Complex composite structures manufactured using a low-pressure vacuum bag-only (VBO) method are more susceptible to defects than flat laminates because of the presence of complex compaction conditions at corners. This study investigates the contribution of multivariate processing parameters such as bagging techniques, curing profiles, and laminate structures on laminates’ shape conformation. Nine sets of laminates were produced with a concave corner and another nine sets with a convex corner, both with a 45° inclined structure. Three-way analysis of variance (ANOVA) was performed to quantify thickness variation and spring effect of laminated composites. The analysis for concave and convex corners showed that the bagging techniques is the main factor in controlling the laminate thickness for complex shape applications. The modified (single) vacuum-bag-only (MSVB) technique appeared to be superior when compared to other bagging techniques, exhibiting the least coefficients of variation of 0.015 and 0.016 in composites with concave and convex corners, respectively. Curing profiles and their interaction with bagging techniques showed no statistical significance in the contribution toward laminate thickness variation. The spring effect of laminated composites was investigated by calculating the coefficient of determination (R²) relative to that of the mold. The specimens exhibited a good agreement with R² values ranging from 0.9824 to 0.9946, with no major data offset. This study provides guidelines to reduce thickness variations and spring effect in laminated composites with complex shapes by the optimum selection of processing parameters for prepreg processing.

Erosion-corrosion is an ineluctable flow assurance problem confronted in hydrocarbon transportation and production systems. In this work, the effect of sand fines velocity on the erosion-corrosion behavior of AISI 1018 carbon steel long radius 90° elbows was experimentally and numerically investigated for liquid-solid flow conditions. Experiments were effectuated for sand fines of mean diameter 50 µm circulated in a flow loop with three different velocities (0.5, 1 and 2 m/s). To elucidate the erosion-corrosion mechanism and degradation rate, the material loss analysis, multilayer paint modeling (MPM) and microscopic imaging technique were employed, with computational fluid dynamics (CFD) and discrete phase modeling (DPM) also capacitating to evaluate the erosion distribution. It was perceived that increasing slurry velocity significantly changes the particle-wall impaction mechanism, leading to an increase in material degradation in the elbow bottom section up to 2 times in comparison to the low transport velocity. The erosion scars and pits development at the elbows internal surface was found to govern the wear mechanism in the carbon steel and made downstream section susceptible to erosion and corrosion. The material removal mechanisms were ascertained to change from cutting to pitting and plastic deformation with an increase of sand fines transportation velocity from 0.5 m/s to 2 m/s.

Due to environmental concerns, plastic recycling and natural fiber composites have been given more attention lately. In Malaysia, mengkuang leaf fiber (MLF) has been identified as a potential candidate to be used as a reinforcing fiber. The combination of recycled polypropylene (r-PP) and MLF could result in an inexpensive and sustainable composite. However, the mechanical properties of this composite have not been fully studied. The aim of this work was to evaluate tensile, flexural and impact properties of r-PP/MLF composites with and without sodium hydroxide (NaOH) treatment and maleic anhydride-grafted polypropylene (MAPP). The composite consisted of 60 wt.% of r-PP and 40 wt.% of MLF. The composite was compounded by twin-screw extruder and test specimens were fabricated using an injection molding process. Generally, the tensile and flexural properties showed improvements, especially those with MAPP and alkaline treatment, compared to neat r-PP. Improvements in tensile strength and modulus of approximately 28% and 224% were achieved for r-PP/Treated MLF/MAPP composite respectively. However, an adverse effect was observed in the impact strength of the composite, which was expected due to the nature of short fiber employed in this work.

This article investigated the mechanical performance and corrosion behaviour of a diffusion-bonded A5083 aluminium/A36 mild steel dissimilar joint with a Gallium (Ga) interlayer. The bonding parameters were the bonding temperature (525 and 550 °C), holding time (60 and 120 min) and surface roughness (800 and 1200 grit). Property characterisation was achieved using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) analysis, Vickers microhardness tester, Izod impact tester and potentiodynamic polarisation testing. The results revealed that the significance of the bonding parameters was in the order bonding temperature > surface roughness > holding time. Increasing the bonding temperature resulted in an increase in the impact strength and a corresponding reduction in the corrosion rate and microhardness. However, increasing the grit size decreased the microhardness and a corresponding increase in the impact strength and corrosion rate. The impact strength and corrosion rate decreased with the increasing holding time while the microhardness followed a reverse trend. It was also discovered that incorporating the Ga interlayer resulted in a 67.9% improvement in the degradation rate.

Carbon fiber precursor was derived from Polyacrylonitrile (PAN) polymer, pitch based and cellulose rayon. Until now, the best precursor for carbon fibre is PAN polymer. This is because PAN polymer precursor have higher carbon content when subjected to heat treatment process. After spinning process, the PAN fibre will be soaked in a chemical before proceed to heat treatment process. The process is known as post spinning treatment process. In this study, oleic acid and the commercial chemical were applied as post treatment spinning chemical. After post spinning treatment, the fibre will be heat treated in 2 temperature zone represent stabilize and pre-carbonized region. The stabilize region is fixed at 250°C and the pre-carbonized region at 500°C. After heat treatment process, the fibre will be mechanically characterized using the low force single column universal tensile machine. Scanning Electron Microscope (SEM) micrograph was used to determine fibre diameter and surface microstructure. From the study, the tensile strength of PAN fiber post treated with oleic acid was lowered almost 50%. For pre carbonized process, PAN fiber post treated with an oleic acid increase by 73%. This show that oleic acid can be used as post spinning treatment chemical in carbon fibre conversion process.

Thermoplastic polymer such as high density polyethylene (HDPE) can be troublesome to manufacture due to its high viscosity of molten resin. To improve the manufacturability, polymer additive is a preferred method due to its low cost compared to changing the die geometry, process control setting and molecular weight of the resin. However, the influence of the additive to the mechanical and physical properties of HDPE was not fully understood. Therefore, the aim of this paper was to evaluate the effects of fluoropolymer and calcium stearate on melt flow index (MFI) and mechanical properties of HDPE. Twin screw extruder was used for compounding and injection molding was employed to produce the specimens. MFI, tensile and flexural tests were carried out according to their respective ASTM standards. An improvement of 20% in MFI was observed when 0.1% of fluoropolymer was added to HDPE. Adding calcium stearate to the mixture did not make any significant impact to MFI and mechanical properties. Tensile properties of HDPE remained almost the same with and without the additives. However, flexural property of HDPE reduced quite significantly with the additives.