ABSTRACT The effect of soaking time and temperature response for coconut and raffia fibre reinforced composite on their mechanical properties have been studied. Tensile and compression test for treated and untreated were performed using a universal testing machine (Monsanto Tensometer). The conditioned samples in each case show better tensile and compressive strength compared to the untreated samples. Raffia fibre reinforced polyester showed a better mechanical and moisture absorption properties at various operating temperature in the study

Christian Sunday Chukwuekezie

Christopher Chukwutoo Ihueze

Gaius Debi Eyu

Jamaliah Idris

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                                         VOL. 9, NO. 3, MARCH 2014                                                                                                                     ISSN 1819-6608            
ARPN Journal of Engineering and Applied Sciences 
 
©2006-2014 Asian Research Publishing Network (ARPN). All rights reserved. 
 
www.arpnjournals.com 
 
 
336
HYGROTHERMAL RESPONSE OF PLANT FIBRE 
REINFORCED COMPOSITES 
 
Christian Sunday Chukwuekezie1, Christopher Chukwutoo Ihueze2, Jamaliah Idris1 and Gaius Debi Eyu1 
1Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Skudai, Johor Bahru, Malaysia 
2Department of Industrial/Production Engineering, Nnamdi Azikiwe University, Awka, Nigeria 
E-Mail: feldeg2002@yahoo.com 
 
ABSTRACT 
The effect of soaking time and temperature response for coconut and raffia fibre reinforced composite on their 
mechanical properties have been studied. Tensile and compression test for treated and untreated were performed using a 
universal testing machine (Monsanto Tensometer). The conditioned samples in each case show better tensile and 
compressive strength compared to the untreated samples. Raffia fibre reinforced polyester showed a better mechanical and 
moisture absorption properties at various operating temperature in the study. 
 
Keywords: fibre, raffia, tensile strength, composite, reinforced polyester. 
 
1. INTRODUCTION 
The great desires for novel materials for 
fabrication, aerospace and transportation industry has 
gained the attention of researchers in recent time. Higher 
demand for materials overall performance has led to the 
increasing research efforts towards eco-friendly 
composites because of their mechanical properties, such as 
high stiffness, high strength and light weight. These 
qualities make composite materials more superior 
compared to many conventional engineering materials [1, 
2]. Composites are generally categorized as Ceramic 
Matrix Composites (CMC), Metal Matrix Composite 
(MMC), Polymer Matrix Composites (PMC), Inter-
Metallic Composites (IMC) and Carbon-Carbon 
Composites. However, Polymer matrix can be classified 
as; short fibre and continuous fibre composites. 
Continuous composites are mainly reinforced with high 
performance fibres such as carbon and Kevlar; they are 
mainly used for aircraft applications. On the other hand, 
short fibre composites are commonly reinforced with 
chopped fibres such as glasses, graphite and plant fibres. 
The numerous applications of composites are 
dependent mainly on the mechanical property. Stiffness of 
continuous fibres is predictable by using such scheme as 
rule of mixture, however due to fibre dispersion, fibre 
volume fraction, aspect ratio and quality of fibre interface, 
short fibre stiffness cannot be predicted [3-7]. Good 
dispersion of the fibre in the polymer matrix enhances the 
performance of short fibre composites [8]. The 
increasingly cost of hydrocarbon base-plastic and the need 
for more eco-friendly materials in recent time makes plant 
fibres more desirable candidates as reinforcing materials in 
composites. Plant fibres can give an aspect ratio (L/D) of 
about 200 for good performance after melt processing [9]. 
They are abundant and relatively cheap [10-14]. 
Hygrothermal sensitive of GRP composite properties 
using computer integrated finite element methods to 
predict the displacement of GRP at the nodes at elevated 
temperature has been studied [15], it showed that GRP 
composite has ultimate strength of 133 MPa at 200C-
1200C. Similarly, optimization methods of golden section 
search and quadratic interpolation to optimize the 
polynomial model developed by [16] for glass fibre 
reinforced polyester composites commonly used in 
structural and mechanical parts revealed that GRP 
composites have optimum strength of 7-61 MPa at 
temperature range of 200C-1200C. Compatibility between 
two phases of matrix and fibre poses great challenge 
because of the hydrophilic nature of natural fibres and 
hydrophobicity of polyester resin. This study focuses on 
the analysis of the effect of hydothermal response of plant 
fibre reinforced polyester resin composites. 
 
2. EXPERIMENT 
 
2.1. Materials and equipment 
The materials used for the study were basically 
coconut fibre, raffia fibre polyester resin, cobalt 
(accelerator), MEKP catalyst, binders; gel coat resins 
release agent and mould. Paint brushes, rollers and electric 
cutting machine were used as simple tools for the study. 
 
2.2. Methods 
 
2.2.1. Fibre extraction  
The coconut husk was detached from the nut and 
soaked in water for some days to accelerate fermentation 
and subsequently washed thoroughly to eradicate 
contaminants. However, the white fibrous stem of raffia 
stem was soaked in water for fermentation for three weeks 
and thereafter washed thoroughly to remove non-fibre 
constituents. 
 
