH9aqpcaWGdbWdamaaBaaaleaapeGaaGymaaWdaeqaaOWdbiabgUcaRiaadoeapaWaaSbaaSqaa8qacaaIYaaapaqabaGcpeGaeyOeI0Iaam4qa8aadaWgaaWcbaWdbiaaigdaa8aabeaak8qacaWGdbWdamaaBaaaleaapeGaa[email protected][email protected]

Where subscripts 1 and 2 are referring to warp and weft yarn respectively and C is the fractional yarn cover which can be calculated from Equation. (6) [20].

Fractionalyarnscover, C n =s× ( N n / f d )× d n × 10 3     (6) [email protected]@[email protected]@+=feaaguart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLnhiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=xfr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaaeaaaaaaaaa8qacaWGgbGaamOCaiaadggacaWGJbGaamiDaiaadMgacaWGVbGaamOBaiaadggacaWGSbGaamyEaiaadggacaWGYbGaamOBaiaadohacaWGJbGaam4BaiaadAhacaWGLbGaamOCaiaacYcacaWGdbWdamaaBaaaleaapeGaamOBaaWdaeqaaOWdbiabg2da9iaadohacqGHxdaTdaGcaaWdaeaapeGaaiikaiaad6eapaWaaSbaaSqaa8qacaWGUbaapaqabaaapeqabaGccaGGVaGaamOza8aadaWgaaWcbaWdbiaadsgaa8aabeaak8qacaGGPaGaey41aqRaamiza8aadaWgaaWcbaWdbiaad6gaa8aabeaak8qacqGHxdaTcaaIXaGaaGima8aadaahaaWcbeqaa8qacqGHsisl[email protected][email protected]

Where subscript n = 1 or 2 which refer to warp or weft yarn, s is the constant which is equal to 4.44, N is the yarn size calculated from Equation. (1), fd is the fibre density and d is the respective fibre density.

In term of mechanical properties, tensile properties of hemp fabrics were characterized using universal testing machine MTS Alliance RT/10employing ASTM: D 5034 standard method. 75 mm wide test specimens were cut in the desired direction (warp or weft) and then equal numbers of yarns were removed from both sides until the specimen width was reduced to 50 mm. The same procedure was followed for test strips in both warp and weft directions. Tensile tests were performed using a gauge length of 75 mm and a crosshead speed 10 mm/min. The cross-sectional area used to convert load into stress was calculated from the test specimen width and the thickness of fabric obtained from the fabric characterization [19,21,22].

Fabrication method

Resin was prepared by adding MEKP into vinyl ester with the ratio of 1:44 by weight. This prepared resin was then applied on 10 fabric layers (300 × 300 mm for each layer) by employing hand layup technique. Trapped air was gently squeezed out using a roller after pouring the resin on the fabric. This mixture (wet fabrics) was then laid in between of thick glass plates (400 × 400 × 100 mm in dimension) which were coated with polymer mould release agent. This assembles was compressed with a weight placed on top of this mixture to remove the excess resin and the calculated pressure given to this assembly was 4.360 kPa. This mixture was then left for the cure under room temperature for 24 hours. It was afterward post cured in an oven for four hours at 80°C. Four (4) types of composites which differ in their layer orientations were fabricated as shown in Table 1. Since the layer orientations is main focus in this work, it should be mentioned that 0° direction is based on the warp direction of the woven hemp fabric.