Experimental investigation of the effect of weave type on the mechanical properties of woven hemp fabric/epoxy composites

Abstract

Natural fiber composites have a growing popularity as alternative materials to petroleum-based plastics and glass fiber reinforced composites due to various economic and environmental reasons. Textile preforms such as woven, knitted, braided, nonwoven, and multiaxial fabrics are commonly used in composite industry due to their high mechanical properties, tailorability, ease of handling during production, and versatility in material design. A range of properties can be obtained by varying the weave pattern and fabric architecture in woven fabric composites. In this study, epoxy composites reinforced with hemp woven fabrics with four different weave types were produced. The weave types chosen were quasi-unidirectional (UD), plain, basket 2/2, and twill 2/2 which are commonly used in the composite industry. Fabric properties such as yarn angle, yarn density, and crimp ratio were determined to evaluate their possible effect on composite properties. Tensile and three-point flexural tests were conducted in order to determine the effect of weave type on the mechanical properties of the resulting composites. It was found that UD composites show the highest tensile strength, tensile modulus, flexural strength, and flexural modulus in the 0° (yarn) direction. Plain weave fabric composites showed the second highest tensile and flexural strength and moduli followed by basket 2/2 weave composites. Composites reinforced with twill 2/2 woven fabrics showed the lowest mechanical properties due to high yarn crimp and yarn angle, less balanced structure, and resulting shear forces involved during various loading conditions.

Keywords

natural fiber composites hemp fiber woven composites fabric architecture mechanical properties

Introduction

Natural fiber reinforced composites attracted great attention for use in various industries due to increasing economic and environmental concerns.^1–5 Natural fibers such as hemp, flax, jute, kenaf, and coir emerged as high-strength, high-modulus, renewable, sustainable, and biodegradable alternatives to glass fiber which are still widely used in composite industry today.^6–10 Natural fibers are low-density, low-cost, and readily available. They are also CO₂-neutral, that is, they effectively have near-zero carbon footprint. Composites reinforced with natural fibers possess high specific mechanical properties (mechanical property/density) comparable to those of glass fiber reinforced plastics.^1,2 Beside these advantages, natural fiber composites also have certain problems such as the high moisture absorption of natural fibers due to hydrophilic hydroxyl (–OH) groups in their structure and the following deterioration in material properties which is especially problematic in outdoor applications. Another problem with these composites is the low compatibility between hydrophilic natural fibers and hydrophobic polymer resins which results in an insufficient bonding at the fiber/matrix interface. Various surface modification methods have been used to address this issue with successful outcomes.^11–16

