WRAPPINGA technology used to make cylindrical and conical elements by winding and orienting multi-axial unidirectional fibers (UD) and fabric backed with prepreg reinforcement onto a rigid male mould known as a spindle.
At the manual lay-up stage using wrapping technology, perfectly debulked layers on the moulds during layering are achieved by a press or rolling table which eliminates any air trapped between the layers. The table can be heated to facilitate adherence.
The different layers of prepreg material with the characteristics specified for the part to be made, such as the type of fiber, percentage of resin, fiber basis weight and orientation, are cut to the required size and shape by a CNC plotter. The different layers of prepreg are applied by wrapping onto the mould in a specific order (PLY BOOK), according to the plans drawn up to achieve the necessary mechanical requisites.
Thickness is therefore built up by applying the different layers one on top of the other to a plan designed specially for the use the part will be put to. At the end of the layering process the prepregs are pushed against the mould by winding suitably stretched shrink bands produced and customized to our specifications to apply pressure of 6-8 bar during the cure or polimerization cycle. When required by the production cycle, this pressure is augmented by that inside the autoclave.
Wrapping technology combined with autoclave processing provides a number of advantages over other technologies that have medium- high production rates but are less effective, and the system is used for numerous specialist applications (e.g. rollers for different industrial uses, such as printing, paper making and fabrics).
Mechanical featuresThe combination of wrapping and autoclave technologies ensure better mechanical properties than others. Static and dynamic strength and high rigidity are excellent due to the use of prepregs that control uniform distribution of resins and fibers, the almost total or complete elimination of trapped air, and optimum debulking, which are certainly a better solution than resin infusion technologies and in general technologies that use dry reinforcements impregnated during the production cycle. Given equal mechanical properties of the fibers used, trapped air and badly distributed resin can reduce planned performance by up to 30%.
Section and microscope analysis of a layer with trapped air and accumulations of resin. This can reduce planned performance by even more than 30%.
Section and microscope analysis of a layer without air bubbles and accumulations of resin. Here planned performance is fully achieved.