Analitical Modeling of pressure bag technology

Pressure bag technology is a method of producing composite material elements with either cylindrical or non-cylindrical symmetry. The method can use simple, low cost equipment in comparison to other technologies normally used to produce similar elements: filament winding, wrapping and pultrusion. For some years the authors have conducted a theoretical and experimental study to define an analytical model to describe the technological process. The model aims to interrelate the most important parameters of the process, that is pressure, overlap angle, resin viscosity, and unwinding time. The authors have already proposed a simple model to produce tubular elements from a single winding sheet, and in this paper the results of more precise analysis, obtained introducing the variability of unwinding velocity, are reported. Experimental tests have shown, on tubular elements in GFRP, the degree of validity of the proposed model.