Fiber reinforced polymer composite structures and electromagnetic induction …

Description (excerpt)

CROSS REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. patent application Ser. No. 17/779,954 filed May 25, 2022 (pending), which is a U.S. National Stage entry of PCT/JP2020/043228 filed/371(c) date of Nov. 19, 2020 (expired), which claims the benefit of U.S. Provisional Patent Application Ser. No. 62/940,830 filed Nov. 26, 2019 (expired), the contents of all incorporated by reference in their entirety. RIGHTS OF THE GOVERNMENT The invention was made with Government support from the U.S. Air Force. The Government of the United States has the right to practice or have practiced on behalf of the United States this subject invention in all countries. The invention described herein may be manufactured, used, and licensed by or for the Government of the United States for all governmental purposes without the payment of any royalty. FIELD OF THE INVENTION The present invention relates to polymer composites, fiber reinforced polymer composite structures, and electromagnetic induction processing for making same, and the use of such cases as pressure vessels, rocket cases, athletic goods, pipe, and other lightweight structural components. BACKGROUND OF THE INVENTION Fiber reinforced polymeric structures are produced by processes that typically require oven curing of the adhesive polymeric resin system comprising such structures. The use of high temperature resin systems is desired as such systems can impart high temperature strength to the resulting fiber reinforced polymeric structures. Unfortunately, when a high temperature resin is employed, processes are limited to articles that do not contain a heat sensitive material, such as a rocket propellant, because high oven temperatures are required to cure such resins and such elevated temperatures impart excessive thermal energy to the heat sensitive materials. Excessive thermal energy can lead to decomposition of heat sensitive materials or even auto ignition of such heat sensitive materials in the specific case of rocket propellant, creating the conditions for an explosive event. Applicants recognized that the source of the problem was not only the amount of thermal energy provided by a curing oven but even more importantly the rate at which such thermal energy is applied. In short, Applicants recognized that the true source of the problem was the lack of thermal control afforded by typical resin curing methods. Applicants discovered that controlled thermal curing of resins systems having a broad range of curing temperatures could be achieved, without imparting excessive thermal energy to heat sensitive materials, by electromagnetic induction processes that are pulsed processes that can be optionally coupled with cooling steps between pulses. Thus, Applicants disclose electromagnetic induction processes that are pulsed processes that can be optionally coupled with cooling steps between pulses, fiber reinforced polymeric structural cases made by such processes, and articles comprising such cases, as well as methods of using such cases and articles. SUMMARY OF THE INVENTION The present invention relates to resin compositions, fiber reinforced polymeric structures, and electromagnetic induction processes for making same. Such electromagnetic induction processes may be pulsed processes that can be optionally coupled with cooling steps between pulses. The aforementioned fiber reinforced polymeric structures can take forms that include, pipes; pressure vessels, including rocket motor cases and fire extinguishers; golf club shafts; tennis and badminton racquets; skis; snowboards; hockey sticks; fishing rods; bicycle frames; boat masts; oars; paddles; baseball bats; and softball bats. In addition, such fiber reinforced polymeric structures can be supplemented with other materials, such as a rocket propellant, to form articles, for example, a rocket motor. Additional objects, advantages, and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the present invention. <para-num num="[00