Kenaf Fiber Composites Research Articles

Residual Tensile Stress of Kenaf Polyester and Kenaf Hybrid under Post Impact and Open Hole Tensile

Abstract Natural fibres have emerged as the potential reinforcement material for composites and have thus gained an attraction by many researchers. This is mainly due to their applicable benefits as they are light weight and offer low cost compared to synthetic fibre composites. Kenaf fibres recently have been a substitute material in many weight-critical applications in areas such as aerospace, automotive and other high demanding industrial sectors. In this study, natural fibre kenaf composites and kenaf/fibreglass hybrid composites were fabricated by a combination of hand lay-up and cold-press methods. The post impact tensile and open hole tensile of long kenaf fibre composites with and without the addition of fibreglass were further studied. The fracture behaviour verified qualitatively via scanning electron microscopy. A significant improvement in tensile strength and modulus were indicated by the introduction of long kenaf/woven fibreglass hybrid composite. Investigation on the tensile and low velocity impact of kenaf composites and kenaf/fibreglass reinforced polyester resin composites revealed that the composites were seriously impaired when a low energy impact was applied. The tensile strength of open hole long kenaf composites was more notch sensitive than long kenaf/woven glass hybrid composite. Although the hybrid composite was stronger than pure kenaf composites, the damage progression mechanisms in the two materials were very similar. In the above case the polymer matrix failed initially. It is followed by fibre matrix debonding and finally ending in fibre ruptures or pull-outs.

Effect of fibre loading on mechanical and thermal properties of sisal and kenaf fibre-reinforced injection moulded composites

Kenaf and sisal fibres were selected for the development of natural fibre-reinforced thermoplastic composites because they are in abundance in South Africa. These materials can be used in the building industry, where good mechanical and fire resistance properties are required for structural and non-structural applications. High load bearing, moisture and fire can negatively affect the properties of these composites and decrease their performance. The effect of water glass, maleic anhydride-grafted-polypropylene (MAPP) treatment and fibre loadings on mechanical and thermal properties as well as fire resistance of kenaf and sisal fibre-reinforced polypropylene composites were investigated. The fibre-reinforced polypropylene composites were produced by injection and compression moulding processes. A significant improvement of the tensile strength and modulus of kenaf fibre composites was more pronounced when compared to sisal fibre composites. However, the water glass has a slight negative influence on mechanical properties of fibre/polypropylene matrix composites but showed better fire resistance and thermal properties when compared to the untreated fibre/polypropylene composites. Generally, the impact strength of fibre/polypropylene composites decreased with the addition of MAPP. The low impact strength could be the results of weak interfacial bond strength between the fibre and the matrix. The total heat release was reduced by water glass treatment due to the non-flammable polysilicate coating, while the average mass loss rate was slightly reduced by MAPP.

Storage Modulus Analysis of Kenaf Fibre Reinforced Epoxy Composites

This article presents the storage modulus analysis of kenaf fibre composites that reinforced by two different epoxy matrix systems, named epoxy A and epoxy B. These epoxies are commercially available in Malaysia and been used as a polymer matrix in composite research. Composites were made from hand lay out technique and undergo storage modulus evaluation by using dynamic mechanical analysis (DMA). Fibre content ratios were found to affect the storage capacity in both reinforced epoxy system. However, the addition of 45% kenaf fibre volume ratios reinforced into Epoxy A composites exhibits only week improvement as compared to its rival. The possibility of causes might be attributed to the week interfacial between fibre and matrix.

Effect of Environmental Degradation on Mechanical Properties of Kenaf/Polyethylene Terephthalate Fiber Reinforced Polyoxymethylene Hybrid Composite

The main objective of this research is to investigate the effect of environmental degradation on the mechanical properties of kenaf/PET fiber reinforced POM hybrid composite. Kenaf and PET fibers were selected as reinforcements because of their good mechanical properties and resistance to photodegradation. The test samples were produced by compression molding. The samples were exposed to moisture, water spray, and ultraviolet penetration in an accelerated weathering chamber for 672 hours. The tensile strength of the long fiber POM/kenaf (80/20) composite dropped by 50% from 127.8 to 64.8 MPa while that of the hybrid composite dropped by only 2% from 73.8 to 72.5 MPa. This suggests that the hybrid composite had higher resistance to tensile strength than the POM/kenaf composite. Similarly, the results of flexural and impact strengths also revealed that the hybrid composite showed less degradation compared to the kenaf fiber composite. The results of the investigation revealed that the hybrid composite had better retention of mechanical properties than that of the kenaf fiber composites and may be suitable for outdoor application in the automotive industry.

