FR2862016A1 - Shaping procedure for material based on thermosetting resin after polymerisation uses two or more basic components stuck together and placed under load - Google Patents

Abstract

The procedure, e.g. for use with pultruded polymerised materials, consists of sticking together the generally flat facing surfaces of two basic components (4, 6) and placing them in a shaping jig or under load until the adhesive (5) has polymerised. The adhesive used for the procedure has a low elasticity and a high resistance to shearing, while a wedge in the form of a central shoulder (8) can be used to ensure the correct thickness of the adhesive layer.

Description

The present invention relates to a method for shaping a

  piece of composite material based on thermosetting resin and after polymerization.

  This was previously impossible and required that a polymerized part kept its shape permanently. The advantage of being able to post-form them is of great value in the work of pultruded composite materials, because they are manufactured in great lengths (several kilometers) and then used in smaller quantities. The curvatures that we wish to give them a posteriori being different from one time to the other, we can not make them curved. In addition, the pultrusion technology allows only very wide radii of curvature that vary depending on the section, but several meters in all cases. The parts based on thermoplastic resin, which can be post-formed hot, are, for their part, more expensive, less mechanically resistant, and less available on the market, or do not exist in many dimensions. The technique already exists in glulam, but the basic elements are then pre-formed, which implies that the wood is post-formable by another technique, which is not the case of composite material based of thermosetting resin. This is not the glue that keeps the finished product in shape. In our case, the original elements will return to their original form if we remove the glue.

  The shaping method according to the invention makes it possible to produce, from standard parts already polymerized, such as sheets, plates, or profiles, pieces of curved shapes on demand, within the limits of flexural strength. basic materials used. It is then possible to make shaped parts without going through the molding technique, which produces expensive and little mechanical parts because of the low load they contain and involve the manufacture of a mold, often unattainable for single parts or small amounts.

  The principle of the invention is as follows: - Shaping of several rectilinear basic elements glued together (Fig. 1) 30 - Holding in position of the assembly until polymerization of the adhesive (Fig. 2) Removal of the holding system There is then a withdrawal of the assembly which depends on the glue used, applied radii of curvature and sections of the original elements.

  According to the particular embodiments: - The original elements may be two or more depending on the curvature I section report that is desired.

  - The original elements may or may not have different sections.

  - The shaping can be done by a simple charge or a shaper according to the quantities to be produced.

  The accompanying drawings illustrate the invention: FIG. 1 shows the bending loading shaping of two rectilinear basic elements.

  Figure 2 shows the positional retention of the two glued elements of Figure 1 during the polymerization of the glue.

  Figure 3 shows the shrinkage observed on the beam obtained from the two elements of Figures 1 and 2 after removal of the shaping stress.

  Figure 4 shows shaper shaping of two rectilinear basic elements to obtain a crinoline arch.

  FIG. 5 represents the holding in position of the elements of FIG. 4.

  Figure 6 shows the shrinkage observed on the hoop crinoline after output of the shaper.

  Figure 7 shows how a shoulder is made at the time of sanding to ensure the thickness of the glue joint.

  With reference to the drawings of sheet 1/2, FIGS. 1, 2 and 3, for example "beam", the device comprises a first base element (A), here a pultruded fiberglass beam and polyester resin of length 6 m. and a square section of 50 x 50 x 5 x 5, a second base element (C) identical to the first (A), a seal (B) of methacrylate adhesive of thickness in accordance with the manufacturer's specifications, clamps ( D) all on two supports and a load. In Figure 3, we observe the position of the beam before removal (E), which highlights it.

  With reference to the figures of sheet 2/2, FIGS. 4, 5, 6 and 7, for example "crinoline bow", the device comprises a first base element (4), here a pultruded fiberglass and polyester resin plate. of length 2 m and section 50 x 4, a second base element (6) identical to the first (4), a gasket (5) of methacrylate glue of thickness in accordance with the manufacturer's specifications, a part of fixed shaper (1 ), a first movable shaper part (2) and a second movable shaper part (3). In Figure 3, we observe the position of the arch before withdrawal (7), which puts it in evidence. In Figure 7, the thickness of the adhesive joint (5) between the pultruded plates (4) and (6) is guaranteed by a shoulder (8) left at the time of sanding.

