Skip to main content

Data variability and parameter uncertainty in composite shaft structural vibration measurement and numerical model updating

Final Activity Report Summary - UNVICO-2 (Data variability and parameter uncertainty in composite shaft structural vibration measurement and numerical model updating)

The strength to weight ratio of any material is always a major factor in its use. The aviation industry is a good example of this, where aircraft materials need to be as light as possible whilst maintaining a certain degree of strength and durability. However, the reality of this apparently polar ratio is not as simple as it first appears and the consequences of this can have a major impact in the construction of new lightweight composites. This is something that Dr Herman van der Auweraer, Corporate Director for Research and Technology at LMS International, and Dr Marcin Luczak of the UNVICO-2 project are well aware of.

UNVICO-2 is a Marie Curie Intra-European Fellowship dedicated to developing the relevant know-how to better describe the complex nature of composite materials, taking into account variability and uncertainties in test and simulation models, and deriving robust design approaches. UNVICO-2 is a timely project as presently lightweight composite materials are being integrated into many more fields. Traditionally, composites were constrained by high cost and production practicality to high-tech industries, such as transport, aviation and aerospace.

However, with renewed interest in lowering energy consumption offer potential savings in maintenance. For composites to be truly utilised on a mass level, research into them and the systems that form them is imperative and, in addition, the numerous aspects of the strength / durability to weight ratio need to be addressed. The main positive implication for reducing the weight is that movement needs energy, so the less something weighs the less energy it needs. Weight is directly related to energy consumption, and that's where very large interest comes from for using lightweight materials.

Of course, the challenge therefore is to get the materials strong enough to ensure that if you make lighter materials then they still meet all the performance criteria that you require. That's where composites come in. The first step to achieving these performance criteria is in the design and formation of the material. Composite materials offer great flexibility at this stage; as well as being able to be crafted from potentially many different materials, they allow the maker to have a great influence on their internal structure.

In essence, composite materials allow you to design the characteristics of your structure. UNVICO-2 was focused on two particular types of composite materials because they are representative of what is in widespread use in industry. Concerning the aerospace and aircraft industry carbon-fibre plastics were accounted, and wind-turbine industry - which was the other area of the investigation - was glass-fibre reinforced plastics. The main goal of these multidisciplinary projects is to investigate the dynamic properties of fibre reinforced composite structure. Non-destructive experimental and numerical simulation methods were applied.

The test results were used in two ways: for the identification of the mechanical properties of the structure and for non- deterministic updating the finite element model according to range of experimental models obtained from test. In the experimental part, the different test configurations were taken into account. The sources of the test data variability's were the excitation and measurement technique applied for investigated object. The former was performed by means of the random and harmonic, single and multi-point excitation while the latter was contact and non-contact acceleration and velocity measurement. Non-deterministic model updating and verification and validation included uncertainties of its parameters by means of interval and stochastic methods. An optimisation technique for test (sensor number and location) was applied. A number of variable test modal models were statistically assessed to investigate impact of variability source onto modal model parameters.