Fibre Composite Research — Alexander May

Composite test specimen mounted in an Instron tensile testing machine

The Task

Glass and carbon fibre composites are the automotive industry's go-to for lightweight, high-strength parts, but they're costly to produce sustainably. Natural fibre composites — made with plant fibres like hemp and bio-based resins — are being explored as a greener alternative, and some prior research suggested that pairing a natural fibre with a natural resin could actually outperform synthetic combinations mechanically. This research set out to test that: are there real differences in mechanical performance across natural and synthetic fibre/resin combinations, including under different moisture conditions?

Process

Four composite combinations were produced — hemp fibre with bio-epoxy, hemp with synthetic epoxy, glass fibre with bio-epoxy, and glass with synthetic epoxy — using a vacuum infusion method, layering woven fabric in multiple orientations before curing under vacuum. Half of each sample set was submerged in water for five days to simulate high-moisture conditions, with the rest kept dry as a control.

Samples were tensile and flexural tested on an Instron testing machine, following ASTM D3039 and D7264 standards, and the results were analysed statistically using t-tests at a 95% confidence level to determine which factors — fibre type, resin type, or moisture — actually drove differences in strength.

Cut composite test strips of different fibre types laid out for testing — FIG. 06 — Cut hemp and glass fibre composite strips prepared for testing

Results & Conclusion

Fibre type was the only factor that produced a statistically significant difference: glass fibre composites were consistently stronger than hemp fibre composites in both tensile and flexural testing. Neither resin type (bio vs. synthetic epoxy) nor moisture exposure had a significant effect on mechanical strength — contrary to what some prior literature suggested.

Instron display screen showing a force versus displacement graph from a tensile test — FIG. 07 — Force/displacement curve recorded during tensile testing

The conclusion was that, for the combinations tested, natural fibre composites don't offer a mechanical performance advantage over synthetic ones, regardless of resin type or moisture exposure. The main limitation was sample size — budget constraints limited testing to far fewer repeats than the relevant ASTM standards call for, so the recommendation for future work is a larger sample count to build confidence in the results.