Emerging materials are making aircraft lighter

In the aerospace sector, reducing weight is one of the greatest constant priorities. Because of the high technical requirements, economic and legislative drivers, and relatively deep pockets, aerospace is often the first significant adopter of emerging lightweight materials.

IDTechEx has released a new report, “Additive Manufacturing and Lightweight Materials for Aerospace and Defense 2018-2028,” which contains roadmaps, forecasts, company profiles, and technology assessments in one of the key sectors in the adoption of early-stage technologies. This builds upon the company’s reports on composites, lightweight metals, and additive manufacturing.

The world of advanced materials is extensive but making the jump from academic or R&D labs to commercial success is a tortuous and challenging path. Motorsports and sporting goods often provide initial market entries because of lower regulatory barriers, but in many cases, the first industry that allows capacity to scale-up and notable revenues to emerge is the aerospace and defense sector.

Ceramic matrix composites (CMCs), metal matrix composites (MMCs), polymer aerogels, and CNT-yarns are examples of those emerging materials. Another key trend is the evolution of polymer composites.

Ceramic Matrix Composites

CMCs are right on the cusp of rapid growth. Both Ox/Ox (typically alumina/alumina) and SiC/SiC varieties have received significant investments and will begin to reap the rewards. The most significant is the use of continuous ceramic fibres, such as aluminum fibres from 3M (Nextel) and Unifrax (Saffil) and silicon carbide fibres From NGS Advanced Fibers (Nicalon).

Aerospace requires materials that withstand the highest temperatures, which results in the early uptake of CMCs being in jet engines and exhaust nozzles. The materials not only are lighter than the superalloys they are displacing, but they also have an improved cooling efficiency.

Metal Matrix Composites

The use of metals in aerospace structures has gradually diminished, but emerging alloys and the growth of additive manufacturing give metals an improved outlook for the fight back against polymer composites. Aluminum alloys, specifically lithium, beryllium, and scandium varieties, are becoming popular in aerospace, as are titanium aluminide and high-entropy alloys.

MMCs are also having a resurgence after many false starts, driven by technical advancements, predominantly in additive manufacturing, and increased demand as many other materials become exhausted.

MMCs are used in the aerospace and defense industry in highly wear-resistant parts, such as gearboxes, or to enhance aluminum’s strength, stiffness, and corrosion resistance and improve its performance at elevated temperatures.

The long-term proposed applications could be in parts as significant as landing gear, exemplified by a recent grant led by Safran using Alvant (previously CMT) aluminum composite technology.

Polymer Aerogels

When many people think of aerogels, they imagine transparent brittle silica monoliths, but the commercial reality is very different.

The industry is dominated by silica blankets for their superior insulative properties, but there is an emerging type that is highly relevant for aerospace. Polymer aerogels are highly porous, continuous networks (typically polyimides, polyureas, and polyurethanes) and can be made as monoliths or films through either supercritical or ambient-pressure drying methods.

Unlike their silica counterparts, excluding some minor exceptions, monoliths are not brittle and display good strength.

Aerogel Technologies produces a material called Airloy that not only reduces weight over other polymers, but also adds significant insulation and soundproofing for use in aerospace interiors. For exteriors, polymer aerogels offer versatility for use in antennas and with composite material.

CNT-yarns

The role of nanomaterials is highly relevant to aerospace, and the use of pure, continuous CNT-yarns is increasing opportunities for applying these materials.

CNT-yarns can be formed using CVD processes and wet, dry, or electro-spinning methods. The electrical (one-tenth the conductivity of copper) and mechanical properties (10 times the tensile strength of copper) are ever-improving, and more young companies are forming. The interest from aerospace is growing, and the proposed applications include from data transmission cables, EMI shieldings, and motor windings.

Dr. Richard Collins is a technology analyst for IDTechEx, www.idtechex.com.