We have highlighted three key recommendations in the development
of SFRPs with useful properties: (i) for compatibility (viz.
property and processing) with the fibre, a matrix with high-failure
strain and low-processing temperature needs to be selected, (ii)
high fibre volume fractions (ideally above 40%, if not 60%) need
to be employed to ensure the fibres carry a larger fraction of the load, and (iii) long (_4 mm) silk fibres that are not actively surface
treated may provide adequate fibre/matrix adhesion.
Through a cross-comparative study, we found that the specific
flexural properties (strength and stiffness), interlaminar shear
strength and specific impact strength of nonwoven and plain
woven SFRPs was higher than that of flax composites, and more
comparable to, but not better than that of GFRPs. The absolute stiffness
(tensile and flexural) of SFRPs was lower than that of PFRPs
and GFRPs. However, plain woven SFRPs demonstrated high fracture
strain capacities, which may be particularly attractive in applications
where progressive failure or high compliance is required.
In general, it is evident that SFRPs offer some unique property
advantages over PFRPs, and while they do not suffice to replace
GFRPs, SFRPs are an interesting sustainable materials option. Certainly,
depending on the application, factors such as materials
and manufacturing cost, and component operating conditions
and design life (i.e. materials environmental aging properties)
may require scrutiny.