The teaching unit is mandatory.
The teaching unit is taught in English.

 

Outline of teaching unit

3 ECTS / 30 h

 Lectures : 13h30

 Tutorials : 4h30

 Practical works : 8h

Team

Coord. Xavier Colin (xavier.colin@ensam.eu, ENSAM Paris)

Xavier  Colin , ENSAM Paris, Xavier.COLIN@ensam.eu
Lucien Laiarinandrasana, PSL, lucien.laiarinandrasana@mines-paristech.fr
Bruno   Fayolle, ENSAM Paris,  bruno.fayolle@ensam.eu

 

Objectives

To provide to students an overview of the required theoretical concepts for assessing the lifetime of polymeric material engineering components in service conditions.

To show an application of these tools in selected industrial cases.

To tackle the problem of polymer recycling.

Targets

In a first time designed for resisting to static and dynamic loadings, polymer structures are now considered for long term applications (typically for several dozens of years) in more and more aggressive environmental conditions. Designers, familiarized with the domain of mechanical modelling, are more and more fond of kinetic models allowing us to introduce the time factor in the design. Classical approaches, based on the (often unfounded) use of Arrhenius law or other totally empirical models, are less and less compatible with the present requirements of design and one can observe a strong industrial pressure in favour of the development of models for lifetime prediction. The recent activities of the different teachers’ laboratories show well this renewed interest.

Topics

In this course, it not envisaged to make an exhaustive presentation of all types of ageing susceptible to take place in service conditions. This course is aimed to present a general approach for lifetime prediction, applicable to all type of ageing problem of a polymeric material engineering component, and to show the high heuristic value of this approach for selected industrial applications. With this intention the course will be divided into three main parts. In a first part, the most current chemical ageing mechanisms (oxidation, hydrolysis) and their corresponding chemical kinetics will be described. In a second part, a peculiar attention will focus on embrittlement mechanisms at the local and global scales in the absence of mechanical loading. Once the structural embrittlement state well defined, its consequences on the material mechanical properties will be described. The knowledge of the constitutive relations governing the material behaviour will allow the characterization of appropriate concepts of fracture mechanics to be used, in order to assess the residual lifetime of the engineering component. This approach will be applied in selected industrial cases operated in the respective teachers’ laboratories.

Thus, the outline of the course will be :

Oxidation mechanisms, hydrolysis.

Transport properties of molecular species.

Diffusion/reaction coupling.

Stabilization mechanisms.

Chain scissions and crosslinking.

“Hindered” shrinkage of the degraded superficial layer.

Consequences on mechanical properties.

Slow crack growth mechanisms in polymers.

Fracture mechanics for creeping solids: global approach and introduction to local approach.

Embrittlement of PE pipes used for the transport of drinking water.

Creep damage and failure of extruded tubes subjected to internal pressure.

• Chemical ageing mechanisms, kinetic aspects – L 4h30 T 3
• Local and global embrittlement – L 4h30 T 1h30
• Application of fracture mechanics concepts to polymers - L 6h T 3h
• Introduction to polymer recycling - L 1h30
• Selected industrial problems - TP 6h

Examples of Mater projects and PhD theses :

Thermal ageing of epoxy matrix composites (EADS, 2006/09).

Thermal ageing of PBD matrix propellants (SNPE, 2004/07).

Long term properties of hdPE sheaths for pontoon bridges (LCPC, 2007/10).

Thermal ageing of hybrid composite strings used for the reinforcement of electrical wires (EdF, 2007).

Development of models for lifetime prediction for synthetic cables (EdF, 2008/11).

Ageing of PE and Ethylene/propylene copolymers electrical cable insulators in nuclear environment (EdF, 2003/06).

Recycled PET for food packaging: experimental approach and kinetic modelling (2005/08).

Impact of water quality on ageing of innovative products for synthetic material plumbing (CSTB, 2008/11).

Damage and crack growth under creep of extruded polyethylene : local approach – global approach (GdF 2000/03).

Aging effect on creep crack initiation and growth in HDPE (2010/09).

• Aeronautics and space :
• Civil Engineering :
• Electricity :
• Nuclear :
• Food packaging :
• Fluid transport :

Marking

Personal work : Analysis of scientific papers / experimental or computing work. Two formatted A4 pages + oral presentation (15 min).

Bibliography

• X. Colin, B. Fayolle, L. Audouin, J. Verdu & X. Duteurtre, dans « Vieillissement et durabilité des matériaux », Série Arago 28, édité par G. Pijaudier-Cabot, OFTA, Paris, Chap. 3, p. 65, 2003.
• H.B.H. Hamouda, M. Simoes-Betbeder, F. Grillon, P. Blouet, N. Billon, R. Piques, "Creep damage mechanisms in polyethylene gas pipes", Polymer 42 (2001) 5425-5437.
• H. Ben Hadj Hamouda, L. Laiarinandrasana, R. Piques, "Fracture mechanics global approach concepts applied to creep slow crack growth in a medium density polyethylene (MDPE)", Engineering Fracture Mechanics 74 (2007) 2187-2204.