# Flexural Strength Analysis of Starch Based Biodegradable Composite Using Areca Frond Fibre Reinforcement

Authors: Srinivas Shenoy Heckadka; Manjeshwar Vijaya Kini; Raghuvir Pai Ballambat; Satish Shenoy Beloor; Sathish Rao Udupi; Ullal Achutha Kini
Journal: International Journal of Manufacturing Engineering
 (2014)

---

## Abstract

Natural fibres and biodegradable matrices are being considered nowadays as substitutes to synthetic fibre reinforced polymer composites mainly in sectors where high load carrying capacity and high strength are not prerequisites. Present study utilizes biodegradable matrix composite prepared by varying the weight of the base material (95–170 g), binder (5–10 g), and plasticizer (5–20 g) with treated areca frond fibres as reinforcement. Contents are transferred to a pneumatic press, compacted, and subjected to curing.  Taguchi method with L8 orthogonal array was used to reduce the number of experiments. Specimens for the flexural tests are cut out from the prepared laminates and tests are performed using UTM. Maximum flexural strength of 16.97 MPa was obtained with a combination of base (170 g), binder (10 g), and plasticizer (5 g). Analysis of the results indicated that plasticizer has the maximum effect on flexural strength of the biodegradable composites.


---

## Body

## 1. Introduction

### 1.1. Composites

Composites are novel engineering materials made from two or more constituents that remain separate and distinct on a macroscopic level while forming a single component. There are two categories of constituent materials: matrix and reinforcement. At least one portion of each type is required. The matrix material surrounds and supports the reinforcement by maintaining their relative positions. The reinforcement imparts special physical (mechanical and electrical) properties to enhance the matrix properties [1]. A synergism produces material properties unavailable from naturally occurring materials. Composites provide the designer, fabricator, equipment manufacturer, and consumer with sufficient flexibility to meet the demands presented by different environments and special requirements. Thus composites, due to their heterogeneous composition, provide unique flexibility in design along with other attributes like superior directional properties, high specific strength, and stiffness properties. Manufacturing of composites with complex shapes especially moulding with polymer composites, reparability, corrosion resistance, durability, adaptability, and cost effectiveness has attracted their use in several engineering and other applications [2].


### 1.2. Biodegradable Composites

Environmental concerns and stricter government regulations on recycling materials pressed scientists to develop new materials mainly from renewable resources. Using natural fibres in biodegradable matrices can give numerous advantages with regard to fibres traditionally used in composites. The attractive features of these fibres are their abundant availability, low cost, light weight, and high specific modulus in contrast to the synthetic fibres. Biodegradable composites are developed with a perspective of sustainability. The concept is to maximize the performance of the blend and deliver the optimal functional requirements. The hydrophilic nature of the natural polymers together with reinforcing strength of the natural fibres results in environment friendly composite materials. Biodegradable composite are formulated by using a suitable matrix (biodegradable resin) and a reinforcement of natural fibres. Natural fibres such as hemp, sisal, kenaf, bamboo, bagasse, areca, and jute along with biodegradable polymers such as polylactic acid (PLA) [3, 4] and polybutylene succinate (PBS) are extensively used as green composites [5].Normally, natural fibre polymer composites are fabricated by using traditional manufacturing techniques which are designed for conventional fibre reinforced polymer composites and thermoplastics. These techniques include resin transfer moulding, vacuum infusion, compression moulding, direct extrusion, compounding, and injection moulding [6]. However techniques such as compression moulding and hand layup methods have been successfully used for producing biodegradable composites with controllable quality. Venkata Reddy et al. fabricated alkali treated kapok/sisal reinforced polyester composites by hand layup technique [7]. Srinivasababu et al. carried out a study on okra, sisal, and banana fibre reinforced polyester composites using hand layup technique. The variations in mechanical properties and thermal characteristics of these composites are evaluated [8]. Anuar and Zuraida evaluated the improvement in mechanical properties of kenaf bast fibre reinforced thermoplastic elastomer composite using compression moulding technique [9].