Hemp (Cannabis sativa L.) fiber stands out among the other natural fibers due to its high mechanical properties. Hemp fiber reinforced composites have been studied extensively by many research groups. Corbin et al.¹⁷ studied the effect of weave pattern and process parameters on the mechanical properties of woven hemp fabric/epoxy composites made from low-twisted rovings. They produced three types of fabrics with different weaving patterns such as plain weave, satin six weft effect, and twill 6 weft effect. Plain weave fabric composites showed the highest tensile strength and modulus, whereas the satin and twill weave fabric composites showed lower values. Misnon et al.¹⁸ analyzed two different batches of plain weave fabrics for composite reinforcement. They characterized a range of fabric properties such as crimp, density, physical, and mechanical properties. They concluded that both fabrics are suitable for composite reinforcement. Sepe et al.¹⁹ investigated the tensile and flexural properties of alkaline and (3-glycidyloxypropyl) trimethoxysilane-treated plain woven hemp fabric composites. The mechanical test results indicated that silane treatment of hemp fibers improves both tensile and flexural properties of the composites. Song et al.²⁰ studied the viscoelastic behavior of plain and 2/1 twill woven hemp/poly(lactic acid) (PLA) composites. Twill fabric composites provided higher tensile strength and modulus when compared to the plain weave. Storage and loss modulus were also higher in twill fabric composites. The authors attributed these results to the structure of the twill fabric which contains lower number of interlacements when compared to the plain weave. Baghaei et al.²¹ investigated the effect of weave structure on the mechanical behavior and moisture absorption of PLA/hemp woven fabric composites. They studied two different weave patterns such as 8-harness satin and basket. Satin fabric composites had significantly lower porosity and higher mechanical properties compared to the basket weave composites. Abbas et al.²² characterized the mechanical properties of hemp/green epoxy composites by using four different weave structures, namely, matt, satin, hybrid weave A, and hybrid weave B and by adding glass microspheres (GMS) to the resin. The tensile strength of composites with satin weave fabric was better than the other weave types, which was attributed to the longer warp thread float and lesser number of intersection points in satin weave, whereas flexural and pendulum (Charpy) impact test results of the matt weave composite were better due to its stable and robust structure when compared to the other weave types. Antony et al.²³ studied the effect of fiber content and fabric weave pattern on the mechanical properties of hemp fiber woven fabrics/polypropylene composites. They used two different weave types such as Taffeta (plain weave) and serge (2/1 twill weave) with an areal density of 0.29 kg/m² and 0.38 kg/m², respectively. 2/1 twill fabric composites performed better in terms of tensile strength, tensile modulus, shear strength, and shear modulus. Umair et al.²⁴ investigated the effect of weave architecture and glass microspheres percentage on the low velocity impact response of hemp/green epoxy composites. They produced hemp woven fabrics having four different weave structures such as matt, satin, hybrid weave A, and hybrid weave B. Four-layered composites containing glass microspheres (0%, 2%, 3.5%, and 5% on the weight of resin) were fabricated using vacuum bag molding. They found that both weave design and incorporation of glass microspheres show a significant effect on impact properties of the developed composites. The composite sample reinforced with satin woven reinforcement showed maximum value of impact force, whereas composite samples containing 5% glass microspheres exhibited more resilience and stiffness as compared to other structures.

In this study, epoxy composites reinforced with hemp woven fabrics with four different weave types such as quasi-unidirectional, plain, basket 2/2, and twill 2/2 were produced. These weave types were chosen due to their wide-spread usage in the composite industry. The weaving parameters such as the reed density, number of harnesses, and yarn linear density were kept constant for all types of produced fabrics to evaluate the effect of different weave patterns on the resulting fabric parameters such as the areal weight, thickness, warp and weft yarn densities, warp and weft yarn crimp ratios, and warp and weft yarn angles. Consequently, the influence of these fabric parameters on the resulting composite performance was evaluated. Tensile and three-point bending tests were conducted for this purpose. Fracture surfaces and the fiber/matrix interface of the failed composites were analyzed with scanning electron microscopy (SEM).

Experimental procedure

Materials

10-ply hemp yarns with a yarn number of 1042 tex were used as warp and filling (weft) yarns to produce the plain, basket 2/2, and twill 2/2 woven fabrics. Quasi-UD fabrics were produced with a plain weave pattern by using 1042 tex hemp yarns as warp yarns and 38 tex hemp yarns as filling (binder) yarns. West System 105 epoxy resin with 206 slow hardener (West System, Michigan, USA) with a mix density of 1.18 g/cm³ were used with a 5:1 (resin: hardener) ratio to produce hemp woven fabric/epoxy composites.

Yarn pre-treatment

Hemp yarns were pre-treated with alkali solution to improve the fiber-matrix interface of the resulting composites. For this purpose, hemp yarns were treated with 5 wt % NaOH solution at 25° for 30 min. Yarns were then neutralized with 2 wt % acetic acid solution. Finally, the yarns were washed again with distilled water and dried in an air oven at 70°C for 24 h.

Fabric production

Four different types of woven fabrics such as quasi-unidirectional (UD), plain (PL), basket 2/2 (BS), and twill 2/2 (TW) were produced on a laboratory type semi-automatic, 8-harness dobby weaving loom. The same weaving parameters were used to fabricate all four types of fabrics to assess the effect of the weave pattern on the resulting fabric parameters. The same reed with 5 dents/cm was used for all fabric types. The characteristics of the woven fabrics produced are given in Table 1. Figure 1 shows the fabric production process. Fabric types produced in this study are given in Figure 2.

