Methods of forming a part using shape memory polymers

One method of forming a part includes deforming a shape memory polymer from a permanent shape into a temporary shape, where the permanent shape of the shape memory polymer is a predetermined part shape and the temporary shape is a shape larger than the predetermined part shape. The shape memory polymer in each of the permanent shape and the temporary shape defines a cavity therein. The method further includes introducing a molding material into the cavity of the shape memory polymer, and reverting the shape memory polymer back into its permanent shape. Other methods for forming the part are also disclosed herein.

TECHNICAL FIELD

The present disclosure relates generally to forming methods, and more particularly, to a method of forming a part using shape memory polymers.

BACKGROUND

Various automotive and/or aerospace parts including, for example, structural parts, internal cabin parts, and/or the like are often formed using conventional molding processes such as compression molding, injection molding, extrusion molding, blow molding, etc. Although the foregoing molding processes tend to be suitable for forming parts having relatively simple geometries, difficulties may arise when molding parts having geometries with higher complexity. For example, a part may include one or more small, intricate features that may, in some instances, render molding the part using conventional molding techniques rather difficult. Yet further, such small, intricate features may hinder or even prevent removal of the part from a molding tool once the component is formed. In these cases, additional removal procedures using additional machinery and/or materials may be needed to remove the part from the molding tool, which may, in some instances, increase forming time and/or costs and/or energy consumption associated with such removal procedures.

SUMMARY

Methods of forming a part are disclosed herein. One example of the method includes deforming a shape memory polymer from a permanent shape into a temporary shape, wherein the permanent shape is a predetermined part shape, and the temporary shape is a shape larger than the predetermined part shape. The shape memory polymer in each of the permanent shape and the temporary shape defines a cavity therein. The method further includes introducing a molding material into the cavity of the shape memory polymer and reverting the shape memory polymer back to its permanent shape.

DETAILED DESCRIPTION

Embodiment(s) of the method as disclosed herein may advantageously be used to form a part having at least one die-locked feature. The embodiment(s) of the method at least 1) allow the part to be easily removed from a forming tool without having to employ additional machinery, materials, and/or labor, especially when the part includes at least one die-locked feature, 2) are relatively simple to use, are relatively inexpensive to perform, and may be applied for forming a number of different parts, and 3) allow the formation of the part, as well as those parts including one or more die-locked features, without having to employ alternative and/or additional molding techniques or processes.

Various examples of the part forming method are disclosed herein. Generally, the methods include using a shape memory polymer as a mold. Some embodiments of the method include the use a molding material, designated as reference numeral18(see, e.g.,FIGS. 1C-1E), which may, in an example, be a low pressure molding compound or other reinforced and/or non-reinforced materials that may be introduced into the shape memory polymer mold. Other embodiments of the method include the use of another molding material, designated as reference numeral18′ (see, e.g.,FIGS. 1G-1H, theFIG. 2series, and theFIG. 3series), which is a liquid resin used in combination with a preform. Further details of the methods and the materials (e.g.,18,18′) used in such methods will be discussed further hereinbelow.

Referring now to the drawings, an example of one method of forming a part is schematically depicted together inFIGS. 1A through 1E, and another example of this method is schematically depicted together inFIGS. 1A,1B, and1F through1H.

In both of the foregoing examples, the method begins by forming a shape memory polymer10into a shape where inner surface(s) thereof (e.g., inner surface11as shown inFIG. 1A) conforms to a predetermined shape of a part20(shown inFIGS. 1E,1H,2E,2G, and3D) to be formed. As used herein, the term “predetermined part shape” refers to the desirable shape of the ultimately formed part. Generally, the predetermined part shape is any desirable simple or complex, regular or non-regular geometric shape, including solid parts and hollow parts. In some instances, the predetermined part shape also includes at least one die-locked feature. A “die-locked feature” refers to feature(s) of the part that cause die-lock of the part in the molding tool. “Die-lock” occurs when the part cannot be removed from the molding tool using conventional removal methods because of the geometry of the part.

It is to be understood that although the various embodiments of the method disclosed herein may be applied to parts having simple or complex geometries without die-locked features, the examples depicted in the Figures, however, include at least one die-locked feature16. In the examples shown inFIGS. 1A through 1H, the die-locked feature16is shown as an undercut. In the examples shown inFIGS. 2A through 2Eand inFIGS. 3A through 3D, the die-locked feature16is shown as a dove tail.

