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The problem posed by the company EFD Induction deals with the process of induction tempering.Tempering is part of the heat treatment for workpieces made of steel. During the hardening of thesteel, the phase martensite has formed, which has high hardness but is very brittle. In order to improvethe properties of the workpiece, tempering is performed, where the part is heated up again to a denedtemperature. During this additional heating, some of the internal stresses in the martensitic phase arereleased. Regarding the microstructure of the steel, carbides are formed during the heating that lead toa removement of the excess hardness and an overall improvement of the toughness of the steel.Therefore, tempering results in an increase of ductility at the cost of a reduction of hardness. Basedon the desired properties of the nal product, the tempering process needs to be controlled to achievethe required properties. The parameters to be controlled are the temperature and the heating time.One way of tempering is to use a furnace, where the parts are heated at constant temperature for aspecied time duration. The usual heating times are in the range of one hour. On the other hand, thetempering can be done using inductive heating. The advantage of induction tempering is that the heatis generated directly in the part. As a consequence, the heating times are much shorter, usually in therange of 10 to 30 seconds, see Fig. 1, which makes the process very energy ecient.

The aim of the current study is to demonstrate the effect of inter-ply delamination on stiffness degradation of multi-ply woven composites. Such a demonstration becomes possible due to new technique of modelling textile laminates. It is based on set of boundary value problems for unit cell of a single ply, where boundary conditions imitate interaction with the other plies. Once these problems are solved, local stress distribution and stiffness of the laminate are determined analytically as function of number of the plies and local stress/strain fields obtained in these problems. Hence, it opens the road for an efficient modelling of delamination, which is described as gradual reduction of plies in the laminate.

The paper presents an overview of the multi-level modelling of textile composites in the ITOOL project, focusing on the models of textile reinforcements, which serve as a basis for micromechanical models of textile composites on the unit cell level. The modelling is performed using finite element analysis (FEA) or approximate methods (method of inclusions), which provide local stiffness and damage information to FEA of composite part on the macro-level.