Table 1.

Characteristics of the woven fabrics used for composite production.

Fabric type	Fabric parameters			Hemp yarn parameters
Fabric type	Weave type	Areal weight (gr/m²)	Thickness (mm)	Warp yarn (tex)	Filling yarn (tex)
UD	UD	618	1.84	1042	38
PL	Plain (1/1)	740	2.55	1042	1042
BS	Basket (2/2)	828	2.77	1042	1042
TW	Twill (2/2)	844	2.98	1042	1042

Composite production

Compression molding technique was used to produce hemp/epoxy composites. Each composite sample consisted of two layers of woven fabrics stacked one on top of the other so that the warp yarns are aligned in the testing (material) direction. For example, plain weave composite sample consisted of two plain woven fabric layers aligned such that warp yarns are aligned in the material direction. Similarly, UD, basket, and twill weave composites composed of two layers of UD, basket, and twill woven fabrics, respectively. First, two layers of woven fabrics were impregnated with epoxy resin mixture and placed in a steel mold. Then, the mold is closed and placed in a compression molding press and compressed at room temperature using a pressure of 6 bar (0.6 MPa). The mold was kept under pressure for 24 h for further curing. After the curing is complete, the mold was opened and the composite plates with dimensions of 300 x 300 mm (length x width) were removed from the mold.

Fabric geometric characterization

Determination of yarn densities

Yarn density measurements were carried out for warp and filling yarns. The number of yarns in 5 cm was considered for yarn density measurements.

Determination of yarn crimp

In woven fabric structure, especially at the interlacement points, warp and filling yarns follow curved paths and the yarns become curved. This is referred to as the “yarn crimp.” The length of the path that warp and filling yarns follow in the fabric structure is called the “uncrimped yarn length.” In this work, guide yarns were used in order to be able to measure the uncrimped yarn lengths. First, the guide yarn was inserted in the structure following the exact same yarn path as the yarn (i.e., warp or filling yarn) whose uncrimped length is to be measured. Then, the ends of this guide yarn were marked before it is withdrawn from the structure. The distance between the markings on the straightened guide yarn gives the uncrimped yarn length. The yarn crimp was then calculated using the following formula

Y a r n c r i m p (%) = \frac{U n c r i m p e d y a r n l e n g t h - c r i m p e d y a r n l e n g t h}{c r i m p e d y a r n l e n g t h} x 100

(1)

Determination of yarn angle

The warp angle (θ_w) between the warp yarn and filling yarn in the fabric length direction (x-axis) was determined as shown in Figure 3.

Composite testing

Composite tensile and three-point flexural tests were conducted in accordance with ASTM D3039²⁵ and ASTM D790²⁶ standards, respectively, using a Shimadzu AG-X 50 universal testing machine equipped with a 50 kN load cell. All tensile tests were carried out in warp (0°) direction. 3-point flexural tests were carried out flatwise such that the tensile load generated on the back side of the specimen is in the direction of the warp yarns. Specimen dimensions for the tensile tests were 250 x 25 mm (length x width). Gauge length was 150 mm. Crosshead speed was 2 mm/min. Specimen dimensions for the three-point flexural tests were 92 x 15 mm (length x width) with a span length of 72 mm. Loading rate was 2 mm/min for the flexural tests. Three specimens were tested for each sample group and the average results were reported with standard deviations.

Flexural strength (σ_fM) and modulus of elasticity (E_B) of the composite plates were calculated by means of the equations (2) and (3), respectively.

σ_{f M} = \frac{3 P L}{2 b d^{2}}

(2)

E_{B} = \frac{L^{3} m}{4 b d^{3}}

(3)

where p is the load at a given point on the load–deflection curve; L is the support span; b is the width of beam tested; d is the depth of the beam tested; and m is the slope of the tangent to the initial straight-line portion of the load-deflection curve.

Scanning electron microscopy analysis

Fracture surfaces of the composite samples were sputtered with gold–palladium and observed on a FEI Quanta FEG 450 scanning electron microscope. The SEM was operated at an accelerating voltage of 10 kV.

