College of Agricultural Sciences and Fisheries Technology

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Browsing College of Agricultural Sciences and Fisheries Technology by Author "Ansell, Martin P."

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    Fatigue evaluation and dynamic mechanical thermal analysis of sisal fibre–thermosetting resin composites
    (Elsevier, 2007-08-10) Towo, Arnold N; Ansell, Martin P.
    Sisal composites were manufactured in a hot press from as-received and 0.06 M NaOH treated sisal fibres with polyester and epoxy resin matrices. Tensile tests were conducted on the composites to establish loading levels for fatigue testing. A fatigue evaluation of the sisal fibre–thermosetting resin composites was undertaken at loading levels of 75%, 60%, 50% and 35% of static tensile strength and at an R ratio of 0.1. S–N curves for the composites are presented for untreated and 0.06 M NaOH treated sisal fibres. Epoxy matrix composites have a longer fatigue life than polyester matrix composites. The effect of chemical treatment on fatigue life is significantly positive for polyester matrix composites but has much less influence on the fatigue life of epoxy matrix composites. Dynamic mechanical thermal analysis (DMTA) was conducted on samples from failed epoxy resin fatigue specimens and the influence of fatigue history on the Tanδ peak temperatures and Tg of the composites is examined. Significant shifts in Tg are observed following fatigue testing. The fatigue performance of natural fibre composites suggests that they are suitable for use in dynamically loaded structures and may be used as a substitute for Glass Fibre Reinforced Plastic composites in fatigue.
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    Fatigue of sisal fibre reinforced composites: Constant-life diagrams and hysteresis loop capture
    (Elsevier, 2007-09-06) Towo, Arnold; Ansell, Martin P.
    Composite materials have been manufactured using untreated or 0.06 M NaOH treated sisal fibre bundles in a polyester or epoxy matrix. Mechanical tests have been conducted to establish the static properties of the composites which have been used to calculate the maximum loads used during fatigue testing. Composites containing alkali treated fibre bundles have better mechanical properties than those with untreated fibre bundles. Alkali treatment has the greatest effect for polyester resin matrices. S–N diagrams constructed from fatigue data at stress ratios of R = 0.1 (tension–tension) and R = -1 (reversed loading) show improvement in the fatigue lives of composites following alkali treatment of sisal fibre bundles. Constant-life diagrams for epoxy matrix composites with untreated or alkali treated fibre bundles show the superiority of the alkali treated fibre composites for low cycle fatigue. Composites loaded in tension–tension fatigue (R = 0.1) exhibit hysteresis loops with diminishing loop area with increasing number of cycles. The composites loaded in reversed loading fatigue (R = -1) generate loops with increasing loop area with increasing number of cycles. Failure modes in tension–tension and reversed loading are very different with a distinctive buckling failure mode at R = -1.
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    Shear strength at Sisal fibre-polyester resin interfaces: use of inverse gas chromatography to study pretreatment effects
    (Taylor & Francis, 2012-04-02) Price, G J; Pastor, M L; Towo, A N; Packham, D E; Ansell, Martin P.
    Inverse gas chromatography, IGC, has been used to investigate changes to the surface of Sisal fibres on treatment with sodium hydroxide. By determining the retention of a series of alkane probes and of probes with acidic or basic character, it was shown that little change to the chemical nature of the surface occurs as measured by the enthalpy of adsorption of alkane probes or the dispersion component of the surface free energy. This IGC study supports the conclusion of previous work involving S.E.M. which suggested that the major effect of the treatment was the removal of weak or adventitious layers from the substrate surface, thus increasing the interfacial shear strength when incorporated into polyester resin.
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    Weibull analysis of microbond shear strength at sisal fibre-polyester resin interfaces
    (VSP, 2005) Towo, Arnold; Ansell, Martin P.; Pastor, M-L; Packham, D
    An analysis has been made of the tensile strength of sisal fibres and the interfacial adhesion between fibres and polyester resin droplets. Density and microscopy methods were used to determine the cross-sectional area of the sisal fibres. The average tensile strength of treated sisal fibres decreased by a modest amount following treatment with 0.06 M NaOH. However, this treatment resulted in a substantial increase in the interfacial shear strength at the sisal fibre to polyester resin interface. Weibull analysis has been used successfully to analyse variability in tensile strengths and interfacial shear strength using probability of failure plots. Scanning electron microscopy has revealed the shape of resin droplets on the surface of treated and untreated sisal fibres and contact angles are much lower for droplets on treated fibres. Damage to the surface of fibres has been examined following shear testing. Weibull analysis is an effective tool for characterising highly variable fibre properties and evaluating the level of adhesion between polymer resin and the fibre surface.