KENAF/RECYCLED JUTE NATURAL FIBERS UNSATURATED POLYESTER COMPOSITES: WATER ABSORPTION/DIMENSIONAL STABILITY AND MECHANICAL PROPERTIES

Effects of water absorption on the flexural properties of kenaf-unsaturated polyester composites and kenaf/recycled jute-unsaturated polyester composites were investigated. In the hybrid composites, the total fiber content was fixed to 20 wt%. In this 20 wt%, the addition of jute fiber varied from 0 to 75%, with increment of 25%. The result demonstrates the water absorption and the thickness swelling increased with increase in immersion time. Effects of water absorption on flexural properties of kenaf fiber composites can be reduced significantly with incorporation of recycled jute in composites formulation. The process of absorption of water was found to approach Fickian diffusion behavior for both kenaf composites and hybrid composites.

Effects of LENR addition on mechanical properties of kenaf fibre reinforced epoxy composites

Effects of liquid epoxidized natural rubber (LENR) on the mechanical behaviour of kenaf fibre reinforced epoxy composite were studied. Kenaf fibres (Hibiscus cannabinus, L. family Malvaceae) and thermoset matrices were hand-laid up and characterized in terms of its mechanical properties. The objective of this research is to investigate the effect of LENR to the flexural and impact properties of the kenaf fibre reinforced epoxy composites. The fibres were alkali treated before use as reinforcement in the epoxy resin matrix. Five different fibre concentrations of 5%, 10%, 15%, 20% and 25% by weight have been used (with and without addition of liquid epoxidized natural rubber). Flexural, impact and DMTA tests of rubber toughened epoxy reinforced kenaf fibre composites were performed. The fractured surfaces of these composites were investigated by using scanning electron microscopic technique (SEM) to determine the interfacial bonding between the matrix and the fibre reinforcement. It was found that the addition of LENR increased the flexural strength, flexural modulus and impact strength by 17.6%, 11% and 47% respectively.

Effects of Processing Temperature and Chemical Treatment on Tensile Strength of Kenaf Fiber - Reinforced Polypropylene Waste Composites

In this research, the influence of processing temperatures and fiber chemical treatments to mechanical properties of polypropylene (PP) waste – kenaf fiber composites was investigated. Results from experimental and theoretical calculation of composite tensile strength were compared. The composites were made of PP wastes and unidirectional kenaf fiber, and manufactured by hot press molding. The processing temperature variations were 175 oC, 185oC and 195 oC. The chemical treatment used were alkaline and permanganate treatment. Kenaf fiber – PP composites were successfully made with the void volume fraction less than 5%, maximum fiber volume fraction 48% and maximum longitudinal tensile strength 110 MPa or 238% higher than PP’s strength. For non- and alkali treated fiber composites, 185oC was the optimum processing temperature. Elevated processing temperature up to 195oC could decrease composite strength due to the degradation of fiber-matrix interface. The effect of permanganate treatment did not significantly affect the composites strength. However, the improvement of interfacial properties at elevated temperature was found by the use of permanganate treatment.

The Effect of Alkali Treatment Mechanical Properties of Kenaf Fiber Epoxy Composite

Increasing worldwide environmental awareness is an encouraging scientific research into the development of cheaper, more environmentally friendly and sustainable construction and packaging materials. Kenaf fibre is a natural fibre which is growing in popularity due environmental issues and its properties as filler. Epoxy is a versatile thermosetting polymer which has a low curing temperature and used in making carbon fibre and glass composites. In this paper the properties of kenaf bast fibre epoxy reinforced composite have been investigated. The effects of alkali surface treatment of the fiber on the composite properties are also investigated. A hand layup method was use to fabricate the test specimens. Generally, all the treated fibre composites performed better than the untreated fibre with an improvement approximately 5% to 10%. Epoxy has the highest tensile strength and flexural strength among all specimens. The 24wt% treated kenaf fibre composites has the highest tensile strength, 27.72MPa and flexural strength, 56.91MPa. The kenaf fiber weight fraction of 40% gave the highest impact strength. The impact strength of the 40wt% kenaf fiber increased 14.3% after alkali treatment.

