Montreal Space Symposium

Thermoplastic composite materials (TPC) have been used for a number of years in the space industry. One of the most famous applications of TPCs is on the Canadarm2, a robotic arm used on the International Space Station, which has been in service since 2001. The initial planned lifespan for Canadarm2 was of 10 years, however, because Canadarm2 is still very useful in current missions, the plan is now to extend its service life until 2028. The low Earth orbit is now littered with millions of manmade debris resulting from decades of space
exploration. Space structures are now more likely to be impacted by debris than ever before.

This paper presents the development of a repair method for hypervelocity impact damage on the Canadarm2 structure. Since the thermoplastic composites have the advantage of being re-processable, we use induction welding to repair the damaged laminates. An induction welding process that allows the repair of large areas was developed. This method allows thewelding of patches over a damaged area in a continuous fashion by moving the part to be repaired under an induction coil.

Laminates that were damaged via a hypervelocity impact show a residual flexural rigidity of 75% and 45% compared to intact laminates for the entry and secondary exit damage respectively. After repair using a quasi isotropic 8 ply patch [0, 90, ±45]s, the secondary exit damage shows a flexural rigidity of 300% compared to an intact laminate and a maximum flexural strength of 130% compared to intact laminates.

Finally, a finite element model of a laminate and patch was developed. The finite element model of an intact laminate converges to a rigidity within 3% of the experimental results. The finite element model of an intact laminate and patch shows a rigidity within 2% of the experimental results. Due to the high increase in rigidity of the repaired laminates, different patch stackups can be simulated. This allows to determine an ideal patch that would allow repaired laminates to have closer mechanical properties to that of intact laminates.

Keywords: repair, composite materials, welding, induction, thermoplastic