Could Hemp Fiber Make Aerospace Materials More Sustainable?

Industrial hemp is usually discussed as a source of cannabinoids, food ingredients, textiles or building materials. Its stalks, however, contain cellulose-rich fibres that can reinforce lightweight composites. That has placed hemp within the search for alternatives to glass and carbon fibre in industries where reducing weight can reduce material and energy use.

A new comparative study examined how hemp, flax and abaca fibres respond to sodium hydroxide treatment, a common process used to prepare plant fibres for composites.¹ The results suggest that hemp occupies a potentially useful middle ground. It retained a highly crystalline cellulose structure comparable to flax while developing a roughened surface that may help it bond with a polymer matrix. It also avoided the more severe surface disruption observed in abaca.

The findings do not demonstrate that hemp is ready to replace carbon fibre in aircraft. The researchers did not manufacture or mechanically test finished composites. What they provide is an early material-screening comparison that helps explain where treated hemp might fit, what could make it useful, and which problems still prevent it from becoming an aerospace-grade material.

Why Natural Fibres Need Surface Treatment

A composite combines a reinforcing material with a surrounding matrix, often a polymer. The reinforcement helps carry loads, while the matrix holds the structure together, transfers stress and protects the reinforcement from damage.

Plant fibres can be attractive reinforcements because they are renewable and less dense than conventional glass fibre. However, raw plant material contains cellulose, hemicellulose, lignin, pectin, waxes and oils. These components create a chemically and physically complex surface that may bond poorly with hydrophobic polymers. Plant fibres also readily interact with water, potentially causing swelling, dimensional changes and deterioration at the fibre-matrix interface.

Alkali treatment, sometimes called mercerization, uses sodium hydroxide to remove some non-cellulosic material and expose more of the underlying cellulose microfibrils. The objective is not simply to clean the fibre. A controlled amount of surface roughness can give the surrounding polymer more area and texture to grip.

There is a narrow processing window. Insufficient treatment can leave contaminants that interfere with adhesion. Excessive exposure can damage the fibre itself, increase porosity or expose more water-attracting hydroxyl groups. Treatment must therefore be optimized for each plant rather than applied as a universal recipe.

How The Researchers Compared Hemp, Flax And Abaca

The researchers treated commercially sourced hemp, flax and abaca fibres with a 5% sodium hydroxide solution at approximately 30°C. Samples remained in the solution for one, two or three hours. The same concentration and temperature were used across all three fibre types, allowing their different responses to be compared under consistent conditions.

Four forms of analysis were used:

• Gravimetric measurements tracked water uptake.
• X-ray diffraction assessed cellulose structure and crystallinity.
• Electron microscopy revealed changes to the fibre surfaces.
• Infrared spectroscopy identified characteristic chemical groups.

Hemp Retained A Highly Ordered Cellulose Structure

X-ray diffraction confirmed that all three treated fibres retained the cellulose I structure normally associated with plant material. Flax recorded the highest crystallinity index at 73.31%, but hemp followed extremely closely at 72.82%. Abaca was substantially lower at 59.82%.

Higher crystallinity can be associated with greater stiffness and structural order, although it does not independently predict the strength of a finished composite. Fibre orientation, defects, length, matrix selection, adhesion and manufacturing quality also influence performance. Still, hemp’s near match with flax suggests that its internal cellulose structure survived the treatment well.

The microscopy results add another layer. Hemp developed an interconnected network of raised fibrils and moderate surface roughness. This could be useful because roughened fibres may offer better mechanical interlocking with a polymer. Abaca showed much deeper grooves, localized pitting and material loss, while flax remained comparatively smooth and intact.

Hemp consequently appears neither untouched nor severely degraded. It displayed a controlled-looking surface modification while retaining high crystallinity. That combination makes it a credible candidate for additional composite testing, but it is not proof of improved adhesion because the study did not measure interfacial bond strength.

Water Absorption Remains The Central Problem

The most important warning came from the water-uptake test. Hemp’s reported value rose from 0.9 g in the untreated condition to 4.6 g after one hour, 4.7 g after two hours and 6.04 g after three hours of alkali treatment. Abaca also increased continuously. Flax rose sharply during the first two hours before falling from 8.1 g to 6.9 g after three hours, which the researchers interpreted as possible structural degradation from prolonged exposure.

