Note: Descriptions are shown in the official language in which they were submitted.
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Method of Manufacturing a Stiff Engineered Composite
This invention relates to a method of manufacturing a stiff engineered
composite. More particularly, this invention relates to a method of producing
stiff
mycelium bound parts.
As is known, conventional methods for producing nonstructural boards
rely on compressing wood veneer sheets, fibers, or particles and binding them
together with resin to form composites like hardwood plywood and medium
density fiberboard, which are used for applications such as furniture and
fixtures,
cabinetry, paneling, molding and athletic equipment. The ingredients for these
typical non-structural boards require considerable pre-processing, and the
feedstocks, especially timber and resins, are subject to considerable price
volatility. Additionally, many of the resins used to produce non-structural
boards
are carcinogenic and can emit volatile organic compounds (VOCs).
Much like nonstructural boards, structural boards are produced by
compressing wood veneer sheets, fibers, or particles and binding them together
with resin to form composites like oriented strand board (OSB) and softwood
plywood. OSB and softwood plywood are used for applications such as wall
sheathing, floor sheathing, and concrete framework. These structural boards
face the same concerns that nonstructural boards face because they use similar
feedstocks and resins.
Many structural and nonstructural boards are used for applications in
furniture, cabinetry, and fixtures where they must be cut, milled, and sanded
to
form the desired shape. Such post processing is expensive and time consuming
and creates material waste as the products are shaped. Plastics are also used
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for these applications and require expensive tools and machines for molding in
their production processes.
US Published Patent Application 2008/0145577 describes various
techniques for making self-supporting composite bodies comprised of discrete
particles and a network of interconnected mycelium cells bonding the particles
together. As described therein, the composite bodies may be formed into panels
as well as into panel systems with a composite core.
It is an object of this invention to provide an improved process for the
manufacture of a compressed composite body of particle/mycelium.
Briefly, the invention provides a method of achieving adhesion between a
matrix of fungal mycelium and a slurry of particles and/or fibers (natural or
synthetic) through a heated compression process.
US Published Patent Application 2008/0145577 has demonstrated that
fungal mycelium can bind natural (lignocellulosic and chitinous waste streams)
and/or synthetic (fiberglass) particles together during a controlled
incubation
process. The mycelium in the latter instance serves as a grown adhesive,
digesting a portion of the particles and fibers while encapsulating the slurry
in a
network of a vegetative tissue.
The process described within demonstrates that the extracellular matrix of
mycelium, known as the matrix layer of the cell wall and comprised of
polysaccharides (alpha and beta glucans), polymerized amino sugars (N-
glucosamine, chitin), monoproteins, and phosopholipids, can serve as a
traditional adhesive when heated and dried concurrently. The mycelium is
either
grown on, or mixed with, an engineered substrate of natural and/or synthetic
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particles and/or fibers and then compressed under heat and dried to desired
geometry.
The heating of the mycelium matrix actually provides value in two places,
which makes this process distinctly different from the prior art. The fungal
cell
wall is comprised of chitin and glucans. The glucans, when heated and
saturated
with the moisture embedded within the composite, begin to flow like a
traditional
resin and when dried stick the particles together beyond the traditional
mycelium
matrix.
By creating sheets of material made from particles bound together with
mycelium (hereinafter "the biocomposite material") and compressing these
sheets together, bio-based nonstructural boards can be created with
feedstocks.
The sheets of biocomposite material can be grown together or compressed
together with heat to set and dry the final product. The sheets of
biocomposite
material can vary in product density, fiber content, particle size, and fiber
orientation to selectively promote specific mechanical properties (screw hold
strength, core shear, modulus of elasticity).
Further, a large mass of mycelium can be cultivated on particles or fibers,
milled to a consistent particle size and then pressed in a constrained heated
tool.
Additionally, VOCs are not a concern for structural boards produced in
this manner because no VOC emitting resins are used in the production process,
and the cross-linking occurs between the biochemical construct of the fungal
cell
wall.
