| CPC B64C 3/26 (2013.01) [B29C 65/081 (2013.01); B64C 3/185 (2013.01); B64F 5/10 (2017.01); B29L 2031/3085 (2013.01)] | 14 Claims | 

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               1. A method, comprising: 
            arranging a thermoplastic rib with a thermoplastic spar, a first flange of the thermoplastic rib abutted against the thermoplastic spar; and 
                ultrasonic welding the first flange of the thermoplastic rib to the thermoplastic spar using a tilted ultrasonic horn, a centerline of the tilted ultrasonic horn angularly offset from the first flange of the thermoplastic rib by an acute angle during the ultrasonic welding; 
                wherein the first flange of the thermoplastic rib is abutted against an exterior surface of the thermoplastic spar. 
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