### 1.3. Taguchi Concept

Taguchi method is one of the effective techniques to reduce number of experiments while retaining quality of data collection. The first step in designing the experiments is the proper selection of factors and levels. In the present study, three main factors base material (A), binder (B), and plasticizer (C) in two levels (Level 1 and Level 2) are considered.Thian et al. have investigated the sintered properties such as sintering temperature, heating rate, holding time, and cooling rate of Ti-6Al-4V/HA tensile bars using Taguchi method using L9 3-level orthogonal array [1]. Majdzadeh-Ardakani and Nazari fabricated thermoplastic nanocomposites using melt extrusion technique. The effects of clay cat-ion, water, polyvinyl alcohol, clay contents on clay intercalation, and mechanical properties are also investigated according to the Taguchi experimental design method [10]. Palanikumar studied the influence of drilling parameters such as spindle speed and feed rate on the thrust force, surface roughness, and delamination characteristics of the composites using Taguchi’s L16, 4-level orthogonal array [11]. Satapathy et al. have investigated the processing and characterization of epoxy matrix composites reinforced with short flakes obtained from the scales of a typical fresh water fish and also reported erosion wear characteristics. Analysis of variance (ANOVA) is performed and signal to noise (S/N) ratios are determined. Experimental results revealed that the rate of erosion by impact of solid erodent is greatly influenced by various control factors [12]. Pal and Gauri studied the effectiveness of five performance metrics that are used for optimization of multiple response problems. Multiple regression-based weighted signal-to-noise ratio as a performance metric is the most effective in finding an optimal solution for multiple response problems [13].


## 1.1. Composites

Composites are novel engineering materials made from two or more constituents that remain separate and distinct on a macroscopic level while forming a single component. There are two categories of constituent materials: matrix and reinforcement. At least one portion of each type is required. The matrix material surrounds and supports the reinforcement by maintaining their relative positions. The reinforcement imparts special physical (mechanical and electrical) properties to enhance the matrix properties [1]. A synergism produces material properties unavailable from naturally occurring materials. Composites provide the designer, fabricator, equipment manufacturer, and consumer with sufficient flexibility to meet the demands presented by different environments and special requirements. Thus composites, due to their heterogeneous composition, provide unique flexibility in design along with other attributes like superior directional properties, high specific strength, and stiffness properties. Manufacturing of composites with complex shapes especially moulding with polymer composites, reparability, corrosion resistance, durability, adaptability, and cost effectiveness has attracted their use in several engineering and other applications [2].


## 1.2. Biodegradable Composites

Environmental concerns and stricter government regulations on recycling materials pressed scientists to develop new materials mainly from renewable resources. Using natural fibres in biodegradable matrices can give numerous advantages with regard to fibres traditionally used in composites. The attractive features of these fibres are their abundant availability, low cost, light weight, and high specific modulus in contrast to the synthetic fibres. Biodegradable composites are developed with a perspective of sustainability. The concept is to maximize the performance of the blend and deliver the optimal functional requirements. The hydrophilic nature of the natural polymers together with reinforcing strength of the natural fibres results in environment friendly composite materials. Biodegradable composite are formulated by using a suitable matrix (biodegradable resin) and a reinforcement of natural fibres. Natural fibres such as hemp, sisal, kenaf, bamboo, bagasse, areca, and jute along with biodegradable polymers such as polylactic acid (PLA) [3, 4] and polybutylene succinate (PBS) are extensively used as green composites [5].Normally, natural fibre polymer composites are fabricated by using traditional manufacturing techniques which are designed for conventional fibre reinforced polymer composites and thermoplastics. These techniques include resin transfer moulding, vacuum infusion, compression moulding, direct extrusion, compounding, and injection moulding [6]. However techniques such as compression moulding and hand layup methods have been successfully used for producing biodegradable composites with controllable quality. Venkata Reddy et al. fabricated alkali treated kapok/sisal reinforced polyester composites by hand layup technique [7]. Srinivasababu et al. carried out a study on okra, sisal, and banana fibre reinforced polyester composites using hand layup technique. The variations in mechanical properties and thermal characteristics of these composites are evaluated [8]. Anuar and Zuraida evaluated the improvement in mechanical properties of kenaf bast fibre reinforced thermoplastic elastomer composite using compression moulding technique [9].


