SELECTION OF CFRP CURING TECHNOLOGIES FROM ENERGETIC POINT OF VIEW

Kurzfassung

Fibre reinforced composite is an innovative material which became irreplaceable in the aeronautic branch. Several primary and secondary parts of modern aircraft and helicopter systems are manufactured of thermosetting or thermoplastic material reinforced by carbon or glass fibres. Due to an enormous number of composite parts, several material combinations and manufacturing processes are established nowadays. Polymerization (curing) of matrix material is the essential step of each manufacturing process and is required as soon as thermosetting resins are treated. The most common curing techniques are based on convective energy transport in an oven or an autoclave; or on conduction from an electrically heated solid or a fluid. Besides these two options, several innovative techniques were developed and partly established in the past – such as inductive, infrared or microwave heating – which are based on energy transport by electromagnetic fields. The decision in favour or against certain curing technique is mostly made on basis of manufacturers experience, customer request, available equipment or financial resources. This paper is intended as a help during the decision-making process by introduction of an additional criterion – the energetic impact of a curing technology and its compatibility with parts to be manufactured. In the first step the aimed part is described by a set of quantifiable parameters: e.g. size, complexity, reinforcing material, manufacturing process etc. Let be supposed, that convective heating is applicable limitless (suitable to heat up and cure all composite parts notwithstanding its parameters mentioned above) (BILD. 1). However, due to physical or parameter-dependent constraints (thermal mass, air flow velocity or temperature) the heat flow is mostly limited. Therefore such crucial values as process time or energy consumption are somehow limited as well. In the second step it is assumed, there are regions (set of parameters) where the use of non-convective heating techniques and energy transport mechanisms is more reasonable from the energetic point of view. That means higher heat flows can be achieved, leading to shorter process time and lower overall energy consumption. This idea is depictured below (BILD. 2). This paper shows how the most reasonable curing technique can be selected for a representative part based on its quantifiable parameters and the database developed at the German Aerospace Centre in Braunschweig. The database contains energetic properties of several heating technologies (microwave and fluid) and evaluates their applicability with respect to part parameters. The impact of this approach will be shown and evaluated in terms of achievable energy savings.