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

开发了复合管上的预成型内螺纹。两端带有螺纹的复合管是使用带有阳螺纹的心轴制成的。螺纹可应用于具有可调端部配合的支杆和带螺纹盖的复合压力容器，从而可拆卸进行检查和维修。将碳纤维增强塑料（CFRP）预浸料铺在心轴上，用收缩带包裹，然后在烤箱中固化。线是内置的，无需使用机器切割，并且线上的纤维通过线和管连续，以实现高强度。线的形状交替为圆形，凸形和凹形，以使CFRP预浸料能够铺好。制作并测试了两种类型的样本。样品A的上铺顺序为[0 / h / 90 / h / 0 / h _（1/2） ] _s，样本B的值为[0 / h / 90 / h / 90 / h / 0 / h / 90 / h / 90 / h / 90 / h / 90 / h / 0 / h / 90/90/0] ，其中“ h”表示沿着螺纹凹入部分的螺旋层。载荷和应变之间的关系是非线性的，因为螺纹是圆形的。但是，一个简单且封闭的形式分析模型能够预测螺纹的强度和螺纹的设计。将该模型与实验结果进行了比较。另外，还报道了在混合动力火箭发动机的压力容器中使用螺纹。燃烧测试没有失败。试验后的目视检查表明，螺纹和管子没有损坏，因此可以用于高压和高温火箭发动机。