There are significant mechanical advantages garnered from compressing
sheets of mycelium bound particles into a single cohesive product with
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heightened temperatures (200 F - 650 F) while compressing the biocomposite
material at a pressure of from 10 to 1500 psi.. These advantages include
enhanced modulus of rupture and elasticity (stiffness), and the ability to
layer
sheets of varying particles size to achieve greater stiffness or dimensional
stability (squareness, flatness).
Other materials, including veneers, textiles, or laminates, that are
comprised of wood, plastics (polyester scrim), foam, natural fibers, stone,
metal,
or the like can be grown and bound to the face or internal structure of the
mycelium and particle sheets. These laminates can be stacked and interlaid to
the mycelium colonized particle sheets, and then compressed to a desired form
(flat or molded).
Structural boards can be created by compressing thick blocks of grown
material or layered sheets of grown material (particles and/or fibers bound by
mycelium) while drying with heat (radiation, conduction, or convective).
Orienting particles within an engineered substrate and then preliminarily
binding these with mycelium creates a bio-based product that does not emit
VOCs.
The compressed biocomposite material can be easily and cheaply shaped
during production. The grown material can be compressed in an inexpensive
mold (fiberglass, carbon fiber, composite, wooden and/or metal, e.g.
aluminum),
giving the material the desired shape and material properties without creating
waste. The final product can be dried in the tool to promote cross-linking
between the natural polymers within the mycelium, which can occur within the
magnitude of minutes.
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The grown material can also be compressed in a conductive tool that is
heated as well to the final shape, either with a heated platen or inserted
cartridges.
These and other objects and advantages of the invention will become
more apparent from the following detailed description taken in conjunction
with
the accompanying drawings wherein:
Fig. 1 schematically illustrates the steps in the method of manufacturing a
stiff engineered composite in accordance with the invention.
Referring to Fig. 1, in accordance with the method of the invention, an
engineered substrate bound with mycelium 10 is grown into a sheet of
appropriate dimensions in step 1. In this respect, the basic steps of the
method
include:
1. Obtain substrate constituents, including fungal inoculum, a bulking
collection of particles and/or fibers, a nutrient source or variety of
nutrient
sources, and water.
2. Combine the substrate constituents by mixing together in
volumetric or mass ratios to obtain a solid media with the inoculum (cell
and/or tissue culture) added during or following the mixing process.
3. Place the growth media in an enclosure or series of enclosures of
the desired geometry.
4. Allow the mycelia to grow through the substrate, creating a
composite with a geometry matching the enclosure. This may be either
the final geometry or the near net geometry of the final product.
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4a. For
parts that are dried in compression, the mycelium does not
have to grow on the engineered substrate but could be grown in a
secondary process and thoroughly intermixed to distribute culture just
prior to compressive drying (conduction, convection, radiation).
5. Repeat steps 1-3
for applications where materials are layered or
embedded to create the desired final composite media. Alternatively to
steps 3 and 4, the growth media may be grown as a solid mass, and then
ground up for later steps or placed in an enclosure of the desired shape
and then be allowed to regrow into that shape.
5a. Repeat steps 1-3
for applications where the materials are grown
and colonized, and then alternative to steps 3 and 4, the growth media is
milled or particlized into the uniform size. The resultant particles are then
compressed into a constrained and heated tool.
In step 2 of the method, the engineered substrate 10 containing some
residual moisture and, for example in the form of a flat rectangular plate or
tile, is
placed in a compression fixture 11, for example, a pinch press 11. As
illustrated,
the pinch press 11 has a bottom platen 12 that can be heated and that is
formed
with a mold body 13 of predetermined shape, for example, of semi-cylindrical
shape. The pinch press 11 also has a top platen 14 for engaging on the bottom
platen 12 with a cavity 15 within the platen 14 for mating about the mold body
13. Typically, when the platens 12, 14 are closed together, a semi-cylindrical
gap
exists between the mold body 13 and the cavity 15.
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Typically, the engineered substrate 10 should contain a minimum of 10%
moisture by weight. Steam may also be injected during compression to induce
the adhesion.
Since the glucans are activated by steam, the engineered substrate 10
should contain a minimum of 40% moisture by weight so that the moisture may
be transformed into steam during the heated pressing process as otherwise live
steam would be injected into the dry mass during compression to induce the
adhesion.