## 1.3. Taguchi Concept

Taguchi method is one of the effective techniques to reduce number of experiments while retaining quality of data collection. The first step in designing the experiments is the proper selection of factors and levels. In the present study, three main factors base material (A), binder (B), and plasticizer (C) in two levels (Level 1 and Level 2) are considered.Thian et al. have investigated the sintered properties such as sintering temperature, heating rate, holding time, and cooling rate of Ti-6Al-4V/HA tensile bars using Taguchi method using L9 3-level orthogonal array [1]. Majdzadeh-Ardakani and Nazari fabricated thermoplastic nanocomposites using melt extrusion technique. The effects of clay cat-ion, water, polyvinyl alcohol, clay contents on clay intercalation, and mechanical properties are also investigated according to the Taguchi experimental design method [10]. Palanikumar studied the influence of drilling parameters such as spindle speed and feed rate on the thrust force, surface roughness, and delamination characteristics of the composites using Taguchi’s L16, 4-level orthogonal array [11]. Satapathy et al. have investigated the processing and characterization of epoxy matrix composites reinforced with short flakes obtained from the scales of a typical fresh water fish and also reported erosion wear characteristics. Analysis of variance (ANOVA) is performed and signal to noise (S/N) ratios are determined. Experimental results revealed that the rate of erosion by impact of solid erodent is greatly influenced by various control factors [12]. Pal and Gauri studied the effectiveness of five performance metrics that are used for optimization of multiple response problems. Multiple regression-based weighted signal-to-noise ratio as a performance metric is the most effective in finding an optimal solution for multiple response problems [13].


## 2. Experimental Details

### 2.1. Fibre Extraction and Treatment

Areca fronds are collected from locally available areca plantations. Fronds thus obtained are soaked in water for 4 days. The soaking process loosens the fibres and can be extracted out easily [14]. The Areca frond fibres are separated from the fronds using a wire brush. Finally, the fibers are washed again with fresh water and dried at room temperature. The dried fibres are “untreated fibres.” The extracted areca frond fibres are treated with 1 N solution of Na2CO3 where the total volume of solution was 10 times the weight of the fibres. The fibers are kept in this alkaline solution for 12 h at room temperature. Finally fibres are dried at room temperature for 48 h to get the “alkali treated fibres” [15]. Figure 1 shows the extracted and treated areca fibres. Chemical composition of areca frond fibres is Hemi cellulose (35–64.8%), Lignin (13–24.8%), and ash (4–4.4%) [16].Areca frond fibre extraction and treatment: (a) extracted fibres; (b) treated fibres.
(a)
(b)


### 2.2. Matrix Preparation

Figure2 shows the basic ingredients of the biodegradable matrix.Figure 2
Constituents of biodegradable matrix.The preparation of biodegradable matrix starts by weighing the constituents of the Base material (corn starch powder, water, and vinegar). The weighed ingredients are then transferred into a mixing vessel and evenly mixed by using a magnetic stirrer. Binders (methyl cellulose and resorcinol) and plasticizer (glycerol) are added to the mix and stirred for about 15 minutes. Further the mixture is transferred to a steel vessel and heated at 140°C until it turns into a semisolid paste [14]. As the matrix mixture turns into a semisolid paste the fibres are added to the mix and the contents are transferred to a mould (300 mm × 300 mm) and spread evenly to obtain a homogenous distribution using hand layup technique. Figure 3 shows the preparation of biodegradable matrix composites. The mix is compacted to form sheets using pneumatic press. The inner walls of the mould are coated with a thin layer of wax as a release agent. Further composites are cured in a hot chamber (steam heating) at 85°C for 24 h.Preparation of biodegradable matrix composites: (a) mixing and heating of matrix constituents; (b) compaction.
(a)
(b)


### 2.3. Designing the Experiment

In this study, main factors considered are base material (A), binder (B), and plasticizer (C) in two levels (Table1). The factors and their levels have been selected based on past literature, practical aspects, and results of screening tests. For Taguchi method with three factors and two levels for each factor, a standard L8 orthogonal array is employed as shown in Table 2. The uncoded units of Taguchi L8 orthogonal array are provided in Tables 3 and 4. Flexural strength is used for response calculations.Table 1
Selected factors and their respective levels (coded units).
Factors
Level 1
Level 2
Base material (A)
−1
+1
Binder (B)
−1
+1
Plasticizer (C)
−1
+1Table 2
TaguchiL
8 orthogonal array of designed experiments (coded units).
Experiment number
Factors
Base material,   A
Binder,  B
Plasticizer,  C
1
−1
−1
−1
2
−1
−1
+1
3
−1
+1
−1
4
−1
+1
+1
5
+1
−1
−1
6
+1
−1
+1
7
+1
+1
−1
8
+1
+1
+1Table 3
Selected factors and their respective levels (uncoded units).
Factors
Level 1
Level 2
Base material, A (g)
95
170
Binder, B (g)
5
10
Plasticizer, C (g)
5
20Table 4
TaguchiL
8 orthogonal array of designed experiments (uncoded units).
Experiment number
Combination of  factors and levels
Factors
Base material,  A (g)
Binder,  B (g)
Plasticizer,  C (g)
1
A1B1C1
95
5
5
2
A1B1C2
95
5
20
3
A1B2C1
95
10
5
4
A1B2C2
95
10
20
5
A2B1C1
170
5
5
6
A2B1C2
170
5
20
7
A2B2C1
170
10
5
8
A2B2C2
170
10
20


