Natural Fiber Composites for Sustainable Model Rocketry: Bamboo and Jute as Alternatives to Fiberglass

Abstract

The search for sustainable alternatives to synthetic composites has become increasingly relevant in aerospace engineering education and student rocketry. Fiberglass is widely used for rocket fuselages due to its favorable balance of performance and cost, but it is energy-intensive, non-biodegradable, and environmentally burdensome. This study provides the first demonstration of natural fiber composites applied to student rocket fuselages, evaluating bamboo and jute as sustainable alternatives to fiberglass. Fiberglass, bamboo, and jute laminates were fabricated following the procedures of the RocketWolf team at CEFET/RJ. The fuselages were characterized by parachute ejection tests, surface roughness analysis, and flight simulations using OpenRocket software. Additional data such as laminate mass, wall thickness, fiber–resin ratio, and cost analysis were incorporated to provide a comprehensive assessment. Results revealed contrasting behaviors: untreated bamboo composites showed poor resin impregnation, brittle behavior, and lack of structural stability, confirming their unsuitability without chemical treatment. Jute composites, in contrast, achieved adequate impregnation, cylindrical geometry, and superior surface roughness (Ra = 37 µm) compared to fiberglass with paint (62 µm) or envelopes (52 µm). Both fiberglass and jute fuselages successfully passed parachute ejection tests, while simulations indicated apogees close to 1 km, fulfilling competition requirements. The jute fuselage also presented slightly improved stability margins. Economically, jute was ~492% cheaper than fiberglass in fiber-only comparison but absorbed more resin; nevertheless, real purchase prices favored jute. These findings confirm that jute composites are a technically feasible, cost-effective, and sustainable substitute for fiberglass in student rocket fuselages. Beyond technical validation, this work demonstrates the educational and environmental benefits of integrating natural fibers into academic rocketry, bridging sustainability, performance, and innovation.

1. Introduction

Natural fiber composites have attracted increasing attention as sustainable alternatives to synthetic reinforcements. Compared to glass and carbon fibers, natural fibers offer distinct advantages: they are renewable and biodegradable, have lower embodied energy, and generate a smaller environmental footprint across their life cycle [1,2,3,4,5]. Moreover, natural fibers can contribute to greenhouse gas mitigation strategies, since their carbon content can be recovered or accounted for in carbon credits after disposal [3]. Classical works such as Baillie (2005) [4] and John & Thomas (2008) [6] introduced the concept of “green composites,” while more recent reviews highlight that these materials are now progressing beyond environmental advantages, showing promising mechanical performance in lightweight applications [7,8,9,10].

Bamboo and jute are among the most studied natural fibers. Bamboo has been recognized for its high tensile strength, stiffness, and potential in structural applications [7,11]. Chen (2024) [12] even described bamboo as a naturally optimized fiber-reinforced composite, though processing challenges such as surface impurities and resin impermeability persist. Recent reviews by Behera et al. (2025) [13] and Shettigar et al. (2025) [14] emphasize that bamboo composites can only achieve long-term durability and competitive performance when chemical treatments such as alkalization or silane modification are applied. In contrast, jute fibers are already widely used in textiles and industrial applications, with several studies confirming their potential as sustainable reinforcements in polymer matrices [8,15]. A 2025 review by Iqbal et al. [15] considered jute one of the most promising fibers for scaling sustainable composites, while Medina Agurto et al. (2025) [16] experimentally showed how the volume fraction of jute fibers in epoxy strongly influences tensile and flexural properties.

The interest in natural fibers has also extended into aerospace and automotive industries. Balo et al. (2024) [10] reviewed early aerospace applications, showing potential for secondary structures and interior panels. Sarasini et al. (2018) [17] and Peças et al. (2018) [18] reported natural fiber composites applications, highlighting reductions in weight and CO₂ emissions. More recently, studies reinforced that natural fibers can be incorporated into structures, contributing not only to performance but also to sustainability [19,20,21]. Yudha et al. (2025) [22] advanced the discussion by investigating hybrid composites combining bamboo and glass fibers, showing that hybridization may overcome limitations of single-fiber composites.