Results and discussion

Geometric characterization of woven fabrics

Geometric characteristics of the woven fabrics used for composite reinforcement are listed in Table 2 and depicted in Figure 4. Plain woven fabric showed lower crimp ratio and warp yarn angle when compared to those of 2/2 basket weave and 2/2 twill weave. The lower degree of crimp is the outcome of the low warp angle in the plain woven fabric which indicates that the warp yarn had to travel a shorter path when compared to the basket and twill weaves. It also implies that the warp yarns in plain woven fabrics are more aligned in the loading (0°) direction. Warp density was the same for plain, basket, and twill weave fabrics whereas unidirectional (UD) fabric had higher warp density when compared to other weave types used in this study. Filling yarn density was lowest for the plain weave which is followed by twill weave and basket weave.

Table 2.

Geometric characteristics of the woven fabrics used for reinforcement.

Fabric types	Warp yarn crimp ratio (C_w, %)	Filing yarn crimp ratio (C_f, %)	Warp yarn angle (θ_w°)	Filling yarn angle (θ_f°)	Density (ends/5 cm)
Fabric types	Warp yarn crimp ratio (C_w, %)	Filing yarn crimp ratio (C_f, %)	Warp yarn angle (θ_w°)	Filling yarn angle (θ_f°)	Warp	Filling
UD	—	—	0	0	30	—
PL	1	2	7	9	26	10
BS	3	4	9	10	26	17
TW	6	7	10	12	26	12

Tensile properties of the composites

Tensile and flexural test results of the composites along with the fiber weight fraction ratios are shown in Table 3. Tensile test results of the composites are also depicted in Figure 5. It is important to note that the plain, basket, and twill woven fabrics all yielded similar fiber weight fraction ratios of around 31–33 wt %, whereas unidirectional fabric composites yielded higher fiber weight fraction ratio of 39.5 wt % with the same weaving parameters. It is noteworthy that the UD fabric yielded higher fiber weight fraction ratio in the composite structure (Table 3), although the fabric areal weight was lower than the other woven fabric types produced (Table 1). This is due to the fact that UD fabric composites contain less resin-rich areas when compared to other weave types, resulting in a higher fiber ratio. In fabric types that contain warp-filling interlacement points such as plain, basket, and twill weave, these interlacement points act as resin reservoirs. Hence, plain woven fabric composite with the highest number of interlacements had the lowest fiber ratio.

Table 3.

Tensile and flexural test results of the hemp/epoxy woven composites.

Specimen code	Fiber weight fraction (%)	Composite thickness	Tensile strength (MPa)	Tensile modulus (GPa)	Tensile elongation at max. load (%)	Flexural strength (MPa)	Flexural modulus (GPa)	Flexural elongation at max. load (%)
UD	39.47	2.55	147.77 (4.1419)	8.0199 (0.2029)	3.9735 (0.2407)	189.62 (7.7279)	10.9064 (0.4364)	3.3930 (0.1901)
PL	30.78	4.42	84.27 (1.8178)	4.7258 (0.1154)	3.6897 (0.1224)	129.65 (1.0182)	6.6966 (0.3024)	3.1518 (0.0084)
BS	33.12	4.40	73.49 (2.8125)	4.5226 (0.0753)	3.7320 (0.1511)	122.05 (2.0774)	6.4363 (0.1004)	3.3251 (0.1384)
TW	32.07	4.45	66.56 (2.5082)	4.1752 (0.0872)	3.4583 (0.0690)	113.28 (0.0608)	6.7207 (0.2985)	2.9138 (0.2888)
Neat epoxy*	—	—	50.33	3.1715	4.5	81.35	3.1026	-

Standard deviations are given into parenthesis.

^aNeat epoxy data is obtained from the producer’s data sheet MPa: Megapascals, GPa: Gigapascals.