### 2.4. Signal-to-Noise (S/N) Ratio

The Taguchi method is commonly used to verify the robustness of products. The method helps to identify control factors that reduce variability by minimizing the effects of uncontrollable factors. Taguchi method often uses a 2-step optimization process. In step 1 use theS/N ratio to identify those control factors that reduce variability. In step 2, identify control factors that bring the mean to target and have little or no effect on theS/N ratio. The signal-to-noise (S/N) ratio measures how the response varies relative to the nominal or target value under different noise conditions. Table 5 shows theS/N ratios for different characteristics. For the present study, “larger is better aspect” is considered.Table 5
S/N ratios for different characteristics.
S
/
N ratio
Description
Equation
Larger is better
Maximize the response
S
/
N
i
=
-
10
log
⁡
(
∑
(
1
/
Y
u
2
)
/
N
i
)
Smaller is better
Minimize the response
S
/
N
i
=
-
10
log
⁡
(
∑
(
Y
u
2
)
/
N
i
)
Note:i = experiment number;  u = trial number;   N
i = number of trials for experiment i.


### 2.5. Flexural Testing

Composite specimens are tested for flexural strength according to ASTM D 790 [17, 18]. Experiments are performed using Universal Testing Machine and Instron (Model 3366). Test specimens with dimensions 64 × 12 × 5 mm and cross head speed of 2 mm/min are used. Figure 4 shows the UTM test rig.Figure 4
Flexural specimen testing.


## 2.1. Fibre Extraction and Treatment

Areca fronds are collected from locally available areca plantations. Fronds thus obtained are soaked in water for 4 days. The soaking process loosens the fibres and can be extracted out easily [14]. The Areca frond fibres are separated from the fronds using a wire brush. Finally, the fibers are washed again with fresh water and dried at room temperature. The dried fibres are “untreated fibres.” The extracted areca frond fibres are treated with 1 N solution of Na2CO3 where the total volume of solution was 10 times the weight of the fibres. The fibers are kept in this alkaline solution for 12 h at room temperature. Finally fibres are dried at room temperature for 48 h to get the “alkali treated fibres” [15]. Figure 1 shows the extracted and treated areca fibres. Chemical composition of areca frond fibres is Hemi cellulose (35–64.8%), Lignin (13–24.8%), and ash (4–4.4%) [16].Areca frond fibre extraction and treatment: (a) extracted fibres; (b) treated fibres.
(a)
(b)


## 2.2. Matrix Preparation

Figure2 shows the basic ingredients of the biodegradable matrix.Figure 2
Constituents of biodegradable matrix.The preparation of biodegradable matrix starts by weighing the constituents of the Base material (corn starch powder, water, and vinegar). The weighed ingredients are then transferred into a mixing vessel and evenly mixed by using a magnetic stirrer. Binders (methyl cellulose and resorcinol) and plasticizer (glycerol) are added to the mix and stirred for about 15 minutes. Further the mixture is transferred to a steel vessel and heated at 140°C until it turns into a semisolid paste [14]. As the matrix mixture turns into a semisolid paste the fibres are added to the mix and the contents are transferred to a mould (300 mm × 300 mm) and spread evenly to obtain a homogenous distribution using hand layup technique. Figure 3 shows the preparation of biodegradable matrix composites. The mix is compacted to form sheets using pneumatic press. The inner walls of the mould are coated with a thin layer of wax as a release agent. Further composites are cured in a hot chamber (steam heating) at 85°C for 24 h.Preparation of biodegradable matrix composites: (a) mixing and heating of matrix constituents; (b) compaction.
(a)
(b)


