Unlike fibers, planar reinforcements, such as flakes and ribbons, provide reinforcement in two directions. If such reinforcements are arranged parallel to their principal plane in a composite material, they thus provide a distinctly higher performance than fiber reinforcements for two-dimensional loading conditions. This higher performance amounts to about a factor three for the Young's modulus and a factor two for the tensile strength. However, in spite of this obvious advantage, composites with planar reinforcements are as yet relatively unknown. This is mainly due to the fact that planar reinforcements are not as readily available as fiber reinforcements and therefore not much work has been done on them. The present article gives first a short outline of the theory of Lhe elastic and tensile properties of composites with planar reinforcements. Then, a non-exhaustive review is presented of the work on composites with planar reinforcements, with particular attention given to recent developments. A final aim of this article is that by showing the merits of planar reinforcements as compared to presently existing fiber reinforcements, it may contribute to their use in the design of composite structures.
Currently,
air permeable chemical/biological (CB) protective garments
are based on activated carbon technology, which reduces moisture vapor
transport needed for evaporative cooling and has potential to absorb
and concentrate toxic materials. Researchers are exploring classes
of sorbent materials that can selectively accumulate and decompose
target compounds for potential to enhance protective suits and allow
for novel filtration devices. Here, the metal–organic frameworks
(MOFs) UiO-66-NH2 and HKUST-1 have been identified as such
materials. To better understand how MOFs can perform in future CB
protective systems, atomic layer deposition (ALD) and solution deposition
were used to modify nonwoven polypropylene and flame-resistant fabrics
with HKUST-1 and UiO-66-NH2. Air permeation, water vapor
transport, filtration efficiency, and chemical reactivity against
chemical agent simulants were assessed in relation to ALD thickness
and MOF crystal size. MOF deposition on substrates decreased both
air and chemical permeation while increasing filtration efficiency
and chemical sorption. Moisture vapor transport was not affected by
MOF growth on substrates, which is promising when considering thermal
properties of protective garments. Future work should continue to
explore how MOF deposition onto fiber and textile substrates impacts
transport properties and chemical absorbance.
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