When the mechanical properties of the composites are considered, unidirectional (UD) hemp/epoxy composites showed the highest tensile strength and modulus as can be expected. Tensile strength and modulus of the UD composites were 75 and 70% higher, respectively, than those of the plain woven composite samples. On the other hand, tensile strength and modulus of the UD composite were 193 and 153% higher, respectively, than the unreinforced (neat) epoxy. This can be attributed to the fact that in UD fabrics, hemp yarns are perfectly aligned in the loading direction (0°) without interlacements which leads to higher fiber fraction and lower number of resin pools in the composite structure. The alignment of the yarns in the loading direction also ensures that the applied load can be taken up more effectively by the reinforcing fibers. It is a well-known fact that the interlacements in woven fabric structure disturb the alignment of the warp yarns in the loading direction (0°) and reduce the effective amount of fibers that are aligned in the loading direction. In addition, when the load is applied to the UD fabric composite, the yarns in the structure can get closer because there is not any filling yarn that could inhibit the close-packing of the warp yarns. However, it is important to keep in mind that these UD composites cannot be considered as fully unidirectional due to the yarn twist and binding yarns in the structure. Yarn twist is the major reason which limits the mechanical properties of discontinuous natural fiber composites. Plain woven fabric composites showed the second highest tensile strength and modulus after the UD composites followed by basket and twill weave. Twill woven fabric composites showed the lowest tensile strength and modulus. This was attributed to the fact that the plain woven fabric had the lowest warp angle and yarn crimp ratio (Table 2) and has a more balanced structure with homogenous distribution of the warp yarns. Basket weave, for example, creates resin-rich areas in the structure. When the load is applied, the resin-rich areas fail first resulting in stress-concentration points that act as the weakest link in the structure and pave the way for the final catastrophic failure. Ahmad et al.²⁷ reported similar results for flax/epoxy composites where 2/2 basket woven fabric composites show lower values of tensile strength and modulus when compared to the plain weave. In this study, twill weave showed the lowest tensile strength and modulus due to the fact that twill weave has the least balanced structure with its diagonal pattern. This type of structure is thought to generate shear loads under tensile loading that reduced the mechanical performance of the twill woven composites. Higher warp angle and crimp ratio (Table 2) of the twill fabric is also thought to be responsible for its inferior strength properties. Previous studies showed that the decrimping of yarns in twill fabric due the straightening results in transverse shearing of yarns.²⁸ Chairman et al.²⁹ reported that plain weave basalt/epoxy composites exhibit better mechanical properties compared with twill weave composites. They attributed this result to the greater stability and symmetry of the plain weave as well as the higher contact area with the polymer resin which leads to greater frictional force and resistance to slippage of yarns in the fabric. Venkateshwaran et al.³⁰ also obtained similar results to ours in their study where they compared the mechanical properties of banana/epoxy composites made using three different weave types such as plain, twill, and basket. Plain weave architecture had better tensile strength when compared to twill and basket weave. They attributed this result to balanced interlacement of the fibers in the plain fabric structure. Zhou et al.³¹ compared the tensile properties of plain and 2/2 twill carbon fabric/epoxy composites. Similar to our study, they reported that the crimp ratio is the critical factor that governs the mechanical properties of the composites. But contrary to our results, they found that the twill 2/2 carbon fabric has lower crimp ratio and higher mechanical properties compared with the plain woven composites. The difference may have resulted from the fact that in our study, twill fabric has higher warp angle and therefore a higher crimp ratio compared to the plain weave which resulted in lower mechanical properties. On the other hand, stiff and thick hemp yarns with a near-circular cross-section make loose floating over and under the weft yarns increasing the uncrimped yarn length. The fact that plain, basket, and twill weave types showed lower elongation values when compared to that of UD composites is an indicative of premature failure of these samples due to the stress-concentration points. Another reason for the higher elongation values of the UD composites is that the UD fabrics were used in composite production in loose form (without any tension). Therefore, there are undulations (waviness) in hemp yarns. When the load is applied, this waviness is removed and yarns are aligned in the loading direction. This also causes higher strain values for the UD composites.

