Description

Fiber-reinforced polymer matrix composites (PMC) possess outstanding structural properties, including high strength and stiffness, low density, and highly tunable properties. However, their application is limited where elevated temperature stability is required, e.g., during high-speed flight, in engine exhaust systems, or as support for high-power electronics. Mechanical properties are greatly reduced above the glass transition temperature of the matrix and thermal decomposition will occur as the temperature is further increased. Damage may form in PMCs after only short exposure to high temperature including delamination, matrix cracking, and plastic deformation. Service temperatures for typical aerospace grade epoxies are ~150°C, whereas even the best high temperature structural polymers, bismaleimides and polyimides, typically have service temperatures <250°C. Active cooling through a vascular network provides a platform for thermal regulation, allowing for on-demand, adaptive heat removal and preservation of material properties. In actively cooled composites, coolant is pumped through a microvascular channel network to remove heat and maintain structural performance. In this article we present results from thermomechanical testing of actively cooled PMCs. Microchannels are formed in PMCs using Vaporization of Sacrificial Components (VaSC). In the VaSC process, sacrificial fibers composed of poly(lactic acid) treated with tin(II) oxalate catalyst are embedded into the PMC during normal processing, then removed during a postcure at 200°C for 24 h under vacuum. Stress, strain, material temperature, and heat removal by the cooling network are monitored during thermomechanical loading. Actively cooled specimens are compared to nonactively cooled control specimens.

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Thermomechanical characterization of actively cooled vascularized composites

Fiber-reinforced polymer matrix composites (PMC) possess outstanding structural properties, including high strength and stiffness, low density, and highly tunable properties. However, their application is limited where elevated temperature stability is required, e.g., during high-speed flight, in engine exhaust systems, or as support for high-power electronics. Mechanical properties are greatly reduced above the glass transition temperature of the matrix and thermal decomposition will occur as the temperature is further increased. Damage may form in PMCs after only short exposure to high temperature including delamination, matrix cracking, and plastic deformation. Service temperatures for typical aerospace grade epoxies are ~150°C, whereas even the best high temperature structural polymers, bismaleimides and polyimides, typically have service temperatures <250°C. Active cooling through a vascular network provides a platform for thermal regulation, allowing for on-demand, adaptive heat removal and preservation of material properties. In actively cooled composites, coolant is pumped through a microvascular channel network to remove heat and maintain structural performance. In this article we present results from thermomechanical testing of actively cooled PMCs. Microchannels are formed in PMCs using Vaporization of Sacrificial Components (VaSC). In the VaSC process, sacrificial fibers composed of poly(lactic acid) treated with tin(II) oxalate catalyst are embedded into the PMC during normal processing, then removed during a postcure at 200°C for 24 h under vacuum. Stress, strain, material temperature, and heat removal by the cooling network are monitored during thermomechanical loading. Actively cooled specimens are compared to nonactively cooled control specimens.