CA2172793A1 - Resin transfer molding process - Google Patents
Resin transfer molding processInfo
- Publication number
- CA2172793A1 CA2172793A1 CA 2172793 CA2172793A CA2172793A1 CA 2172793 A1 CA2172793 A1 CA 2172793A1 CA 2172793 CA2172793 CA 2172793 CA 2172793 A CA2172793 A CA 2172793A CA 2172793 A1 CA2172793 A1 CA 2172793A1
- Authority
- CA
- Canada
- Prior art keywords
- placing
- fiber
- mold cavity
- mat
- set forth
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Abstract
A method for manufacturing a fiber-reinforced polymer object in a resin transfer molding process, the method comprising the steps of (a) providing a mold defining a mold cavity and including an inlet passage communicating with the mold cavity, (b) placing in the mold cavity a preform including continuous strand mat adjacent the inlet passage and chopped fiber spaced from the inlet passage, (c) introducing resin into the mold cavity via the inlet passage, and (d) curing the resin.
Description
RESIN TRANSFER MOLDING PROCESS
BACKGROUND OF THE INVENTION
The invention relates to resin transfer molding (RTM), and more particularly to fiber preforms used in resin transfer molding.
The RTM process involves injecting or transferring resin into a mold containing fiber reinforcement. The fiber reinforcement can be a preform having generally the shape of the part to be molded. The benefits of a preform are shape, size, loadability and minimal expense. The preform can be made of chopped or short fibers and a resin binder. A chopped fiber preform is typically made by spraying chopped fibers and resin onto a form having the shape of the part to be molded.
Preforms can also be made with continuous strand mat (CSM) or woven mat made with long, interwoven, continuous strand fibers. It can be difficult and expensive to make preforms from continuous strand mat.
SUMMARY OF THE INVENTION
A disadvantage of using chopped fiber preforms is that the flow of resin into the mold can dislodge the chopped fibers near the injection port. When this happens, the dislodged fibers are transported along with the resin flow, dislodging even more fibers.
Eventually, the fibers can pile up and prevent further resin flow, resulting in a scrap part.
To overcome the problem of dislodging fibers near the injection port, the invention uses both chopped fibers and CSM in a preform. An insert or section of CSM or woven mat is used in the preform at the point that will be nearest the injection port. The remainder of the preform is made with chopped fibers in the conventional manner. The size of the CSM insert depends on the amount of resin and the rate of resin flow required to fill the mold. Typically, the mat is big enough to allow the flow front area at the transition to chopped fiber to be large enough to reduce resin velocity through the chopped fiber to tolerable levels.
Alternatively, or in combination with the foregoing, a thin mat or veil can be placed over one or both sides of the chopped fiber preform. The thin mat is placed on the form used to spray up the preform.
Chopped fiber and binder are then sprayed on the form as is conventional. This effectively attaches the mat to one side of the chopped preform. If desired, another mat can be draped on the other side of the chopped preform. The chopped preform gives shape to the mat while the mat imparts stability to the chopped fiber to prevent dislodging during resin transfer.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings.
DESCRIPTION OF THE DRAWINGS
Fig. 1 is an exploded perspective view of a mold used in a resin transfer molding process embodying the invention.
Fig. 2 is a top plan view, partially broken away, of the closed mold containing a preform in accordance with the invention.
Fig. 3 is a view taken along line 3-3 in Fig. 2.
-Fig. 4 is a view similar to Fig. 3 showing another preform.
Fig. 5 is a view similar to Fig. 4 showing still another preform.
Fig. 6 is a partial sectional view of a form used to make the preform shown in Fig. 2.
Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of the construction and the arrangements of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Fig. 1 shows a mold 10 used in a resin transfer molding process. The mold 10 includes an upper mold half 14 and a lower mold half 18. The upper mold half 14 has therein (see Fig. 3) an inlet passage 22. It should be noted that the mold halves 14 and 18 can have any number of inlet passages. When closed, the mold halves 14 and 18 define a mold cavity 26 having the shape of a fiber-reinforced polymer or plastic part (not shown) to be molded.
The part is molded by placing a fiber preform 30 in the mold cavity 26 and then introducing or injecting resin into the mold cavity 26 via the inlet passage 22.
