3D braided composited tubes with throat sections and manufacture method thereof

A manufacture method of a three dimensional (3D) braided composite tube with a throat section includes: providing an assembled mandrel comprising an upper mandrel and a lower mandrel, and braiding an 3D braided inner layer on the upper mandrel; winding fiber yarns to form a fiber yarn layer over the 3D braided inner layer; tightening the 3D braided inner layer to the assembled mandrel by an appropriate tension force when winding; and infiltrating resin and increasing temperature to cure the resin for obtaining a composite tube with a narrower throat section. The present invention takes advantage of winding fiber yarn outer layer to keep the radius of the throat of the 3D braided inner layer to meet design requirement. Additionally, the hoop strength of the throat section is increased so that the metal shell can be made thinner to reduce the weight of the rocket nozzle.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a three dimensional (3D) braided composite tube, and more particularly, to a 3D braided composite tube with a narrower throat section and a manufacture method thereof.

2. Description of the Related Art

Braiding technologies are widely applied to the manufacture of fabrics, in which fiber yarns are interlaced woven in plane form. Braiding technologies also apply to the composite material and are widely used in many fields, such as vehicle, aviation, navigation, medical treatment, etc.

The composite material manufactured by lamination of fabrics is generally called two dimensional (2D) composite materials, in which the fabrics are used as reinforcement. The main drawback of the laminated 2D composite material is poor interlaminar properties. As an example, the insulation of a rocket nozzle is used in a high temperature (over 2000° C.) and shear force environment caused by hot air flow. Under such severe environment the laminated composite insulation would suffer pre-mature ply lift and/or spallation if the ply angle was not properly designed to avoid being parallel or vertical to air flow.

By adding thru-the-thickness reinforcement, the three dimensional (3D) woven composite material demonstrate much higher interlaminar strength over 2D woven composite material. However, most 3D technologies sacrifice the in-plane properties because of the reduction of the thru-the-thickness fiber content.

Therefore, the 3D braiding technology is introduced to improve interlaminar strength without sacrificing the in-plane properties of the composite structure. The fiber content of the 3D braided composite material is higher than that of the general 3D technologies, so the in-plane property is maintained. However, there are difficulties to manufacture hollow structures with a narrower throat section for used in, for example, a rocket nozzle by 3D braiding technologies.

FIG. 1illustrates cross-section of a conventional rocket nozzle100. For clearly showing the direction of the rocket nozzle100, it also shows the rocket motor110inFIG. 1. The rocket nozzle100includes a convergent section120, a throat section130and a divergent section140, and the rocket nozzle100is basically a tube having larger radius at each end than the middle. The inner layer of the rocket nozzle100is an insulated layer150that reduces the heat via ablation to protect the shell160.

FIG. 2illustrates that the insulated layer150is manufactured on a mandrel200by a 3D braiding technology. Tension of fiber yarn210in the insulated layer150prevents it from contacting the mandrel200while braiding. The convergent section220, the throat section230and the divergent section240of mandrel200are respectively correspond to the convergent section120, the throat section130and the divergent section140ofFIG. 1. The fiber yarn210in the insulated layer150being not able to contact to mandrel200make the radius of the throat section larger than desired, as a result, the propulsion of the rocket nozzle is reduced.

There thus exists a need and a demand for an improvement in the methods for making a 3D braided composite tube with a narrower throat section to overcome the difficulty in prior art.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention to provide a 3D braided composite tube with a throat section and a manufacture method thereof.

For achieving the object above, a 3D braided composite tube with a throat section is disclosed according to one embodiment of the present invention. The step of the manufacture method comprises: providing an assembled mandrel comprising an upper mandrel and a lower mandrel; separating the lower mandrel from the upper mandrel and braiding an 3D braided inner layer on the upper mandrel, then tightening the 3D braided inner layer to the upper mandrel at the upper larger radius portion and the throat portion by binding devices; combining the lower mandrel with the upper mandrel and fixing the lower mandrel to the upper mandrel by a fixing device, then tightening the 3D braided inner layer to the lower mandrel by another set of binding devices; removing the binding devices, followed by winding fiber yarns over the inner layer from the middle portion of the assembled mandrel toward two ends thereof to the binding devices at ends for forming a fiber yarn outer layer over the 3D braided inner layer; and infiltrating resin into the 3D braided inner layer and the fiber yarn outer layer, followed by increasing temperature to cure the resin for obtaining a composite tube.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made to the drawings to describe exemplary embodiments of the present 3D braided composite tube and manufacture method thereof in detail. The following description is given by way of example, and not limitation.

Referring toFIG. 3, which schematically illustrates cross-section of the 3D braided composite tube of the present invention. Referring toFIGS. 4˜8, which schematically illustrates cross-section of the 3D braided composite tube of the present invention. These figures also illustrate the manufacture method of the 3D braided composite tube of the present invention.FIG. 4shows the first step (Step 1) of the manufacture method.FIG. 5shows the second step (Step 2) of the manufacture method.FIGS. 6-7show the third step (Step 3) of the manufacture method.FIG. 8shows the fourth step (Step 4) of the manufacture method. As shown inFIG. 3, the 3D braided composite tube300comprises: a 3D braided inner layer310, a fiber yarn outer layer320wound over the 3D braided inner layer310, and a throat section340located at the middle portion of the 3D braided composite tube300. The 3D braided composite tube300further comprises a convergent section330and a divergent section350. The convergent section330allows one side of the 3D braided composite tube300to converge toward one side of the throat section340, and the divergent section350allows another side of the throat section340to diverge toward another side of the throat section340.

