Reaching greater depths with 3D printing

Syntactic foam is a strong and buoyant material commonly used in the manufacturing of submarines. Now, a team of researchers have developed a method of 3D printing components of syntactic foam that could take submarines to greater depths. Nikhil Gupta, Associate Professor of Mechanical and Aerospace Engineering at New York University’s Tandon School of Engineering, joins Hari Sreenivasan to discuss this innovation.

TRANSCRIPT

SYNTACTIC FOAM IS A STRONG AND BUOYANT MATERIAL COMMONLY USED IN THE MANUFACTURING OF SUBMARINES.

NOW, A TEAM OF RESEARCHERS HAVE DEVELOPED A METHOD OF 3-D PRINTING COMPONENTS OF SYNTACTIC FOAM THAT COULD TAKE SUBMARINES TO GREATER DEPTHS.

NIKHIL GUPTA, ASSOCIATE PROFESSOR OF MECHANICAL AND AEROSPACE ENGINEERING AT NEW YORK UNIVERSITY'S TANDON SCHOOL OF ENGINEERING JOINS US TO DISCUSS THIS INNOVATION.

FIRST OF ALL, WHAT IS SYNTACTIC FOAM?

WHAT MAKES IT DIFFERENT THAN THE FOAM THAT I HAVE COMING OUT OF SOAP SUDS AT HOME?

YEAH.

SO THE COMMON FORM THAT YOU ARE FAMILIAR WITH, IT HAS GAS BUBBLES INSIDE.

BUT IN THIS SYNTACTIC FOAM, WHAT WE DO IS WE PUT HOLLOW GLASS PARTICLES.

SO YOU CAN IMAGINE VERY TINY PING PONG BALLS WITH VERY THIN SHELL BUT A LOT OF AIR INSIDE.

SO THEY ARE VERY GOOD IN COMPRESSION, AND, UNDERWATER, ALL THE TIME THE COMPRESSION IS THE TYPE OF PRESSURE WHICH IS APPLIED ON A MATERIAL.

SO THEY WORK VERY WELL UNDERWATER CONDITIONS.

SO THEY'RE -- THIS KIND OF -- THE IMPROVEMENT IS WHAT?

IS IT IN BUOYANCY?

IS IT IN STRENGTH?

SO, IN THESE CASES, WHEN THE SUBMARINE IS DESIGNED TO GO FOR 4,000 METERS OR MORE, THE PRESSURE IS TREMENDOUS, AND WHAT WE HAVE SEEN PREVIOUSLY IS THAT, WHEN MULTIPLE SECTIONS ARE JOINED FOR MATERIALS, THE JOINT ITSELF IS THE WEAK PART.

EITHER THE JOINT FAILS, OR IF THE JOINT IS TOO STRONG, THEN THE MATERIAL RIGHT NEXT TO THE JOINT FAILS.

SO NOW THE PREFERENCE IS TO 3-D PRINT THESE IN ONE SECTION, AND WHEN WE TRIED TO DESIGN MATERIAL FOR THESE SUBMARINES, THERE'S NOT ONE PROPERTY THAT WE ARE ALWAYS LOOKING FOR.

WE ARE NOT LOOKING FOR THE LIGHTEST MATERIAL.

WE ARE NOT LOOKING FOR THE STRONGEST MATERIAL.

WHAT WE ARE LOOKING FOR IS A COMBINATION OF PROPERTIES THAT GIVES YOU THE RIGHT COMBINATION TO GO AT THAT DEPTH AND ALSO COME BACK.

SO YOU HAVE TWO DIFFERENT SAMPLES HERE.

WHAT'S THE DIFFERENCE BETWEEN THEM?

IN THIS CASE, THIS IS THE MORE TRADITIONAL MATERIAL.

IT'S A HIGH-DENSITY POLYETHYLENE, AND THIS IS THE NEW SYNTACTIC FOAM PART THAT WE HAVE 3-D PRINTED.

THE NEW PART IS 25% LIGHTER, COMPARED TO THE TRADITIONAL DESIGN.

AND THE MAJOR ADVANTAGE IS THAT NOW WE CAN 3-D PRINT THE WHOLE SUBMARINE.

THESE ARE UNMANNED AUTOMATED VEHICLES WHICH ARE 24 INCH OR EVEN 4 OR 5 FOOT LONG.

SO THEY CAN BE 3-D PRINTED IN JUST ONE STRUCTURE.

SO THERE'S NO JOINTS INSIDE, NO AREAS OF WEAKNESS?

SO THAT'S WHAT 3-D PRINTING HAS ALLOWED US TO DO.