The resin is cured to provide the final part having the shape of the mold cavity 26. The resin transfer -molding process as thus far described is conventional and will not be described in greater detail.
In accordance with the invention, the preform 30 includes: a section or insert 34 of continuous strand mat adjacent the inlet passage 22; and chopped fiber and binder 38 spaced from the inlet passage 22. In other words, a continuous strand fiber mat 34 is located in the mold cavity 26 adjacent the inlet passage 22, and chopped fiber 38 is located in the remainder of the mold cavity 26. The chopped fiber 38 is shown partially overlapping the mat 34 in Fig. 3.
The chopped fiber 38 can also completely overlap the continuous strand mat 34 above and/or below the mat.
The size of the mat should be such that the flow front area at the transition from the mat 34 to the chopped fiber 38 is large enough to reduce resin velocity through the chopped fiber to tolerable levels.
It should be noted that the preform 30 can include any number of separate inserts or mats 34, depending on the number of and location of inlet passages.
The manner in which the preform 30 is made is illustrated in Fig. 6. The preform 30 is made on a form 42 having the shape of the part to be molded. The CSM insert 34 is placed on the form 42 at the point that will be nearest the injection passage 22. The remainder of the preform 30 is made with chopped fibers 38 in the conventional manner, by spraying chopped fibers and resin onto the form 42. A conventional spray gun 46 is shown in Fig. 6. The insert 34 and chopped fiber 38 can be placed on the form 42 in either order, or the chopped fiber 38 can be sprayed on the form 42 before and after the insert 34 is positioned.
An alternative preform 100 is shown in Fig. 4.
The preform 100 includes a thin mat or veil 104 on one side of chopped fiber 108 and a thin mat or veil 112 on the other side of the chopped fiber 108. The mat 104 is placed on the form (not shown) used to spray up the preform 100. Chopped fiber and binder are then sprayed onto the form 100. This attaches the mat 104 to the underside of the chopped fiber 108. The mat 112 is then placed on top of the chopped fiber 108. The chopped fiber 108 gives shape to the mats 104 and 112 while the mats stabilize the chopped fiber 108.
Another alternative preform 200 is shown in Fig.
BACKGROUND OF THE INVENTION
The invention relates to resin transfer molding (RTM), and more particularly to fiber preforms used in resin transfer molding.
The RTM process involves injecting or transferring resin into a mold containing fiber reinforcement. The fiber reinforcement can be a preform having generally the shape of the part to be molded. The benefits of a preform are shape, size, loadability and minimal expense. The preform can be made of chopped or short fibers and a resin binder. A chopped fiber preform is typically made by spraying chopped fibers and resin onto a form having the shape of the part to be molded.
Preforms can also be made with continuous strand mat (CSM) or woven mat made with long, interwoven, continuous strand fibers. It can be difficult and expensive to make preforms from continuous strand mat.
SUMMARY OF THE INVENTION
A disadvantage of using chopped fiber preforms is that the flow of resin into the mold can dislodge the chopped fibers near the injection port. When this happens, the dislodged fibers are transported along with the resin flow, dislodging even more fibers.
Eventually, the fibers can pile up and prevent further resin flow, resulting in a scrap part.
To overcome the problem of dislodging fibers near the injection port, the invention uses both chopped fibers and CSM in a preform. An insert or section of CSM or woven mat is used in the preform at the point that will be nearest the injection port. The remainder of the preform is made with chopped fibers in the conventional manner. The size of the CSM insert depends on the amount of resin and the rate of resin flow required to fill the mold. Typically, the mat is big enough to allow the flow front area at the transition to chopped fiber to be large enough to reduce resin velocity through the chopped fiber to tolerable levels.
Alternatively, or in combination with the foregoing, a thin mat or veil can be placed over one or both sides of the chopped fiber preform. The thin mat is placed on the form used to spray up the preform.
Chopped fiber and binder are then sprayed on the form as is conventional. This effectively attaches the mat to one side of the chopped preform. If desired, another mat can be draped on the other side of the chopped preform. The chopped preform gives shape to the mat while the mat imparts stability to the chopped fiber to prevent dislodging during resin transfer.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings.
DESCRIPTION OF THE DRAWINGS
Fig. 1 is an exploded perspective view of a mold used in a resin transfer molding process embodying the invention.
Fig. 2 is a top plan view, partially broken away, of the closed mold containing a preform in accordance with the invention.
