Fraunhofer Institute for Structural Durability and System Reliability LBFFrom injection-molding simulation to component testing: Fraunhofer LBF's Department of Lightweight Structures has designed the "MultiTester", a new type of specimen for internal pressure testing. Using the MultiTester, the entire processing chain can be investigated. This includes the rheological balancing of the component, injection molding, material characterization and component testing. For designing durable lightweight structures with integrated functions, knowledge about system-influencing factors on durability and reliability is indispensable.
Making better use of lightweight potentials
New test specimen for internal pressure: MultiTester
Filling study: Injection mol- ding analysis of the MultiTester
Tested MultiTester (internal pressure)
Challenge
The proportion of plastics in the lightweight sector is rising steadily. At present, components are often dimensioned in line with conventional methods, which, as a general rule, involve safety factors and reduction factors. Although this is a valid method for engineering plastic components, with a view to structural durability and lightweight structures it is not sufficiently close to reality. In addition, possible interactions between different influencing factors are not taken into account. And, estimating the reduction factors leads to an uncertainty, which, in turn, may result in over-dimensioning or under-dimensioning of the component. The potentials these materials can offer with regard to lightweight design are, in many cases, not exploited to the full extent.
Solution
An appropriate method of dimensioning plastic components with a view to structural durability and lightweight structures is experimental simulation. Using this method means taking account of possible interactions between the various influencing factors and looking at the complete system, consisting of
- material,
- manufacturing technique
- geometry,
- environmental influence and
- external loading
in its entirety.
Main features
The MultiTesters is manufactured by injection molding. The MultiTester's modular design allows specific factors which have an impact on the mechanical properties of unreinforced and reinforced plastics to be investigated:
- Fiber orientation,
- Weld line strength,
- Influence of process parameters during injection molding,
- Various types of loading (static, dynamic and cyclic)
- Environmental factors such as temperature, humidity, media and aging.
The MultiTester also enables validation of numerical material models that have been developed on the basis of simple conventional test specimens.