In an embodiment, the shape memory polymer10is originally formed into a permanent shape. Forming the shape memory polymer10into its permanent shape may be accomplished, for example, by molding the shape memory polymer using a molding tool. After being molded, the shape memory polymer is heated to a temperature sufficient to deform the shape memory polymer within the molding tool, thereby rending it removable from the molding tool. The temperature sufficient to deform the shape memory polymer is a temperature above a switching temperature of the shape memory polymer. The switching temperature will be described in further detail below. During removal of the shape memory polymer from the molding tool, the shape memory polymer may be maintained in its heated state (or reheated if cooled) to return the shape memory polymer to its permanent shape and thereafter cooled under no external constraints to set the permanent shape. The shape memory polymer may be a thermoplastic polymer or a thermoset polymer. If the shape memory polymer is a thermoplastic polymer, the recovery of the permanent shape of the shape memory polymer is enabled by physical cross-links present in the polymeric structure. If the shape memory polymer is a thermoset polymer, the recovery of the permanent shape is enabled by the covalent cross-links. In either case, the presence of physical or covalent cross-links allows for the reversion of the shape memory polymer from another shape (e.g., a temporary shape as described in further detail below) to its permanent shape by releasing stored energy imparted to the system during the deformation at a suitable temperature and subsequent cooling to set a new shape.

The permanent shape of the shape memory polymer10, as referred to herein in reference toFIGS. 1A through 1H, corresponds to the predetermined part shape. In its permanent shape, as shown inFIG. 1A, the shape memory polymer10includes at least the die-locked feature16and a cavity12defined in the shape memory polymer10. The cavity12, in some embodiments, includes a valve14operatively connected thereto. In an embodiment, the cavity12may include more than one valve14. As will be described in further detail below, the valve(s)14may be used to control a flow of fluid into or out of the cavity12. In a non-limiting example, the valve(s)14may be used to allow a molding material to be introduced into the cavity12. In another example, the valve(s)14may be used to allow a gas, water, or a solvent into or out of the cavity12in order to increase/decrease pressure or to draw a vacuum from inside the cavity12at one or more instances during a molding process, which will be described further below. In some instances, multiple valves14may be used to simultaneously inject material and draw a vacuum.

Referring now toFIG. 1B, the shape memory polymer10is deformed from its permanent shape into a temporary shape. The shape memory polymer10′ in its temporary shape includes any shape that is volumetrically larger than the predetermined part shape and, thus, the permanent shape of the shape memory polymer10. The temporary shape10′ may be configured so that the predetermined part shape may be removable therefrom. For purposes of illustration, the shape memory polymer10′ in its temporary shape is depicted inFIG. 1Bas a rectangular shape including the cavity12′ defined therein.

In an embodiment, deformation of the shape memory polymer10(i.e., in its permanent shape) into the shape memory polymer10′ (i.e., in its temporary shape) is accomplished by heating the shape memory polymer10to a temperature above its switching temperature Tsw(shown inFIG. 4). As used herein, the “switching temperature” (Tsw) of the shape memory polymer10,10′ refers to the temperature at which the shape memory polymer becomes substantially easily deformable and, in combination with a force (as will be described in further detail below), may be switched from its permanent shape into its temporary shape. The switching temperature (Tsw) also refers to the temperature at which the shape memory polymer reaches its low modulus state and may spontaneously revert from its temporary shape back into its permanent shape (which will also be described in further detail hereinbelow). It is to be understood that the switching temperature varies depending on the chemistry of the shape memory polymer selected. Non-limiting examples of suitable shape memory polymers include epoxy-based systems, acrylate-based systems, styrene-based systems, or olefin-based systems that may also include fillers (e.g., inorganic fillers) or other active materials (such as, e.g., shape memory alloy wires, magneto-responsive fillers, electroactive fillers, photo-responsive organic dyes, and/or the like). It is to be understood that fillers may be reinforcing fillers, which improve the mechanical properties of the shape memory polymer.