Despite these advances, challenges remain. Natural fibers show variability in properties due to species, growth conditions, and processing [23]. They are hydrophilic, absorbing moisture that compromises dimensional stability [24,25]. To address this, numerous surface modification techniques have been developed, including alkaline, silane, acetylation, and enzymatic treatments, which improve adhesion to polymer matrices and increase durability [21,26,27]. Islam et al. (2025) [27] showed that treated bamboo short fibers could achieve competitive mechanical properties, while Parveez et al. (2022) [19] reinforced that chemical modifications are essential for aerospace-level reliability. Jute composites have similarly benefited from modern processing: Sultana et al. (2023) [28] showed competitive thermomechanical performance in short jute fiber reinforced polypropylene, and Das et al. (2021) [29] confirmed tensile and impact resistance of jute–epoxy composites comparable to fiberglass. More advanced designs, such as auxetic jute composites [30], further expand their potential for energy absorption applications.

Model rocketry provides an ideal context to explore these sustainable materials. It is a multidisciplinary academic activity integrating propulsion, aerodynamics, recovery, avionics, and structures [31,32]. The structural subsystem, particularly the fuselage, is critical not only for supporting other subsystems but also for influencing aerodynamic drag through its surface roughness [6,31]. Traditional fuselages are built with fiberglass due to favorable balance of cost and performance, but the environmental burden of synthetic composites is increasingly difficult to justify in educational contexts [5,18]. In addition, OpenRocket simulations [33] and aerodynamic analyses [31] show that small improvements in surface roughness can significantly affect drag and apogee, reinforcing the relevance of exploring alternative fuselage materials.

This study addresses this gap by investigating bamboo and jute composites as fuselage materials for academic rockets. Laminates were fabricated following the procedures adopted by the RocketWolf team in the Helder 1 rocket, developed for the 2023 Latin American Space Challenge (LASC). Comparative analyses included sealing and parachute ejection tests, surface roughness characterization, and flight simulations. By combining experimental results with critical comparisons to literature, this research evaluates whether natural fibers can serve as cost-effective, sustainable, and technically feasible alternatives to fiberglass in student rocketry.

2. Materials and Methods

2.1. Fabrication of Fiberglass Baseline Laminates

The RocketWolf student team at CEFET/RJ traditionally employs fiberglass for the fabrication of rocket fuselages, using PVC tubes as cylindrical molds. Each PVC tube is positioned on a custom lamination support to facilitate handling and ensure dimensional stability during processing. To prevent adhesion between resin and mold, the tube is first treated with Marbocote PR 5050 release agent (Redelease, São Paulo, Brazil), compatible with epoxy, polyester, and silicone rubbers. After drying, the mold is wrapped with two to three layers of cellophane film to ensure efficient demolding.

The fibers are weighed before lamination, and this mass is used to calculate the resin–hardener mixture, set at two-thirds of the fiber mass. Epoxy Resin 2001 (Redelease) and Hardener 3154 (Redelease) were mixed at a 2:1 ratio, with a working time of ~30 min. During this period, the resin was evenly distributed across the fibers to ensure homogeneous impregnation before exothermic curing began. A peel ply layer of nylon fabric was applied to the outer surface, improving finishing quality and preventing excess resin accumulation. Each laminate underwent an initial 24 h curing stage, after which the tube was removed from the mold and the peel ply discarded. A further 24–48 h post-curing at ambient conditions completed the process [9,10].

In this work, the fiberglass fuselage section was fabricated with four layers of woven fiberglass mats, resulting in a final upper fuselage of 97.5 cm of length, mass of 1053 g and an average wall thickness of 0.24 cm. The fiber-to-resin ratio was maintained at 3:2, with all processes carried out under 22 °C and 86% relative humidity. The fiberglass used was a commercial chopped strand mat (Redelease, Brazil), commonly employed by the RocketWolf team for fuselage fabrication. The fiber-to-resin mass ratio was maintained at 3:2, corresponding to an approximate fiber volume fraction of 40%.

The epoxy system used in all laminations consisted of Epoxy Resin 2001 (Redelease, Brazil) and Hardener 3154 (Redelease, Brazil) mixed at a 2:1 mass ratio, with a working time of approximately 30 min. This formulation was selected due to its proven compatibility with both glass and natural fibers and its use in previous RocketWolf fuselage manufacturing.

