Gilbert D. Sylva (died 13 September 2015) was an American engineer and friction stir welding expert.
Gil Sylva graduated at Illinois Institute of Technology. He started his career by working for 13 years from 1986 to 1999 as an engineer at Martin Marietta Astronautics in Denver, Colorado. At that time, he represented his employer in the first Group Sponsored Project that developed friction stir welding at TWI in Cambridge, UK.  
Then, he worked for about two years from August 1999 to October 2001 as Senior Engineer/Scientist at the Boeing, Delta IV Facility in Decatur, Alabama. In August 2005 he moved as to Spirit AeroSystems, where he worked for more than 5 years until August 2010 as Sr. FSW Engineer MR&D. Starting in 2011, he worked as Sr. Engineer, Materials and Processes for 2 years at Eclipse Aerospace, Inc until 2013.
He died on September 13, 2015, after sustaining a head injury during a fall, from which he was unable to recover.
"Melting a material can actually decrease the strength of the weld," said Gil Sylva, who was part of the Group Sponsored Project at TWI, in which FSW was developed from laboratory curiousity to the first industrial applications.
"In FSW, you’re not adding anything to the metal that is lower in strength. Rotational and downward force plasticize the metal by generating friction heating, forming a joint with a grain structure that is finer than the parent metal, making for a virtually seamless and extremely strong joint."
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