AND WHAT ARE THE CORDS OR THE CABLES OR THE WIRES NEXT TO THEM?

SO THESE ARE THE CABLES THAT YOU COMMONLY SEE IN A 3-D PRINTER -- ABS OR PLA-TYPE FILAMENTS.

NOW WE HAVE -- IN OUR LAB, WE CREATED THIS HIGH-DENSITY POLYETHYLENE, WHICH IS AN INDUSTRIAL FILAMENT THAT CAN BE USED FOR PRODUCTION-GRADE PARTS, AND THE THIRD ONE IS SYNTACTIC FOAM FILAMENT, WHICH LOOKS EXACTLY LIKE THE SAME.

AND OUR IDEA IS THAT WE WANTED TO USE THE 3-D PRINTERS WHICH ARE COMMERCIALLY AVAILABLE.

WE DO NOT WANT TO CREATE A NEW 3-D PRINTER BECAUSE NOW YOU HAVE TO CREATE CONFIDENCE IN THE NEW HARDWARE, AND PEOPLE HAVE TO HAVE MORE EXPENSES.

SO THAT'S WHY WE WENT WITH THE ROUTE OF CREATING A FILAMENT THAT WORKS WITH ORDINARY 3-D PRINTERS, AND THEN WE CAN PRINT THE NEW SUBMARINE-GRADE PARTS FROM THAT.

AND YOU CREATED AN ONLINE DESIGN TOOL FOR THIS, AS WELL?

YES. SO WE WERE RECENTLY GRANTED A PATENT, AND THE PATENT IS TO FIND OUT HOW MANY OF THESE PARTICLES OF WHAT SIZE AND WHAT THICKNESS CAN BE USED.

AND THE PATENT, WHAT REALLY IT DOES IS THAT IT GIVES YOU THE OPTIMIZATION OF DENSITY, THERMAL CONDUCTIVITY, THERMAL EXPANSION, AND ALSO STRENGTH OR STIFFNESS OR ANY OTHER PARAMETERS THAT YOU HAVE IN MIND.

WE CAN FIND THE COMPOSITION OF THESE COMPLEX MATERIALS THROUGH OUR DESIGN TOOL.

SO WHAT'S THE KIND OF 5-YEARS-OUT EFFECT HERE?

YOU'RE GOING TO SEE MOST SMALL UNMANNED SUBMARINES BE PRINTED?

SO THAT'S WHAT WE ARE HOPING, BECAUSE THE FAILURE AT THE JOINTS IS A BIG PROBLEM, AND ONE FAILURE MEANS THAT THE WATER GOES INSIDE.

THE RETRIEVAL OF THE SUBMARINE ITSELF IS VERY DIFFICULT AFTER THAT.

SO 3-D PRINTING, IT ALLOWS US TO ELIMINATE ALL THE JOINTS IN THE STRUCTURE.

YOU CAN PUT THE ELECTRONICS AND CAMERAS DURING THE PRINTING PROCESS AND SEAL THE SUBMARINE COMPLETELY, AND THE PERFORMANCE IS EXPECTED TO BE BETTER.

ARE THERE OTHER APPLICATIONS BESIDES SUBMARINES THAT THIS TYPE OF FOAM WOULD WORK FOR?

THIS FOAM HAS BEEN USED A LOT.

IS ONE OF THE EXAMPLES.

IT'S THE NAVY'S LATEST COMPOSITE SHIP.

DECK HOUSE IS MADE OF SYNTACTIC FOAM BECAUSE OF STEALTH AND LIGHTWEIGHT.

THEY ARE ALSO USED IN AEROSPACE APPLICATIONS, LIKE AIRCRAFT NOSE CONE FILLINGS, LEADING EDGES, OR FLOORBOARDS.

AND IS IT EXPENSIVE TO PRINT AND MAKE?

THE FOAM ITSELF IS NOT EXPENSIVE, MAINLY BECAUSE THE HOLLOW PARTICLES ARE VERY INEXPENSIVE.

SO THE POLYMER IS THE EXPENSIVE PART.

YOU REPLACE 40% TO 50% POLYMER WITH CHEAPER HOLLOW PARTICLES.

BUT THE 3-D PRINTING PROCESS ITSELF IS EXPENSIVE RIGHT NOW BECAUSE IT'S A NEW PROCESS.

WE ARE STILL WORKING WITH THE PROCESS, CONTROLLING OTHER PARAMETERS, BUT WE HOPE THAT, IN FUTURE, PRICE WILL COME DOWN WHEN THE TECHNOLOGY MATURES.

OKAY. NIKHIL GUPTA, THANKS FOR JOINING US.

THANK YOU VERY MUCH.