2.2. Bamboo Fiber Laminates

Bamboo fibers were obtained from commercial suppliers in Brazil, typically intended for artisanal or textile applications (Figure 1). Although bamboo is well known for its high tensile strength and stiffness [5], its raw fibers present challenges such as impermeability and poor adhesion to polymeric resins. The bamboo fibers were manually cut to an average length of 20–30 mm, corresponding to an aspect ratio of approximately 40:1. Microscopic characterization is planned for a future study, as the present work focused on macroscopic feasibility testing. To preliminarily assess its behavior, laminations were first carried out in flat plates rather than cylindrical molds, simplifying the analysis of resin impregnation and mechanical feasibility.

The wooden base molds were prepared with two layers of Marbocote PR 5050 release agent. Aluminum and wood strips were fixed to delimit the rectangular laminate dimensions and to provide lateral pressure during curing. Fibers were cut into small, uniform strips and distributed randomly on the mold. The resin–hardener mixture was prepared as described previously, with a 30 min manipulation window. Fiberglass mats were laminated as a baseline, rotating the mats 90° in successive layers to ensure multidirectional reinforcement. Bamboo, lacking woven mats, was instead laminated as random short fibers. After impregnation, laminates cured for 24 h before demolding, followed by an additional 24 h post-curing under controlled conditions.

Despite these efforts, raw bamboo fibers showed poor resin absorption. Resin accumulated at the base of the laminate without penetrating the fibers, producing brittle composites with compromised mechanical integrity (Figure 2). Literature indicates that alkaline treatment can remove lignin and waxes, improving wettability and adhesion, thus enabling structural applications [25]. In this work, only two layers of bamboo fibers were attempted, but the resulting laminates failed to achieve uniform impregnation, preventing reliable measurements of mass and thickness.

2.3. Jute Fiber Laminates

Jute fibers were obtained in woven mat form (Figure 3), which significantly facilitated lamination into cylindrical tubes. The process followed the same steps as for the Helder 1 rocket fuselage, with one key difference: due to the higher permeability of natural fibers, the resin and hardener consumption was ~2.5× greater than that required for fiberglass of equivalent fiber mass. Visual inspection during lamination was used to ensure adequate impregnation.

After curing, the jute tubes were sanded, cleaned with acetone, and covered with a low-cost polymeric envelope typically used for furniture finishing (Figure 4). The external polymeric envelope applied on the jute fuselage was a commercial polyethylene-based film (PVC-free), typically used for furniture surface finishing. This step provided improved surface finishing and reduced roughness, mimicking the role of automotive paint or protective envelopes used in fiberglass rockets. The resulting jute composites presented cylindrical geometry, absence of visible voids, and promising tensile and flexural resistance comparable to fiberglass tubes (Figure 5).

The jute fuselage section was produced with two layers of woven mats, resulting in a final upper fuselage of 97.5 cm of length, mass of 2734 g and an average wall thickness of 0.98 cm. As with fiberglass, the fiber-to-resin ratio was kept at 3:2, under environmental conditions of 22 °C and 86% relative humidity.

2.4. Experimental Tests

Three sets of tests were performed to evaluate composite performance:

1.

Sealing and Ejection Test—Initially conceived as a hydrostatic test, the sealing capacity was evaluated through parachute ejection tests due to equipment constraints. Tubes of fiberglass and jute were tested using identical parameters: 4 g of black powder, 17 cm tube length, and equivalent parachute-to-recovery system distance (Figure 6). Successful ejection confirmed system viability.

2.

Surface Roughness Test—Surface roughness was measured using a Surftest S210 profilometer (Mitutoyo, IL, USA), capable of recording Ra (average roughness), Rz (mean peak-to-valley height), Ry (maximum height), and Rt (total roughness) [13]. Each tube underwent five measurements. Samples included: (i) fiberglass tube painted with automotive coating (Helder 1), (ii) fiberglass tube with protective automotive envelope (Helder 2, under fabrication), and (iii) jute tube with furniture envelope.

3.

Flight Simulation—OpenRocket v15.03 [33], an open-source simulation software, was used to compare fiberglass and jute rockets. All rocket components (motor, avionics, recovery, fins, nose cone, and internal structures) were kept constant, with only the fuselage material modified. The densities of each laminated fuselage were determined experimentally using a direct mass-to-volume ratio (Figure 7) based on the cylindrical geometry of the specimens after 48 h of curing under controlled environmental conditions (22 °C and 86% RH). This ensured realistic input parameters for OpenRocket simulations. The jute density used in the simulation was 1.037 g/cm³, a value similar to polystyrene. Aerodynamic properties and surface roughness were integrated into the models (Figure 8).