After positioning of the engineered substrate 10 on the mold body 13 of
the pinch press 11, the top platen 14 is lowered onto the bottom platen 12 in
order to compress, trim and dry the biocomposite material of the substrate 10.
During operation, the pinch press 11 is heated to 300 F while
compressing the biocomposite material of the substrate to between 10psi and
1500 psi. The length of time that the biocomposite material of the substrate
10 is
retained within the pinch press 11under heat and pressure is sufficient to the
reduce the moisture content of the material to less than 10% by weight and to
promote cross-linking between the natural polymers within the mycelium. The
biocomposite material can also be held in the pinch press 11 for a time
sufficient
to achieve a product stiffness that is sufficient to remove the compressed
material from the pinch press 11 ("tool" or "buck").
In step 3 of the method, with the pinch press 11 opened, a compressed
monolithic body 16 is removed from the pinch press 11. As illustrated, the
monolithic body 16 has a semi-cylindrical shape and is characterized as being
a
rigid shell.
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Variations
Additional methods can also be used to produce desirable properties in
the final composite.
1. The substrate of engineered particles and/or fibers
("biocomposite
material"), either colonized with mycelium (bioactive) or intermixed with
mycelium (inactive), can also include cation salts (divalent Na2+ and the
like)
that can assist with cross-linking between the polysaccharides and amino
sugars. Acids (hydrochloric, acetic, lactic) can be provided as well to ensure
the
substrate stays protonated.
a. The cation salts can be applied during initial substrate preparation
and sterilization.
b. The cations can be applied in a solution by either vacuum
infusing
the solution into the substrate or immersing the substrate in a cation
solution for
a certain period of time.
2. Surface treatments, such as laminates, veneers, or supplemental
fibers, can be bound to the engineered substrate. For example, a laminate can
be placed on the face of the engineered substrate during the initial growth
step.
This is "colonization". Alternatively, a laminate may be applied to the
engineered
substrate just before pressing and bound with only the glucans.
The laminate treatments are applied to the surfaces, or in between tiles if
multiple colonized blocks are used, and pressed with a heated platen until the
biocomposite material is < 10% moisture.
Laminations and inserts can also be pressed into the surface of a
colonized engineered substrate, again using the adhesion from the glucans. The
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laminations can include non-woven textiles, woven products (jute, fiberglass),
and Kraft paper, which become an integrated component of the final part.
Inserts can be positioned in either the lower or upper platens of the
compression tooling, and can be pressed into the biological composite during
the
setting process.
3. The biocomposite material can also be dried to a particular
moisture content with conduction, convection, and/or radiation at atmospheric
pressure, and then compression dried to complete the process.
4. The biocomposite material can be dried to a moisture content of
between 6% and 30% during the heated compression stage to retain enough
moisture to impart electrical conductivity such that the resultant compressed
monolithic body can be powder coated since a powder coating process requires
the material to be electrically conductive and moisture, rather than metals
salts,
is used to impart this characteristic.
a. The heated
compression tool, which forms the final product
geometry, can include surface finishes that translate to the final part.
5. The colonized biocomposite material can be compressed and dried
with a series of heated rollers that narrow in cross-section as the material
is
conveyed through the process.
Sheets of biocomposite material can be grown together or compressed
together with heat to set and dry the final product. The sheets of
biocomposite
material can vary in product density, fiber content, particle size, and fiber
orientation to selectively promote specific mechanical properties (screw hold
strength, core shear, modulus of elasticity). Additionally, VOCs are not a
concern
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for structural boards produced in this manner because no VOC emitting resins
are used in the production process, and the cross-linking occurs between the
biochemical construct of the fungal cell wall.
There are significant mechanical advantages garnered from compressing
sheets of mycelium bound particles into a single cohesive product with
heightened temperatures (200 F - 650 F). These advantages include enhanced
modulus of rupture and elasticity (stiffness), and the ability to layer sheets
of
varying particles size to achieve greater stiffness or dimensional stability
(squareness, flatness). Other materials, including veneers, textiles, or
laminates,
that are comprised of wood, plastics (polyester scrim), foam, natural fibers,
stone, metal, or the like can be grown and bound to the face or internal
structure
of the mycelium and particle sheets. These laminates can be stacked and
interlaid to the mycelium colonized particle sheets, and then compressed to a
desired form (flat or molded).
