Production of GFRP air pipes using lightweight gypsum patterns removable in a recyclable way

Nowadays every industrial company needs to decrease the materials waste and increase their recyclability, especially in the composite manufacturing field, where the environmental effects are a relevant aspect. In order to produce high quality composite pipes via autoclave with high flexibility in terms of producible shapes, an interesting solution is the use of gypsum as material for the patterns. In this case, the easiest and fastest procedure to remove the gypsum patterns would through its immersion in water involving large amount of wasted gypsum to dumps. Therefore, this paper aims to make more eco-friendly the production of GFRP air pipes by reducing the raw material and to make in the same time faster and more recyclable the removing process of the gypsum patterns. For this purpose, a vegetable protein with foaming power was added to the gypsum mixture in order to produce lighter gypsum and reduce the raw material. In addition, to remove the gypsum patterns also allowing their recyclability, an innovative vibration technique was proposed. In this technique, a vibration load was applied to the gypsum pattern in order to destroy it without damage the GFRP sample. The gypsum pieces are then available for the recycling, decreasing the amount of wasted gypsum to dumps. The feasibility of the process was investigated and the mechanical properties in terms of flexural and compression strength, before and after a recycle for both the conventional gypsum and the foamed ones, were studied.