As shown inFIG. 3, wherein the 3D braided composite tube300is upside-down to the rocket nozzle100ofFIG. 1, that is, the convergent section330is downward and the divergent section350is upward. In the present invention, it starts to braid the fiber yarn from the divergent section because the fiber yarn is relatively easy to attach on the convergent section. The braiding direction of the present invention is from top to bottom on a braiding machine of prior art. The fiber yarn outer layer320is wound with tension over the 3D braided inner layer310on a filament winding machine of prior art, followed by a resin infiltration process to combine both layers. Thereby, 3D braided inner layer310is tightened and forced to contact the mandrel throughout the resin infiltration process.

Referring toFIGS. 4˜8, which illustrate the manufacture method of the 3D braided composite tube of the present invention. Note that the braided thickness is changed with the tube radius, and for simplified description in the embodiment, the thickness illustrated in each figure is the same. The steps of the manufacture method is described as follow:

Step 1: providing an assembled mandrel410composed of an upper mandrel411and a lower mandrel412, and attaching the upper mandrel411to a seat400of a braiding machine (not shown) with screw or any adequate way. Subsequently, separating the lower mandrel412to a distance from the upper mandrel411so that the lower mandrel412will not interfere the braiding operation on the upper mandrel411, then braiding 3D braided inner layer310on the upper mandrel411until it exceeds the required length of the composite tube. Specifically, in step 1, there is no interference between the upper mandrel411and the lower mandrel412while braiding the 3D braided inner layer420, so the 3D braided inner layer420can better attach onto the upper mandrel411in spite of the effect of the tension force460. After the 3D braided inner layer420is done, binding devices430,440and450are respectively tightened to bind the 3D braided inner layer420to the upper mandrel411, as shown inFIG. 4.

Step 2: pushing the lower mandrel412upward to combine with the upper mandrel411, and fixing the lower mandrel412to the upper mandrel411by a fixing device500, then tightening the 3D braided inner layer420to the lower mandrel412by binding devices510,520. Specifically, the position of the seat400of the braiding machine is adjusted during the tightening process so that tension force530working on the 3D braided inner layer420is partially released to facilitate the binding process. The tension force530is totally released after the 3D braided inner layer420is tightened, and the assembled mandrel410with the 3D braided inner layer420is removed from the seat400, as shown inFIG. 5. Subsequently, the assembled mandrel410with the 3D braided inner layer420is mounted in a winding equipment (not shown), for example, a filament winding machine for fabricating pressure vessels. Any kind of winding equipment and the like can be used.

Step 3: removing the middle binding device430and winding fiber yarns from middle portion of the assembled mandrel400toward two ends to the end binding devices respectively (for example, binding devices440,510) so as to form fiber yarn outer layer600over the 3D braided inner layer420, as shown inFIG. 6. Specifically, an appropriate tension force is applied on the fiber yarn during winding to force the 3D braided inner layer420tightly contact with the assembled mandrel410. The binding devices440,510are selectively removed as required to continue the winding process as shown inFIG. 7.

Step 4: put the assembled mandrel410with the 3D braided inner layer420and the fiber yarn outer layer600into a pressure vessel (not shown) containing resin, which is selected from a group consisting of epoxy resin, phenolic resin and furan resin, then close and seal the pressure vessel and apply pressure into the sealed pressure vessel to force the resin to infiltrate into the 3D braided inner layer420and the fiber yarn outer layer600. Meanwhile, the temperature is increased to converting the resin to B-stage. Subsequently, the mandrel410with the 3D braided inner layer420and the fiber yarn outer layer600is put into a vacuum bag (not shown) and moved to an autoclave to cure the B-staged perform to a composite part. After the curing process, the fixed device500is removed and the upper mandrel411and the lower mandrel412are disassembled from two ends of the composite part800, which is a 3D braided composite tube with a narrower throat section, as shown inFIG. 8. The composite tube800is optionally put in an oxygen-free environment and the temperature is gradually increase to 800˜900° C. to carbonize the matrix. The densification process of infiltrating, curing and carbonization is repeated until the desired density of the composite is achieved. Thereafter, the temperature is optionally increased to 2600° C. to transfer the carbon matrix to graphite to further improve the ablation ability. Moreover, the composite tube800comprising a 3D braided inner layer810and a fiber yarn outer layer820can be cut to obtain a required cut section, which is used as the rocket nozzle, for example, the required cut section between the dashed lines830and840is equivalent with the 3D braided composite tube300ofFIG. 3and for another condition dividing the composite tube800into two parts necessarily by cutting between the dashed lines850and860while combining a shell and an insulating layer.

When the 3D braided composite tube300of the present invention, which comprises a 3D braided inner layer310and a fiber yarn outer layer320, is used in a rocket nozzle as ablative, the ablation rate is decreased so the thrust of the motor can be maintained. Moreover, the hoop strength of the throat section is increased thanks to the fiber yarn outer layer320so that the metal shell can be made thinner to reduce the weight of the rocket nozzle.