## 2.3. Designing the Experiment

In this study, main factors considered are base material (A), binder (B), and plasticizer (C) in two levels (Table1). The factors and their levels have been selected based on past literature, practical aspects, and results of screening tests. For Taguchi method with three factors and two levels for each factor, a standard L8 orthogonal array is employed as shown in Table 2. The uncoded units of Taguchi L8 orthogonal array are provided in Tables 3 and 4. Flexural strength is used for response calculations.Table 1
Selected factors and their respective levels (coded units).
Factors
Level 1
Level 2
Base material (A)
−1
+1
Binder (B)
−1
+1
Plasticizer (C)
−1
+1Table 2
TaguchiL
8 orthogonal array of designed experiments (coded units).
Experiment number
Factors
Base material,   A
Binder,  B
Plasticizer,  C
1
−1
−1
−1
2
−1
−1
+1
3
−1
+1
−1
4
−1
+1
+1
5
+1
−1
−1
6
+1
−1
+1
7
+1
+1
−1
8
+1
+1
+1Table 3
Selected factors and their respective levels (uncoded units).
Factors
Level 1
Level 2
Base material, A (g)
95
170
Binder, B (g)
5
10
Plasticizer, C (g)
5
20Table 4
TaguchiL
8 orthogonal array of designed experiments (uncoded units).
Experiment number
Combination of  factors and levels
Factors
Base material,  A (g)
Binder,  B (g)
Plasticizer,  C (g)
1
A1B1C1
95
5
5
2
A1B1C2
95
5
20
3
A1B2C1
95
10
5
4
A1B2C2
95
10
20
5
A2B1C1
170
5
5
6
A2B1C2
170
5
20
7
A2B2C1
170
10
5
8
A2B2C2
170
10
20


## 2.4. Signal-to-Noise (S/N) Ratio

The Taguchi method is commonly used to verify the robustness of products. The method helps to identify control factors that reduce variability by minimizing the effects of uncontrollable factors. Taguchi method often uses a 2-step optimization process. In step 1 use theS/N ratio to identify those control factors that reduce variability. In step 2, identify control factors that bring the mean to target and have little or no effect on theS/N ratio. The signal-to-noise (S/N) ratio measures how the response varies relative to the nominal or target value under different noise conditions. Table 5 shows theS/N ratios for different characteristics. For the present study, “larger is better aspect” is considered.Table 5
S/N ratios for different characteristics.
S
/
N ratio
Description
Equation
Larger is better
Maximize the response
S
/
N
i
=
-
10
log
⁡
(
∑
(
1
/
Y
u
2
)
/
N
i
)
Smaller is better
Minimize the response
S
/
N
i
=
-
10
log
⁡
(
∑
(
Y
u
2
)
/
N
i
)
Note:i = experiment number;  u = trial number;   N
i = number of trials for experiment i.


## 2.5. Flexural Testing

Composite specimens are tested for flexural strength according to ASTM D 790 [17, 18]. Experiments are performed using Universal Testing Machine and Instron (Model 3366). Test specimens with dimensions 64 × 12 × 5 mm and cross head speed of 2 mm/min are used. Figure 4 shows the UTM test rig.Figure 4
Flexural specimen testing.


## 3. Results and Discussion

Results of the flexural strength tests performed on the fabricated biodegradable matrix composite are given in Table6.Table 6
Flexural strength results.
Experiment number
Combination of factors and levels
Factors
Response
Base  A (Wt. grams)
Binder  B (Wt. grams)
Plasticizer  C (Wt. grams)
average maximum flexural strength   (MPa)
1
A1B1C1
95
95
95
10.48
2
A1B1C2
95
95
170
4.59
3
A1B2C1
95
170
95
6.49
4
A1B2C2
95
170
170
3.38
5
A2B1C1
170
95
95
4.13
6
A2B1C2
170
95
170
2.81
7
A2B2C1
170
170
95
16.97
8
A2B2C2
170
170
170
6.64The maximum value of flexural strength is 16.97 MPa and minimum value is 2.81 MPa.Based on ranking of the factors using Taguchi analysis, plasticizer has the maximum effect (Table7). Ranking obtained by Taguchi method points out that plasticizer is ranked 1 followed by binder (rank 2) and base material (rank 3).Table 7
Response table for signal-to-noise ratios.
Larger is better
Level
Base (A)
Binder (B)
Plasticizer (C)
1
14.42
13.04
17.70
2
15.58
16.97
12.31
Delta
1.16
3.93
5.39
Rank
3
2
1Referring to Figure5 the graph for Base material is very close to being parallel to mean line, indicating that it has a very low effect on the flexural strength. Both Binder and Plasticizer have steep slopes indicating that they are important factors contributing to increase in flexural strength.Figure 5
Response plot for flexural strength.


## 4. Conclusions

The conclusions are as follows.(i)
Optimal combination of the factors and levels for the biodegradable matrix composite is base material (170 g), binder (10 g), and plasticizer (5 g).
(ii)
The flexural strength of the laminate obtained suggests that the laminate could be used to fabricate products like pen stand, packaging boxes, and similar products.



---

*Source: 769012-2014-11-13.xml*