INVESTIGATION OF MECHANICAL PROPERTIES OF POLYESTER FIBER, ACRYLIC FIBER AND POLYAMIDE FIBER REINFORCED COMPOSITES

Abstract

Abstract

Composite materials are materials obtained by combining materials with two or more different properties that are used by people for thousands of years to solve problems without being aware of them. Polymer based composite materials have recently been developed to improve the properties of these materials, as they have many superior properties as well as insufficient strength. Depending on technological developments, different types of composites have been produced using different types of matrix and reinforcement.

The purpose  of this study, a new composite material using by polyester fibers, acrylic fibers and polyamide fibers  combining with araldite resin is  produced  and  examined its  mechanical properties. The new  composites were produced by the method of  hand lay-up . The mechanical properties such as tensile strength, impact strength, flexural strength and interlaminar shear strength (ILSS) were performed. Based on the applications of the mechanical tests of the composite samples, increasing of the fiber type and rate were seen an increase or decrease in mechanical properties.

Keywords: Polyester Fiber, Acrylic Fiber, Polyamide Fiber, Araldite Resin, Composite Materials

PACS: 72.80.Tm

1. INTRODUCTION

The polymers play very important role in our daily life. They can be combined with different materials to achieve special properties according to end use applications. Polymer based composites are being used more and more intensively in space, aviation, medicine, automotive, textile, construction, building and other developing technologies. Reinforcing fibers, which are generally used in polymer composites, provide strength and other desirable properties to the composite material [1,2]. In parallel with these developments, working on fibers with better mechanical properties and higher heat-resistant, non-cracking, high impact strength and hard polymer matrices continue in the world [3-7].

Today, most of the synthetic polymer fibers in use span applications such as clothing, carpets, ropes and reinforcement materials. Some of these fibers include polyamides such as nylon, polyesters (as PET, PBT), PP, PE, vinyl polymers (as PVA, PVC), PU and acrylic fibers (e.g. PAN), [8,9].

Polyamide refers to family of polymers called linear polyamides made from petroleum. The generic name polyamide fibre has the same meaning as nylon fibre, but nylon fibre is used principally in countries [10]. Polyamides generally are tough, strong, durable fibers useful in a wide range of textile applications. The distinguishing characteristics are high elasticity, tear and abrasion free, low humidity absorption capability, fast drying, no loss of solidity in a wet condition, crease free, and rot and seawater proof. Application areas range from underwear to outdoor sports clothing [11], from automotive to aerospace [12].

PET is the world's most widely used fiber in a variety of forms. PET is widely used in both fiber and filament forms as a strong, dimensionally stable fiber. Large quantities of PET fibers are also used for both woven and nonwoven fabrics used for industrial and technical applications. Polyester fibers have many excellent properties such as high strength, good stretchability, durability and easy care characteristics [13].

Acrylic fiber is named as acrylonitrile containing at least 85% of its chemical structure according to ISO (International Standards Organization) definition. Since acrylonitrile, which is predominantly homopolymerized with 100% acrylonitrile polymerization, is hard, brittle and difficult to paint, it has been converted into copolymers by the addition of a second monomer and is particularly suitably used in textiles. Acrylic fibers have a wide range of uses such as knitting, hand knitting, carpet, blankets, velvet, socks [14]. Also acrylic fibre has been extensively used in a number of industrial applications for example as a cursor for carbon fiber, as substitute for asbestos in-fibre reinforced cement, and in hot gas and wet filtration [15].

 

2. EXPERIMENTAL PROCEDURE

2.1. Experimental Preparation and Mechanical Analysis

RENLAM LY113 araldite resin (Huntsman) as the resin, Ren HY97 (Huntsman) as reaction initiator and Benzyldimethylamine (BDMA-Eastman) as accelerator were used in the composite matrix formulation. Acrylic fiber (Acrylic Tow, Type Extra / Gloss Dtex 2,2 - Lotno / Apre E-4316 / RA-01 Ktex 97) supplied from Aksa Acrylic Industry Company and polyester fiber and aramid fiber supplied from private sector were used as reinforcing materials.

Composite materials using by polyester fibers, acrylic fibers and polyamide fibers combining with araldite resin is produced and examined its mechanical properties. Composite materials were produced by the method of hand lay-up. The mechanical properties such as tensile strength, impact strength, 3-point bending strength and interlaminar shear strength (ILSS) were investigated.

In this study, two-piece semi-open mold made of stainless steel was produced to prepare standard tensile and impact samples (Figure 1). Surfaces of the mold that are in contact with the composite are grind to prevent adhesion.

 

Figure 1. Mold in which composite samples are produced.

