Basic guidelines for choosing autoclave curing tool material to make composite parts. CFRP vs INVAR36

Abstract

The correct selection of a curing tool, to make Carbon Fiber composite (CFRP) parts, is key to the success of a project. The trend in the Aeronautical industry is the reduction of costs and structural weights. The required curing tools are getting bigger and complex, which is a challenge for the manufacturers of the parts and tools. The high temperature autoclave curing cycles present a serious drawback to the use of conventional tooling materials, which has forced the development of molds made of materials with a low coefficient of thermal expansion to solve the problems arising from the different behavior of parts and molds during cycles and to ensure the tight geometric tolerances required. INVAR 36 and CFRP material with high performance resin have become standards for the manufacture of molds. The objective of the study is the comparison of properties and performance of this type of materials, as well as an estimation of the costs associated with each one, with the aim of helping the selection of the most appropriate for use in an industrial environment of high production rates. The method used consisted in the compilation of the technical characteristics of the materials that affect the performance of the tools, as well as the results of research projects and experience of the behavior in service. In addition, a simulation of costs associated with the development, manufacture, putting into production and maintenance of the molds was carried out. The results allow to evaluate qualitatively the performance of the molds manufactured with these materials as well as to have basic guidelines for the correct evaluation of them.