2.2.2. Surface modification 
Surface treatment enhances mechanical 
properties; the fibres were immersed in 12.5g/dm3 sodium 
hydroxide solution for 24 hours and double washed with 
distilled water to remove the alkali and afterward air dried. 
 
2.2.3. Fibre loading formation 
The fibre loads were formed using strand mat 
approach. Fibres were cut (50mm) in length and randomly 
                                         VOL. 9, NO. 3, MARCH 2014                                                                                                                     ISSN 1819-6608            
ARPN Journal of Engineering and Applied Sciences 
 
©2006-2014 Asian Research Publishing Network (ARPN). All rights reserved. 
 
www.arpnjournals.com 
 
 
337
distributed on the surface of the formica covered with 
PVA binder. And thereafter, pressed with a roller to ensure 
adequate binding of the fibres. Figure-1 shows the two 
samples of the fibre load formed. 
 
 
(a) Raffia mat 
 
(b) Coconut mat 
 
Figure-1(a)-(b). Formed fibre load samples. 
 
2.2.4. Preparation of composites 
Composites were made from the processed fibre. 
Prior to curing, the matted fibres were accelerated with 
MEKP and then catalyzed using cobalt as catalyst. Curing 
was done followed by fibre impregnation within the 
formica mould as shown in Figure-2. After reasonable and 
uniform impregnation, the male mould was placed on the 
female mould containing the impregnated fibre to ensure 
proper compression. The sample was left in the mould for 
24 hours for proper curing time. The sample was then 
removed after the demoulding and cut into different 
dimensions for the various tests. The dimensions used for 
the test were 300×21×5.2 mm3 and 40×20×20 mm3 for the 
tensile and compression tests, respectively. 
 
 
(a)  Gel coat resin 
 
(b) Fibre impregnation 
 
(c) Mould coupling 
 
(d) De-moulding 
 
(e) Tensile sample 
 
(f) Compression mould 
 
Figure-2. Moulds and laminate formation stages. 
 
2.2.5. Mechanical test 
Hounsfield (Monsanto) Tensometer model S/N 
8889 (Universal testing machine) was used for the 
mechanical tests (tensile and compression tests. The test 
reading was taken by sliding the cursor to and fro in 
unison with the mercury head. The movement of the worm 
gear which causes the deformation of the specimen is 
transmitted through a gear train to the recording drum. The 
rotation of the drum is directly proportional to the 
deformation of the test piece. 
 
Tensile test parameters: 
Cross sectional area = 21mm×5.2mm = 109.2mm2   
Gauge length = 5.65√A0                                                                          (1)                                                                                                          
                    = 5.65√109.2 
                    = 59.04m 
Where A0 = cross sectional area 
Compression test parameters: 
 
Cross sectional area = 20mm×20mm = 400mm2 
Gauge length = 20mm. 
 
2.2.6. Moisture absorption 
The weight gained by the condition specimens in 
the study were carefully examined by weighing multiple 
specimens periodically for 4, 8, 12 and 24 hrs at 20, 40, 
60, and 1000C. The percentage weight gain was 
determined as: 
 
M = (M2-M1) ×100%/M1                                                                         (2)                       
M1 = mass of fiber before soaking 
M2 = mass of fibre after soaking     
 
2.2.7. Volume fraction measurement 
The volume fractions of the fibres were evaluated 
based on Archimedes principle, which states that when a 
solid is fully or partially immersed in a fluid, it displaces 
the volume which is equal to the volume of the solid. 
 
Solid volume fraction =     
Fibre volume fraction =  =    (3) 
 
=                                                                    (4)     
                                         VOL. 9, NO. 3, MARCH 2014                                                                                                                     ISSN 1819-6608            
ARPN Journal of Engineering and Applied Sciences 
 
©2006-2014 Asian Research Publishing Network (ARPN). All rights reserved. 
 
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338
3. RESULTS AND DISCUSSIONS  
 
3.1. Tensile test 
Each of the samples was subjected to tensile 
strength test at a constant fibre fraction Vf = 0.35. The 
results from the tensile test show that stress tends to be 
fairly proportional to strain. However, as the soaking time 
increases, the tensile strength increases (reduction in 
strain), stiffness for the treated composites. The untreated 
samples demonstrate reduced tensile strength compared to 
the treated composites under hygrothermal condition as 
shown in Figures 3 and 4. 
 
 
(a)  (b) 
 
(c) 
 
 
Figure-3(a), (b), (c). Tensile stress - strain response of coconut fibre reinforced polyester composite samples 
at 200C, 400C and untreated sample, respectively. 
 
 
(a)  (b) 
 
(c) 
 
      
Figure-4(a), (b), (c). Tensile stress - strain response of raffia fibre reinforced polyester composite samples 
at 200C, 400C and untreated sample, respectively. 
 