2.5. Cost Analysis

Material costs were calculated under two approaches: theoretical estimation and actual purchase values.

• Fiber-only cost (per number of layers): fiberglass = BRL 52.97; jute = BRL 8.95 → jute ~492% cheaper.
• Total cost (fiber + resin consumption): fiberglass = BRL 65.95; jute = BRL 92.42 → jute ~41.5% more expensive due to higher resin absorption.
• Real purchase costs (at the time of fabrication): fiberglass ≈ BRL 25; jute ≈ BRL 19.

The cost analysis refers exclusively to the fuselage material. All other subsystems—nose cone, fins, recovery system, and avionics—remained unchanged. Thus, the comparison isolates the effect of replacing fiberglass with natural fiber composites in the structural shell only. This approach ensures that the cost differences reflect material substitution rather than complete redesign.

3. Results

3.1. Sealing and Ejection Test

The sealing capacity of the composite tubes was evaluated through parachute ejection experiments. Although a hydrostatic test was initially considered, it was replaced by the ejection test due to the permeability of natural fibers and the lack of suitable equipment. Fiberglass and jute tubes were tested under identical conditions: 4 g of black powder, 17 cm tube length, and equivalent parachute-to-recovery system distance (see Figure 6).

Both tubes successfully ejected the parachute, demonstrating the structural capacity of the laminates to withstand sudden pressure increases generated during recovery events. This result confirmed that jute composites provide adequate sealing properties, comparable to fiberglass, and may therefore be considered a viable fuselage material for recovery systems in student rocketry.

Due to equipment constraints, the leak rate and burst pressure could not be directly measured. Instead, functional validation was achieved through successful parachute ejection under repeatable test conditions, confirming sufficient sealing and pressure retention capacity for operational use.

3.2. Surface Roughness Test

Surface roughness directly influences aerodynamic drag and therefore flight performance. The roughness of fiberglass and jute tubes was analyzed using a Mitutoyo Surftest S210 profilometer, which measured Ra (average roughness), Rz (mean peak-to-valley height), Ry (maximum height), and Rt (total roughness) [13]. Three samples were tested:

• Fiberglass fuselage finished with automotive paint (Helder 1).
• Fiberglass fuselage with protective automotive envelope (Helder 2, under fabrication).
• Jute fuselage with polymeric furniture envelope.

Each tube was subjected to five measurements. The results are summarized in

Table 1. Raw roughness measurements (µm).

Sample	Ra (µm)	Ry (µm)	Rv (µm)	Rt (µm)
Fiberglass + Paint	64, 59, 63, 62, 62	95–105	58–62	77–82
Fiberglass + Envelope	50, 54, 51, 53, 52	63–67	74–77	48–52
Jute + Envelope	35, 38, 37, 36, 39	18–22	48–53	63–67

(raw values) and

Table 2. Average roughness values with standard deviation (µm).

Sample	Ra (µm)	Ry (µm)	Rv (µm)	Rt (µm)
Fiberglass + Paint	62.0 ± 1.9	100.1 ± 3.4	60.1 ± 1.2	79.3 ± 2.0
Fiberglass + Envelope	52.0 ± 1.6	65.0 ± 1.8	75.3 ± 1.5	50.0 ± 1.6
Jute + Envelope	37.0 ± 1.6	20.1 ± 1.5	50.2 ± 1.7	65.0 ± 1.7

(mean values ± standard deviation). The jute fuselage presented the lowest mean Ra (37 µm) compared to fiberglass with envelope (52 µm) and with paint (62 µm). Lower Ra values imply reduced aerodynamic drag and potentially more efficient flight profiles. The relatively low standard deviations indicate consistent surface quality across samples.

The lower Ra but relatively higher Ry values observed for the jute + envelope sample arise from the periodic texture of the woven jute mats. This microstructure generates localized height peaks without significantly increasing the average surface roughness, a feature also reported in previous jute composite studies [15,29].

