Materials and surfaces team

Development of polymer materials and composite structures

The poly­mer and com­pos­ite mate­ri­als devel­op­ment activ­i­ty has been strength­ened in recent years by the acqui­si­tion of large-scale exper­i­men­tal resources (6-axis robot with three effec­tors: two ded­i­cat­ed to sewing and one ded­i­cat­ed to cut­ting dry pre­forms, means of pro­cess­ing com­pos­ites by injec­tion or infu­sion, tem­per­a­ture-con­trolled press, twin-screw extrud­er, elec­tro­spin­ning device, etc.).

These means make it pos­si­ble to inte­grate the effects of process­es on the mechan­i­cal and dam­age behav­iour of com­pos­ites, the devel­op­ment of sewn woven com­pos­ite mate­ri­als, nano-rein­forced poly­mers, or com­pos­ites with a nano-filled ther­mo­plas­tic matrix.

These means are used to respond to com­plex sci­en­tif­ic issues, such as under­stand­ing the mech­a­nisms gov­ern­ing the func­tion­al­i­sa­tion of poly­mer and com­pos­ite mate­ri­als (improve­ment of elec­tri­cal and ther­mal con­duc­tiv­i­ty) or the devel­op­ment of core-instru­ment­ed materials.

Mechanical behaviour and durability: multiphysical and environmental coupling

Work on the microstruc­ture-dura­bil­i­ty inter­ac­tions of mate­ri­als focus­es on three fam­i­lies of materials :

• For the met­al alloys, the aim is to under­stand the dam­age mech­a­nisms on a scale includ­ing crys­tal defects of dif­fer­ent dimen­sions (point, dis­lo­ca­tions, grain bound­aries, pre­cip­i­tates…), their evolution/movement over time and to exam­ine the effects asso­ci­at­ed with the dif­fu­sion or seg­re­ga­tion of chem­i­cal species, gap gen­er­a­tion, growth of inter­metallics, diffusion/plasticity/damage inter­ac­tions, effects of the microstruc­ture on dif­fu­sion kinet­ics… This work uses mul­ti-instru­men­ta­tion tech­niques and in-situ tests.
• In the case of nano-rein­forced poly­mers, the research effort con­cerns the devel­op­ment of exper­i­men­tal tech­niques at the appro­pri­ate scales to under­stand the mech­a­nisms behind the effect of rein­force­ment size on the macro­scop­ic prop­er­ties of the com­pos­ite. The team’s exper­tise in the devel­op­ment of nano-rein­forced com­pos­ites with con­trolled rein­force­ment size and vol­ume (or sur­face) frac­tion is used to address the prob­lems of size effect. To con­tribute to the under­stand­ing of these phe­nom­e­na and to quan­ti­fy them, an approach based on mol­e­c­u­lar sim­u­la­tion is proposed.
• Con­cern­ing com­pos­ite mate­ri­als, in addi­tion to exper­tise on under­stand­ing the dam­age mech­a­nisms in 3D-rein­forced com­pos­ites, work is increas­ing­ly ori­ent­ed towards the study of dam­age and ruin mech­a­nisms of ceram­ic matrix and 3D-rein­forced com­pos­ites. The study of these mate­ri­als must be mul­ti-phys­i­cal and it is in this sense that they are stud­ied in this line of research.

Contact mechanics and tribology

This theme con­cerns the study of dry or lubri­cat­ed fric­tion and wear mech­a­nisms. The aim is to under­stand the con­tri­bu­tion of under­lay­ing microstruc­tures, sur­face rough­ness, adhe­sion phe­nom­e­na and physi­co-chem­i­cal inter­ac­tions in rough con­tact mechanics.

This high­ly exper­i­men­tal work is com­ple­ment­ed by mod­el­ling approach­es to pre­dict the tri­bo­log­i­cal behav­iour of sur­faces or the use of mod­el sur­faces as tools for under­stand­ing the ele­men­tary phe­nom­e­na involved  in tri­bo­log­i­cal process­es. The team is also inter­est­ed in the char­ac­ter­i­sa­tion of tri­bo­log­i­cal behav­iour at the nano­met­ric scale using oscil­lat­ing contacts.

This fun­da­men­tal work aims at under­stand­ing the links between fric­tion, chem­istry and sur­face ener­gy. The sec­ond theme con­cerns the integri­ty of sur­faces sub­ject­ed to mechan­i­cal stress. The aim here is to increase the dura­bil­i­ty of mechan­i­cal sys­tems through a bet­ter under­stand­ing of the phe­nom­e­na involved in sur­face degradation.

The ulti­mate aim of this work is to devel­op a method­ol­o­gy lead­ing to rec­om­men­da­tions in terms of choice of mate­ri­als, sur­face treat­ment process­es and rough­ness in order to reduce fric­tion coef­fi­cients and improve the mechan­i­cal and wear resis­tance of materials.