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Tomorrow’s composites

July 23rd, 2018 / By: / Feature

The ability to incorporate new materials into composites could open up another world of possibilities.

Nature-inspired composites developers are looking to the abalone shell for inspiration in creating a structure that has both hard and soft properties for high strength.

In material science, strength alone is often found to have its limitations so that a combination of hard and soft, rigid and flexible is an area of increasing interest for a wide range of applications from building, to sports equipment, to protective apparel.

Composites bring together two or more materials to provide one that has novel features, generally with the purpose of enhancing performance and making it an ideal form to combine qualities.

Strength through biomimetics

Biomimicry and digital technologies are individually making advances, but the increase in data processing capabilities is set to be the real game changer in aligning these fields more effectively. One textile speciality, found in the Kyoto region of Japan is a fine quality of silk overlaid with the thinnest hand-cut sliver of abalone shell. Although one of the strongest materials found in nature, it is used here for its shimmering decorative qualities. The process is extraordinarily labor intensive and highly skilled, making it a highly valued and valuable fabric used in special kimonos and obi.

The abalone has attracted the attention of material scientists, however, because of its strength rather than aesthetics. It’s been featured in almost every biomimicry book written about the extraction of good design from nature; however, commercial products based on its structure have proven to be elusive. Recently published research suggests this may be about to change.

Researchers at the University of Massachusetts and Washington University (St Louis) have developed a nacre-mimetic composite capable of withstanding extreme mechanical forces. (“Nacra” refers to the abalone shell and “mimetic” is an abbreviation of the term biomimetic.)

Technology from Continuous Composites 3D printed the structure of the airfoil with continuous fiberglass, embedded copper wire for circuits that power LEDs, and embedded nichrome wire on the leading edge for de-icing applications. Photo: Continuous Composites.

The researchers have brought together silk fibroin and graphene oxide flakes to fabricate a nanocomposite with a unique multilevel and hierarchical structure. In tests it was found that there is a considerable difference in specific penetration energy where the graphene oxide flakes evolve from isolated sheets that do not interact to partially overlapping, continuous sheets.

The study concludes that the morphologies of nanoscale constituents and their interactions are critical to the scalability of nacre-mimetic nanocomposites of this type. Testing is a vital part of the development process in these new biomimicry composites and often serve as a reminder of the quite unique challenges that material scientists face.

Nano-layered composite (NLC) structures is one process under consideration as a way of producing nacre-mimetic materials. NLC structures are being tested for fatigue by researchers at Northeastern University and the Chinese Academy of Sciences (Shenyang). Looking specifically to overcome issues of structure fatigue in the composite, they are finding some success in the use of a layer-by-layer self-assembly and chemical bath deposition production process. Testing includes the elastic modulus, hardness, fracture toughness, strain amplitude as well as fatigue limits.

Fiber-laying innovations

The increasing cost of specialist, high performance fibers, coupled with the demand for high-strength, low-weight composites, has led to innovative developments in the techniques of fiber-laying technologies. Niche applications have helped to raise the profile and drive developments.

Michigan-based LayStitch™ Technologies produces a number of machines with these capabilities. The company’s FiberPrinter lays out the fiber tow or roving for carbon fiber composites with the fiber then attached by stitching to a substrate, often a nonwoven that can be removed later in the process. It is used across a range of industries from prosthetics to automotive parts.

German manufacturer TFP Technology GmbH works with an automated tailored fiber placement technology (TFP). While most composite manufacturers are keen to only emphasise their advanced technologies, TFP acknowledges their debt to embroidery as “one of the oldest and highest quality textile refining and production techniques.”  The system is capable of working with carbon fiber with a thickness range of 3K-50K as well as glass fiber, aramid, steel, basalt and ceramic.

Idaho-based Continuous Composites has developed a technology that brings together composites with 3D Printing in a technology that they have patented as Continuous Fiber 3D Printing (CF3D). As the fiber is laid, the rapidly curing UV-cure resin is applied without the need for a mould. This offers a significant cost and space saving, as well as allowing novel forms to be created that would not be possible using more conventional composite manufacturing processes.

Different high performance yarns, such as carbon fiber and glass fiber, can be used. Additional functionality can be introduced during the fiber-laying process, which may include fiber optic sensors, copper and nichrome wires. These effectively make this a smart composite, capable of sensing its environment and collecting data, conducting electricity to power LEDs or heating elements, for instance. Reducing the number of stages in the production of the finished composite offers greater production and environmental efficiencies with these two processes coming together.

When glass fiber first became available, though excited by the possibilities, manufacturers complained that their looms struggled with the new fiber with frequent stoppages in production, which made it expensive—prohibitively so for many potential applications. Technological development does not conveniently occur in a synchronised way, then or now. That said, the push towards Industry 4.0 means that manufacturers have to engage with developments in associated areas. For composite manufacturers this can extend to emerging trends in design software and Artificial Intelligence (AI).

Adapting and evolving

Speaking at the recent SmartGometry2018 conference in Toronto, David Benjamin, founding principle of The Living, an Autodesk studio based in New York, spoke of the potential for Generative Design to manage complexity. In Generative Design, Nature’s own ability to adapt and evolve is mimicked. The software system allows designers and engineers to generate thousands of solutions before selecting the one that best suits their needs.

Different requirements and constraints can be loaded into the system, so that in composite terms, for example, the tradeoff between strength and flexibility can be assessed introducing additional criteria such as weight or cost to the evaluation process. While manufacturers already engage with other suppliers and stakeholders, in Generative Design, the computer also becomes one of the co-designers utilizing skills of data visualisation and machine learning to create insights. In proffering multiple design possibilities, the software tests and learns from each iteration so that it becomes a form of (digital) prototyping at a pace that would not be possible within a more conventional system.

Looking to the future, one of David Benjamin’s projects is titled “Bio Computational Evolution: The Next Generation of Software for Synthetic Biology.”  The project explores the intersection between synthetic biology, architecture and computation using Autodesk Maya and bespoke scripts. The aim: to create a new field of composite materials with quite unique properties.

 

Marie O’Mahony is an industry consultant, author and academic. She the author of several books on advanced and smart textiles published by Thames and Hudson and Visiting Professor at the Royal College of Art (RCA), London.