This outcome suggests that the jute laminate, despite its natural origin, can achieve superior surface finishing when combined with low-cost envelopes, potentially reducing aerodynamic drag. These results were later incorporated into OpenRocket simulations to improve predictive accuracy of aerodynamic performance.

3.3. Flight Simulations

OpenRocket v15.03 [33] was used to evaluate the influence of fuselage materials on flight performance. The software allows for detailed modeling of rocket geometry, motor thrust, recovery systems, and environmental conditions. In this work, all parameters—motor, avionics, recovery system, fins, nose cone, and internal 3D-printed components—were kept constant. Only the fuselage material was varied.

The fiberglass model used the known density of glass composites, while the jute model incorporated an experimentally determined density of 1.037 g/cm³, measured after lamination. This value is close to that of polystyrene, ensuring adequate comparability between the models. Although OpenRocket does not allow direct input of surface roughness parameters, the lower Ra values obtained for jute (Section 3.2) were considered qualitatively in the analysis, since smoother surfaces are expected to reduce aerodynamic drag.

Simulation results indicated minimal differences between fiberglass and jute rockets in terms of apogee, flight time, and landing velocity (

Table 3. Average roughness values with standard deviation.

Parameter	Jute Simulation	Fiberglass Simulation—Helder 1
Configuration	RocketWolf J1—Jute	RocketWolf J1—Fiberglass
Motor burnout velocity (m/s)	59.47	59.37
Apogee (m)	975.0	973.0
Launch velocity (m/s)	52.32	52.27
Optimal delay (s)	12.21	12.21
Maximum velocity (m/s)	152	157
Maximum acceleration (m/s2)	151	151
Time to apogee (s)	14.6	14.6
Total flight time (s)	18.6	18.6
Velocity at ground impact (m/s)	5.36	5.36

). Both models achieved an apogee close to 1 km, one of the primary competition criteria. The jute rocket also showed slightly improved stability margins, likely associated with its higher density and lower measured surface roughness.

Taken together, the simulations strengthen the feasibility of replacing fiberglass with jute composites in academic rocketry without compromising flight performance. Moreover, the combination of comparable apogees, structural stability, and potential aerodynamic benefits highlights the practical viability of jute fuselages in student rocketry projects.

3.4. Cost Results and Trade-Offs

Material costs revealed contrasting outcomes depending on the evaluation approach:

• Fiber-only comparison: jute was ~492% cheaper than fiberglass (BRL 8.95 vs. BRL 52.97).
• Total cost with resin consumption: fiberglass remained cheaper (BRL 65.95 vs. BRL 92.42), since jute absorbed significantly more resin.
• Real market prices (at the time of purchase): fiberglass ≈ BRL 25; jute ≈ BRL 19, showing that in practice, jute was the more economical option.

Taken together, these results confirm that jute composites combine functional performance (parachute ejection and structural stability), aerodynamic potential (lower Ra), and economic viability (cheaper in practice), despite higher theoretical resin-related costs.

4. Discussion

The experimental results highlighted clear contrasts between bamboo and jute composites, while also providing insights into their broader implications for sustainable aerospace applications.

It is important to note that this study was designed as a proof-of-concept validation within the educational rocketry context, prioritizing operational testing (ejection and simulation) over full mechanical characterization. Although tensile, flexural, and impact tests were not conducted here, such mechanical analyses are currently under development and will be presented in future studies. This clarification delineates the scope of the present work without compromising its relevance to functional aerospace applications.

Untreated bamboo fibers produced brittle laminates with poor resin impregnation, consistent with the literature that describes waxes, lignin, and hemicellulose as barriers to adhesion [11,24]. These results confirm that raw bamboo is unsuitable for structural use in rocketry. However, this limitation should not be interpreted as a definitive barrier. Studies have showed that chemical treatments—such as alkaline, silane, or enzymatic methods—can substantially improve matrix infiltration and interfacial bonding [21,26,27]. Islam et al. (2025) [27], for instance, reported that chemically modified bamboo short fibers achieved tensile and flexural properties approaching those of conventional synthetic composites. Similarly, Parveez et al. (2022) [19] highlighted that treated bamboo laminates exhibited improved long-term stability, which is essential for aerospace environments. In this sense, the present findings reinforce the view that bamboo has potential, but only if integrated with proper surface modification processes.

