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Evaluation of selected properties and surface quality of cured pre-impregnated carbon-fiber fabrics after exposure to sulphuric acid

Kojnoková Tatiana, Nový František, Markovičová Lenka, Harea Evgheni, Harea Evghenii

Production Engineering Archives

2023

Vol. 29, Iss. 1

1--6

This paper deals with changes in selected properties of composite material and surface degradation after exposure to an acidic environment. A carbon fiber-reinforced composite (CFRP) produced from prepregs was tested. The weight change, micro-hardness, and surface degradation of the CFRP composite made of cured pre-impregnated laminates were evaluated in this study. Material consisting of a DT121R epoxy resin matrix with high reactivity and high viscosity, with two reinforcing carbon fabrics layers, is characterized by a low value of tensile strength. Evaluation of changes in the material properties was performed before and after exposure to specific environmental conditions, which are achieved by using a chemical solution of 15% H2SO4 at various temperatures. Subsequently, the effect of 15% H2SO4 at various temperatures on the material properties was monitored. The specimens were immersed in the solution for up to 3 and 6 weeks at the temperatures of 23°C, 40°C, and 60°C. It was found out, that the degradation of the composite material is conditioned by the aging of the epoxy resin (matrix). Carbon fibers (reinforcement) are relatively stable. The weight change, micro-hardness, and surface quality depend on the time of exposure to acidic solution and temperature. The micro-hardness tests show a significant influence on exposure time. The biggest changes in weight change and surface quality of the CFRP composite were observed after exposure at the temperature of 60°C.

An impact of engine downsizing on change of engine weight

Sroka Z. J., Cieślak M.

Journal of KONES

2015

Vol. 22, No. 2

213--219

One of the trends for development of internal combustion engine is downsizing, which in its final form leads to reduction of fuel consumption and limitation of carbon dioxide concentration in the exhaust gases. The obvious effect of reducing the volume of a cylinder is to reduce the dimensions of the various components, e.g. piston with rings and pin, connecting rod, crankshaft, engine block etc. Changes of geometric dimensions also affect the change in mass of each element and consequently − the whole engine. Expected weight reduction will be a benefit in considering downsizing techniques as another significant development trend in automotive applications associated with a reduction in the weight of the complete vehicle – called “light weight vehicle”. The paper discusses the various forms of downsizing (by stroke, by diameter and mix) and their impacts on the changes in engine mass. The engine Subaru Flat 4, constructed with standard components in terms of design and materials was tested by virtual recognition in mass changes. Original drawings of components and sets have been simplified by for example does not account for chamfers and chops. When calculating also omitted the weight of typical accessories (e.g. fuel lines or electronic components), assuming that each considered option has the same equipment. The highest change in the weight of minus 7.27 % relative to the standard engine was done with downsizing by diameter and smallest one (-6.09 %) by downsizing mix.