Predicting the tensile and compressive modulus of electrospun fiber mat‐reinforced hydrogels using the Halpin–Tsai equations

• Published in: Journal of applied polymer science 2024-06, Vol.141 (21), p.n/a
• Main Authors: Beckett, Laura E., Lewis, Jackson T., Tonge, Theresa K., Korley, LaShanda T. J.
• Format: Article
• Language: English
• Subjects: biomedical applications; Biomedical materials; biomimetic; Composite materials; composites; Fiber volume fraction; Hydrogels; Mathematical models; Mechanical properties; Mechanical tests; Modulus of elasticity; Polycaprolactone; Polyethylene glycol
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.55415

The reinforcement of mechanically‐weak hydrogels to yield composites with increased stiffness, strength, or toughness is a well‐established approach. In particular, introducing electrospun nanofibers into hydrogels is a common strategy for biomedical applications, as the resulting hierarchical structure mimics biology and allows for control over fiber diameter and alignment and tuning of mechanical properties. However, further study of the link between the constituent materials and the mechanical properties of the composite is uncommon. One potential model to understand the mechanical properties of fiber‐reinforced hydrogels involves the Halpin–Tsai equations, which relate the modulus values of the fibers and hydrogel matrix and the fiber volume fraction, to the modulus of the composite. To assess the application of this model to fiber‐reinforced hydrogels, predicted values were compared with experimental values from mechanical testing of a poly(ethylene glycol) (PEG) matrix reinforced with an electrospun polycaprolactone (PCL) fiber mat. Although the equations described these systems well in tension, providing a facile approach to identify a fiber volume fraction that will achieve a desired modulus, the Halpin–Tsai approach was less successful under compression. This study motivates additional investigation of the role of structural features of hydrogel composites in determining mechanical properties to enable design of materials for specific applications. The potential for utilization of the Halpin–Tsai equations to predict the mechanical properties of electrospun fiber‐reinforced hydrogels was investigated by comparing predicted values for the modulus with those obtained experimentally. Structural features, such as fiber diameter and alignment; and matrix porosity, were varied. The Halpin–Tsai equations showed good agreement in tension, but less so in compression, suggesting potential features of hydrogels that are currently not accounted for by the model.