1. Composites Molding
2. Shape Memory Molds
1. Composites Molding
1. “Composite molding generally involves molding a combination of different materials, each having a particular mechanical strength in a different direction, to form a final product that has mechanical strengths in multiple directions. Many popular forms of composite molding involve the use of carbon fibers or another similar component and a resin material, the molded combination of which results in a relatively strong part or component, particularly with respect to the weight of the part. Generally, fibers and resin are placed over or into a mold and are then cured under increased heat and pressure. Fibers typically come in sheet form, which can include "prepreg" or resin impregnated sheets, and are often layered into the mold sheet by sheet. Such a layering process is often performed manually by an operator, as are other steps in a typical composite molding of a part.
Because resins tend to stick to mold surfaces, removal of a finished part from a mold can be a tricky process that often also involves manual intervention by an operator. Despite the application of a temporary release coating to inner mold surfaces prior to placing in the composite materials, the removal of a finished part from a composite mold still can involve prying and peeling the part away from the inner mold surfaces. Surface defects and blemishes on composite molded parts often occur as a part of the molding and mold removal process, which results in many parts having unique defects or appearances. Further, temperature discrepancies from molded part to molded part using traditional composite molding processes can also result in blemishes or defects that are different for each part. Due to these particular examples and other concerns that relate to composite molding, many composite molding processes are highly manual labor intensive by nature, and often result in the formation of parts that are not fully consistent from part to part.”
[Choiniere et al, US Patent 8,27,075 (9/4/2012)]
2. Shape Memory Molds.
Composite parts, such as those in aircraft, are constructed using various production methods, such as filament winding, tape placement, overbraid, chop fiber roving, coating, or hand lay up based on rigid tooling. Removing the tool or mandrel from the cured part after curing is difficult, costly, and time-consuming. There is a need for improved methods for separating cured parts from the tooling.
Havens et al developed a method and apparatus for fabricating a composite part with shape memory polymer (SMP) tooling. The SMP structure is shaped, heated and, then, attached to a rigid tool. During composite molding, the assembly is heated and cured. When the composite is cured and cooled, the SMP part of the tooling shrinks away from the cured composite material facilitating removal. This shape memory material may be an epoxy, a styrene copolymer, cyanate esters, polyurethanes, polyethylenes, styrene-butadiene copolymers, polyisoprenes, acrylics and norbornene copolymers, napthalene polymers or malemides.
US Patent 8,951,375 (February 10, 2015), “Methods and Systems for Co-Bonding or Co-Curing Composite Parts using a Rigid/Malleable SMP Apparatus,” David E. Havens, Matthew C. Everhart, Randy Kysar, Carl Ray Fiegenbaum, Jeffrey W. Priest, Delbert Leon Strelow, Kevin John Ford, and Kristin Dru Pickell (Spirit AeroSystems, Inc., Wichita, Kansas, USA).
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Roger D. Corneliussen
Maro Polymer Links
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Copyright 2012 by Roger D. Corneliussen.
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* Date of latest addition; date of first entry is 9/7/2012.