Natural Fibre and Hybrid Composite Thin-Walled Structures for Automotive Crashworthiness: A Review
Monica Capretti, Giulia Del Bianco, Valentina Giammaria, Simonetta Boria · 2024 · 49 citationsRead the paper
Natural fibres, valued for their low density, cost-effectiveness, high strength-to-weight ratio, and efficient energy absorption, are increasingly emerging as alternatives to synthetic materials in green composites. Although they cannot fully replace synthetic counterparts, like carbon, in structural applications due to their inferior mechanical performance, combining them through hybridization presents a potential solution. This approach promotes a balance between environmental benefits and mechanical efficiency. Recently, the transportation sector has shifted its focus towards delivering lightweight and crashworthy composite structures to improve vehicle performance, address safety concerns, and minimise environmental impact through the use of eco-friendly materials. The crashworthiness of energy absorbers, typically thin-walled structures, is influenced by several factors, including their material and geometric design. This paper presents a comprehensive overview of recent studies focused on the crashworthiness of fibre-reinforced, thin-walled composites under axial crushing. It explores different aspects, such as their materials, cross-sections, stacking sequences, triggering or filling mechanisms, and the effect of loading rate speed. Emphasis is placed on natural-fibre-based materials, including a comparative analysis of synthetic ones and their hybridization. The primary objective is to review the progress of solutions using green composites as energy absorbers in the automotive industry, considering their lightweight design, crashworthiness, and environmental sustainability.
What the full text shows
Shown in the lab- Flax/epoxy circular tubes achieved high energy absorption comparable to GFRPs. — SEA of 41 J/g and CFE of 0.8 (Quasi-static axial crushing; smallest diameter, highest number of layers, and highest L/D ratio)
- Circular cross-sections provide superior energy absorption and stability compared to square cross-sections. — SEA of 74 J/g (circular) vs 55 J/g (square) for certain composites; CFE decreased by ~30% for square (Axial crushing of composite tubes)
- Silk/epoxy and ramie/epoxy square tubes show significantly lower energy absorption than flax circular tubes. — SEA of 5 J/g (Quasi-static crushing)
- Increasing the cone vertex angle reduces energy absorption in oil palm frond/epoxy structures. — SEA decreased by ~50% compared to circular tubes of the same material (Truncated cones under axial compression)
- Oil palm frond/epoxy cones exhibit much lower energy absorption than carbon/epoxy. — SEA 77% lower than C/E (OP/E SEA: 3-7 J/g) (Truncated cones under axial compression)
- Increasing the diameter-to-thickness ratio in hybrid J-G-reinforced epoxy square tubes reduces energy absorption. — SEA reduced by almost 50% when width increased from 50mm to 100mm (Square cross-section, constant thickness)
- Setup
- Review of multiple experimental studies involving various natural fibres (flax, jute, silk, ramie, cotton, oil palm frond, coconut coir) and synthetic fibres (glass, carbon) in epoxy or polyester matrices.
- How
- The paper is a comprehensive review of existing literature and experimental studies on the axial crushing of natural fibre composites (NFCs) and hybrid thin-walled structures. It analyzes the impact of geometry (circular, square, conical), material composition, and structural modifications (triggering, foam filling) on crashworthiness.
- Limitations
- NFCs are not yet viable full replacements for synthetic composites in structural automotive crash-boxes due to inferior mechanical performance. · General rules for dynamic vs. quasi-static loading are difficult to establish because effects depend on material and crushing mechanisms. · Recycling of FRPs remains challenging due to high energy costs and material degradation.
Summarized by Gemma 4 from the open-access full text · 8 Oct 2026. Read it