The Mechanical and Physical Properties of Thermoplastic Natural Rubber Hybrid Composites Reinforced with Hibiscus cannabinus, L and Short Glass Fiber

Thermoplastic natural rubber hybrid composites reinforced with kenaf and short glass fibers were compounded by melt blending method using an internal mixer, Thermo Haake 600P. Thermoplastic natural rubbers (TPNR) were prepared from polypropylene (PP), natural rubber (NR) and liquid natural rubber (TPNR) with ratio 70:20:10, which were blended using internal mixer for 12 minutes at 180°C and rotor speed 40 r.p.m. Glass fiber was treated with silane coupling agent while TPNR reinforced kenaf fiber composite is using MAPP as a compatibilizer. TPNR hybrid composite with kenaf/glass fibers was prepared with fiber content (5, 10, 15, 20 volume % of fiber). Mechanical properties of the composites were investigated using tensile test[ 1 ], flexural, impact, and hardness test and scanning electron microscope (SEM)[ 1 ]. The incorporation of the treated or untreated fiber into TPNR has result in an increment of almost 100% of flexural modulus and impact strength as compared to TPNR matrix. However, the maximum strain decreased with increasing fiber content. The optimum composition for hybrid composite is at the fiber ratio of 30% kenaf fiber and 70% glass fiber. The SEM micrograph had shown, that the composite with coupling agent or compatibilizer promote better fiber-matrix interaction.

Flexural behaviour of pultruded jute/glass and kenaf/glass hybrid composites monitored using acoustic emission

Abstract The flexural (before and after cyclic loading up to 50% of ultimate load) and indentation behaviour of pultruded jute/glass and kenaf/glass hybrid polyester composites has been monitored using acoustic emission, and compared with that of kenaf fiber composites. In all hybrids, natural fiber content was 40 wt.%, while glass fiber one was 25 wt.%. Acoustic emission (AE) has been used for real-time monitoring during flexural and indentation loading: the analysis concentrated on AE resuming during reloading (Felicity ratio) and AE activity at low loads during unloading (crack closure effect). The results show that the introduction of this large amount of reinforcement appears quite effective on jute fiber reinforced laminates, although with a significant effect of fiber architecture, whilst it did not yield comparable results in kenaf fiber laminates. This was attributed to the insufficient fiber impregnation and to the need for improving the control of fiber orientation in the laminate.

Properties of kenaf fiber/polylactic acid biocomposites plasticized with polyethylene glycol

AbstractBiocomposites of kenaf fiber (KF) and polylactic acid (PLA) were prepared by an internal mixer and compression molding. PLA was plasticized with polyethylene glycol (PEG) (10 wt%) and evaluated as the polymer matrix (p‐PLA). Fiber loadings were varied between 0 and 40 wt%. The tensile, dynamic mechanical, and morphological properties and water absorption behavior of these composites were studied. Reinforcing effect of KF was observed when fiber loading exceeded 10 wt% despite of the inferior fiber‐matrix adhesion observed via scanning electron microscopy (SEM). Un‐plasticized PLA/KF composite exhibited higher tensile properties than its plasticized counterpart. Fiber breakage and heavily coated short pulled‐out of fibers were observed from the SEM micrographs of the composite. The presence of PEG might have disturbed the fiber‐matrix interaction between KF and PLA in the plasticized composites. Addition of PEG slightly improved the un‐notched impact strength of the composites. Dynamic mechanical analysis showed that the storage and loss moduli of p‐PLA/KF composites increased with the increase in fiber loading due to increasing restrictions to mobility of the polymer molecules. The tan delta of the composites in contrast showed an opposite trend. p‐PLA and p‐PLA/KF composites exhibited non‐Fickian behavior of water absorption. SEM examination revealed microcracks on p‐PLA and p‐PLA/KF surfaces. POLYM. COMPOS., 31:1213–1222, 2010. © 2009 Society of Plastics Engineers

Crystallization behavior of poly(hydroxybytyrate-co-valerate) in model and bulk PHBV/kenaf fiber composites

