Gerrit Pierreux

Algemene informatie

Kb 109
Prof. dr. ir. Pyl


Multi-scale modelling, Composites, Crushing


Burgerlijke Bouwkunde - VUB-Bruface - Class of 2013


In crushing, the amount of energy absorbed during impact (defined as a rapid transient phenomenon, involving high inertial forces and generally leading to severe damage) plays a critical role in the design of sacrificial elements in the multiple industries. In the automotive industry for example “crashworthiness” is one of the major driving attributes for lightweight vehicle development programs. Crashworthiness is generally defined as the ability of a structure to protect its occupants during an impact. In wind turbine applications, blades are frequently prone to bird and hail impact; in order to maintain their structural integrity and performance, they should show adequate “damage tolerance”. Having high specific properties (relative to the material density), fibre reinforced polymers (FRP) is getting the interest of industry for these type of applications among many others.

Although internationally much research effort has been devoted over the past decades (and is still being spent) to understand and to simulate the behaviour of composite materials and composite structures under crushing, it is a strong belief of many companies that actual, industrially relevant tools for adequately and accurately simulating the outcome of an impact are still in their infancy. The models available in commercial FE-packages, sometimes lack predictive accuracy and often involve non-physical parameters estimated using trial and error or inverse fitting. Crushing in composites is by nature a phenomenon that involves dissipation and degradation mechanisms at various scales. If generally applicable predictive capabilities are the objective, it is of most relevance that the material models allow to obtain a clear view on the (exact) nature and spread of damage. As a result, the present proposal aims at a progress beyond the state of the art, through linking and translating fine scale modelling at the scale of constituents to models which can account for damage onset and growth at the macro- or structural scale.

In the project, the multi-scale framework will be built up, starting with the selection of a micro-scale approach (i.e. at the level of constituents) to account for the dissipation and degradation mechanisms associated with crushing. Based on the individual failure models for each fine scale failure mechanism, scale transitions will be used to allow computations at the structural scale. These scale transitions for laminae undergoing bending will be involve a computational homogenisation strategy towards the average behaviour of solid-like shell elements accounting for geometrical non-linearities in order to represent reinforced laminae. The scale transitions will be kept independent from the material models used at the scale of constituents, which will pave the way to address complex microstructures or complex composite systems with physically-based damage models. After the validation of the whole framework for square tubes composed of an axial reinforcement made of continuous fibres, more complex composite tubes will be analyzed by means of the developed framework. In a last stage, a feasibility study of the integration of the developed methodologies into commercial codes will be investigated.

The expected outcome of this project is a validated physically-based multi-scale strategy to address quasi-static crushing of composite systems, with a quantified level of agreement between the available experimental data and the model prediction, that can subsequently be applied for more complex microstructures.

Design and implementation by aware