METHOD FOR FORMING A FIBER REINFORCED STRUCTURE

Abstract: A method of molding in a single operation an integral fiber structure (10) including a laminate fiber section (12), joined to a hollow fiber section (16) comprises the steps of providing a mold (18) having a pair of mold pieces (20, 22) disposed to be opened or closed and including inner complementary surfaces (24, 26) leading to second surfaces (30, 32) for forming a cavity (34); placing first fiber material (12, 28) comprising a laminate having one or more layers on at least one of the inner complementary surfaces (24, 26) of said mold pieces (20, 22) when said mold (18) is open; placing second fiber material (14, 15) leading from said first fiber material (12, 28) on the inner surfaces (30, 32) of said cavity (34) of said mold pieces (20, 22); placing an inflatible member (31) in said second fiber material (14, 15) disposed in said cavity (34); closing said mold (18); inflating said inflatible member (31); injecting resin to impregnate said first (12, 28) and second fiber materials (14, 15), and curing said resin to form said integral solid fiber structure (10) with said laminate integrally joined to a hollow section (16) formed in said cavity (34).

Description: The invention relates to a method for forming a fiber reinforced structure having a sheet-like laminate fiber section joined to a hollow fiber section. Methods for forming only a hollow fiber reinforced structure are described in EP-A1 0234341 (this document falls under Article 54(3)), and EP-A1 0212140. According to these methods a mold is provided having a pair of mold pieces disposed to be opened or closed, the mold pieces having inner cavity forming surface portions spaced apart from each other by a given distance forming a cavity for defining the hollow section. Further fiber material is placed on the cavity forming surface portions of said cavity of said mold pieces. After that an inflatable member is placed between said fiber material placed on said cavity forming portions. Then said mold is closed and said inflatable member is inflated. Now resin is injected to impregnate said fiber material. Finally said resin is cured to form said hollow fiber reinforced structure formed in said cavity. In many automotive and other products, it is necessary to form parts in which a sheet-like laminate consisting of one or more layers joined to hollow sections to form integral structures. Such automotive parts for example may include rear panels, dashes, fire walls or the like. The invention is based on the problem to provide a reliable method for forming a reinforced structure including a sheet-like laminate fiber section joined to a hollow fiber section in a single molding operation. In accordance with the present invention this problem is solved by a method comprising the following steps: a) providing a mold having a pair of mold pieces disposed to be opened or closed, the mold pieces having inner cavity forming surface portions spaced apart from each other by a given distance forming a cavity for defining the exterior of the hollow section, the mold pieces further including inner complementary surface portions extending from the cavity forming surface portions and defining the sheet-like section extending from the hollow section; b) placing first fiber material on at least one of the complementary surface portions of said mold pieces when said mold is open; c) placing second fiber material leading from said first fiber material on the cavity forming surface portions of said cavity of said mold pieces; d) placing an inflatable member between said second fiber material placed on the cavity forming portions; e) closing said mold; f) inflating said inflatable member; g) injecting resin to impregnate said first fiber material and said second fiber material; h) curing said resin to form said fiber reinforced structure with said sheet-like laminate section integrally joined to said hollow section formed in said cavity. The present invention provides a method for fabricating in a single molding operation a structure comprising a solid laminate containing a local hollow section. The method overcomes the problem of making large intricate structures generally characterised by comparatively thin, fiber reinforced plastic sheets which contain local areas of hollow section for added strength. Preferably said first fiber material completely fills the space between said complementary surface portions when said mold is closed. Advantageously the mold surfaces define an automotive rear panel. It is convenient that a single piece of fiber material covers both a complementary mold surface portion of one mold piece and its adjacent cavity forming surface portion. In a preferred method the step g) comprises injecting the resin into a side of the mold where ends of the complementary mold surface portions meet. In the following embodiments of the invention are further explained by means of the accompanying drawings, wherein Fig. 1 is a cross-sectional view of a rear panel for an automobile, in accordance with the present invention, and Figs. 2 to 4 illustrate cross-sectional broken away views of portions of different embodiments of the present invention. Referring to Fig. 1, a cross-sectional view of a rear panel in an automobile, for example, comprises an irregular surface made up of solid laminate sections 12 and a hollow section 14 made up of an irregular surface to form a hollow area 16. In the present invention, the parts illustrated in Fig. 1 are made up of a reinforced fiberglass material. The present invention is directed toward a method for molding a single laminate layer section, such as section 12, with a multi-layered or hollow section which may be made up of a section 14 leading to section 12 and an addition piece 15 which may be molded with the section 14 to form the hollow area 16. The hollow area 16 is used in areas where stronger or stiffer sections are required. These sections could be in areas of the rear panel, dash members or where a hollow conduit is beneficial in an automobile. A method of forming a structure such as the structure 10 is illustrated in Figs. 2, 3 and 4 in which slightly different embodiments are involved. Most of the elements illustrated in Figs. 2, 3 and 4 are substantially the same as that illustrated in Fig. 1 and therefore the same reference numbers will be assigned. The only difference in the Figures 2, 3 and 4 with respect to Fig. 1 are in the specific structures formed and in the areas at which the hollow areas are joined to the single layer laminate portion of the fiber material. Referring to Fig. 2, a mold 18 comprises an upper mold piece 20 and a lower mold piece 22. The mole 18 is adapted to be opened and closed by conventional means with the position illustrated in Fig. 2 illustrating the mold 18 in a closed position. The mold pieces 20 and 22 include complementary sections 24 and 26, adapted to receive the fiberglass piece 12 and the end 28 of the fiberglass piece 15. The material between the area between the complementary pieces, which may or may not be flat areas, is referred to as, a laminate having a single layer. The surfaces 24 and 26 are referred to as being complementary because they are shaped in the opposite way so as to accommodate the pieces 12 and the end piece 28. In practicing the present invention, the fiber material 12 is pre-placed within the inner wall of the upper mold piece 20. The piece 15 is pre-placed in the lower mold piece 22 in the manner illustrated in Fig. 1 When the mold 18 is closed, a cavity is formed between sections 30 and 32 on the inner surfaces of the mold pieces 20 and 22. Prior to closing the mold 18, an inflatible member or bladder 31 pre-placed between the fiber pieces 14 and 15 inside the cavity 34 of the mold. After the fiber reinforced pieces are preformed on the inner surfaces of the mold pieces with the inflatible member 31 is inserted between the fiber material in the cavity of the mold, the mold pieces 20 and 22 are closed in the manner illustrated in Fig. 2. At this point, pressure is applied into the inflatible member 31 from a source of pressure 36, which may be compressed air or other suitable gas material. After the mold 10 has been closed and pressure applied to the inflatible member 31, resin from a source 38 is injected through a pump 40 into the fiber reinforced material between the mold pieces. As the resin is injected into the fiber, air is vented from the fiber pieces through a vent 42. Perimeter feeding of the resin and venting of the air may be employed as described in the EP-A1-0234341. The details relating to grooves for feeding the resin and venting the air are not illustrated because they are only indirectly related to the present invention. Figs. 3 and 4, illustrate different embodiments of the present invention in which different ways for joining a laminate or single layer section of fiber reinforced material to the hollow section are illustrated. The mold shapes are slightly different to accommodate the different manners of joining the fiber. The resin transfer molding steps are the same as described in connection with Fig. 2. In Fig. 3, the complementary mold areas 45 and 47 are flat to receive flat section of fiber 44 and 46 therebetween. The pieces 44 and 46 continue and are placed inside the cavity 34 of the mold. The inflatible bag is placed in the cavity and the subsequent steps are followed as previously described. In Fig. 4, the complementary sections 48 and 50 are related flat to receive fiber section 52 therebetween. A fiber section 52 forms part of the hollow area to be formed in the cavity 34 of the mold. An end section 54 is folded over in the direction leading to the cavity 34. The various subsequent steps in the molding process is the same as those described in connection with Fig. 2.