This creates a fundamental engineering trade-off. Alkali treatment may create a cleaner, rougher surface for bonding, yet the same treatment can increase porosity and expose sites that interact with water. A fibre that bonds well when dry may still perform poorly after humidity cycles if moisture penetrates the composite and weakens its interface.

This is why moisture control during hemp fibre processing is not merely an agricultural concern. Moisture affects consistency from retting through storage, manufacturing and service life. Future systems may need optimized treatment times, coupling agents, hydrophobic coatings or matrices that better isolate the fibres from their environment.

Where Hemp Could Realistically Enter Aerospace

The most credible aerospace path begins away from wings, fuselages and other primary load-bearing structures. Carbon fibre offers performance, manufacturing maturity and qualification history that plant fibres cannot currently match. Even glass fibre has much lower intrinsic moisture sensitivity.

Hemp is more plausible in interior panels, acoustic components, insulation and other secondary structures where low density and adequate stiffness may be more valuable than maximum strength. Its possible acoustic role is supported by separate research into long-lasting hemp soundproofing materials, while agricultural machinery research shows how hemp composites could reduce the weight of vehicle components.

Aircraft use would nevertheless impose requirements that extend far beyond fibre crystallinity. Interior materials must satisfy demanding rules for flammability, heat release and smoke. The Federal Aviation Administration’s cabin-panel guidance illustrates how complete composite assemblies, including finishes and adhesives, must be evaluated rather than judging a material from its reinforcement alone.

The Bigger Opportunity Is A Materials Platform

The broader opportunity is not one dramatic replacement claim. Hemp could become a configurable industrial feedstock whose performance begins with cultivar selection and continues through cultivation, retting, fibre separation, surface treatment, matrix selection and component design.

Previous research has already shown that cultivation and processing choices can affect hemp fibre yield and composite performance. This has led to the idea of a farm-to-factory hemp biocomposite system. In such a market, manufacturers would not purchase generic hemp biomass. They would require fibre supplied to defined standards for cellulose content, length, moisture, treatment history and mechanical properties.

That shift could create higher-value markets for growers, but it would also raise the bar for traceability and consistency. Aerospace suppliers need repeatable materials. Variation caused by genetics, weather, harvest timing or retting could become a commercial obstacle unless processors can measure it and sort fibre accordingly.

Sustainable Does Not Automatically Mean Low Impact

Hemp is renewable, but sodium hydroxide treatment adds chemical consumption, rinsing, neutralization and wastewater. A lighter component may reduce operational energy, yet those savings must be weighed against cultivation inputs, transportation, fibre processing, polymer production and end-of-life options.

The study acknowledges this issue and suggests that reusing alkali solution could reduce part of the treatment burden. A convincing sustainability case will ultimately require life-cycle assessment of a finished component against the material it replaces. Comparing fibre density alone is not sufficient.

What Researchers Still Need To Prove

The paper is best understood as a screening study, not a validation of an aerospace-ready composite. It did not test tensile strength, flexural strength, fatigue, thermal stability, flammability or long-term durability. Untreated fibres were not included in the X-ray diffraction and infrared comparisons, so the precise chemical and structural changes caused by treatment could not be quantified. Replicate records were also unavailable for the water test, preventing statistical analysis.

For now, the strongest conclusion is narrower but still meaningful. Hemp retained nearly the same cellulose crystallinity as flax and developed a moderately fibrillated surface without the extensive disruption seen in abaca. Those characteristics justify further development for lightweight, non-primary composite components. The study does not put hemp into an aircraft, but it helps move the crop from a general sustainability idea toward an engineering material with measurable advantages, identifiable limitations and a clearer route to qualification.

References:

¹ Rudesh, C. P., Singh, N., Singh, S., Gahlot, N. K., Saluja, R. K., Madan, R., Gautam, R. K. S., Shrivastava, P., & Msomi, V. (2026). Comparative characterization of NaOH-treated abaca, flax, and hemp fibers for sustainable composite applications. Materials Today Communications, Article 116150. https://doi.org/10.1016/j.mtcomm.2026.116150