Although interfacial adhesion was not quantified in this work, visual inspection during lamination and post-curing revealed good resin wetting in jute composites and poor impregnation in untreated bamboo fibers. This observation aligns with the well-known role of lignin and wax layers in limiting matrix adhesion [21,24].

In contrast, jute laminates fabricated with woven mats showed excellent compatibility with epoxy resin, leading to uniform cylindrical geometry and consistent structural stability. The surface roughness results were particularly significant: jute tubes presented an Ra of 37 µm, smoother than both fiberglass fuselages with paint (62 µm) and protective envelopes (52 µm). This outcome aligns with previous reports that jute composites can provide competitive or even superior surface finishing compared to glass composites [15,16]. Recent studies further corroborate these findings: Sultana et al. (2023) [28] showed the thermomechanical robustness of jute–polypropylene composites, while Das et al. (2021) [29] showed that jute–epoxy laminates achieved tensile and impact resistance comparable to fiberglass. The smoother finish observed in this work suggests that jute could even offer aerodynamic benefits in real flights, an advantage not often associated with natural fibers.

The parachute ejection tests confirmed that both fiberglass and jute fuselages could withstand the pressure loads associated with recovery system activation, ensuring operational reliability. OpenRocket simulations supported this, with both rockets achieving apogees close to 1 km, which is the primary competition requirement. Interestingly, the jute model presented slightly higher stability margins. Although OpenRocket does not allow direct integration of surface roughness parameters, the lower Ra values obtained experimentally suggest that the aerodynamic drag of jute fuselages could be reduced in real conditions, potentially leading to even better performance than indicated by the simulations.

Cost evaluation revealed a nuanced scenario. While resin absorption increased the theoretical cost of jute (~41.5% higher than fiberglass), real purchase prices were lower for jute (BRL 19 vs. R$ 25). This reflects findings in the literature, where natural fibers are described as simultaneously cost-effective and resource-intensive, depending on resin demand and processing requirements [15,18]. For student teams operating with limited budgets, the practical cost advantage of jute is a decisive factor, even if laboratory cost models suggest otherwise. This duality underscores the importance of analyzing sustainability not only from a technical perspective but also in terms of real-world accessibility and affordability.

Differences in wall thickness and mass between the fiberglass and jute fuselages result primarily from the higher permeability and resin uptake of natural fibers. These variations were quantified and integrated into the density-based flight simulations to ensure consistent comparability. The adjustments confirmed that the observed flight performance differences were not artifacts of mass variation but reflected material properties and surface characteristics.

The results obtained here resonate with broader international studies on natural fiber composites. Sarasini et al. (2018) [17] and Balo et al. (2024) [10] highlighted the potential of natural fibers in lightweight aerospace panels, while Peças et al. (2018) [18] emphasized their environmental benefits in automotive applications. Khan et al. (2024) [20] and Yudha et al. (2025) [22] discussed hybridization strategies that combine natural fibers with glass or nanoparticles, achieving improved durability and mechanical performance while retaining sustainability advantages. Tahir et al. (2025) [30] further introduced auxetic jute composites with enhanced energy absorption, reinforcing that jute continues to evolve as a versatile material for advanced applications. Against this backdrop, the present study adds novelty by addressing student rocketry fuselages—an application rarely explored, where structural stability and aerodynamic surface quality are critical for mission success.

Beyond the technical dimension, this work carries an important educational message. By demonstrating that natural fibers can replace fiberglass in student rockets, it opens the door for future competitions and training programs to adopt sustainable materials. This not only reduces environmental impact but also promotes sustainability as an integral part of aerospace education. Such integration aligns academic projects with global priorities for eco-innovation and prepares future engineers to design with both performance and responsibility in mind.

In summary, the discussion shows that untreated bamboo is currently unsuitable for rocket fuselages but remains promising if chemically modified. Jute composites, on the other hand, have already showed structural viability, smoother surfaces, competitive costs, and functional reliability. These findings position jute as a strong candidate for immediate adoption in educational rocketry, while also highlighting bamboo as a material of future interest pending adequate treatment.

To consolidate these findings, future studies should also evaluate long-term durability under hygrothermal conditions, as recommended in recent aerospace composite research [34], along with thermal behavior analyses such as thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Furthermore, hybridization strategies (e.g., jute + glass, bamboo + nanoparticles) may balance sustainability with enhanced performance [20,22]. Mechanical tests such as tensile, flexural, impact, and fatigue will be incorporated in future work to expand quantitative understanding of the structural behavior.