                                         VOL. 9, NO. 3, MARCH 2014                                                                                                                     ISSN 1819-6608            
ARPN Journal of Engineering and Applied Sciences 
 
©2006-2014 Asian Research Publishing Network (ARPN). All rights reserved. 
 
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339
3.2. Compression test 
The compressive strength of material is the 
ultimate stress required to cause deformation under 
compressive loading. Figures 5 (a), (b) show that lower 
temperature (200C), the rate of failure was higher than at 
higher temperature for the treated sample as shown in 
Figure-5(b). Overall, the untreated samples show the 
highest deformation as shown in Figure-5(c) and 6(c). The 
maximum yield stress of compression test is much higher 
compared to tensile test; since the plant fibres are chop 
strand fibres. Hence higher resistance to compression load 
than the tensile. Coconut fibre showed a higher 
compression loading resistance than raffia. 
 
 
(a)  (b) 
 
(c) 
 
 
Figure-5(a), (b), (c). Compression stress-strain response of coconut fibre reinforced polyester composite 
sample at 200C, 400C and untreated sample, respectively. 
 
 
(a) 
 
(b) 
 
(c) 
 
 
Figure- 6(a), (b), (c). Compression stress-strain response of raffia fibre reinforced polyester composite 
sample at 200C, 400C and untreated sample, respectively 
                                         VOL. 9, NO. 3, MARCH 2014                                                                                                                     ISSN 1819-6608            
ARPN Journal of Engineering and Applied Sciences 
 
©2006-2014 Asian Research Publishing Network (ARPN). All rights reserved. 
 
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340
3.3. Ultimate tensile strength  
Figures 7 and 8 show the ultimate tensile strength 
of the two fibre composites. Raffia fibre reinforced 
polyester demonstrates the highest ultimate tensile 
strength of 22.89 MPa at 200C compared to coconut fibre 
reinforced polyester with 14.65 MPa at 400C after 4 hours, 
respectively. However, the ultimate strength of both 
samples decrease as temperature and soaking time 
increases as a result of debonding at the fibre-matrix 
interface caused by high moisture absorption, hence a 
reduction in mechanical properties. 
 
 
 
Figure-7. Ultimate tensile strength vs time graph of raffia 
fibre reinforced polyester composite (treated), Vf = 0.35. 
 
 
 
Figure-8. Ultimate tensile strength vs time graph of 
coconut fibre reinforced polyester composite 
(treated), Vf = 0.35. 
 
3.4. Moisture absorption 
Figures 9 and 10 shows the graph of moisture 
absorption against time for coconut and raffia fibre 
reinforced polyester for treated samples at various 
temperatures. It is evident that as temperature increases the 
moisture absorption increases. This could be as a result of 
diffusion due to dryness in the micro-pores, hence the 
affinity for moisture thus increased. Overall, raffia fibre 
showed significant moisture absorption at 200C and 400C. 
 
 
 
Figure-9. Moisture absorption vs time,  of coconut fibre 
reinforced composite at  Vf = 0.35. 
 
 
Figure-10. Moisture absorption vs time, of raffia fibre 
reinforced composite at Vf = 0.35. 
 
4. CONCLUSIONS 
 The effect of moist and temperature on the 
mechanical properties of coconut and raffia fibre 
reinforced polyester composites has been studied and the 
following conclusions can be drawn from the study; 
 
a) The maximum yield stress of compression test is 
much greater than the tensile test results due to the 
chopped strand fibres which possess high resistance to 
compression load. 
b) The mechanical behaviour of coconut and raffia fibres 
as reinforcement for polyester resins shows that plant 
fibres possess acceptable mechanical properties 
similar to the synthetic counterparts. 
c) Fibre reinforced polyester developed in the study is 
environmentally friendly. Moreso, the hand lay -up 
technique utilized in the study is economically 
suitable though labour intensive. 
 
REFERENCES  
 
[1] G.M. Newang. 1993. Polymer-Matrix Composites in 
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[2] T.W. Clyne and D. Hull. 1996. Introduction to 
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[3] J.R. White and S.K. De. 1996.  Survey of Short - Fibre 
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[4] M.G. Brader and A.R Hill. 1993. Short-Fibre 
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[5] G.G. Nando and B.R. Gupta. 1996. Short - Fibre 
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[6] D.N.S Han and S.T Sean. 1993. Composites from 
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                                         VOL. 9, NO. 3, MARCH 2014                                                                                                                     ISSN 1819-6608            
ARPN Journal of Engineering and Applied Sciences 
 
©2006-2014 Asian Research Publishing Network (ARPN). All rights reserved. 
 
www.arpnjournals.com 
 
 
341
[7] S.M. Shaler. 1993. Mechanics of the interface in 
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[14] P. Gatenholm and J. Felix. 1993. Methods for 
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HYGROTHERMAL RESPONSE OF PLANT FIBRE REINFORCED COMPOSITES

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HYGROTHERMAL RESPONSE OF PLANT FIBRE REINFORCED COMPOSITES

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