Method and device for infrared welding of polymer composites

1 . A system for infrared welding a first workpiece made of carbon-fiber reinforced thermoplastic polymers (CFRTP) to a second workpiece made of CFRTP, the first and second workpieces each having a respective portion that is substantially flat, the respective portions of the first and second workpieces forming a weld joint between them, the system comprising:

an upper tool, for holding the first workpiece;

a lower tool, for holding the second workpiece, wherein the upper tool and/or the lower tool is/are configured to move in a vertical direction to alter a distance between them in order to apply a welding pressure to form the weld joint; and

a movable infrared heating means, configured to move in a transverse direction between an operative position between the upper tool and the lower tool for simultaneously heating the respective portions of the first workpiece and the second workpiece, and a resting position away from the first workpiece and the second workpiece;

wherein the upper and the lower tools each comprise:

a holder configured to hold either the first workpiece or the second workpiece during the heating such that the respective portion for forming the weld joint extends off the holder in a cantilevered manner; and

a pusher configured to move vertically with respect to the holder between a pusher resting position during the heating and a pusher operative position during the welding pressure, wherein in the pusher resting position, the pusher is spaced from the respective portion of the first workpiece or second workpiece that extends off the holder, so as to enable the respective portions of the first and second workpieces to be surrounded by air during the heating, and wherein in the pusher operative position, each pusher contacts the respective portions of the first and second workpiece that extend off the holder to apply the welding pressure and form the weld joint.

2 . The system according to claim 1 , wherein the system further comprises an upper screen and a lower screen configured to move in the transverse direction independently from the movable infrared heating means, the upper and lower screens being configured to move between a screen operative position and a screen resting position, wherein in the screen operative position, the upper and lower screens partially shield the first and the second workpiece from radiations emitted by the movable infrared heating means.

3 . The system according to claim 2 , wherein the upper and the lower screens are configured to move in opposite directions.

4 . The system according to claim 1 , further comprising springs on the holder of each of the upper tool and lower tool to maintain the pusher resting position, and the system comprises actuators to compress the springs to move each pusher into the pusher operative position.

5 . The system according to claim 1 , further comprising a heating means for heating each holder and/or each pusher.

6 . A method for infrared welding a first workpiece made of carbon-fiber reinforced thermoplastic polymers (CFRTP) to a second workpiece made of CFRTP, the first and second workpieces each having a respective portion that is substantially flat, the respective portions of the first and second workpieces forming a weld joint between them, the method being carried out with a system comprising:

an upper tool, for holding the first workpiece;

a lower tool, for holding the second workpiece, wherein the upper tool and/or the lower tool is/are configured to move in a vertical direction to alter a distance between them in order to apply a welding pressure to form the weld joint; and

a movable infrared heating means, configured to move in a transverse direction between an operative position between the upper tool and the lower tool for simultaneously a heating the respective portions of the first workpiece and the second workpiece, and a resting position away from the first workpiece and the second workpiece;

wherein the upper and the lower tools each comprise:

a holder configured to hold either the first workpiece or the second workpiece during the heating such that the respective portion for forming the weld joint extends off the holder in a cantilevered manner; and

a pusher configured to move vertically with respect to the holder between a pusher resting position during the heating and a pusher operative position during the welding pressure, wherein in the pusher resting position, the pusher is spaced from the respective portion of the first workpiece or second workpiece that extends off the holder, so as to enable the respective portions of the first and second workpieces to be surrounded by air during the heating, and wherein in the pusher operative position, each pusher contacts the respective portions of the first and second workpiece that extend off the holder to apply the welding pressure and form the weld joint, the method comprising:

heating the respective portions of the first and second workpieces with the movable infrared heating means, while the first and second workpieces are held in the cantilevered manner, and while each pusher is spaced from the first and second workpieces, so that the respective portions are surrounded by air;

moving the movable infrared heating means away from the heated respective portions of the first and second workpieces to the resting position;

moving each holder closer to one another; and

applying the welding pressure with each pusher to bond the heated respective portions and form the weld joint.

7 . The method according to claim 6 , wherein the system further comprises an upper and a lower screen configured to move in the transverse direction independently from the movable infrared heating means, the upper and lower screen being configured to move between a screen operative position and a screen resting position, wherein in the screen operative position, the upper and lower screens partially shield the first and the second workpiece from radiations emitted by the movable infrared heating means, and the method further comprising, prior to the step of heating, a step of pre-heating, during which the movable infrared heating means is in the operating position and the upper and lower screens are in the screen resting position.

8 . The method according to claim 7 , wherein during the pre-heating the first and second workpieces are brought to a homogeneous temperature of about 100° C.

9 . The method according to claim 7 , wherein during pre-heating, the movable infrared heating means delivers energy by flashing infrared lights.

10 . The method according to claim 7 , wherein after pre-heating and before heating, the movable infrared heating means are switched off in the operative position until the temperature through-out the first and second workpiece homogenizes.

11 . The method according to claim 7 , wherein before the step of heating, each of the upper screen and lower screen are brought to the screen operative position.

12 . The method according to claim 7 , wherein each holder and/or each pusher is heated during at least one of the steps of: pre-heating, heating, moving the movable infrared heating means to the resting position, moving each holder closer to one another, or applying the welding pressure.