The method of the invention allows a final part to have a density between
18 and 60 lbs/ft3, an elastic modulus up to 440 ksi and a modulus of rupture
as
high as 2500 psi.
Further Variations
Where the growth media is grown as a solid mass and then ground up to
produce particles or pellets with mycelium therein, the particles may be
poured
into an enclosure of the desired shape and then heated and pressed with the
process parameters described above. In this embodiment, the final product has
a Modulus of Rupture of 111 psi and a Modulus of Elasticity of 2840 psi.
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The method provides for crosslinking to occur between the glucans in the
mycelia that are solubilized during the compression and moisture release
process. This can be further mediated with mild acids that assist in
protonating
and cross-linking.
Example 1:
1. Kenaf pith (screened over a 0.375" screen, 42% of mass), maltodextrin
(1.6% of mass), calcium sulfate (0.4% of mass), and water (56% of
mass) are mixed in an autoclavable bag to form the substrate for fungal
growth. For five liters of substrate, the amount of Kenaf pith is 670 grams
2. The bag is sterilized in a pressure cooker at 15 psi and 240 F for 60
minutes.
3. Millet grain spawn containing fungal tissue is mixed into the substrate
(10% [m:m].
4. Plastic tool molds that are 6 inches long, 6 inches wide, and 1 inch
deep
are filled with inoculated substrate.
5. The substrate is allowed to colonize in the tools for 7 days at
ambient
laboratory
conditions (75 F, 20% relative humidity, 2000 ppm CO2)
6. .. Wooden veneers that are 6 inches wide by 6 inches long and a square of
porous plastic with the same dimensions are soaked in 10% hydrogen
peroxide for 30 minutes. This is a chemical disinfection method that also
imparts the correct amount of water, since hydrogen peroxide oxidizes to
water.
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7. The substrates in the form of tiles are ejected from the mold and
stacked
in groups of three with a wooden veneer at each surface and interface
and the porous plastic square on the side that will be next to an air inlet
during compression.
8. The stack of tiles, veneers, and porous plastic is compressed to
approximately 3 times density in a compression frame with an air inlet for
forced aeration on one side and holes for passive ventilation on the other.
For example, as described in US Patent Application Serial No.
14/336,385, filed July 21 2014 and published as US 2015/0038619, the
disclosure of which is incorporated herein.
9. The compression frame is hooked up to an air pump and the compressed
substrate is subjected to forced aeration for 5 days. Alternatively, the
compressed substrate may be dried within the compression frame with
convective or conductive drying.
10. The compressed composite body is ejected from the compression frame
and placed in an aluminum collar of the same exterior dimensions that
surrounds the periphery of the compressed composite body. This collar
that has the desired features, locks and creates the features and
dimensions required of the final part.
11. A heated platen press (at a force of 20 ton and 600 F) is compressed
onto the pre-compressed body for two minutes, such that the body is
dried to < 10% moisture content.
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The resulting part has a density of 20 lbs/ft3, a modulus of elasticity around
80
ksi, a modulus of rupture around 800 psi, and a screw hold strength around 100
lbf.
In this example, the biocomposite material is subjected to compression
alone to form a compressed monolithic body, e.g. as described in as described
in US 2015/0038619, and then subjected to heat and pressure to promote cross-
linking between the natural polymers within the mycelium.
Example 2:
1. Kenaf pith (screened over a 0.375" screen, 42% of mass), maltodextrin
(1.6% of mass), calcium sulfate (0.4% of mass), and water (56% of mass)
are mixed in an autoclavable bag to form the substrate for fungal growth.
2. The bag is sterilized in a pressure cooker at 15 psi and 240 F for 60
minutes.
3. Millet grain spawn containing fungal tissue is mixed into the substrate
(10% [m:m].
4. Plastic tool molds that are 6 inches long, 6 inches wide, and 1 inch
deep
are filled with inoculated substrate.
