缠绕张力对干法缠绕复合材料结构残余应力及回弹变形的影响

Investigation on the influence of winding tension on residual stress and spring-in deformation of dry wound composite structure

开展纤维缠绕结构缠绕与固化后残余应力评估是开展缠绕工艺优化设计、实现服役前预应力设计的重要前提。本文采用干法缠绕工艺,基于钢芯模和尼龙6(PA6)芯模分别制备了恒定张力(40 N)、内松外紧(20 N-40 N-60 N)和内紧外松(60 N-40 N-20 N)3种不同张力制度的复合材料缠绕圆筒,通过测试切割过程应变释放量与回弹变形对内部残余应力进行对比分析。借助生死单元法,建立了复合材料圆筒的逐层缠绕过程分析模型,模拟缠绕后残余应力分布;并基于CHILE(Tg)本构模型,开展了复合材料圆筒固化过程模拟,预测固化后残余应力及切割后回弹变形。研究表明:固化应力与缠绕张力均对总残余应力产生贡献,但由于固化过程剩余缠绕张力进一步放松,固化后总残余应力水平低于缠绕残余应力与固化应力之和。固化过程不会改变缠绕张力对最终残余应力分布的影响;缠绕张力对总残余应力的影响程度与芯模材质相关,芯模热变形越大,缠绕张力的影响越弱。当采用相同芯模时,内松外紧(20 N-40 N-60 N)张力制度产生的切割回弹角最小,内紧外松(60 N-40 N-20 N)张力制度产生的回弹角最大;当采用相同张力制度时,PA6芯模制备的缠绕圆筒试样切割后回弹角远大于钢芯模制备试样。

The evaluation of residual stress after winding and curing process is the basement for the optimization design of winding process scheme and the achievement of pre-service stressing design.In this paper,three kinds of winding tension strategies,e.g.constant tension(40 N),loose inside and tight outside tension(20 N-40 N-60 N),and tight inside and loose outside tension(60 N-40 N-20 N),were used to prepare the composite winding cylinders on the steel mould and polyamide 6(PA6)mould by the dry winding process,respectively.The internal residual stresses were analyzed by measuring the released strain and spring-in angle during cutting process.With the aid of element birth and death technique,numerical model of the layer-by-layer winding process were created and the distributions of residual stress during winding were calculated.Subsquently,the curing process was simulated based on the constitutive model of CHILE(Tg).The after-curing residual stress and after-cutting spring-in deformation were predicted.It is shown that both the curing stress and the winding tension stress contribute to the total residual stresses.However,due to the further releasing of winding residual tension during the curing process,the total residual stresses are lower than the sum of the winding residual stresses and curing residual stresses.The impact of the winding tension strategies on total residual stresses is not affected by curing operation.The contribution of winding tension to the total residual stress is affected by the mould material used.The larger thermal deformation of the mould,the weaker the influence of winding tension strategy.For the situations with same mould,the winding cylinder with loose inside and tight outside(20 N-40 N-60 N)tension strategy shows the smallest after-cutting spring-in angle and the one with tight inside and loose outside(60 N-40 N-20 N)tension strategy shows the largest after-cutting spring-in angle.For the cases with same tension strategy,the winding cylinders made on PA6 mould give much larger after-cutting spring-in angle than that made on steel mould.