Fig. 3 is a view taken along line 3-3 in Fig. 2.
-Fig. 4 is a view similar to Fig. 3 showing another preform.
Fig. 5 is a view similar to Fig. 4 showing still another preform.
Fig. 6 is a partial sectional view of a form used to make the preform shown in Fig. 2.
Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of the construction and the arrangements of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Fig. 1 shows a mold 10 used in a resin transfer molding process. The mold 10 includes an upper mold half 14 and a lower mold half 18. The upper mold half 14 has therein (see Fig. 3) an inlet passage 22. It should be noted that the mold halves 14 and 18 can have any number of inlet passages. When closed, the mold halves 14 and 18 define a mold cavity 26 having the shape of a fiber-reinforced polymer or plastic part (not shown) to be molded.
The part is molded by placing a fiber preform 30 in the mold cavity 26 and then introducing or injecting resin into the mold cavity 26 via the inlet passage 22.
The resin is cured to provide the final part having the shape of the mold cavity 26. The resin transfer -molding process as thus far described is conventional and will not be described in greater detail.
In accordance with the invention, the preform 30 includes: a section or insert 34 of continuous strand mat adjacent the inlet passage 22; and chopped fiber and binder 38 spaced from the inlet passage 22. In other words, a continuous strand fiber mat 34 is located in the mold cavity 26 adjacent the inlet passage 22, and chopped fiber 38 is located in the remainder of the mold cavity 26. The chopped fiber 38 is shown partially overlapping the mat 34 in Fig. 3.
The chopped fiber 38 can also completely overlap the continuous strand mat 34 above and/or below the mat.
The size of the mat should be such that the flow front area at the transition from the mat 34 to the chopped fiber 38 is large enough to reduce resin velocity through the chopped fiber to tolerable levels.
It should be noted that the preform 30 can include any number of separate inserts or mats 34, depending on the number of and location of inlet passages.
The manner in which the preform 30 is made is illustrated in Fig. 6. The preform 30 is made on a form 42 having the shape of the part to be molded. The CSM insert 34 is placed on the form 42 at the point that will be nearest the injection passage 22. The remainder of the preform 30 is made with chopped fibers 38 in the conventional manner, by spraying chopped fibers and resin onto the form 42. A conventional spray gun 46 is shown in Fig. 6. The insert 34 and chopped fiber 38 can be placed on the form 42 in either order, or the chopped fiber 38 can be sprayed on the form 42 before and after the insert 34 is positioned.
An alternative preform 100 is shown in Fig. 4.
The preform 100 includes a thin mat or veil 104 on one side of chopped fiber 108 and a thin mat or veil 112 on the other side of the chopped fiber 108. The mat 104 is placed on the form (not shown) used to spray up the preform 100. Chopped fiber and binder are then sprayed onto the form 100. This attaches the mat 104 to the underside of the chopped fiber 108. The mat 112 is then placed on top of the chopped fiber 108. The chopped fiber 108 gives shape to the mats 104 and 112 while the mats stabilize the chopped fiber 108.
Another alternative preform 200 is shown in Fig.
5. The preform 200 includes elements of the preforms 30 and 100, and common elements have been given the same reference numerals. The preform 200 includes a CSM insert 34, chopped fiber 38, and thin mats or veils 104 and 112 on both sides of the chopped fiber 38. The mat 104 is placed on a form (not shown), the insert 34 is placed on the mat 104, chopped fiber and binder 38 are sprayed onto the form, and the mat 112 is then placed on top of the chopped fiber 38.
Various features of the invention are set forth in following claims.
Various features of the invention are set forth in following claims.
Claims (22)
1. A method for manufacturing a fiber-reinforced polymer object in a resin transfer molding process, said method comprising the steps of (a) providing a mold defining a mold cavity and including an inlet passage communicating with the mold cavity, (b) placing in the mold cavity a preform including continuous strand mat adjacent the inlet passage and chopped fiber spaced from the inlet passage, (c) introducing resin into the mold cavity via the inlet passage, and (d) curing the resin.
2. A method as set forth in Claim 1 wherein step (b) includes manufacturing the preform by (e) providing a form, (f) placing continuous strand fiber mat on the form, and (g) placing chopped fiber and a binder on the form.
