ASSESSING THE ECONOMIC AND ENVIRONMENTAL POTENTIAL OF OUT OF - PDF document

18 TH INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS ASSESSING THE ECONOMIC AND ENVIRONMENTAL POTENTIAL OF OUT OF AUTOCLAVE PROCESSING R.A. Witik 1 , F. Gaille 2 , R. Teuscher 1 , H. Ringwald 3 V. Michaud 1 , Jan-Anders Månson 1 1 Laboratoire de Technologie des Composites et Polymères (LTC), Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland. 2 EADS Deutschland, Innovation Works, Dept LG_CT, D-81663 Munich, Germany. 3 Institute of Aircraft Design, Pfaffenwaldring 31, 70569, Stuttgart. ( robert.witik@epfl.ch ) Keywords : Life cycle assessment, cost modelling, out of autoclave, resin infusion 1 Introduction 2 Approach and methods The rapid growth of the aviation industry A case study approach is applied where coupled with rising fuel costs and concerns over the production costs are estimated using technical cost environment are keeping airframe manufacturers modelling (TCM) and related environmental impacts under pressure to improve aircraft efficiency. are quantified with life cycle assessment (LCA). A Lighter airframe structures offer a direct means of 400 x 400 x 4 mm carbon fibre reinforced panel was raising aircraft fuel efficiency thus reducing chosen as a functional unit to be produced with the emissions and lowering operating costs. However, as following 5 material/curing scenarios: aircraft structures also account for a large proportion of their cost, it is imperative that focus remains on Scenario 1 (Auto PP) , Autoclave processing with keeping manufacturing costs low. unidirectional (UD) carbon fibre (CF) prepreg. The use of composite materials has steadily Scenario 2 (Therm PP) , Thermal oven curing with increased in recent years in an effort to achieve a CF OOA prepreg system. greater weight savings in aircraft. Until recently the standard method for curing composites for primary Scenario 3 (Micro PP) , Microwave oven curing aircraft structures has been the autoclave. Heat and with a CF OOA prepreg system. pressure are applied to vacuum bagged prepreg laminates enabling high fibre volume fraction and Scenario 4 (Therm inf) , Thermal oven curing with low void content components to be produced. liquid resin infused (LRI) CF non-crimp fabric However, the use of autoclaves is also accompanied (NCF). by apparent high costs, which stem from high acquisition and operating costs. The reduction of Scenario 5 (Micro inf), Microwave oven curing these operating costs is a priority for airframe liquid resin infused (LRI) CF non-crimp fabric manufacturers, thus stimulating the recent interest in (NCF). out of autoclave (OOA) processing. The ovens and autoclave chosen for the study were of comparable volume (0.79 m 3 for the thermal The primary focus of this work is to quantify oven and autoclave, 0.65 m 3 for the microwave). the economic and environmental differences between autoclave curing and other selected OOA processes through a comparison that assumes 2.1 Cost modelling appropriately sized ovens and autoclaves. Cost modelling is carried out using a technical Key parameters affecting costs are identified along cost model developed at EPFL which is based upon with environmentally dominant stages of the an activity based costing (ABC) approach [1]. A production process is defined which contains all the manufacturing processes. relevant processes equipment and labour to produce a specific component. The process is then segmented

into discrete quantifiable activities and a cost Inventory analysis determines the inputs and estimate is prepared for each activity from input outputs of the system related to raw materials, waste parameters such as labour requirements and costs flows and emissions. (direct and indirect), cycle times, materials costs, Impact assessment translates the contributions of equipment costs, production volumes, energy use, the emissions, waste and resources determined in the scrap, reject rates and overheads. Costs for each inventory analysis into potential environmental activity are then combined in order to give a total impacts, cost for the production process. Plant installation and maintenance costs can also be included along Interpretation where the results from the impact with depreciation periods. Dedicated and utilisation assessment are summarised, conclusions are drawn based amortisation scenarios are also possible where and recommendations made against the original equipment or production cell costs can be allocated study goals. to a single product or to multiple products. Final part costs can be obtained as a function of volume 2.3 Assumptions and data together with a segmentation of total cost which identifies the relative contribution of each A typical LCA study would consider all phases production parameter. Input data are typically of a component’s life cycle (raw materials, obtained from industrial sources, commercial manufacture, use, and end of life). In this study only estimates for materials and equipment, and the first two phases are considered (materials and laboratory based tests. manufacture) as we assume only small weight variations based upon final geometry. Therefore, the remaining life cycle phases (use and end of life) are 2.2 Life cycle assessment assumed to be identical. Production of the raw LCA is a structured internationally materials such as carbon fibres, epoxy resin and standardised methodological framework used for consumables are considered as well as their estimating and assessing environmental impacts transportation from their initial production site to the attributed to the lifecycle of a product or service [2]. location of panel. Intermediate production processes The methodology considers a product’s full lifecycle such as conversion of carbon fibre to prepreg and from the extraction of raw materials to manufacture, carbon fibre to NCF have also been included. Life use and finally disposal. Consideration of the cycle inventory (LCI) data was primarily sourced complete life cycle enables the full impact of a from the Ecoinvent database for [3]. Inventory data product to be established together with the relative for carbon fibre production is not present in this contributions from each life cycle phase. The database and was sourced from literature [4]. All approach therefore helps to avoid impact shifting transportation was assumed to be via truck, total where environmental burdens are decreased in one distances covered by materials were 1500 km and area, perhaps during process improvement, only to 2500 km for the infusion materials and prepregs be increased in another. LCA is therefore a very respectively. The materials used in the comparison useful decision support tool, which can complement were MTM 44-1 for the pre-preg and Saertex 540 other methods, such as cost evaluation, to support gsm NCF combined with RTM 6 for the infusion. the development of sustainable manufacturing practices. The LCA framework consists of the The panel production process assumes that an following four stages: automated cutting machine with a cost of 110 k€ is used to cut the plies required for each scenario (8 for Goal Scope and Definition describes the purpose of NCF, 14 for PP) as well as the associated the study, the level of detail and also the boundaries consumable materials. A cutting speed of 0.5 m/s of the product system to be studied. A functional was assumed and a 60s change over time was unit is defined to which all impacts are allocated. included for each material which required cutting. Compiling of cut materials into kits took a further 5 mins. A 20% cut waste factor was assumed for all sheet materials and disposal assumed transportation