Figure 6 shows the tensile stress versus strain curves of the tested composite samples. Curves clearly show three distinct stages such as initial loading, crimp/waviness removal, and final loading. In the first linear stage, the tensile load is taken up by the polymer resin and transferred to the fibers. Second stage is the crimp removal, where the crimp and waviness in the textile structure is removed by the applied load. In unidirectional (UD) and basket weave (BS), the crimp/waviness removal stage took longer when compared to plain (PL) and twill (TW) woven fabric composites. In the UD composites, the waviness removal stage took place as the yarns aligned in the loading direction becoming more compact and more closely arranged. After the removal of the yarn crimp, composite samples entered the final loading stage where the load is predominantly taken by the reinforcing fibers until the final failure.

Flexural properties of the composites

Flexural test results of the composites are shown in Table 3 and depicted in Figure 7. In flexure test, the front side of the specimen takes up compressive loads while the back side experiences a tensile load. Flexural strength and modulus of the UD composites were 46% and 63% higher, respectively, than those of the plain woven composite samples. Flexural strength and modulus of the UD composite were 133% and 251% higher, respectively, than the unreinforced (neat) epoxy. Flexural strength of the plain, basket, and twill composites followed the same trend as the tensile strength values, plain woven fabric composites showed the highest strength followed by the basket weave and twill weave. Similar to the tensile strength, decrimping of yarns in twill fabric due the straightening is thought to result in transverse shearing of yarns and reduced the flexural strength.²⁸ It is noteworthy that the difference between the flexural strength values of the composites was lower when compared to that in tensile strength values. This was attributed to the fact that tensile strength is more sensitive to imperfections and resin-rich areas in the composite structure and these make a greater difference in the tensile results when compared to the flexural properties. Composites followed a different trend in terms of flexural modulus. Twill weave composites showed similar modulus values with the plain weave while the basket weave showed the lowest flexural modulus. In this case, it is reasonable to think that the resin-rich areas created between the warp-weft interlacement points in the basket weave reduced the flexural modulus. Venkateshwaran et al.³⁰ obtained similar results in their study where they compared the flexural properties of banana/epoxy composites made using three different weave types such as plain, twill, and basket. Plain weave architecture had better flexural strength when compared to twill and basket weave. They attributed this result to balanced interlacement of the fibers in the plain fabric structure. Adekunle et al.³² also showed that the flexural and tensile strength and moduli of the plain woven flax fabric composites was superior when compared to the twill 2/2 and basket weave. Figure 8 shows the flexural stress versus strain curves of the tested composite samples. Composites behaved in a linear manner at the early stages of loading and then transformed into pseudoplastic region before reaching a maximum stress and then failed abruptly.

Fracture analysis

Figure 9 shows pictures of the post-tensile specimens. Unidirectional fabric composites showed crack propagation in the longitudinal (warp) direction unlike the other samples which is possibly due to earlier rupture of some of the yarns and the shear loads induced during the tensile loading. Low transverse properties of this specimen due to the lack of reinforcement in that direction further accelerated the crack propagation in the longitudinal direction. It can be seen that the PL showed a more regular crack propagation path in the transverse direction when compared to the other weave types indicating a more balanced fabric structure and even distribution of the tensile load. This is thought to be among the factors which led to higher mechanical properties of the plain woven composites when compared to the basket and twill weaves. Basket and twill woven fabric composites showed saw-teeth fracture pattern illustrating an irregular load distribution between the fiber and matrix phases. Resin-rich areas in basket and twill weaves are also clearly visible which creates stress-concentration points reducing the homogeneous load distribution throughout the structure.

Figures 10 and 11 show the SEM pictures of the fractured surfaces of the composite samples after tensile tests. Composite failure consisted different mechanisms such as total yarn rupture, yarn failure due to fiber pull-out from the yarn structure, brittle matrix cracking, and fiber pull-out from the matrix although the latter not played a major role in composite fracture. Ahmad et al. ²⁷ observed similar fracture behavior for woven flax/epoxy composites except the fact that the fiber pull-out from the matrix was more predominant. In this study, it can be seen that the fibers were successfully wetted out by the resin due to alkaline treatment. Composite failure took place predominantly as total yarn and fiber fracture, fiber pull-out from the yarns, and matrix cracking. Fiber pull-out from the matrix was limited which indicates a good fiber-matrix adhesion. Rough fiber surfaces also show that the fiber-matrix bonding is successful. Fiber tearing was accompanied by brittle matrix cracking which is a characteristic of the epoxy resin. Protruded fibers at the crack surfaces indicate that the fibers sustained the load after the matrix had failed.

