The effect of material selection and manufacturing process on the surface finish of carbon fibre composites

Using a design of experiment (DOE) approach, this work investigated the surface finish of as-moulded and painted carbon fibre composite laminates manufactured by two alternative methods, autoclave and a rapid curing process—Quickstep™. The effect of two fibre architectures on the surface finish of unidirectional and 2 × 2 twill laminates combined with a surfacing film was studied using surface profilometry and wave-scan distinctness of image (DOI) techniques. Investigation of the as-moulded surface finish showed that the autoclave cured laminates had lower surface roughness than the Quickstep laminates in terms of arithmetic mean (Ra), maximum peak to valley height (Rt), skewness (Rsk) and kurtosis (Rku). Interaction effects showed that the surfacing film reduced the Rsk and Rku when combined with the unidirectional fibre architecture but increased with the twill material. The autoclave manufactured panels combined with the unidirectional material improved the painted surface finish as identified by the DOI and long-term waviness main effect plots. Surface roughness results could not detect the influence of manufacturing and material variables on the painted surface finish. The painting process caused the microsurface defects to be concealed, resulting in defects of larger structure sizes to remain as observed using the wave-scan DOI technique

Advances in the development of rare earth metal and carboxylate compounds as corrosion inhibitors for steel

Research into non-toxic rare earth metal organic compounds providing an alternative to chromates as corrosion inhibitors was pioneered by research at Monash University almost 20 years ago. Further work at Monash and Deakin universities developed lanthanum 4 hydroxy cinnamate, which proved to be as effective as chromate for steel in chloride solution. Recently, attention has turned to substituting the cinnamate anion with 4-methylbenzoyl propanoate. There has also been the development of other non-toxic compounds with the dual functionality of inhibitor and biocide, with a view to combating microbiologically influenced corrosion. A compound 2-methylimidazolinium 4-hydroxycinnamate was synthesised, with corrosion studies showing it to be an effective inhibitor for steel. In this paper, an overview is provided of the recent research in this new area of corrosion inhibition at Deakin and Monash Universities, the mechanisms through which these protective films are thought to form and provide corrosion protection are also discussed

Tailoring the Chain Packing in Ultrathin Polyelectrolyte Films Formed by Sequential Adsorption: Nanoscale Probing by Positron Annihilation Spectroscopy

Depth profiling experiments by positron annihilation spectroscopy have been used to investigate the free volume element size and concentration in films assembled using the layer-by-layer (LbL) adsorption method. Films prepared from strong polyelectrolytes, weak polyelectrolytes, hydrogen-bonding polymers, and blended polyelectrolyte multilayers have different chain packing that is reflected in the free volume characteristics. The influence of various parameters on free volume, such as number of bilayers, salt concentration, solution pH, and molecular weight, has been systematically studied. The free volume cavity diameters vary from 4 to 6 Å, and the free volume concentrations vary from (1.1–4.3) × 10²⁰ cm^–3, depending on the choice of assembly polymers and conditions. Films assembled from strong polyelectrolytes have fewer free volume cavities with a larger average size than films prepared from weak polyelectrolytes. Blending the weak polyanion poly­(acrylic acid), PAA, with the strong polyanion poly­(styrene sulfonate), PSS, to layer alternately with the polycation poly­(allyamine hydrochloride), PAH, is shown to be a viable method to achieve intermediate free volume characteristics in these LbL films. An increase in salt concentration of the adsorption solutions for films prepared from strong polyelectrolytes makes these films tend toward weaker polyelectrolyte free volume characteristics. Hydrogen-bonded layered films show larger free volume element size and concentration than do their electrostatically bonded counterparts, while reducing the molecular weight of these hydrogen-bonded polymers results in slightly reduced free volume size and concentration. A study of the effect of solution pH on films prepared from weak polyelectrolytes shows that when both polyelectrolytes are substantially charged in solution (assembly pH = 7.5), the chains pack similarly to strong polyelectrolytes (i.e., lower free volume concentration), but with smaller average cavity sizes. These results give, for the first time, a clear indication of how the free volume profile develops in LbL thin films, offering numerous methods to tailor the Ångström-scale free volume properties by judicious selection of the assembly polymers and conditions. These findings can be potentially exploited to tailor the properties of thin polymer films for applications spanning membranes, sensing, and drug delivery