Interfacial Shear Strength of Kenaf Single Fibre Reinforced Polyester Matrix: Observation of Fibre Fracture and Matrix Debonding

This paper describes an analysis of the parameters that affect the interfacial properties of kenaf fibre reinforced with polyester matrix. Kenaf fibre bundles were subjected to water treatment through soaking and ultrasonication technique. The specimens of dumbbell shape were fabricated containing kenaf single fibres embedded in polyester matrix. The interfacial shear strength was determined through single fibre fragmentation test. This test was used as a means of investigation, and the observation of fibre fracture and matrix debonding was done using ligt microscope equipped with polarizer light.

Investigation of Chemical and Physical Surface Changes of Thermally Conditioned Glass Fibres

A number of analytical techniques were applied to investigate changes to the surface of unsized boron-free E-glass fibres after thermal conditioning at temperatures up to 700 °C. Novel systematic studies were carried out to investigate the fundamental strength loss from thermal conditioning. Surface chemical changes studied using X-ray photoelectron spectroscopy (XPS) showed a consistent increase in the surface concentration of calcium with increasing conditioning temperature, although this did not correlate well with a loss of fibre strength. Scanning electron microscopy fractography confirmed the difficulty of analysing failure-inducing flaws on individual fibre fracture surfaces. Analysis by atomic force microscopy (AFM) did not reveal any likely surface cracks or flaws of significant dimensions to cause failure: the observation of cracks before fibre fracture may not be possible when using this technique. Fibre surface roughness increased over the whole range of the conditioning temperatures investigated. Although surface roughness did not correlate precisely with fibre strength, there was a clear inverse relationship at temperatures exceeding 400 °C. The interpretation of the surface topography that formed between 400–700 °C produced evidence that the initial stage of phase separation by spinodal decomposition may have occurred at the fibre surface.

Impact Behaviour of Glass Fribre /Epoxy Composites with Nano-Enhanced Resin after Water Exposure

Impact behaviour of glass fibre /epoxy composites with nano- SiO2 modified resin was studied in terms of low velocity impact after water exposure. Nanocomposites with 1%, 2%, 3% 5% 7% nano-SiO2 (Nanopox- Evonic) were investigated. Peak impact load and impact damage area as a function of nanoparticle contents were compared for dry specimens and for samples exposed to water (0.7 %wt. 1.7% water absorbed) at 1J, 2J 3J impact energies. For unmodified composite peak force was higher than for 3% modified specimens and higher for dry specimens than those exposed to water. Impact damage areas were plotted as a function of water contents for modified and unmodified samples. Failure modes were illustrated using SEM micrographs. Numeropus matrix cracks were the dominating failure mode in dry speciemens both unmodified and the modified. Fibre fracture was observed at 3J impact energy in all dry unmodified samples, however water exposure prevented early fibre fracture in nanocomposites. The proposed energy absorption mechanism is nanoparticles debonding.

A Study on Continuous Flax Fibre Reinforced Polypropylene Composite in Stamp Forming Process

This study investigates the forming behaviour of flax fibre reinforced polypropylene composites through stamp forming. A real time photogrammetric three dimensional strain measuring system was employed to capture the surface motion and compute strain deformation during forming. Failure mechanisms exhibited in the flax/polypropylene composites at different forming temperatures were determined by visual and microscopical examinations. Fibre fracture was identified as the major failure mode. At a forming temperature of 160 °C, fibre pull out was also observed in addition to fibre fracture. A study of forming modes exhibited at various forming temperatures illustrated that there is an optimal temperature window for forming. A key finding from this work is that the matrix shear deformation can aid in superior forming for this class of material systems.