抗氧化碳/碳复合材料螺钉设计方法研究

Design method of anti-oxidation C/C composite screw

针对C/C复合材料紧固件失效模式多、承载低且无设计标准的特点,本文对影响沉头螺钉承力的公称直径D、钉头高度H、钉头角度α、螺纹啮合深度h等4个设计变量进行分析,结合抗氧化C/C复合材料力学性能特点,提出抗氧化C/C复合材料螺钉的设计方法,分析涂层对螺钉承载的影响,给出设计变量与材料性能之间关系:H>D×σ_(t)/(4×ζ)、α>ctan(ζ/σ_(c))、h>3H(螺牙进行抗氧化涂层处理后可稍微减小h,但也需大于2H)。该设计方法消除螺纹拉脱、钉头拉脱/压溃等C/C复合材料螺钉的失效模式,大幅度提升螺钉承载能力。设计验证实验,通过实验考核螺钉结构形式及设计方法的正确性,验证抗氧化涂层工艺对螺钉承载的影响。

In light of many failure modes,low bearing capacity,and lack of a design standard for C/C composite fasteners,this paper analyzes the four design variables of countersunk head screws-nominal diameter D,nailhead height H,countersunk head angleα,and length of thread engagement h,considers the mechanical performance characteristics of anti-oxidation C/C composite,and proposes a design method of anti-oxidation C/C composite screw.The effect of anti-oxidant coating on the screw bearing is analyzed,and the relationship between design vari-ables and material properties is given:H>D×σ_(t)/(4×ζ);α>ctan(ζ/σ_(c));h>3H(h can slightly be reduced after anti-oxidation coating treatment of thread,but it also needs to be greater than 2H).The design method eliminates the failure modes of C/C composite screws,such as thread pulling off and nail head pulling off/squashing to collapse,significantly improving the bearing capacity of the screws.The design verification test verifies the correct-ness of the screw structure and design method,as well as the influence of the anti-oxidation coating process on screw load.