Processing and Characterization of Welded Bonds Between Thermoset and Thermoplastic Composites

Report No. ARL-TR-2484
Authors: Stephen H. McKnight, Bruce K. Fink, Veronique Monnard, P.E. Bourban, Jan-Anders E. Manson, Douglas A. Eckel II, and John W. Gillespie Jr.
Date/Pages: May 2001; 42 pages
Abstract: To assemble complex structures with short cycle times, the feasibility of welding thermoplastic (TP) to thermoset (TS) composites is demonstrated using a phenomenological approach. The effect of the thermal degradation of the TS composite (AS4/3501-6) on its shear strength is assessed in order to minimize the TS degradation during the welding process. The degradation is reported to decrease the shear strength in an exponential way. A layer of TP (polysulphone PSU) is cocured at the surface of the AS4/3501-6 laminate during its cure cycle in an autoclave. Two laminates are then welded together using a resistance welder. The highest shear strengths, which are close to the shear strength of bulk AS4/3501-6 autoclave-processed baseline, occur for a welding time and temperature of 10 s and 300 deg C, respectively. Higher and lower temperatures induce degradation and low consolidation of the weld, respectively. The welding interface between the TP layers is the strongest, while failure is mixed and occurs at interfaces between TS and TP and at interfaces between TP and heating element at the fiber/matrix interfaces. Further investigations are required to optimize the welding processing parameters and to identify the bonding, degradation, and failure mechanisms using a more fundamental and molecular approach.
Distribution: Approved for public release
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Last Update / Reviewed: May 1, 2001