Struts and methods utilizing a locking collar nut

A composite tube assembly comprising:

• a composite tube comprising a variable diameter portion comprising a first frustoconical portion and a second frustoconical portion,
• wherein a diameter of the composite tube at an interface between the first frustoconical portion and the second frustoconical portion is a maximum diameter value with respect to the first frustoconical portion and is a maximum diameter value with respect to the second frustoconical portion;
• a locking wedge disposed at least partially around a circumference of the first frustoconical portion;
• a locking collar nut disposed at least partially around a circumference of the locking wedge;
• and
• an end fitting disposed at least partially around a circumference of the second frustoconical portion, wherein the end fitting is coupled to the locking collar nut;
• a locking key in contact with the locking collar nut and the end fitting;
• and
• a jam nut threadedly engaged to the end fitting,
• wherein the first frustoconical portion and the second frustoconical portion comprise a metallic insert.