Apr 4, 2018 | By David

Suong Van Hoa, a researcher at Canada’s Concordia University has made an impressive breakthrough that should point the way forward for the future proliferation of ‘4D’ printing of composites. He has developed a technique than enables objects to be 3D printed in a way that allows for future transformations after printing, when an environmental stimulus like light or heat is applied to the material. A ‘4D’ printing process like this means that composite objects can be printed without a mold, and this new technique should drastically speed up and simplify the construction of these elaborate structures.

(credit: Van Hoa)

Most shape-shifting ‘4D’ objects are made from a much softer material than the composites that Suong Van Hoa, professor in the Department of Mechanical, Industrial and Aerospace Engineering in Concordia’s Faculty of Engineering and Computer Science (ENCS), has been experimenting with. They usually tend to have a rubbery or gel-like texture, and various environmental mechanisms like moisture or light can be applied to them after 3D printing, to create more complex curved shapes.

The resin materials that were used to 4D print composites, on the other hand, are much stiffer and lighter. They are similar to the kinds of materials used in the aerospace industry. Van Hoa initially got his idea from work he was doing with aerospace companies, creating composite structures using automation and robotics. This is what eventually led him to the idea of indirectly manipulating interactions between the structure and the environment, to eliminate the need for a mold.

''4D printing allows us to make curved composite structures without the need to make curved moulds,'' says Van Hoa''My main finding is that one can make curved composite pieces (long continuous fibres that have high mechanical properties) more quickly and economically... 4D printing of composites utilizes the shrinkage of the matrix resin, and the difference in coefficients of thermal contraction of layers with different fibre orientations to activate the change in shape upon curing and cooling.''

Shrinkage in a material is what is known as an anisotropic property. Anisotropy can be defined as how a material acts while bearing loads along different axes. So the fibers of a material will change shape in a particular way when exposed to heat, for example. Van Hoa’s ingenious method turns a material’s shrinkage, a deformation property normally thought of as a problem to be overcome, into the solution to a different problem.

(credit: Van Hoa)

Effectively, his technique allows for the composite structure to mold itself, after printing. A structure will change shape over time depending the material properties, the fibre orientation, the lay-up sequence and the manufacturing process. Planning these elements before and after printing will enable the designer to program a desirable transformation into the object.

Van Hoa sees potential for this kind of ‘4D’ printed composite in advanced aerospace applications, amongst other things. ''They would be useful for space structures like satellites, where the structures are subjected to extreme temperature fluctuation,” he says. “The structure can open up during the day (when the temperature is high) to collect the solar energy, and close up at night to provide protection for its interiors.''

Van Hoa announced his latest discovery in the journal Advanced Manufacturing: Polymer & Composites Science.

 

 

Posted in Printing Technology

 

 

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