Zoheir Aboura’s team, ful­ly aware of the envi­ron­men­tal impact that aero­nau­tics has on the plan­et, devel­ops and main­tains part­ner­ships with numer­ous indus­tri­al­ists such as Safran, to meet the tech­no­log­i­cal chal­lenges of the aero­nau­tics, space and defence sec­tors. Com­pos­ite mate­ri­als are popular.

Zoheir Aboura is a uni­ver­si­ty pro­fes­sor. He heads the Mate­ri­als and Sur­faces research team in the UTC-Rober­val lab­o­ra­to­ry (Mechan­i­cal Engi­neer­ing, Acoustics and Mate­ri­als). His work is based, among oth­er things, on the devel­op­ment of knowl­edge on the mechan­i­cal behav­iour of com­pos­ite mate­ri­als. Pro­fes­sor Aboura’s team devel­ops and main­tains part­ner­ships with many indus­tri­al­ists inter­est­ed in the results of his research, par­tic­u­lar­ly in the devel­op­ment of orig­i­nal inves­ti­ga­tion tech­niques for the detec­tion, mon­i­tor­ing and under­stand­ing of dam­age mech­a­nisms, which are very com­plex in the case of com­pos­ite mate­ri­als, par­tic­u­lar­ly with 3D rein­force­ment archi­tec­tures. In par­tic­u­lar, the Safran indus­tri­al group has been seek­ing answers to the tech­no­log­i­cal chal­lenges brought up by the require­ments of aero­nau­tics, space and defence. «The devel­op­ment of new mate­ri­als in the aero­nau­ti­cal sec­tor is based on strong cli­mat­ic chal­lenges. Organ­ic or ceram­ic com­pos­ite mate­ri­als have very high spe­cif­ic prop­er­ties (ratio between intrin­sic prop­er­ty and den­si­ty) and are there­fore becom­ing very com­pet­i­tive. They make it pos­si­ble to light­en struc­tures. This is the key word in aero­nau­tics. This opens the way to ener­gy sav­ings and con­se­quent­ly to a reduc­tion in the impact on the envi­ron­ment,» explains Zoheir Aboura. 

Intelligent materials

Cur­rent research work is geared towards the devel­op­ment of mate­ri­als for the aero­nau­tics, space and auto­mo­tive indus­tries that are both ‘intel­li­gent’ and ‘com­mu­ni­cat­ing’, enabling them to mon­i­tor their state of health con­tin­u­ous­ly. This means that it is pos­si­ble to reduce safe­ty coef­fi­cients (dimen­sion­ing to the min­i­mum) and there­fore poten­tial­ly less weight and there­fore less fuel, less pol­lu­tion, but also more safe­ty. The suc­cess sto­ry of these new mate­ri­als is based on per­for­mance gains and reduc­tions: reduc­tion of pol­lut­ing gas emis­sions, reduc­tion of debris, noise, reduc­tion of engine mass­es and increased effi­cien­cy. «The stakes are enor­mous. At the UTC-Rober­val lab­o­ra­to­ry, a team of six researchers, three PhD stu­dents and three post-docs are work­ing on these sub­jects. Envi­ron­men­tal pro­tec­tion is impor­tant. We have been con­tribut­ing to this for a long time by try­ing to make the struc­tures lighter. When I start­ed, I was already focussed on these issues. Now we are even more alert. Col­lab­o­rat­ing with indus­tri­al­ists who are con­cerned about this is also very impor­tant for us, as it enables us to apply the prod­ucts of our research,» insists Zoheir Abura. 

Engineers in action 

Safran achieved a real tech­no­log­i­cal break­through when it intro­duced 3D-rein­forced com­pos­ite mate­ri­als into its engines, under the impe­tus of Bruno Dambrine, a senior expert at Safran. Thus, under his lead­er­ship, the first work began in 1995–1996, in search of can­di­date mate­ri­als for the pro­duc­tion of fan blades to replace tita­ni­um. UTC was involved very ear­ly on in the ini­tial research to sup­port the indus­tri­al­ist Safran. A decade lat­er and sev­er­al hun­dred thou­sand hours of research, tests and cal­cu­la­tions, the LEAP engine was cer­ti­fied (2016). It was the devel­op­ment of 3D woven rein­force­ment com­pos­ites obtained by RTM (Resin Trans­fer Mould­ing) injec­tion that enabled the cre­ation of a new gen­er­a­tion of blades and fan cowl­ing in the LEAP engine. This has tru­ly rev­o­lu­tion­ary engine design. Lighter and stronger than the met­als and alloys they replace, com­pos­ite mate­ri­als rep­re­sent a major area of progress for the aero­nau­tics industry. 

They are one of the major inno­va­tions of the new LEAP engine, select­ed by Air­bus to pow­er its A320neo, by Boe­ing for its 737- MAX, and by COMAC for its C‑919. The LEAP engine has reduced its weight by 450 kg, is less pol­lut­ing (16% reduc­tion in CO2 emis­sions and 50% reduc­tion in NO) and allows a 15 dB reduc­tion in noise lev­els. Ongo­ing research into new gen­er­a­tions of mate­ri­als (such as ceram­ic matrix com­pos­ites for very high tem­per­a­ture appli­ca­tions) and their intro­duc­tion into engines offers the prospect of addi­tion­al weight sav­ings and effi­cien­cy. «There is still a lot of work for our engi­neers and doc­tors in these areas. Devel­op­ing new mate­ri­als, under­stand­ing their behav­iour, devel­op­ing robust mod­els, inte­grat­ing them into the com­pu­ta­tion­al codes for the most accu­rate dimen­sion­ing (reduc­tion of safe­ty fac­tors, also known as ‘igno­rance fac­tors’, he concludes. 

These are all levers that will help reduce our impact on the envi­ron­ment. We train our engi­neers and doc­tors with this in mind. They will be major play­ers in com­pa­nies in the future and will there­fore have a key role to play in reduc­ing our envi­ron­men­tal foot­print. Glob­al warm­ing affects us all and is there­fore becom­ing everyone’s business.