In addition to heating the shape memory polymer10to switch it from its permanent shape to its temporary shape, a force is applied inside the cavity12to allow such transformation. An example of a suitable force that may be applied inside the cavity12includes pressure. In some instances, the pressure inside the cavity12may be increased by introducing therein a gas, water, or other material through the valve14. In these instances, the gas, water, or other material may be heated or cooled so that the shape memory polymer10remains at the appropriate temperature above its switching temperature during the deformation. Yet another example of a suitable force that may be applied inside the cavity12includes a mechanical force. Such mechanical forces may be applied inside the cavity12by, e.g., injecting a material inside the cavity12through the valve(s)14, applying a tensile force to an outer surface of the shape memory polymer10(e.g., pulling the shape memory polymer open using gripping features (e.g., eyelets) located on the outer surface of the shape memory polymer), or the like. It is also to be understood that when one or more forces are applied inside the cavity12in addition to heating the shape memory polymer10, the heat and the force may be applied sequentially or substantially simultaneously.

Once the shape memory polymer10has been changed from its permanent shape into its temporary shape, the temporary shape of the shape memory polymer10′ may be fixed or otherwise set by cooling the shape memory polymer10′ to a temperature below its switching temperature Tsw.FIG. 4shows that the shape memory polymer10′ is cooled to about room temperature (RT). It is to be understood, however, that any temperature below the switching temperature Tswwill suffice to set the shape memory polymer10′ into the temporary shape. In a non-limiting example, the shape memory polymer10′ is cooled to a temperature ranging from about 10° C. to about 20° C. below its switching temperature.

The examples of the method of forming the part further include introducing the molding material18into the cavity12′ of the shape memory polymer10′ in its temporary shape. In one example of the method, the molding material18is a low-pressure molding compound, which is injected into the cavity12′ (as shown inFIG. 1C) through the valve(s)14. Non-limiting examples of low-pressure molding compounds include a sheet molding compound including a crystallizable polyester resin (e.g., LPMC™, manufactured by Preferred Molding Compounds, Ontario, Calif.), a low pressure casting compound (e.g., plaster of Paris), a liquid rubber, or combinations thereof. Further, the molding material18generally has substantially the same volume as the final part20(as shown inFIG. 1E).

After the molding compound18has been introduced into the cavity12′, the shape memory polymer10′ is then reverted back into its permanent shape (as shown at reference numeral10inFIG. 1D). In an embodiment, reverting the shape memory polymer10′ back into its permanent shape is accomplished by heating the shape memory polymer10′ to a temperature above its switching temperature Tsw(as shown inFIG. 4), thereby reaching the low modulus and deformable state of the shape memory polymer. In this state, the shape memory polymer10′ reverts back into its original permanent shape10. It is to be understood that reversion of the shape memory polymer10′ may be accomplished by applying heat. It is to be understood that because the reversion of the shape memory polymer10,10′ from its temporary shape back into its permanent shape is due, at least in part, to stored energy within the polymer network, a force is generally not required to complete the reversion.

Once the temporary-shaped shape memory polymer10′ has been reverted back into its permanent shape, the shape memory polymer10is cooled to a temperature below its switching temperature Tsw. At this temperature, the shape memory polymer10is set into its permanent shape. Cooling the shape memory polymer10also conforms the low-pressure molding compound18inside the cavity12,12′ into the predetermined part shape defined by the inner surface(s) (e.g., the inner surface11) of the shape memory polymer10. In an example, the low-pressure molding compound18is then cured at a temperature Tc(as shown inFIG. 4), which is below the switching temperature Tswof the shape memory polymer10. In another example, the low-pressure molding compound18is pre-cured at a first curing temperature Tc1, which is lower than the switching temperature Tsw, to conform the material18to the part shape, and then the material18is post-cured at a second curing temperature Tc2, which is higher than the switching temperature Tsw. It is to be understood that generally it does not matter if the shape memory polymer deforms at the second curing temperature Tc2(which is higher than the switching temperature Tsw) because the pre-curing of the low-pressure molding compound18imparted, to the compound18, the predetermined part shape and the shape memory polymer is thereafter no longer used for forming the part20.