 

2.1.1. Tensile analysis

The tensile tests of composite specimens were subjected to uniaxial tension with a constant tensile speed of 5 mm/min and corresponding stress-strain values were recorded for maximum tensile strength determination with respect to fiber orientation. Tensile analysis was applied on a Zwick Z010 universal tensile device.

 

2.1.2. Flexural analysis

Flexural strength of the composite laminates were determined via 3-point bending tests done according to ASTM D790-02 standart. Flexural analysis was applied with test speed of 5 mm/min on a Zwick Z010 universal tensile device. Span to depth ratio was hold as 16:1.

 

2.1.3. Interlaminar shear strength (ILSS) analysis

The interlaminar shear strength test samples (ILSS) according to ASTM D2344 standard was prepared and all of the tests made on a Zwick Z010 universal tensile device and applied with a test speed of 5 mm/min.

 

2.1.4. Impact analysis

The impact strength of the unnotched specimens was tested using a 5.4 J izod impact hammer on the Zwick B5113.30 Izod Impact Device according to the ASTM D 256 standard.

 

2.2. Calculation of mold volume and resin formulation

Volume of the mold: V = a x b x c= 11,5 x 19,5 x 0,4 = 89,7 cm³

                                          Resin formülation: 100 gr araldite resin (LY113)

 32 gr hardener (HY97)

            15 drops BDMA (accelerator)

 

2.3. Density of Fibers

Table 1. Density of Fibers

	Polyester fiber	Polyamide fiber	Acrylic fiber
Density (gr/cm3)	1,15	1,076	1,23

 

2.4. Calculation of the weights of the fibers in the mold

2.4.1. Mass account for Acrylic Fibers

%40 Acrylic Fiber:                       %50 Acrylic Fiber:                 %60 Acrylic Fiber:

m = d . v . 0,4                                  m = d . v . 0,5                           m = d . v . 0,6

m = 1,23 . 89,7 . 0,4                        m = 1,23 . 89,7 . 0,5                 m = 1,23 . 89,7 . 0,6

m = 44,132 gr.                                 m = 55,165 gr.                          m = 66.199 gr              

 

2.4.2. Mass account for Polyester Fiber

 

%40 Polyester Fiber:                 %50 Polyester Fiber:             %60 Polyester Fiber:

m = d . v . 0,4                               m = d . v . 0,5                            m = d . v . 0,6

m = 1,15 . 89,7 . 0,4                     m = 1,15 . 89,7 . 0,5                  m = 1,15 . 89,7 . 0,6

m = 41,262 gr.                              m = 51,577 gr.                           m = 61,893 gr.

 

2.4.3. Mass account for Polyamide Fiber

 

%40 Polyamide Fiber:           %50 Polyamide Fiber:           %60 Polyamide Fiber:

m = d . v . 0,4                                  m = d . v . 0,5                                   m = d . v . 0,6

m = 1,076 . 89,7 . 0,4                      m = 1,076. 89,7 . 0,5                       m = 1,076. 89,7 . 0,6                  

m = 38,606 gr.                                m = 48,258 gr.                                 m = 57,910 gr.

 

Table 2. Weights of Fibers In The Mold

Materials	Fiber Weights of Fibers In The Mold (gr)
	% 40	% 50	% 60
Polyester fiber	41,262	51,577	61,893
Polyamide fiber	38,606	48,258	57,910
Acrylic fiber	44,132	55,165	66,199

 

2.5. Preparation of the composite samples

The prepared composite matrix resin consists of 100 gr of araldite resin (Renlam LY113), 32% (32 gr) of Ren HY97 and 15 drops of BDMA. Composite samples were prepared by hand lay-up method. After addition of one coat of resin into the open mold, the fibers cut according to the mold size to provide the weights indicated in Table 2 were placed as shown in Figure 1. The resin was applied to the intermediate layer and the top layer with the aid of a brush. The same procedures were applied to all fibers to produce composite platters containing 40%, 50% and 60% of individually polyester, acrylic and aramid fibers. Due to the difficulty of wetting the fibers of resin, it was not possible to prepare samples with more than 60% by weight of fibers.

The upper mold was closed and compressed with the help of tacks to allow the resin to wet the fibers well and to remove air bubbles in the structure. After standing for 24 hours at room temperature, the composite layers removed from the mold were first of all edge trimmed, then the layers were cut according to the standards specified in the relevant standards and the burrs formed at the edges were sanded.

3. RESULTS and DISCUSSION

In this study, the mechanical properties of the composite materials were investigated in consideration of the weight and fiber volume fractions at different ratios. For each result given in the tables, five samples were produced for each test and averaged.

