The Center for Lightweight-Production-Technology (ZLP) aligns within the programmatic research approach of the German Aerospace Center (DLR) with its core disciplines in aeronautics, space, transport and energy. ZLP seeks to enhance aeronautical research by taking production technology into account, which complements the interdisciplinary approach of DLR in research on the air transport system. Thus, fundamental assessment capabilities beginning with materials up to maintenance, repair, overhaul (MRO) will be researched. ZLP’s concept was designed by the DLR-Institutes Institute of Composite Structures and Adaptive systems, Institute of Structures and Design and the Institute of Robotics and Mechatronics; it covers the complete process chain for composite parts. ZLP is building upon the institutes’ research portfolio consisting of materials research, design, technology and assembly. ZLP bridges the gap to industrial application in terms of technology and manufacturing.
ZLP North in the building CFK-Nord at the site Stade
Research for aeronautics, wind energy and automotive industry
The ZLP in Stade addresses aeronautics, automotive industry as well as wind energy. The research portfolio includes the following topics:
- Combined automated fibre placement (AFP) with automated tape laying (ATL),
- Fully automated resin transfer moulding (RTM) processes for high volume parts,
- Online quality assurance in autoclave processes,
- Processing of thermosets and prepregs,
- Tooling technology, and
- Process simulation.
The Department "Composite Process Technology" of the Institute of Composite Structures and Adaptive Systems is working on three main topics at the site Stade.
Combining automated fiber placement (AFP) and automated tape laying (ATL) on a flexible production plant by means of simultaneous working, robot based layup units
Today’s production of large scale parts out of CFRP is dominated by the use of prepreg material. Machining development has reached a high level of maturity for this purpose, but the existing single layup systems cannot meet the demand of high productivity needed for aircraft production in high quantities. Due to this, a multi layup approach is done within the ZLP to demonstrate high productivity on an industrial scale. The project covers the development of production processes for large scale, highly integrated components made of composite materials in automated fiber layup technologies. In this regard, a research facility is developed on the basis of several coordinated, robot based layup units that can be moved on a rail system. The rail system is split into a manufacturing loop, that allows a circumferential movement around a double-sided molding tool and a connected maintenance loop. In addition, the robot units are equipped with fiber placement or tape laying heads that can be used simultaneously and enables a high flexibility of the manufacturing process. The aim of the project is the development of a production technology that allows a lay up rate of more than 150 kilograms per hour of prepreg material.
Online quality assurance in autoclave processes
Autoclaves are today and in the longer term an integral part of the chain of production of CFRP components. Through the processes taking place in the autoclave, the system influences the material properties and component geometry. Therefore, procedures are to be designed with respect to the parameter measurement, simulation and presentation of heat transfer processes. One aim of the project is the recording of the exact temperature distribution on the component in order to minimise heating and holding times by new criteria for the autoclave controls. Hence, a procedure for quality-assured production of large structures of carbon fibre will be developed. Another aim is the use of a simulation method to obtain a process prediction, with which thermal inertia could be observed beforehand in order to optimise the cycle time. In a further step this information could be used to reduce the required heating and holding phases for homogeneous heating of the component by systematic manipulation of the hot air flow inside the autoclave. An additional option is the integration of alternative heating systems to critical areas of the component, specifically and locally limited to heat and thus achieves the homogenisation of the temperature field more quickly. A quality-assured production in the autoclave is based on a fundamental understanding of the processes in the autoclave. Hence, the research platform of the autoclave is equipped with extensive sensing systems. These data bases provide, which models are to be built that allow an active intervention in the autoclave process. This happens within a simulation of flow, heat transfer processes and the representation of the polymer reaction. The intended purpose is the virtual autoclave. To gain a fundamental understanding of industrial processes an industrial scale was considered by the size of the autoclave which was chosen to have an inner diameter of 5.8 metres and a loading length of 20 metres. The overall objective is the most cost-optimised production of high quality large components with small production variations. This should be obtained by using a thermal and pressure management for time optimisation and quality assurance during the process. A representation of the technology on an industrial scale is necessary, because a lot of effects can not be simulated in the laboratory. Therefore, the research facility has a dimension that allows for the manufacturing of aircraft fuselage components of short range aircraft in its entirety.
Fully automated resin transfer moulding (RTM) processes for high volume parts
Due to their cost effectiveness and good material properties, epoxy resins are used for most high performance composite parts. But those parts have not yet conquered the mass market, as no production technology appears capable in delivering high quantities of parts. This is mainly driven by a still high degree of manual labor in today’s production technology. To introduce composite components in high quantities to the market, process technology has to be created first. Short cycle times, automated handling, material development are in the focus of the current demand. Within the project’s approach the fundamental engineering is done for the development of a production facility with a productivity of 100,000 complex composite parts per annum. Therefore a multi-functional production chain is built, which has the potential to simulate practical application in the fields of automation by considering the full scale of a component. To achieve this goal in productivity resin transfer moulding technology offers the best outcomes in regards to automation and reliability. The ZLP in Stade seeks to demonstrate a complete process chain in RTM technology to provide a fundamental understanding of the design of industrial processes. To increase the degree of the technology’s maturity ZLP focuses on:
- The fully automated production chain for complex composite parts,
- The reduction of manufacturing costs through automation, and
- The reduction of process times.
Due to the demand of flexibility of the process chain the following different component classes are in the scope of research:
- 3D-scale components with complex partial structures, and
- Curved, profiled frames.
In both the aeronautic and automotive industries an application is provided.