At the curing temperature Tcor Tc1, the low-pressure molding compound18is set into the predetermined part shape and forms the part20. Curing may be accomplished at a temperature below the switching temperature of the shape memory polymer10,10′ when the molding material18has predetermined curing kinetics (i.e., when the reaction time for curing is significantly longer than the time for switching the shape memory polymer back to its permanent shape when heated above its switching temperature Tsw, which is above the curing temperature Tc). The reaction time for curing is generally dependent upon the molding material18selected and the curing temperature Tcof the molding material18relative to the switching temperature Tswof the shape memory polymer. In a non-limiting example, if the curing temperature Tcranges from about 10° C. to about 30° C. below the switching temperature Tsw, then a targeted reaction time for curing would be about ten times longer than the time for switching. It is to be understood that the curing temperature Tcof the molding material18may be any temperature that is less than the switching temperature Tswof the shape memory polymer10,10′ (and, in some instances, is room temperature). It is further to be understood that having the curing temperature Tcbelow the switching temperature ensures that the shape memory polymer10is not prematurely and undesirably switched to a temporary shape.

After the part20is formed (i.e., the molding compound18has been cured), the shape memory polymer10is deformed back into the temporary shape (as shown at reference numeral10′ inFIG. 1E). It is to be understood that in the instant method step (i.e., when the shape memory polymer10is deformed back into the temporary shape after the part20is formed), the temporary shape may be any shape having a cross-section that is larger than that of the part20. In the example shown inFIG. 1E, the temporary shape is the same shape as the temporary shape10′ described above in conjunction with, e.g.,FIG. 1B. Deforming the shape memory polymer10back into the temporary shape (10′) may be accomplished by heating the shape memory polymer10to a temperature above its switching temperature Tsw(as shown inFIG. 4). A force is also applied to the cavity12of the shape memory polymer10by, for example, pressurizing the cavity12or applying a mechanical force to the cavity12. In an embodiment, prior to setting, or during the setting of, the shape memory polymer10′ in its temporary shape, the valve(s)14are removed from the shape memory polymer10′ and an end24of the shape memory polymer10′ is opened up (as shown inFIG. 1D) so that the part20may be removed from the cavity12′. In an example, the valve(s)14may be clamped or otherwise attached to the shape memory polymer10′ so that when heat is applied to the end24, and the valve(s)14are removed, the end24of the shape memory polymer is deformed to its more open temporary shape for removal of the part20therefrom. In another example, the valve(s)14may be removed while the shape memory polymer10is in its permanent shape, and then the shape memory polymer10′ may be deformed to its temporary shape for removal of the part20therefrom. It is to be understood that because the valve14has been removed, in addition to heating the shape memory polymer10′, deforming the shape memory polymer10′ into its more open temporary shape may be accomplished using an externally applied mechanical force instead of using pressure. The shape memory polymer10′ is then cooled to a temperature below its switching temperature Tswin order to set the open-ended version of the temporary shape. The shape memory polymer10′ may then be used to form another part of the same shape.

Referring back toFIG. 1B, and then toFIGS. 1F through 1H, another example of the method is depicted. After the shape memory polymer10has been deformed from its permanent shape and set into its temporary shape, as shown inFIG. 1B, and before the molding material18′ (in this example, the liquid resin is used as the molding material18′) is introduced into the cavity12′, a three-dimensional fiber preform22is introduced into the cavity12′ (as shown inFIG. 1F). It is to be understood that the preform22may be made of a material that is deformable, and may be shaped to include die-locked features. Thus, the shape of the three-dimensional fiber preform22(as shown in the pertinent Figures) corresponds to the predetermined part shape.

After introducing the three-dimensional fiber preform22into the cavity12′, the shape memory polymer10′ is reverted back into its permanent shape, as shown inFIG. 1G. This may be accomplished, for example, by heating the shape memory polymer10′ to a temperature above its switching temperature Tsw. In an embodiment, heating may begin at an end of the shape memory polymer10′ (e.g., the end farthest from the valve14) and gradually continued along the shape memory polymer10′ until an opposite end of the shape memory polymer10′ is heated. As a result, the shape memory polymer10′ gradually deforms from the temporary shape back into the permanent shape, which conforms around the preform22. It is to be understood that the gradual deformation of the shape memory polymer10back into the permanent shape allows for a good fit between the preform22and the shape memory polymer10(including the die-locked feature16) in its permanent shape. It is further to be understood that proper selection of the heat to be applied to gradually deform the shape memory polymer10back into the permanent shape depends, at least in part, on the shape of the preform22and the permanent shape of the shape memory polymer10. Thereafter, the shape memory polymer10(now in its permanent shape) is cooled to a temperature below its switching temperature Tswto set the permanent shape of the shape memory polymer10.

