Instability-Driven Shape Forming Of Fiber Reinforced Polymer Frames

Thin fiber reinforced polymer (FRP) composites are widely implemented in adaptive and morphing structures. However, realization of the necessary complex 3-dimensional FRP structures requires the use of expensive molds thereby limiting the design space and flexibility. Using the elastic strain energy of pre-stretched membranes holds potential for addressing this challenge. In this work, a novel manufacturing technique for fabricating 3-dimensional FRP structures moldlessly is presented where pre-stretched membranes are used to drive out-of-plane buckling instabilities of FRP composite shells. To explore the potential of this approach, a simple square frame design is investigated. An analytical model based on high deformation beam buckling theory is developed for understanding the parameters driving the out-of-plane behavior of these structures. Experimental and finite element results are used for model validation and reveal excellent agreement, with errors less than 10% over a large portion of the design space. Analytical and finite element models demonstrate that the out-of-plane deformation can be tailored by varying the structure's geometric and material parameters. A new design space for FRP composite laminates is characterized, enabling highly flexible design. The manufacturing and modeling techniques can be extended to other geometries for the realization and analysis of arbitrarily complex surfaces.