Lightweight modular hybrid electro-mechanical collapsible and expandable mandrel for forming prismatic and non-prismatic hollow bars and/or cylinders for use as building materials and method for making same

A method for manufacturing prismatic or non-prismatic hollow bars of various cross-sections, comprising:

• providing an elongated modular collapsible and expandable mandrel for forming prismatic or non-prismatic hollow bars of various cross-sections, comprising:
• a plurality of outer segments configured to define a prismatic or non-prismatic mandrel outer surface;
• a plurality of hub assemblies with each hub assembly comprising a central hub and a plurality of support members spaced-apart around a perimeter of the central hub, each support member is pivotally attached to a respective one of the plurality of outer segments by a first end of a link with the second end of the link pivotally attached to its respective central hub;
• and
• means for moving each central hub linearly causing each of its links to pivot toward or away from, depending upon the direction of axial movement of the central hub, a longitudinal axis of the means for moving each central hub linearly while the central hub moves linearly thereby expanding or contracting the cross-sectional dimension of the respective portions of the mandrel to which each of the plurality of hub assemblies is attached;
• linearly moving each central hub to expand or contract as desired the cross-sectional dimension of the respective portions of the mandrel to which each of the plurality of hub assemblies is attached;
• wrapping GFRP or RFP material containing epoxy resin around the mandrel outer surface;
• curing the GFRP or RFP material containing epoxy resin;
• linearly moving each central hub to contract each cross-sectional dimension of the respective portions of the mandrel to which each of the plurality of hub assemblies is attached enough to remove the cured GFRP or RFP epoxy material.