Still with reference toFIG. 1G, the molding material18′ is introduced into the cavity12(not shown inFIG. 1G) of the shape memory polymer10such that it impregnates the three-dimensional preform22. As previously mentioned, in this embodiment, the molding material18′ is a liquid resin. Non-limiting examples of suitable resins includes epoxies, polyesters, vinyl esters, or urethanes. In an example, the molding material/resin18′ may be introduced into the cavity12via injection through the valve14in the presence of a vacuum (drawn via another valve, not shown) or, otherwise, without a vacuum.

The molding material/resin18′ is thereafter cured at a temperature below the switching temperature Tswof the shape memory polymer10when the resin18′ has predetermined curing kinetics. At this temperature, the molding material18′ is set into the predetermined part shape and forms the part20′, as shown inFIG. 1H.

After the part20′ is formed, the shape memory polymer10is deformed back into its temporary shape (as shown at reference numeral10′ inFIG. 1H). Deforming the shape memory polymer10may be accomplished by heating the shape memory polymer10to a temperature above its switching temperature Tswand applying pressure or a mechanical force to the cavity12or to an outside surface of the shape memory polymer10, as described hereinabove. As previously described, in an embodiment, prior to, or while, setting the shape memory polymer10′ in its temporary shape, the valve(s)14are removed from the shape memory polymer10and an end24of the shape memory polymer10is opened up (as shown inFIG. 1G) so that the part20′ may be removed from the cavity12′.

Thereafter, the resultant shape memory polymer10′ is cooled to a temperature below its switching temperature Tswto set the temporary open-ended shape. While the shape memory polymer10′ is in its temporary open-ended shape, the part20′ is then removed from the cavity12′.

Another example of the method of forming a part20is schematically depicted inFIGS. 2A through 2E, while still another example of the method is schematically depicted inFIGS. 2A through 2C,2F,2G, and2E.

In both of the examples of theFIG. 2series, the shape memory polymer is a die (referred to herein as reference numeral100when the shape memory polymer is in its permanent shape, and by reference numeral100′ when the shape memory polymer is in its temporary shape) of a forming tool30. Another die32of the tool30is formed from a non-shape memory polymer (i.e., a material that is not a shape memory polymer such as, for example, a metal, a glass, a ceramic, or a polymer without shape memory properties). In a non-limiting example, the die100,100′ is an upper die of the forming tool30and the other die32is a lower die of the forming tool30. With reference now toFIG. 2A, the shape memory polymer100for either of the examples shown inFIGS. 2A through 2Gis provided in its permanent shape, which conforms to the predetermined part shape (similar to the examples depicted inFIGS. 1A through 1H). The shape memory polymer100includes a cavity120defined therein. The lower die32is shown as having a relatively flat surface34. It is to be understood that the lower die32may have any suitable shape so long as the shape of the lower die32does not result in die-locking of the formed part.

The examples of the method depicted inFIGS. 2A through 2Gbegin by deforming the shape memory polymer100from its permanent shape into a temporary shape, as shown fromFIG. 2AtoFIG. 2B. Also similar to the examples of the method depicted inFIGS. 1A through 1H, the temporary shape of the shape memory polymer (referred to herein by reference numeral100′) is a shape that is larger than the predetermined part shape and includes a cavity120′ defined therein (as shown inFIG. 2B). Deforming the shape memory polymer100into its temporary shape may be accomplished, for example, by heating the shape memory polymer100and, in some instances, applying a force. Thereafter, the temporary shape of the transformed shape memory polymer100′ is set by cooling the shape memory polymer100′ below its switching temperature Tsw.

A preform22′ is placed on the flat surface34of the lower die32, and the cavity120′ of the shape memory polymer100′ in its temporary shape is aligned with the preform22′ (also shown inFIG. 2B). Thereafter, the upper die (i.e., the shape memory polymer100′ in its temporary shape) is drawn toward the lower die32such that the cavity120′ substantially surrounds the preform22′ (as shown inFIG. 2C), leaving a gap36between the preform22′ and an inner surface of the shape memory polymer100′.

In the example of the method depicted inFIGS. 2A through 2E, the shape memory polymer100′ is reverted back into its permanent shape by heating the shape memory polymer10′ in its temporary shape (as shown inFIG. 2D). The permanent shape of the shape memory polymer100(as shown inFIG. 2E) is set by cooling the shape memory polymer100to a temperature below its switching temperature Tsw.