The kinetics of non-isothermal crystallization and melting behavior of poly(hydrohybutyrate-co-valerate) (PHBV) in model, bulk and compatibilized (PHBV)/kenaf fiber composites were investigated using differential scanning calorimetry (DSC). Analysis of the non-isothermal crystallization data was carried out based on the Avrami and Mo’s models. Activation energies of the crystallization process were determined by the Kissinger approach, and were in the range between 41 and 48 kJ/mol for all investigated samples. It was shown that the kenaf fibers, as well as their content, do not affect significantly the crystallization kinetics of PHBV matrix. The results indicate that crystallization behavior of polymer resin in bulk composites is not affected by the melt processing, thus suggesting absence of degradation processes.

Long‐term water uptake behavior of lignocellulosic‐high density polyethylene composites

AbstractComposites of different lignocellulosic materials and high‐density polyethylene were prepared and their long‐term water absorption behaviors were studied. Wood flour, rice hulls, newsprint fibers, and kenaf fibers were mixed with the polymer at 25 and 50 wt % fiber contents and 1 and 2% compatibilizer, respectively. Water absorption tests were carried out on injection‐molded specimens at room temperature for five weeks. Results indicated a significant difference among different natural fibers with kenaf fibers and newsprint fibers exhibiting the highest and wood flour and rice hulls the lowest water absorption values, respectively. Very little difference was observed between kenaf fiber and newsprint composites and between rice hulls and wood flour composites regarding their water uptake behavior. The difference between 25 and 50% fiber contents for all composite formulations increased at longer immersion times, especially for the composites with higher water absorption. Kenaf fiber composites containing 50% kenaf fibers exhibited the highest water diffusion coefficient. A strong correlation was found between the water absorption and holocellulose content of the composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3907–3911, 2006

The effect of alkalization and fibre alignment on the mechanical and thermal properties of kenaf and hemp bast fibre composites: part 2 – cashew nut shell liquid matrix

Long and random hemp and kenaf fibres were used in as-received condition and alkalized in a 6% NaOH solution. They were combined with cashew nut shell liquid (CNSL) resin and hot-pressed to form natural fibre, natural matrix composites. The mechanical properties of the composites were investigated to observe the effect of fibre alignment and alkalization. A general trend was observed whereby alkalized and long fibre composites gave higher flexural modulus and flexural strength with alkalized long kenaf–CNSL composite giving superior mechanical properties. A general trend was also observed for the overall mechanical test results of the composites whereby high flexural modulus and high flexural strength are associated with a low work of fracture. Wide endothermic peaks present in differential thermal analysis thermograms for all of the composites indicated the presence of moisture which leads to inferior mechanical properties. Dynamic mechanical thermal analysis carried out on the composites showed that the alkalized fibre composites have higher E ′ and lower tan δ, corresponding to the trends of higher flexural modulus and lower work of fracture respectively.

The effect of alkalization and fibre alignment on the mechanical and thermal properties of kenaf and hemp bast fibre composites: Part 1 – polyester resin matrix

Long and random hemp and kenaf fibres were used in the as-received condition and alkalized with a 0.06 M NaOH solution. They were combined with polyester resin and hot-pressed to form natural fibre composites. The mechanical properties of the composites were measured to observe the effect of fibre alignment and alkalization. A general trend was observed whereby alkalized and long fibre composites gave higher flexural modulus and flexural strength compared with composites made from as-received fibres. Alkalized long kenaf–polyester composites possessed superior mechanical properties to alkalized long hemp–polyester composites. For the hemp–polyester composites a high flexural modulus and a high flexural strength are associated with a low work of fracture. Scanning electron microscopy micrographs of the treated hemp and kenaf fibres showed the absence of surface impurities which were present on the untreated fibres. Apparent density measurements on hemp and kenaf fibres did not show a significant change after alkalization with 0.06 M NaOH. Wide endothermic peaks present in differential thermal analysis thermograms for all of the composites indicated the presence of moisture which leads to inferior mechanical properties. Dynamic mechanical thermal analysis carried out on the polyester matrix composites showed that the alkalized fibre composites have higher E ′ values corresponding to higher flexural moduli. Any correlation between fibre surface treatment and the work of fracture and tan δ of composites is less clear.