5. Conclusions

This study investigated bamboo and jute fiber composites as sustainable alternatives to fiberglass in student rocket fuselages, fabricated and tested following the methodology adopted by the RocketWolf team at CEFET/RJ. The results generated a comprehensive picture of the structural, aerodynamic, economic, and educational feasibility of natural fibers in aerospace education.

• Bamboo composites: Untreated bamboo fibers proved unsuitable, producing brittle laminates with poor resin impregnation and structural weakness. Despite bamboo’s recognized potential due to its high tensile strength, this study confirmed that without chemical modification, it cannot be considered for aerospace use. This reinforces the consensus in the literature that chemical treatments such as alkalization, silane, or enzymatic modification are indispensable to remove surface barriers and improve adhesion [23,24,25], which is recommended for future investigation. The limitation encountered here highlights a key research direction: the adaptation of bamboo through proper surface modification remains essential for its future application in aerospace composites.
• Jute composites: In contrast, jute laminates exhibited excellent processability and functional performance. With two layers of woven mats, jute fuselages achieved uniform cylindrical geometry, adequate resin impregnation, and a final mass of 2734 g with 0.98 cm thickness, compared to fiberglass fuselages with 1053 g and 0.24 cm thickness. Surface roughness results were particularly promising: jute presented an Ra = 37 µm, lower than fiberglass with automotive paint (62 µm) and fiberglass with a protective envelope (52 µm). This smoother finish indicates reduced aerodynamic drag potential, an advantage not usually attributed to natural fibers.
• Performance validation: Functional tests confirmed the technical viability of jute fuselages. Both fiberglass and jute composites successfully withstood parachute ejection, demonstrating resistance to sudden internal pressure peaks. OpenRocket simulations, using measured densities (fiberglass standard vs. jute 1.037 g/cm³), indicated comparable apogees (~1 km), flight times, and descent velocities, with jute showing slightly higher stability margins. While surface roughness cannot be directly integrated into the software, empirical data suggest that smoother jute fuselages may offer additional aerodynamic benefits in real flights.
• Economic perspective: The economic analysis showed dual outcomes. When considering only fiber costs, jute was ~492% cheaper than fiberglass (BRL 8.95 vs. BRL 52.97). However, when resin consumption was included, jute appeared ~41.5% more expensive (BRL 92.42 vs. BRL 65.95). Importantly, real purchase prices at the time of fabrication favored jute (BRL 19 vs. BRL 25). This duality highlights that while natural fibers may increase resin demand, their market accessibility and lower acquisition costs can still make them attractive for student teams operating under limited budgets.
• Educational and sustainability implications: Beyond technical validation, the study showed the broader educational value of integrating sustainable materials in academic rocketry. Student rocketry competitions generate significant composite waste, usually fiberglass, which has long-term environmental impacts due to its non-biodegradable nature. By adopting natural fibers such as jute, students not only reduce the environmental footprint of their projects but also engage in experiential learning about eco-innovation. This represents an important cultural shift, aligning aerospace education with global sustainability goals.
• Novelty and contribution: The originality of this work lies in demonstrating, for the first time, that jute composites can successfully replace fiberglass in student rocket fuselages without compromising structural integrity or flight performance. While natural fibers have been tested in automotive and aerospace secondary structures [10,17,18], their application in fuselages subjected to recovery system loads and aerodynamic demands had not been validated before. This makes the present study a pioneering step in sustainable aerospace materials research.

To consolidate these findings, future research will include standardized mechanical tests (tensile, flexural, compression, and impact) and fractographic analysis to evaluate fiber–matrix adhesion. Additional studies on moisture absorption and long-term hygrothermal aging are also planned, given the hydrophilic nature of natural fibers. Moreover, the use of bio-based epoxy resins will be explored to achieve a fully biodegradable composite system.

In summary, untreated bamboo is not viable for student rocket fuselages but remains promising once chemically modified. Jute composites, on the other hand, showed structural, aerodynamic, economic, and educational feasibility, establishing themselves as a realistic and sustainable substitute for fiberglass. This work not only contributes to material science but also reinforces the potential of student rocketry as a platform for advancing sustainability in aerospace engineering education.