5. The substrate is allowed to colonize in the tools (molds) for 7 days at
ambient laboratory conditions (75 F, 20% relative humidity, 2000 ppm
CO2)
6. The colonized substrate is ejected from the plastic tool that granted
the
growing mass its original structure and placed in an aluminum collar that
is perforated to allow for water to escape.
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7. The colonized substrate is placed in a heated platen press (20 ton,
600 F)
and is compressed for four minutes, such that the part is dried to < 10%
moisture content. The colonized substrate requires between 25psi and
5000 psi to achieve the maximum compression required.
The resulting part has a density of 34 lbs/ft3, a modulus of elasticity around
132
ksi, a modulus of rupture around 1698 psi, and a screw hold strength around 24
lbf at half an inch thickness. By way of comparison, a composite for packaging
made in accordance with the methods described in US Published Patent
Application 2008/0145577 has a density of from 5 to 8 lbs/ft3.
Example 3:
1. Kenaf pith (screened over a 0.375" screen, 42% of mass), maltodextrin
(1.6% of mass), calcium sulfate (0.4% of mass), and water (56% of mass)
are mixed in an autoclavable bag to form the substrate for fungal growth.
2. The bag is sterilized in a pressure cooker at 15 psi and 240 F for 60
minutes.
3. Millet grain spawn containing fungal tissue is mixed into the substrate
(10%) [m:m].
4. Growth enclosure molds that are fabricated out of thermoformed
polyethylene plastic to the final product geometry or near net shape are
filled with inoculated substrate.
5. The substrate is allowed to colonize in the tools (molds) for 7 days at
ambient laboratory conditions (75 F, 20% relative humidity, 2000 ppm
002)
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6. The colonized substrate is ejected from the plastic tool that granted
the
growing mass its original structure and placed in a structural enclosure of
the final product configuration. This second enclosure permits conductive
heating and is designed to allow for the installation of embedded inserts
or secondary components. The tool is perforated to allow for water to
escape.
7. The colonized substrate in the second enclosure is placed in a heated
platen press (20 ton, 600 F) and is compressed for four minutes, such
that the part is dried to < 10% moisture content.
The resulting part has a density of 29 lbs/ft3, a modulus of elasticity around
120
ksi, a modulus of rupture around 819 psi, and a screw hold strength around 132
lbf at an inch thickness.
Example 4:
1. Kenaf pith (screened over a 0.375" screen, 42% of mass), maltodextrin
(1.6% of mass), calcium sulfate (0.4% of mass), and water (56% of mass)
are mixed in an autoclavable bag to form the substrate for fungal growth.
2. The bag is sterilized in a pressure cooker at 15 psi 2. and 240 F for 60
minutes.
3. Millet grain spawn containing fungal tissue is mixed into the substrate
(10% [m:m].
4. Plastic tool molds that are 18 inches long, 18 inches wide, and 1 inch
deep are filled with inoculated substrate.
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5. The substrate is allowed to colonize in the tools (molds) for 7 days at
ambient laboratory conditions (75 F, 20% relative humidity, 2000 ppm
CO2)
6. The colonized substrate, in the form of a sheet, is ejected from the
plastic
tool and aligned in a heated pinch press of a desired geometry.
7. The colonized part is pressed and heated (300 F) for one minute, such
that the part is dried to < 10% moisture content, molded to the desired
shape, and excess material trimmed from the final product.
Example 5
1. Fabricate the biocomposite material into a flat blank board of 1.25"
thickness with a 0.25" hemp nonwoven matt grown into either face.
2. Press the flat blank board into the predetermined curved shape, such
as a
shape for a chair back, along with surface features under a compressive
force of 3000 psi and 340 F for 10 minutes to lock the surface features
and get the board to below 10% moisture.
The surface feature may be obtained by embossing at least one face of
the board with a predetermined sculptured feature using an embossing surface
on the face of the press that is pressed against the board.
When using a mold (tool), a mold release, such as a spray release or a
parchment paper, may be used on the surfaces of the mold to enable an easy
ejection of the colonized substrate from the mold.