Conclusions

Natural fiber composites attracted great attention due to their high mechanical properties and environmentally friendly nature. As the industrial usage of these materials becomes more commonplace, the need to characterize and improve their properties increases. In this work, we characterized epoxy composites reinforced with hemp woven fabrics of four different weave structures such as quasi-unidirectional, plain, basket 2/2, and twill 2/2 which are in common use in the composite industry. Fabric properties such as the yarn angle, yarn density, and crimp ratio were determined to evaluate their possible effect on composite properties. Tensile and three-point flexural tests were conducted in order to determine the effect of weave type on the mechanical properties of the resulting composites. It was found that quasi-unidirectional composites show the highest tensile strength, tensile modulus, flexural strength, and flexural modulus in the 0° (yarn) direction. Plain weave fabric composites showed the second highest tensile and flexural strength and moduli followed by basket 2/2 weave and twill 2/2 weave composites. Composites reinforced with twill 2/2 woven fabrics showed the lowest mechanical properties due to high warp yarn angle and resulting high yarn crimp, less balanced structure, and resulting shear forces involved during various loading conditions. Mechanical properties were found to be closely related with the fabric geometry. Tensile and flexural properties generally improved as the warp angle becomes smaller and yarn crimp becomes lower. Scanning electron microscopy analysis suggested a good fiber-matrix bonding without a major fiber pull-out mechanism.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by Yozgat Bozok University Scientific Research Projects Coordination Unit, Turkey [grant number 6608-AMYO/20-431].

ORCID iD

Nesrin Sahbaz Karaduman

References

Wambua

Ivens

Verpoest

. Natural fibres: can they replace glass in fibre reinforced plastics? Compos Sci Technol 2003; 63: 1259–1264

Joshi

S V.

Drzal

Mohanty

, et al.

Are natural fiber composites environmentally superior to glass fiber reinforced composites?

Compos Part A Appl Sci Manuf 2004; 35: 371–376.

Onal

Karaduman

. Mechanical characterization of carpet waste natural fiber-reinforced polymer composites. J Compos Mater 2009; 43: 1751–1768.

Mohanty

Misra

Hinrichsen

. Biofibres, biodegradable polymers and biocomposites: an overview. Macromol Mater Eng 2000; 276–277: 1–24.

Faruk

Bledzki

Fink

H-P

, et al. Progress report on natural fiber reinforced composites. Macromol Mater Eng 2014; 299: 9–26.

Summerscales

Dissanayake

NPJ

Virk

, et al. A review of bast fibres and their composites. Part 1 – fibres as reinforcements. Compos Part A Appl Sci Manuf 2010; 41: 1329–1335.

Summerscales

Dissanayake

Virk

, et al. A review of bast fibres and their composites. Part 2 – composites. Compos Part A Appl Sci Manuf 2010; 41: 1336–1344.

Faruk

Bledzki

Fink

H-PP

, et al. Biocomposites reinforced with natural fibers: 2000-2010. Prog Polym Sci 2012; 37: 1552–1596.

Bledzki

Gassan

. Composites reinforced with cellulose based fibres. Prog Polym Sci 1999; 24: 221–274.

10.

Mohanty

Misra

Drzal

. Sustainable bio-composites from renewable resources: opportunities and challenges in the green materials world. J Polym Environ 2002; 10: 19–26.

11.

Sair

Oushabi

Kammouni

, et al. Effect of surface modification on morphological, mechanical and thermal conductivity of hemp fiber: characterization of the interface of hemp –polyurethane composite. Case Stud Therm Eng 2017; 10: 550–559.

12.

Chimeni

Toupe

Dubois

, et al. Effect of hemp surface modification on the morphological and tensile properties of linear medium density polyethylene (LMDPE) composites. Compos Inter 2016; 23: 405–421.

13.

Chimeni

Toupe

Dubois

, et al. Effect of surface modification on the interface quality between hemp and linear medium-density polyethylene. J Appl Polym Sci 2016; 133: 43802.

14.

Karaduman

Gokcan

Onal

. Effect of enzymatic pretreatment on the mechanical properties of jute fiber-reinforced polyester composites. J Compos Mater 2012; 47: 1293–1302.

15.

Karaduman

Onal

. Dynamic mechanical and thermal properties of enzyme-treated jute/polyester composites. J Compos Mater 2012; 47: 2361–2370.

16.

Sayeed

MMA

Rawal

Onal

, et al. Mechanical properties of surface modified jute fiber/polypropylene nonwoven composites. Polym Compos 2014; 35: 1044–1050.

17.

Corbin

Soulat

Ferreira

, et al. Towards hemp fabrics for high-performance composites: influence of weave pattern and features. Compos Part B Eng 2020; 181: 107582.

18.

Misnon

Islam

Epaarachchi

, et al. Analyses of woven hemp fabric characteristics for composite reinforcement. Mater Des 2015; 66: 82–92.

19.

Sepe

Bollino

Boccarusso

, et al. Influence of chemical treatments on mechanical properties of hemp fiber reinforced composites. Compos Part B Eng 2018; 133: 210–217.

20.

Song

Lee

, et al. Viscoelastic and thermal behavior of woven hemp fiber reinforced poly(lactic acid) composites. Compos Part B Eng 2012; 43: 856–860.

21.

Baghaei

Skrifvars

Berglin

. Characterization of thermoplastic natural fibre composites made from woven hybrid yarn prepregs with different weave pattern. Compos Part A Appl Sci Manuf 2015; 76: 154–161.

22.

Abbas

Shahid

Nawab

, et al. Effect of glass microspheres and fabric weave structure on mechanical performance of hemp/green epoxy composites. Polym Compos 2020; 41: 4771–4787.

23.

Antony

Cherouat

Montay

. Effect of fibre content on the mechanical properties of hemp fibre woven fabrics/polypropylene composite laminates. Polym Compos; 29: S790–S802.

24.

Umair

Hussain

Abbas

, et al. Effect of weave architecture and glass microspheres percentage on the low velocity impact response of hemp/green epoxy composites. J Compos Mater 2021; 55: 2179–2195.

25.

ASTM D3039 . Standard test method for tensile properties of polymer matrix composite materials. West Conshohocken, PA: ASTM, 2008, p. 13.

26.

ASTM D790 . Standard test methods for flexural properties of unreinforced and reinforced plastics and electrical insulating materials. West Conshohocken, PA: ASTM, 2010, p. 11.

27.

Ahmad

Yuvaraj

Bajpai

. Influence of reinforcement architecture on static and dynamic mechanical properties of flax/epoxy composites for structural applications. Compos Struct 2021; 255: 112955.

28.

Erol

Powers

Keefe

. Effects of weave architecture and mesoscale material properties on the macroscale mechanical response of advanced woven fabrics. Compos Part A Appl Sci Manuf 2017; 101: 554–566.

29.

Anand Chairman

Jayasathyakawin

Kumaresh Babu

, et al. Mechanical properties of basalt fabric plain and twill weave reinforced epoxy composites. Mater Today Proc 2021; 46: 9480–9483.

30.

Venkateshwaran

ElayaPerumal

Arwin Raj

. Mechanical and dynamic mechanical analysis of woven banana/epoxy composite. J Polym Environ 2012; 20: 565–572.

31.

Zhou

Sun

Meng

, et al. Experimental investigation on the effects of fabric architectures on mechanical and damage behaviors of carbon/epoxy woven composites. Compos Struct 2021; 257: 113366.

32.

Adekunle

Cho

S-W

Patzelt

, et al. Impact and flexural properties of flax fabrics and lyocell fiber-reinforced bio-based thermoset. J Reinf Plast Compos 2011; 30: 685–697.