Hoa’s team creates composite structures using an automated fiber placement machine that is similar to a large 3D printer. The machine unrolls carbon fiber prepreg with 10-micron fiber filaments in ultra-thin layers at 90-degree angles from each other onto a flat mold. The layers are then compacted together and cured at 180 C in either an autoclave or oven to create the solid laminate. After curing, the composite structure is cooled to 20 C. During this process, the flat structure becomes curved. The fourth dimension refers to this altered configuration.

The ACTE wings are made from corrugated composites to provide stiffness in the span direction and flexibility in the chord direction. They feature two primary parts – a rigid support section and the active compliant trailing edge, which is fabricated from GFRP skins. Sliding between the upper and lower wing skins, which are connected by linear pair guides, allows the ACTE to achieve a large, continuous bending deformation.

While Hoa and his students are currently refining the analysis, design, manufacturing and testing of the ACTE wings, they have their eyes set on future applications that offer promise for commercialization. For instance, 4D composite printing is well suited for vertical-axis wind turbines, where the main rotor shaft is arranged vertically.

“There are a lot of twists and complex curvature,” he says. “If you were to make a mold, it would be very costly. I have also seen manufacturers construct a flat piece that they bend, and it cracks in multiple places. We should be able to utilize the properties of composites to do a better job.”

Hoa wants to spread the word about the potential of 4D printing.

“When people see 4D printing, they think about plastics. Few people are familiar with the technique for composites,” he says. “Hopefully, people will be open to the new technology.”


Suong Hoa, co-director of the Concordia Centre for Composites at Concordia University, has developed a 4D composite printing technique.

Photo Credit: Concordia University

Solving the Housing Shortage

Project: Sustainable 3D-printed Houses

School: The University of Maine

Location: Orono, Maine

Principal Investigator: Habib Dagher

A team of researchers at the Advanced Structures and Composites Center (ASCC) at the University of Maine are turning to technology to solve a societal concern. They believe 3D printing can help fill the void in low-income housing.

“In the United States, there’s a need for 8 million low-income houses,” says Habib Dagher, professor of civil and structural engineering at the University of Maine and director of the ASCC. “To solve the problem, we need to automate processes and drive costs out of the system. It’s not an easy road forward.”