Tailored susceptors for induction welding of thermoplastic
AssigneeThe Boeing Company
InventorsKarl A. Hansen, C. David Lunden
Life of this patent
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Abstract
To obtain more uniform heating across the susceptor when welding composite parts using induction heating, we create edge regions of lower absolute impedance or a lower longitudinal impedance than the transverse impedance to counterbalance the higher current density and current that occurs near the edges. We achieve lower impedance at the edges by altering the aspect ratio (length/width) of openings in the susceptor, by folding the susceptor over onto itself, or both. Uniform heating is important to obtaining a uniform, consistent weld on which aerospace designers can rely.
Claims22
A susceptor for use in thermoplastic welding of composite parts, comprising a sheet of electrically conductive material having a thickness of about 0.075-0.25 mm and having a uniform distribution of substantially uniform size, diamond-shaped openings extending through the material, said openings having a length and a width defined by straight lines of the material of approximately uniform thickness of about 0.18 mm, the aspect ratio of the length to the width being greater than 1.0 to provide a longitudinal impedance along the susceptor less than the transverse impedance so that the susceptor heats more uniformly than susceptors with uniform longitudinal and transverse impedance when subjected to the varying magnetic field created with a cup coil induction coil.
A method for thermoplastic welding to join two resin composite parts using induction to heat a susceptor along a bond line, comprising the steps of:
- (a) positioning a tailored susceptor and a thermoplastic resin between the two resin matrix composite parts to define the bond line, the susceptor having edge treatment to adjust the longitudinal impedance of the susceptor in edge regions over the longitudinal impedance in a central portion of the susceptor to promote current flow near the edges relative to the central portion so that the susceptor heats relatively uniformly when subjected to the varying magnetic field of a cup coil induction coil;
- (b) heating the susceptor with the induction coil to create a substantially uniform temperature in the bond line and to melt the resin;
- (c) resolidifying the resin to form a thermoplastic weld between the two composite parts.
An integral composite sandwich structure comprising;
- a first non-metallic member;
- a second non-metallic member;
- a thermoplastic resin layer inserted between said non-metallic members for joining the first and second non-metallic members to define a bond line;
- an eddy current conducting sheet of material disposed between said nonmetallic members adjacent the resin layer;
- the conducting sheet being tailored at the edges to achieve more uniform heating in the bond line and having a plurality of openings the openings having a length dimension and a width dimension, the ratio of the length dimension to the width dimension being at least two and wherein the openings in the eddy current conducting sheet are diamond shaped.
A susceptor for use in thermoplastic welding of composite parts, comprising a sheet of material susceptible to heating by induction, the sheet having edge portions having greater thickness than the center portion to provide a higher surface area for distributing current and a lower impedance in the edges, both the center portion and the edge portions including a plurality of openings.
A method for thermoplastic welding using induction heating, comprising the steps of:
- (a) positioning a tailored susceptor and a thermoplastic adhesive between two resin matrix composite parts to define a bond line, the susceptor having edge treatment to adjust the impedance to promote current flow near the edges relative to the center so that the susceptor heats relatively uniformly;
- (b) heating the susceptor with an induction coil to melt the adhesive;
- (c) resolidifying the adhesive to form a thermoplastic weld between the two composite parts.
Dependencies are inferred from the claim text.