Fiber Reinforced Soft Composites with Tunable Extensibility, Stiffness, and Strength for Synthetic Bio-tissue Applications

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We have developed a method to incorporate wrinkled fabric structures into elastomer composites with controlled wavelength. 3D printing is used to create molds with controlled shape. Fabric is compressed between these molds, and then the edges of the fabric are immersed in melted wax. When the wax solidifies, the fabric can be removed from the mold, and the fabric maintains the imposed wrinkled structure. The wrinkled fabric is then placed into a reactor, and pre-polymer solution is injected and exposed to UV light, to synthesize the elastomer. Finally a laser cutter is used to cut the sample to the desired shape. The proposed method works well to design extensible fabric-reinforced soft materials.These samples have been mechanically characterized, and the resulting properties are unique compared to regular soft materials. The incorporation of a wrinkled structure of fabric introduced a new transition point during tensile testing. Initial stress-strain behavior appears linearly elastic, closely matching that of the matrix. A transition strain occurs, where the composite quickly becomes stiff, and the modulus in this region approaches that of the fabric. The strain at which this transition occurs is controlled by the wrinkled fabric structure. We have demonstrated that we can cause this transition to occur at strains ranging from 5-30%. This simple method allows for fabrication of J-shaped composites, similar to natural biomaterials.