In an example, the molding material18′ (e.g., similar to those described in reference to the example inFIGS. 1A-1Band1F-1H) is injected, via a valve, an injection port, or the like (for clarity, not shown in theFIG. 2series), into the cavity120of the shape memory polymer100after it is set in its permanent shape (as shown inFIG. 2D). In the instant example, the injected molding material18′ impregnates the preform22′ and conforms to the part shape, as the part shape is defined by the inner surface/interior walls of the shape memory polymer100in its permanent shape.

It is to be understood that in another example, the molding material18′ is injected into the cavity120before or while the shape memory polymer100reverts back to its permanent shape (discussed further hereinbelow in reference toFIG. 2F).

Still referring to theFIG. 2A-2Eseries, the injected material18′ is then set, via curing, into the predetermined part shape, thereby forming the part20shown inFIG. 2E). In this non-limiting example, the molding material18′ may be any of the previously described resins, such as, epoxies, polyesters, vinyl esters, urethanes, and/or the like, and/or combinations thereof.

Still with reference toFIG. 2E, after curing the molding material18′, the shape memory polymer100is again deformed, and is converted and set back into its temporary shape100′. After setting the temporary shape of the polymer100′, the upper die (i.e., the shape memory polymer100′ in its temporary shape) is drawn away from the lower die32. The part20is then removed from the molding tool30(not shown in the Figures).

Referring back toFIG. 2C, in the example of the method depicted inFIGS. 2A through 2C,2F, and2G, after the shape memory polymer100is deformed into its temporary shape (100′), the molding material18′ is introduced into the gap36formed between an inner surface38of the cavity120′ and the preform22′. In this example, material18′ introduction is accomplished before reverting or during reversion of the shape memory polymer100′ back into its permanent shape (i.e., introduction occurs while the shape memory polymer100′ is in its temporary shape or as the shape memory polymer100′ is being reverted to its permanent shape) (as shown inFIG. 2F). When the shape memory polymer100′ is reverted back into its permanent shape (as shown at reference numeral100inFIG. 2G), the molding material18′ impregnates the preform22′ and then conforms to the predetermined part shape defined by shape memory polymer100in its permanent shape. The molding material18′ is cured and set into the predetermined part shape, thereby forming the part20(as also shown inFIG. 2G). It is to be understood that the instant example may also be accomplished up-side-down, where the shape memory polymer is the bottom part32of the tool30and the non-shape memory polymer material is the upper part of the tool. In this example, the molding material18′ is poured (rather than introduced via, e.g., injection) into the cavity120,120′.

After curing the molding material18′, the shape memory polymer100may be heated above its switching temperature Tswand converted to a temporary shape100′, as shown inFIG. 2E. The upper die (i.e., the shape memory polymer100′ in its temporary shape) is drawn away from the lower die32, and the part20is removed from the molding tool30.

It is to be understood that the example of the methods described in conjunction with theFIG. 2series may also be accomplished using a bulk molding material18without the preform22′. In such instances, the material18will be injected or otherwise introduced into the cavity120,120′ and cured in the desirable permanent shape100. When using the bulk molding material18, the shape memory polymer100does not have to be switched to a temporary shape prior to injection (if the shape memory polymer is the top part of the tool) or pouring (if the shape memory polymer is the bottom part of the tool). The bulk molding material18then adopts the contour of the part shape defined by the cavity120, and is cured at the curing temperature Tcto form the part20. The part20may be removed from the tool30by heating the shape memory polymer in its permanent shape100to a temperature above its switching temperature Tsw. At this point, the shape memory polymer may be switched in the presence of, e.g., a mechanical force or pressure to a temporary shape100′, thereby allowing relatively easy removal of the part20.

Still another example of the method of forming a part is schematically depicted together inFIGS. 3A through 3D. This example is similar to the examples depicted inFIGS. 2A through 2G, where the shape memory polymer is a die (referred to in this example as1000when the shape memory polymer is in its permanent shape, and as1000′ when the shape memory polymer is in its temporary shape) of a forming tool30′, and another die32of the tool30′ is formed from a non-shape memory polymer. In a non-limiting example, the die1000,1000′ is an upper die of the forming tool30′ and the other die32is a lower die of the forming tool30′. Unlike theFIG. 2series however, the permanent shape of the shape memory polymer1000in this example is a non-predetermined part shape. As shown inFIG. 3A, the permanent shape of the shape memory polymer1000is substantially flat. Further, the temporary shape of the shape memory polymer1000′ conforms to the predetermined part shape. In its temporary shape, the shape memory polymer1000′ includes a cavity1200′ defined therein.