3. A method as set forth in Claim 2 wherein step (g) is performed after step (f).
4. A method as set forth in Claim 2 wherein step (f) is performed after step (g).
5. A method as set forth in Claim 2 wherein step (g) includes placing chopped fiber on the form so that the chopped fiber overlaps the fiber mat.
6. A method as set forth in Claim 2 wherein step (b) further includes the step, after step (g), of placing a thin fiber mat on the form and over the chopped fiber and the continuous strand fiber mat.
7. A method as set forth in Claim 6 wherein step (b) further includes the step, before step (f), of placing a first thin fiber mat on the form, and wherein steps (f) and (g) include placing the chopped fiber and the continuous strand fiber mat over the first thin fiber mat.
8. A method as set forth in Claim 2 wherein step (b) further includes the step, before step (f), of placing a thin fiber mat on the form, and wherein steps (f) and (g) include placing the chopped fiber and the continuous strand fiber mat over the thin fiber mat.
9. A method for manufacturing a fiber-reinforced polymer object in a resin transfer molding process, said method comprising the steps of (a) providing a mold defining a mold cavity and including an inlet passage communicating with the mold cavity, (b) placing continuous strand fiber mat in the mold cavity adjacent the inlet passage, (c) placing chopped fiber in at least a portion of the remainder of the mold cavity, (d) introducing resin into the mold cavity via the inlet passage, and (e) curing the resin.
10. A method as set forth in Claim 9 wherein step (c) includes placing chopped fiber in the mold cavity so that the chopped fiber overlaps the fiber mat.
11. A method as set forth in Claim 9 and further comprising the step of placing a thin fiber mat in the mold cavity and over the chopped fiber and the continuous strand fiber mat.
12. A method as set forth in Claim 11 and further comprising the step of placing a first thin fiber mat in the mold cavity, and wherein steps (b) and (c) include placing the chopped fiber and the continuous strand fiber mat over the first thin fiber mat.
13. A method as set forth in Claim 9 and further comprising the step of placing a thin fiber mat in the mold cavity, and wherein steps (b) and (c) include placing the chopped fiber and the continuous strand fiber mat over the thin fiber mat.
14. A method for manufacturing a fiber-reinforced polymer object in a resin transfer molding process, said method comprising the steps of (a) providing a mold defining a mold cavity and including an inlet passage communicating with the mold cavity, (b) placing in the mold cavity a preform including a thin fiber mat and chopped fiber in overlapping relationship with the thin fiber mat, (c) introducing resin into the mold cavity via the inlet passage, and (d) curing the resin.
15. A method as set forth in Claim 14 wherein step (b) includes manufacturing the preform by (e) providing a form, (f) placing the thin fiber mat on the form, and (g) placing the chopped fiber and a binder on the form.
16. A method as set forth in Claim 15 wherein step (b) includes placing the mat under the chopped fiber.
17. A method as set forth in Claim 15 wherein step (b) includes placing the mat above the chopped fiber.
18. A method as set forth in Claim 17 wherein step (b) further includes the step of placing a second thin fiber mat on the form and under the chopped fiber.
19. A method for manufacturing a fiber-reinforced polymer object in a resin transfer molding process, said method comprising the steps of (a) providing a mold defining a mold cavity and including an inlet passage communicating with the mold cavity, (b) placing a thin fiber mat in the mold cavity, (c) placing chopped fiber in the mold cavity in overlapping relationship with the thin fiber mat, (d) introducing resin into the mold cavity via the inlet passage, and (e) curing the resin.
20. A method as set forth in Claim 19 wherein step (b) includes placing the mat under the chopped fiber.
21. A method as set forth in Claim 19 wherein step (b) includes placing the mat above the chopped fiber.
22. A method as set forth in Claim 21 and further comprising the step of placing a second thin fiber mat in the mold cavity and under the chopped fiber.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US42379395A | 1995-04-18 | 1995-04-18 | |
| US08/423,793 | 1995-04-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2172793A1 true CA2172793A1 (en) | 1996-10-19 |
Family
ID=23680201
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2172793 Abandoned CA2172793A1 (en) | 1995-04-18 | 1996-03-27 | Resin transfer molding process |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2172793A1 (en) |
-
1996
- 1996-03-27 CA CA 2172793 patent/CA2172793A1/en not_active Abandoned
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |