Hemp Fibre Reinforced Polyester Composites Research Articles

Effect of Water Absorption on Mechanical Properties of Treated and Untreated Hemp Fiber Reinforced Polyester Composites

Effect of Water Absorption on Mechanical Properties of Treated and Untreated Hemp Fiber Reinforced Polyester Composites

Impact Properties of the Chemically Treated Hemp Fibre Reinforced Polyester Composites

Plant based hemp fibre properties were found to be highly influenced by changes in the amounts of cellulose, hemicellulose and lignin constituents within the fibre. These fibre constituents play a major role for effective interfacial adhesion between the fibre and the matrix. Chemical treatments such as alkali (NaOH), acetyl (acetic acid & acetic anhydride) and silane (siloxane) treatments have the potential to react with constituent contents by varying their amounts. In this study, hemp fibre was treated with alkali (0–10 % NaOH), acetyl and silane chemicals. Treated fibres were mixed with polyester matrix to produce composites. The effects of chemical treatments on hemp fibres and the resulted polyester matrix composite were analysed through impact testing of the composite samples. Alkali treatments on hemp fibres enhanced the impact resistance properties (around 43 % lower absorbed energy and 40 % higher rebounded energy) of its composites compared to the untreated cases. Lower absorption energy and higher rebounded energy indicates strong interfacial bonding between the fibre and matrix. Improvements are governed by the removal of hemicellulose and lignin from the fibre, which provides a platform for better chemical reactions between fibres and matrix. On the other hand, acetyl treatments on the higher concentrations of NaOH pre-treated fibres reduced the fibres’ ability to support impact loadings (22 % higher rebounded energy compared to the untreated cases). In the two treatment conditions, fibre lessen their strength due to excessive removal of hemicellulose and lignin constituents, and composites exhibited lower impact properties compared to the NaOH treated samples. Similar impact properties were also recorded for alkali pre-treated silanised composites. As alkali pre-treatment removed the hydroxyl groups from the fibre, further silane treatment could not develop silanols to create strong interface bonding. As a result, composites failed under lower impact resistance compared to the NaOH treated samples.

Investigations of Milling Parameters on Hemp Fiber Reinforced Composite Using ANOVA and Regression

The machinability of fiber reinforced composites is emphatically affected not only by the kind of fiber used in the composite but also by its properties. Milling composite materials is a very usual and plays a vital role for the assembly of composite structures. However, milling of composites is a somewhat complicated errand inferable from the heterogeneity of the material and a plenty of different issues, for instance, delamination factor, which show up amid the machining process and are connected with the qualities of the material and the cutting parameters. Present study looks into the influence of spindle speed, feed rate and depth of cut on thrust force, torque and delamination factor in hemp fiber reinforced polyester composites. The composite specimens were formulated using hand lay-up method. The analysis for attaining the optimality condition is performed using ANOVA and regression model. It was observed that the grouping of the inferior value of feed (0.1 mm/rev), lower spindle speed (1500 rpm) as well as the lower depth of cut (1.5 mm) results in minimum delamination factor and torque. The feed was found to be more significant than the depth of cut for thrust force.

Validation of fatigue damage model for composites made of various fiber types and configurations

Empirical model for predicting fatigue damage behavior of composite materials developed recently has been applied to composite materials made of different fibers in various configurations: carbon and glass fiber noncrimp fabric reinforced epoxy composites, chopped strand mat glass fiber-reinforced polyester composites, randomly oriented nonwoven hemp fiber-reinforced polyester composites, and glass/hemp fiber-reinforced polyester hybrid composites. The fatigue properties were evaluated in tension–tension mode at stress ratio R = 0.1 and frequency of 1 Hz. The experimental fatigue data were used to determine the material parameters required for the model. It has been found that the model accurately predicts the degradation of fatigue life of composites with an increase in number of fatigue cycles. The scope of applicability of this model has thus been broadened by using the fatigue data of natural fiber and noncrimp fabric composites.

Fire resistance characterisation of hemp fibre reinforced polyester composites for use in the construction industry

This paper presents research pertaining to the fire performance of natural fibre reinforced polymer composites (NFRP). Hemp fibre has been selected as representative of natural fibres used for reinforcement in NFRPs. The fire performance has been examined by a bench scale test method which provides an indicative assessment of the likely performance in full-scale fire resistance tests which are required for materials to meet building standards in the UK. It has been verified in this research that hemp fibres contribute to a thermally resistant char layer in polyester composites. There is an increase in thermal resistance of the char layer at high temperatures with an increase in fibre volume fraction. Ignition is delayed with an increase in fibre volume above 25%. Mechanical degradation occurs at relatively low temperatures which may be associated with the decomposition of hemicellulose and lignin. The desirability of NFRPs in terms of fire performance increases with an increase in fibre volume fraction and material thickness. Untreated hemp fibre reinforced polyester composites in this study have been characterised as having poor fire resistance and would not be expected to pass a full scale fire resistance test in their current state.

RTM Hemp Fibre-Reinforced Polyester Composites

Hemp fibre-reinforced polyester composites were prepared using a Resin Transfer Moulding (RTM) technique and the flexural and impact behaviour investigated. Flexural stress at break and flexural modulus showed an increasing trend with fibre content. Impact strength was found to decrease at low fibre content, then gradually increase with further addition of fibres.