In the instant example, the method begins by placing a preform22′ on the flat surface34of the lower die32(as shown inFIG. 3A). The preform22′ may, for example, have a three-dimensional shape of the initial part and may be made using a variety of processes including, but not limited to, slurry processes, three-dimensional weaving processes, three-dimensional knitting processes, and/or the like. It is to be understood that the preform22′ (for use in the instant example) may have any shape that will provide a suitable amount of structural resistance to the shape memory polymer10when the heat and the force are applied to the shape memory polymer10so that the shape memory polymer10conforms to the predetermined part shape.

Thereafter, the upper die (i.e., the shape memory polymer1000in its permanent shape) is drawn toward the lower die32. During or after the time in which the shape memory polymer1000is drawn toward the lower die32, the shape memory polymer1000is deformed from its permanent shape into its temporary shape (seeFIG. 3B). Deforming the shape memory polymer1000′ into its temporary shape may be accomplished, for example, by heating the shape memory polymer1000in its permanent shape to a temperature above its switching temperature Tsw, and forcing the shape memory polymer1000′ around the preform22′ using, e.g., air or fluid pressure and/or mechanical forces. Thereafter, the conformed shape memory polymer1000′ may be cooled to a temperature below its switching temperature Tswto set the temporary shape. It is to be understood that when the shape memory polymer1000′ is deformed into its temporary shape, the shape memory polymer1000′ substantially surrounds the preform22′ (as shown inFIG. 3B).

With reference now toFIG. 3C, a molding material18′ (e.g., the resin as similarly described for the example of the method depicted inFIGS. 1A,1B and1F through1H) is introduced into the cavity1200′ of the shape memory polymer1000′ in its temporary shape. In an example, the molding material18′ is introduced into the cavity1200′ using a valve, an injection port, or the like (not shown in theFIG. 3series). It is to be understood, however, that if the forming process is accomplished up-side-down (as described above), the molding material18′ may otherwise be poured into the cavity1200′.

The molding material18′ generally conforms to the predetermined part shape defined by the shape memory polymer1000′ in its temporary shape. The material18′ is set into the predetermined part shape by curing, thereby forming the part20(as shown inFIG. 3D). Curing may be accomplished, for example, at a temperature below a switching temperature Tswof the shape memory polymer1000′ in the presence of desired curing kinetics of the molding material18′.

After curing the molding material18′, with reference now toFIG. 3D, the shape memory polymer1000′ is reverted back into its permanent shape (as shown at reference numeral1000). This may be accomplished by heating the shape memory polymer1000′ to a temperature above its switching temperature Tsw, thereby triggering the deformation of the shape memory polymer1000′ from its temporary shape back into its permanent shape. Thereafter, the shape memory polymer1000is cooled to a temperature below its switching temperature Tswto set the permanent shape.

After reverting the shape memory polymer1000into its permanent shape, the upper die (i.e., the shape memory polymer1000now in its permanent shape) is drawn away from the lower die32. The part20is then removed from the molding tool30′.

FIG. 4is mentioned hereinabove, and shows examples of the temperature relationships between various steps of the example method ofFIGS. 1A through 1E. In this graph, it is to be understood that the actual temperatures may depend on the shape memory polymer(s) and molding material(s) used, and may extend above or below the indicated temperatures as much or as little as is desirable or necessary to achieve the desirable result. It is to be further understood that when cooling below Tc, room temperature (RT) does not necessarily have to be obtained. In the examples disclosed herein, it is to be understood that the shape memory polymers10,100,1000act as jackets which surround and shape various molding materials18,18′ and/or preforms22,22′ including the molding material18,18′ into a desirable predetermined part shape by switching (one or more times) between permanent10,100,100and temporary10′,100′,1000′ shapes.

It is to be understood that although the several examples of the method described above may be used to form a part, the part may or may not have at least one die-locked feature. It is to be understood that the instant disclosure should not be limited to parts having die-locked features, nor should it be limited to parts that do not have die-locked features.