Process and compositions for reinforcing structural members

#The present invention relates generally to processes and compositions for reinforcing hollow structural members and more specifically deals with a two-part, resin-based system for reinforcing hollow structural members.

#Motor vehicle collisions are a common occurrence in today's highly mobile society. Motor vehicle designers and manufacturers go to great lengths to protect the vehicle occupants from injury by providing vehicle structures having good strength and energy absorption characteristics. It is also a goal of designers to fabricate motor vehicle structures which can withstand low-speed impacts without requiring substantial repairs. Although motor vehicle designers and manufacturers have succeeded in providing high-strength, energy-absorbing structural components, the restoration of these desirable attributes to a motor vehicle which has been damaged in a collision is of considerable concern to after-market vehicle repair facilities.

#Particularly in the case of metal structural components, the deformation of a structural member during a collision produces a number of unwanted effects in terms of both the relative geometry or shape of the part and with respect to the stength of the metal. It is a goal of the repair facility to restore to the extent possible the original shape of the damaged part so that it can once again carry out its function in the vehicle. It is a further goal, however, of the repair facility to restore the original strength and energy absorption characteristics to the damaged part. While considerable attention has been paid to the restoration of shape in collision damage repair, resulting in numerous metal repair procedures and devices such as frame-straightening machines and the like, the viability of reinforcement techniques in collision repair are less developed. It will be appreciated that the feasibility of reinforcement devices and procedures is determined by a number of factors that go beyond merely restoring strength to the damaged part.

#These and other meritorious advantages and features of the present invention will be more fully understood with reference to the following description of the preferred embodiments of the invention and in connection with the drawings in which:

#FIG. 1 is a perspective view of a portion of an automobile in which the front section of a frame side rail is exposed.

#FIG. 2 is a U-shaped stamping of a side rail showing the composition of the present invention in place in the rail channel with a cover plate shown in exploded view.

#Referring now to FIG. 1 of the drawings, a typical motor vehicle 20 is shown with the front section 22 of frame side rail 24 being exposed. It will be assumed for purposes of this discussion that motor vehicle 20 has been involved in a low-speed front-end collision and that side rail 24, which is typically formed of steel, sustained damage, for example, a crumpling or collapse of front section 22 in region 26. It will also be assumed that front section 22 has now been straightened using conventional frame-straightening techniques such as a frame machine. It will also be assumed that frame side rail 24 is constructed of two U-shaped stampings 28 and 30 welded together by means of a horizontal longitudinal joint or seam (not shown). Since region 26 has been plastically deformed during the collision and during the straightening process, its strength and energy absorption characteristics have been dramatically altered. It will also be noted that region 26 is a natural bend of frame side rail 24. Hence, reinforcement by the conventional method of attaching a metal plate is rendered even more difficult since a metal reinforcing plate would have to conform to the natural bend of region 26. However, the problems inherent in this prior art technique have been avoided by the repair of region 26 using the method and compositions of the present invention.

#Turning now to FIG. 2 of the drawings, an isolated view of region 26 of front section 22 is shown with U-shaped stamping removed and closure palte 32 illustrated as exploded from U-shaped stamping 30. Reinforcement member 34 is seen substantially filling a section of channel 36 and rigidly bonded to the inner surfaces of U-shaped channel 30. While closure plate 32 is shown removed from its attachment at flanges 38 and 40 of U-shaped member 30, in actuality, closure plate 32 is attached to U-shaped stamping 30 by spot welds at flanges 38 and 40 and by the rigid attachment of reinforcement member 34 to closure plate 32. This relationship is illustrated more clearly in FIG. 3 which is a cross-section along lines 3--3 of FIG. 2. There, closure plate 32 is shown welded in place on U-shaped stamping 30 at flanges 38 and 40. It can be seen that reinforcement member 34 completely occupies a portion of channel 36 in contact with the surrounding surfaces. Reinforcement member 34 is in its cured state such that it is a solid body comprising a cross-linked epoxy resin matrix 42 in which particles of filler 44 and expanded microspheres 46 are shown. It is important to point out that reinforcement member 34 is not shown to scale and that the sizes of the expanded microspheres 46 and filler particles 44 are greatly exaggerated for the purposes of illustration. A more detailed explanation of the compositional characteristics of reinforcement 34 will follow. In this manner, reinforcement member 34 serves to reinforce region 26 of frame side rail 24 such that during a subsequent, second collision, region 26 of frame side rail 24 will respond in a fashion closely similar to that of the original part.

#Reinforcement member 34 is preferably formed in the following manner which consititutes the reinforcement repair process of the present invention. Referring now to FIG. 4 of the drawings, the first step of the procedure involves the preparation of the first composition or side A of the invention. Side or part A is prepared by slowly adding a filler and unexpanded, thermally-expandable microspheres to a liquid epoxy resin or prepolymer until a dough-like consistency is attained. The ingredients can be mixed in any convenient container using a conventional mixer, although undue shearing should probably be avoided. As will be more fully appreciated hereinafter, in the most preferred embodiment, side A, and side or part B, are provided pre-mixed in the form of a two-part kit. The mixing or blending together of the ingredients to form side A can be carried out at ambient temperature and pressure with no unusual constraints on the process parameters.