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Research Papers

Curing and Consolidation of Advanced Thermoset Composite Laminate Parts by Pressing Between a Heated Mold and Customized Rubber-Faced Mold

[+] Author and Article Information
Daniel Walczyk

Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180walczd@rpi.edu

Jaron Kuppers

Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180kuppej@rpi.edu

Casey Hoffman

Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180hoffmc@rpi.edu

J. Manuf. Sci. Eng 133(1), 011002 (Jan 05, 2011) (7 pages) doi:10.1115/1.4003125 History: Received June 23, 2010; Revised November 13, 2010; Published January 05, 2011; Online January 05, 2011

Curing and consolidating thermoset composite laminates and sandwich structures typically involves vacuum bagging an uncured and formed layup over a thin-walled mold, placing it in an autoclave, and subjecting the entire unit to temperature, vacuum, and pressure cycles as prescribed by the manufacturer. Autoclaving is generally considered the major bottleneck in manufacturing advanced composite parts because of high capital and consumable costs, energy usage, waste generated, and process scalability. A new curing and consolidation process called “thermal press curing” is presented and demonstrated as an alternative to autoclaving. The process involves compressing a composite laminate between a special mold set––a heated metal mold and a matching rubber-covered mold made of an insulative material––designed to provide uniform temperature and pressure over the metal mold surface, that is, mimic the process conditions provided by an autoclave. The thermal press curing process is demonstrated for the first time using a mold set for a simple two-dimensional axisymmetric shape. An aluminum curing mold with embedded electric resistance cartridge heaters is heuristically designed to provide uniform temperature in operation across the mold surface within 1°C of the target value (177°C). With the mold set compressing an eight-ply carbon/epoxy composite workpiece and well insulated on all sides, the power draw is at least one to two orders of magnitude less than a comparable autoclaving operation. The potential to significantly improve pressure uniformity from the compressed rubber mask is shown by changing the mask shape. Even without an optimized rubber layer shape and thickness, the eight-ply composite part was successfully cured. Finally, a plan for future work is described.

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Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

(a) Loading vacuum-bagged, thermoset composite parts into an autoclave and (b) typical autoclave temperature and pressure profile used for a carbon/epoxy composite system (data taken from Ref. 8)

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Figure 2

Schematic of the thermal press curing process for advanced thermoset composites with a variable thickness rubber mask t(s) shown (left) and molds clamping the formed composite laminate (right)

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Figure 3

(a) Curing mold shape for composite part with dimensions in millimeters shown and (b) corresponding base mold shape

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Figure 4

(a) Insulated mold set with 6.4 mm uniform thickness rubber mask and two embedded cartridge heaters, (b) same mold set with variable thickness rubber mask, and (c) schematic of the mold set fixture in a universal testing machine for compression testing

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Figure 5

(a) Experimental setup to measure temperature uniformity during thermal pressing with 2D mold set and (b) locations along 2D part profile for one-half of mold where temperature measurements were taken

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Figure 6

(a) Experimentally measured pressure distribution along mold/composite interface for 2D mold set for uniform thickness (upper image) and variable thickness (lower image) rubber masks. (b) Locations of pressures reported in Table 3.

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Figure 7

(a) FEA model and (b) simulation results of normal pressure on the surface of the rubber (top view of half the model)

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