Development of pre-molded internal thread on composite tubes

Premolded internal threads on composite tubes were developed. The with both ends made using a mandrel male thread. can be applied to struts adjustable end fits and pressure vessels threaded caps that enable disassembly for inspection repair. Carbon fiber-reinforced plastic (CFRP) prepregs laid up mandrel, wrapped shrink tape, cured in an oven. built-in, without machine cutting, the fibers thread continuous through high strength. was alternately rounded, convex, concave shape CFRP up. Two types of specimen tested. layup sequence A [0/h/90/h/0/h (1/2) ] s , B [0/h/90/h/90/h/0/h/90/h/90/h/90/h/90/h/0/h/90/90/0], where “h” denotes helical layer along part threads. relation between load strain is nonlinear because rounded threads; however, simple closed form analytical model able predict strength design compared experimental results. In addition, application vessel hybrid rocket motor also reported. combustion test proceeded failure. Visual after indicated not damaged, thus, they high-pressure high-temperature motors.