  Example 1: Fabrication of a curved beam from two fiberglass and polyester resin pultruded sections 6 m long and 50 x 50 x 5 x 5 sections.

  This type of beam can be used to build shaped walkways, guardrails or circular platforms of roof domes or timber beams, the list being non-exhaustive. To obtain a minimum of shrinkage, it is advisable to choose a glue with very low elongation, with a very high shear strength. These characteristics are found in methacrylate adhesives, such as MA310 from Plexus (ITW Group). The thickness of the glue joint is of paramount importance, it will be guaranteed by adding a shim between the two beams before gluing. Note that since it is necessary to sand the beams before gluing them, it will be possible to practice a partial bilateral sanding of each of the basic elements, thus forming a central shoulder (8) which will take the place of wedge.

  During loading, there is a risk of lateral sliding of the beams relative to each other. This problem will be solved by adding guides fixed temporarily on one of the beams and welcoming the second with a little play. These guides will preferably be made of a high density polyethylene type material, to prevent the glue from forming. attach on it. There will be enough of them so that the beams can not slip between two of them. When sanded by leaving the shoulder, cleaned the surfaces to be bonded, degreased with acetone, glued, arranged the guides and put under load, clamps (D) are added along the entire length of the beam to ensure a good homogeneity of the tightening of the glue joint. The polymerization of the glue is then expected, then the clamps, the guides and finally the load are removed. We then note the withdrawal (E).

  Example 2: Crinoline arch A crinoline arch is a constituent element of a crinoline ladder. These ladders are commonly made of composite materials for corrosion, mass or magnetic field problems. Since the crinoline is made up of arches and flat tiles and the ladder is made only of rectilinear pieces, the only problematic part is the arch, which is a curved piece. Until then, the arches were made by molding, slow process, expensive, giving a product with poor mechanical characteristics and therefore important section. The production of crinoline hoops according to the invention makes it possible, at the same time, to divide the section by two, to divide the price by three and to multiply the stiffness by two, while being faster to manufacture, which implies less important quantities stored. The method is similar to that of the aforementioned beams, but since the quantities of identical parts to be produced are important, we will go through the technique of the shaper. We will work with two dishes 50 x 4 section and 2 m long When we sanded leaving the shoulder, cleaned the surfaces with acetone, glued, we place the dishes in the shaper (Figure 4). They are then forced to follow the shapes of the shaper (Figure 5) and wait for the polymerization time of the glue. The bow of the shaper is then removed and the withdrawal (7) is noted.

Claims (6)

  1. A method for shaping a piece of composite material based on thermosetting resin and after polymerization.   a) Shaping of the piece by superposition of at least two identical or different base pieces (4 and 6, for example), mutual bonding of their faces of complementary shapes, generally flat, facing one of the and other stressing of the assembly in a shaper (1 and 2) or via a load and holding in position until polymerization of the glue.   b) Removal of the load or withdrawal of the shaper.   2. Method according to claim 1, characterized in that the adhesive used has a low elongation and high shear strength.   3. Method according to claim 1, characterized in that a shim is placed between the base elements, to ensure the thickness of the adhesive joint (5).   4. Method according to claim 3, characterized in that the wedge is materialized by a central shoulder (8) on the faces facing each other of the basic elements, left at the time of sanding.   5. Method according to claim 1, characterized in that guides are fixed temporarily on one of the basic elements, accommodating the other element (s) with a little play, to prevent slippage lateral elements relative to each other.   6. Method according to claim 5, characterized in that the guides are made of a high density polyethylene (HDPE) type of fatty material, in order to prevent the glue from sticking to it. 15 20