Example 6
1. Kenaf pith (screened over a 0.375" screen, 42% of mass), maltodextrin
(1.6% of mass), calcium sulfate (0.4% of mass), and water (56% of mass)
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are mixed in an autoclavable bag to form the substrate for fungal growth.
For five liters of substrate, the amount of Kenaf pith is 670 grams (g).
2. The bag is sterilized in a pressure cooker at 15 psi and 240 F for
60
minutes.
3. Millet grain spawn containing fungal tissue is mixed into the substrate
(10% [m:m].
4. The substrate is allowed to colonize in the tools for 7 days at ambient
laboratory conditions (75 F, 20% relative humidity, 2000 ppm CO2)
5. The colonized substrate is dried to 30% moisture in a forced convection
' oven at 180 F for 12 hours.
6. The resultant mass is hammer milled through a 0.125" screen, and then
passed over a 38 mesh screen to remove fines.
7. The particles are positioned in a heated cavity at 380 F, and then
compressed into the molded cavity with a featured platen under 30 tons of
force. The materials are held for four minutes.
8. The final product is ejected and allowed to cool to room temperature
before loading.
In a further variation of the method, the mycelium can be grown out
separately and then added at a 10% moisture content to a collection of dried
discrete particles as set forth in the following examples.
Example 7:
1. Mycelium is cultivated on malt extract (32 g per liter) for 7 days
at ambient
laboratory conditions (75 F, 20% relative humidity, 2000 ppm 002) until a
sheet of mycelium is formed.
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2. The harvested mycelium sheet is freeze dried.
3. The resultant mass is hammer milled through a 0.0625" screen
4. Kenaf pith is hammer milled through a 22 mesh and over a 38 mesh
screen.
5. The kenaf pith and mycelium fragments are blended together at a 9:1
ratio (m:m)
6. The blended together particles are positioned in a heated cavity at 380
F,
and then compressed into a mold cavity with a featured platen under 30
tons of force and held for four minutes to form a cohesive product.
7. The final product is then ejected from the mold and allowed to cool to
room temperature before loading.
8. The resultant product offered a 31 lbfit3 density, a MoR of 206 psi, and
a
MoE of 27050 psi.
Example 8:
1. Mycelium is cultivated on malt extract (32 g per liter) for 7 days at
ambient
laboratory conditions (75 F, 20% relative humidity, 2000 ppm CO2) until a
sheet of mycelium is formed.
2. The harvested mycelium sheet is freeze dried.
3. The resultant mass is hammer milled through a 0.0625" screen.
4. The mycelium particles are positioned in a heated cavity at 380 F, and
then compressed into a mold cavity with a featured platen under 30 tons
of force and held for ten minutes to form a cohesive product.
5. The final product is ejected and allowed to cool to room temperature
before loading.
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6. The resultant product (i.e. compressed mycelium) offered a 42 lb/ft3
density, an MoR of 507 psi, and an MoE of 48525 psi.
The invention thus provides a compressed composite body of
particle/mycelium that is characterized in being a rigid body having a density
in
the range of from 18 to 60 lbs/ft3, a modulus of elasticity of up to 250 ksi
(1k=
1000 psi) and a modulus of rupture of up to 2500 psi.
The compressed composite bodies of the invention that are pressed to
0.25" or less achieve these above metrics. The use of particles in the bodies
normally obtain a modulus of elasticity under 250 ksi, whereas the use of
fibers
instead of particles can obtain a modulus of elasticity well above 250 ksi
since
the fibers bear more of the tensile strength in flexure.
The compressed composite body made in accordance with the methods
described herein differs from a compressed composite body made in accordance
with the methods described in Patent Application 14/336,385, filed July 21,
2014,
inter alia, in that due to conductive drying, the glucans are cross-linked and
all
the water is removed.
The composite body made in accordance with the invention may be
subjected to further processing steps to achieve a desired final product. For
example, the composite body may be die cut to a desired three-dimensional
shape; drilled or cut to provide openings therein; and the like.
Further, an assemblage of flat sheets of biocomposite material, sheets of
woven or non-woven laminations and inserts of three-dimensional contour (i.e.
inserts on non-flattened shape) may be heated and pressed together.to form a
desired final product having an internal shape corresponding to the inserts.
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