UpDate - Vol. 13, No. 10, Page 6
November 4, 1993
Patent issued on welding method designed by CCM

     A U.S. patent has been issued on "Apparatus and Method for Resistance
Welding," developed by researchers at the Center for Composite Materials
(CCM) in collaboration with the Aluminum Co. of America (Alcoa).
     The automated sequential resistance welding process and equipment were
developed in 1989 as a senior design project by a group of mechanical
engineering students advised by CCM associate director John W. Gillespie Jr.
     The welder enables large, thermoplastic composite parts to be joined
in a step-wise process at reduced power and pressure levels.
     "Thermoplastic polymers can be repeatedly melted and solidifed, in
contrast to thermosets, which are formed by irreversible chemical
cross-linking," Gillespie explained. "Resistance welding is a type of
bonding process that takes advantage of this 'fusible' characteristic of
thermoplastics."
     The welder remains at the center for contact research and provides a
test bed for students investigating various aspects of the resistance
welding process.
     One doctoral candidate, for example, is exploring the welding of
dissimilar materials using a thermoplastic-either in an interlayer or in
the composite itself-as a "hot melt" adhesive.
     With this technique, various joint combinations-including
thermoset-to-thermoset, thermoset-to-thermoplastic and
metal-to-composite-are possible. In another project, a doctoral student is
using the equipment to study vairous on-line, non-intrusive sensing
techniques for process control.
     "We're very pleased that the work of four center-affiliated
undergrads, working with the support of one of our industrial sponsors,
resulted in the design and construction of a piece of equipment that has
proven to be of value in our ongoing research program," Gillespie said.
"Each generation of students refines the patented process and contributes
to our knowledge base on this novel joining method for composites."
                                                  -Diane Kukich