Biocomposites reinforced with natural fibers: 2000–2010

Natural fibres: can they replace glass in fibre reinforced plastics?

In this work, natural fibres (sisal, kenaf, hemp, jute and coir) reinforced polypropylene composites were processed by compression moulding using a film stacking method. The mechanical properties of the different natural fibre composites were tested and compared. A further comparison was made with the corresponding properties of glass mat reinforced polypropylene composites from the open literature. Kenaf, hemp and sisal composites showed comparable tensile strength and modulus results but in impact properties hemp appears to out-perform kenaf. The tensile modulus, impact strength and the ultimate tensile stress of kenaf reinforced polypropylene composites were found to increase with increasing fibre weight fraction. Coir fibre composites displayed the lowest mechanical properties, but their impact strength was higher than that of jute and kenaf composites. In most cases the specific properties of the natural fibre composites were found to compare favourably with those of glass.

Natural fibres: Can they replace glass in fibre reinforced plastics ?

This paper provides a comprehensive overview on different surface treatments applied to natural fibres for advanced composites applications. In practice, the major drawbacks of using natural fibres are their high degree of moisture absorption and poor dimensional stability. The primary objective of surface treatments on natural fibres is to maximize the bonding strength so as the stress transferability in the composites. The overall mechanical properties of natural fibre reinforced polymer composites are highly dependent on the morphology, aspect ratio, hydrophilic tendency and dimensional stability of the fibres used. The effects of different chemical treatments on cellulosic fibres that are used as reinforcements for thermoset and thermoplastics are studied. The chemical sources for the treatments include alkali, silane, acetylation, benzoylation, acrylation and acrylonitrile grafting, maleated coupling agents, permanganate, peroxide, isocyanate, stearic acid, sodium chlorite, triazine, fatty acid derivate (oleoyl chloride) and fungal. The significance of chemically-treated natural fibres is seen through the improvement of mechanical strength and dimensional stability of resultant composites as compared with a pristine sample.

Chemical treatments on plant-based natural fibre reinforced polymer composites: An overview

Compared to most synthetic fibers, natural fibers are low-cost, are easier to handle, have good specific mechanical properties, and require only around 20–40% of the production energy. Using natural materials and modern construction techniques reduces construction waste and increases energy efficiency while promoting the concept of sustainability. Several drawbacks of natural composites which would be even more pronounced in their use in infrastructure include their higher moisture absorption, inferior fire resistance, lower mechanical properties and durability, variation in quality and price, and difficulty using established manufacturing practices when compared to synthetic composites. Many researchers have been working to address these issues, with particular attention paid to the surface treatment of fibers and improving the fiber/matrix interface. Because of their positive economic and environmental outlook, as well as their ability to uniquely meet human needs worldwide, natural composites are showing a good potential for use in infrastructure applications.

Critical review of recent publications on use of natural composites in infrastructure

The development of high performance composites from a cheap natural fiber, jute, as reinforcement is particularly significant from an economic point of view. In this work, jute fiber-unsaturated polyester(GP) composites having appreciable mechanical properties were prepared by using solution impregnation and hot curing methods. Both unbleached (control) and bleached jute slivers with various percentages of fiber loadings were used to prepare the composites and were named JPH (C) i.e., Jute Polyester Hot Curing (control), and JPH (B) i.e., Jute Polyester Hot Curing (bleached), respectively. Mechanical properties such as tensile and flexural strain, toughness, and moduli of both the grades have been compared. Composites having 60 wt% of jute fiber yielded the best results. JPH (B) showed much better flexural properties than JPH (C), although the tensile properties of the latter were better. The inter-laminar shear strength (ILSS) of the JPH (B) was found to be higher than JPH (C). The nature of fiber-resin bonding was studied from scanning electron micrographs of the specimens subjected to tensile and flexural fracture. Dynamic mechanical properties were found to be very high, superior even to those of glass fiber reinforced composites. The flexural storage modulus was found to be 12.3 GPa at 30°C and to decrease slowly with temperature. The major finding in this work is the attainment of high mechanical properties of composite specimens with 60 wt %fiber loading. On a weight and cost basis, bleached jute fibres were found to be better reinforcements than other fibers with usual surface modification by coating or grafting processes.

Novel, low‐cost jute‐polyester composites. Part 1: Processing, mechanical properties, and SEM analysis

Jute–polyester composites were fabricated with untreated (control) and bleached slivers with 60% loading of fiber by weight and were designated as JPH(C) and JPH(B), respectively. Both types of composite specimens were subjected to water absorption and outdoor weathering tests to assess their relative performance under environmental conditions. While both composites showed low water absorption, JPH(B) showed lesser water absorption (8.48%) than did JPH(C) (12.25%). The mechanical properties like tensile and flexural strengths were measured for both the weathered and unweathered specimens and compared. The tensile strength of JPH(C) and JPH(B) decreased while the tensile modulus increased after weathering. The flexural strength, moduli, and ILSS of the weathered specimens were less than those of the unweathered ones. The nature of the fiber–matrix adhesion could be established from these results. The cause of every observation is explained. Thermal analyses (TG/DTG and DSC) of the composite specimens were also done. The overall thermal stability of JPH(C) was found to be better than that of JPH(B). © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1671–1679, 2000

Novel low‐cost jute–polyester composites. III. Weathering and thermal behavior

Jute fibers in the form of slivers have been reinforced with epoxy resins to prepare composites. The solution impregnation method has been adopted in an attempt to increase the percentage of fiber loading. Both untreated (control) and chemically modified (bleached) slivers have been used to prepare composites. The optimization study of fiber loading in composites is done with control slivers through tensile property assessment. Composites having 50% sliver (control) by weight are observed to give the best tensile characteristics. The tensile, flexural, impact, and hardness properties of the composites of both bleached and control slivers have been investigated and it is observed that although the latter have better tensile properties, the former possesses unusually high flexural properties. Both Izod and Charpy impact tests reflect that the composites with bleached slivers have higher impact strengths. In comparison to the composites with control slivers, they also exhibit greater (Rockwell) hardness.

A study on mechanical performance of jute-epoxy composites

The scanning electron micrographs (SEM) were taken at different magnifications with respect of the fractured surfaces of the polymer composites prepared from unsaturated polyester resin and jute sliver with 60% fiber loading by weight. The composite specimens were prepared using both untreated (control) and chemically modified (bleached) jute fibers by solution impregnation and hot curing methods and are designated as JPH-60(C) and JPH-60(B), respectively. The method of preparation of the composite specimens have been discussed. The specimens were subjected to tensile and flexural tests and the fractured surfaces were observed under SEM as stated. The fiber surface morphology was also studied from the SEM photographs in the case of the control and bleached jute filaments. The SEM photographs of the fractured surfaces of the composites showed varied extents of fiber pull-outs under both tensile and flexural failure modes. The nature of interfacial adhesion has been discussed on the basis of the SEM study. ...

H. K. Mishra

Papers

Novel, low‐cost jute‐polyester composites. Part 1: Processing, mechanical properties, and SEM analysis

Novel low‐cost jute–polyester composites. III. Weathering and thermal behavior

A study on mechanical performance of jute-epoxy composites

Novel low-cost jute–polyester composite. ii. sem observation of the fractured surfaces