K. O. Low

The effects of alkali treatment on the interfacial adhesion of bamboo fibres

In the present work, the potential of using bamboo fibres as reinforcement for polyester composites was evaluated. Two types of bamboo fibres were used: untreated and treated with different NaOH concentrations (1, 3, and 5wt%). Mechanical properties of both treated and untreated fibres were investigated. In addition, single-fibre pull-out tests were performed to study the interfacial shear strength of the fibres with the polyester matrix at different embedment length of fibres. Scanning electron microscopy was used to study the surface morphology of the fibres before and after the tests. Results revealed that an untreated fibre has the best strength and stiffness but lowest strain at break. An increase in alkali concentration reduces the strain at failure and ductility of bamboo fibres. However, the strength and stiffness of the fibres were increased. In addition, the interfacial shear strength was improved with longer embedment length and higher NaOH concentration.

Effects of fillers on the fracture behaviour of particulate polyester composites

In the current work, the fracture toughness of sand-particle- and wood-flake-reinforced polyester composites was studied under a linear elastic fracture mechanics approach. The effects of the particulate volume fraction (0–60 vol %) were studied. Scanning electron microscopy was used to observe the damage features on the composite surface. Results showed that sand-particle- and fine-wood-flake-reinforced polymer composites exhibited better results at 40 vol % than at other particulate volume fractions. Meanwhile, coarse-wood-flake-reinforced polymer composites showed higher properties at 30 vol % than at other particulate volume fractions. Observation of the composite surface after tests showed that sand particles have poor interfacial adhesion compared with wood flakes.

Numerical simulation methodology for mode II delamination of quasi-isotropic quasi-homogeneous composite laminates

This work proposed a methodology to obtain the lamina and interface properties using minimal experimental works. Studies were limited to mode II delamination behavior of three quasi-isotropic quasi-homogeneous woven glass/polyester composites. It was found that the fracture toughness of 0//0, 0//45, and 45//45 laminates calculated using experimental calibration method were 0.91 N/m, 0.94 N/m, and 0.51 N/m, respectively. In addition, fiber twisting and shear cusps were observed on the delaminated surfaces of 45°-ply. Subsequently, a methodology was proposed to obtain the lamina properties for the numerical simulation without performing any additional experiment. An approach to account for the shear nonlinearity of the composite laminate due to the existence of 0°-ply was also presented. Finally, it was proposed that for reliable numerical modeling using cohesive zone model, the following parameters were recommended: penalty stiffness = 3 × 106 MPa/mm, interface shear strength = 65 MPa, mesh size = 0.5 mm, and viscosity parameter = 1 × 10−3.

Thickness-dependent non-Fickian moisture absorption in epoxy molding compounds

The objective of this research is to characterize the relationship between the moisture uptake behavior and the thickness in epoxy-based molding compounds (EMCs). Experimental results from the literature were adopted for this purpose. A thickness-dependent moisture uptake model was proposed to describe the moisture uptake behavior. In order to apply the model, a methodology to develop the fictitious Fickian curve was suggested. Subsequently, the relationships between the non-Fickian parameters and the thickness were correlated and compared. Results showed that the apparent diffusivity of the fictitious curve was sensitive to the environmental conditions but not the thickness. In addition, when combining all data, it was found that each normalized non-Fickian parameter could be described by a single equation with respect to the normalized thickness. Based on the thickness-dependent model, the moisture concentration across the thickness was further characterized. In conclusion, the model proposed in this study allows the prediction of moisture uptake behavior at various thicknesses of EMCs. This could greatly reduce the time and cost of extensive experimental works.

Fracture behaviour of glass fibre-reinforced polyester composite

Fracture toughness and critical energy release rate of polyester-reinforced glass fibres were investigated using linear elastic fracture mechanics approach. The effect of fibre volume fraction of chopped strand mat glass fibres in the matrix on the composite properties was considered. Finite-element analysis using FRANC2D/L was adopted for further verification. The results showed a dramatic increase in the values of fracture toughness and critical energy release rate with increasing fibre content. 60% vf of glass fibres enhanced the fracture toughness and critical energy release rate properties of neat polyester by ∼ 22-fold and 1200-fold, respectively. The numerical results showed an agreement with experimental ones.

Impact resistance of short bamboo fibre reinforced polyester concretes

Bamboo fibre is becoming more important as reinforcement in polymer composites owing to its environment sustainability and cost effectiveness. This study examines the performance of bamboo/polyester concretes under impact loading. Specimens at fibre volume fractions of 40 vol.%, 50 vol.% and 60 vol.% and 3 mm, 7 mm and 10 mm fibre lengths were fabricated. Results showed that the optimum impact resistance was attained at 50 vol.%/10 mm, with 16.6 times higher compared to neat polyester. Scanning electron micrographs revealed that the failure mechanisms include matrix cracking, fibre/matrix debonding, fibre pull-out, fibre end damage, fibre splitting and sand particles debonding. In addition, by relating the experimental results to a theoretical model, the damage zone size was found to increase with the fibre length except at 60 vol.%/10 mm, which could be due to fibre–fibre interaction. Results suggest that bamboo fibre is a good candidate to enhance the impact resistance of polyester concrete.