Claims: 1. A method for forming a fiber reinforced structure (10) having a sheet-like laminate section (12) joined to a hollow section (16), the method comprising the following steps: a) providing a mold (18) having a pair of mold pieces (20, 22) disposed to be opened or closed, the mold pieces (20, 22) having inner cavity forming surface portions (30, 32) spaced apart from each other by a given distance forming a cavity (34) for defining the exterior of the hollow section (16), the mold pieces (20, 22) further including inner complementary surface portions (24, 26) extending from the cavity forming surface portions (30, 32) and defining the sheet-like section (12) extending from the hollow section (16); b) placing first fiber material (27, 28) on at least one of the complementary surface portions (24, 26) of said mold pieces (20, 22) when said mold (18) is open; c) placing second fiber material (14, 15) leading from said first fiber material (27, 28) on the cavity forming surface portions (30, 32) of said cavity (34) of said mold pieces (20, 22); d) placing an inflatable member (31) between said second fiber material (14, 15) placed on the cavity forming portions (30, 32); e) closing said mold (18); f) inflating said inflatable member (31); g) injecting resin to impregnate said first fiber material (27, 28) and said second fiber material (14, 15); h) curing said resin to form said fiber reinforced structure (10) with said sheet-like laminate section (12) integrally joined to said hollow section (16) formed in said cavity (34). 2. The method according to claim 1, characterised in that said first fiber material (27, 28) completely fills the space between said complementary surface portions (24, 26) when said mold (18) is closed. 3. The method according to claim 1 or 2, characterised in that the mold surfaces (30, 32, 24, 26) define an automotive rear panel. 4. The method according to one of the preceding claims, characterised in that a single piece (44, 46, 52) of fiber material covers both a complementary mold surface portion of one mold piece and its adjacent cavity forming surface portion. 5. The method according to one of the preceding claims characterised in that step g) comprises injecting the resin into a side of the mold where ends of the complementary mold surface portions meet.

Inventors: FREEMAN, RICHARD BENJAMIN
Applicants: THE BUDD COMPANY
Application year: 1988
Main classification: B29C67
IPC codes: B29C70, B29C43