Table 3. and Figure 2. demonsrates tensile strength of composites molded at different rate. The fiber ratio started at 40% and ended at 60%. In composite samples reinforced polyamide fiber and polyester fiber, the tensile strength increased with increasing fiber amount. The maximum tensile strength value was reached in the composite sample of 50% polyamide fiber reinforced. After this, the tensile strength was reduced. For polyester fiber reinforced composite samples, the maximum tensile strength value was observed in the sample with 60% polyester fiber. In the acrylic fiber reinforced composite samples, the tensile strength value decreased as the fiber ratio increased. The highest tensile strength value was in the composite sample with 40% acrylic fiber.

The tensile test results show that the highest tensile strength in all composite samples was found in composite materials containing 60% polyester fibers.  

Table 3. Tensile test results of composite materials

Materials	40% Fmax (N)	50% Fmax (N)	60% Fmax (N)
Polyamide fiber	140,82	144,4	111,3
Polyester fiber	95,27	172,63	177
Acrylic fiber	51,3	45,65	40,78

 

Figure 2. Tensile strength graphics of composite materials

 

 

 

Table 4. and Figure 3. show the flexural strength values obtained by the 3-point bending test of all the composite samples. Composite samples with polyamide and acrylic fiber reinforcement showed a decrease in flexural strength as the amount of fiber increased. Composite specimens with 40% polyamide fiber reinforcement and 40% acrylic fiber reinforcement showed maximum flexural strength. At the 60% reinforcement ratio, the lowest flexural strength value was observed in both types of fibers. The maximum flexural strength value of polyester fiber reinforced composite specimens was 50%. 60% polyester fiber reinforcement showed lower flexural strength but higher than 40%.

Composite material reinforced 50% polyester fiber in all composite specimens has the highest flexural strength value.

 

Table 4. Three point bending test results of composite materials

 

Materials	40% σfm(Mpa)	50% σfm(Mpa)	60% σfm(Mpa)
Polyamide fiber	86,69	85,49	82,94
Polyester fiber	92,00	140,01	131,13
Acrylic fiber	113,02	97,09	89,76

 

Figure 3. Flexural strength graphics of composite materials

 

Table 5. and Figure 4. show the interlaminar shear strength (ILSS) of the composite specimens at the different rates. It has been observed that for every 3 types of fibers used in this study, the ILSS strength is reduced by increasing the amount of fiber. Polyamide, polyester and acrylic fiber reinforced composite samples with 40% ratio showed the highest ILSS strength, while 60% fiber reinforced composite samples had the lowest ILSS strength value.

The composite specimen reinforced 40% polyester fiber in all composite materials showed the highest interlaminar shear strength value.

 

Table 5. ILSS test results of composite materials

Materials	40%     σfm(Mpa)	50% σfm(Mpa)	60% σfm(Mpa)
Polyamide fiber	199,51	125,03	110,66
Polyester fiber	205,24	148,87	111,29
Acrylic fiber	194,60	138,44	110,98

Figure 4. Inter laminar shear strength (ILSS) graphics of composite materials

 

Table 6. and Figure 5. demonsrate impact strength obtained by the izod impact test of all the composite samples. It has been observed that in all 3 types of fibers used in this study, the increase in the amount of fiber also increases the impact strength. Maximum impact strength was observed in composite specimens reinforced 60% polyamide, polyester and acrylic fiber.

In all composite specimens, the material with the highest impact resistance is composite material with 60% polyamide fiber reinforcement.

Table 6. Impact test results of composite materials

Materials	40% (Kj/m²)	50% (Kj/m²)	60% (Kj/m²)
Polyamide fiber	280,33	302,50	320,75
Polyester fiber	84,75	145,50	174,25
Acrylic fiber	44,50	108	158,75

Figure 5. Izod impact strength graphics of composite materials

 

4. CONCLUSION

Compared to the mechanical properties of composite specimens, composite specimens reinforced polyester fiber have the maximum tensile strength, flexural strength and interlaminar shear strength. The polyamide fiber reinforced composite specimen in all samples has the highest impact strength.

In applications where tensile strength, flexural strength and interlaminar shear strength are mentioned, polyester fiber reinforced composite material can be successfully used. It is clear that polyamide fiber reinforced composites will be successful in many composite applications where tensile, flexural and ILSS strengths are not important at first but impact strength is important.

Composite materials produced with acrylic fiber reinforcement at low ratios may also be preferred where tensile, flexural and interlaminar shear strength is a concern.

 

Keywords

• Polyester Fiber,Acrylic Fiber,Polyamide Fiber,Araldite Resin,Composite Materials

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