Amandeep Singh Virk

Modulus and Strength Prediction for Natural Fibre Composites

Abstract This paper presents a new micromechanical model for the prediction of the tensile modulus and strength of natural fibre reinforced polymer matrix composites. The model addresses issues linked to the statistical variation inherent in fibre reinforcements extracted from plants. The new model introduces a fibre area correction factor (FACF). Modulus and strength are estimated and compared to experimental data for a jute–epoxy composite. The predictions of tensile modulus and strength using the FACF show improvements over those from other micromechanical models presented in the literature.

Tensile properties of jute fibres

Abstract One hundred tensile tests were undertaken at each of five distinct fibre lengths (6, 10, 20, 30 and 50 mm) on a single batch of jute fibres from South Asia. The Youngs moduli were found to be independent of length. The ultimate stress (fracture strength) and fracture strains were found to decrease with increasing fibre length. The variation in mechanical properties at each fibre length was characterised using Weibull statistics based on a maximum likelihood estimate; referred to as point estimates. Two empirical based models (a linear and a natural logarithmic interpolation model) have been developed to estimate the fracture properties at any length between 6 and 50 mm. These two interpolation models were also developed based on maximum likelihood estimates. The point estimates were used to benchmark the performance of the two models. The natural logarithmic model was found to be superior to the linear model.

Physical Characterization of Jute Technical Fibers: Fiber Dimensions

Natural fibers are characterized by large variation in their cross-section, both between fibers and along the length in any single “technical” fiber. This short communication describes an attempt to fully characterize the fiber cross-sectional area using single sample measurements from several fibers. This should enable an improved determination of mechanical properties of natural fibers.

Modelling tensile properties of jute fibres

Abstract This short communication extends earlier modelling of the tensile strength and failure strain of jute technical fibres. A maximum likelihood estimate (MLE) model, a linear model and a natural logarithmic interpolation model (NLIM) are compared. The NLIM model is found to give superior predictions.

Microstructural Characterisation of Jute/Epoxy Quasi-Unidirectional Composites

The elastic properties of a composite can be predicted by micromechanical models based on the properties of the individual constituent materials of the composite and their geometrical characteristics. This paper presents a novel methodology using image analysis to determine (a) the fibre volume fraction and (b) the fibre orientation distribution factor of quasi-unidirectional jute fibre reinforced epoxy resin composites. For fibre volume fraction, digital micrographs were smoothed to reduce noise in the image, an intensity histogram informed selection of the threshold intensity for conversion to a binary image, the image was morphologically closed and opened to remove internal voids and small features respectively and the fibre volume fraction was calculated as the ratio of the detected fibre area to the total image area. For fibre orientation, the image was sharpened with Contrast-Limited Adaptive Histogram Equalisation, a threshold was set for conversion to binary and then a masking image was rotated at a number of seed points over the image to find the angles with the minimum sum of intensity at each point. The data generated was then used to validate new rules-of-mixture equations for natural fibre composites.

A Finite Element Analysis to Validate the Rule-of-Mixtures for the Prediction of the Young’s Modulus of Composites with Non-circular Anisotropic Fibres

This paper considers the rule-of-mixtures in the context of the tensile modulus of unidirectional fibre reinforced polymer (FRP) composites made with fibres of irregular cross-section, having anisotropic mechanical properties. A finite element model is used to generate data for the determination of the tensile modulus of the FRP composite. A range of degrees of anisotropy are considered. The error in the predicted modulus is found to be small for irregular fibres.

Effect of live pressure on overwrap design

This chapter explores the effect of live pressure in pipelines on the design of composite overwrap repairs. At first the incorporation of the live pressure into the design of a repair in existing design codes is reviewed. Next, an analytical method is presented which shows that the live pressure does not have any effect on the repair design and it should not appear in the design equation. Finally, a finite element analysis model is presented that shows conformity with the analytical method and validates the recommendation to remove live pressure from the design codes formulae.