以有限元素法探討子彈衝擊編織布與單向纖維布之行為

Abstract

本研究主要藉由有限元素分析(Finite element analysis)建立單向纖維布(Unidirectional fabric, UD fabric)與編織布(Woven)簡化模型，並探討多層編織布與單向纖維布混疊板受衝擊之行為。首先是單向纖維布的部分，考慮三種單向纖維布模型：全纖維束模型、纖維束與等效均質平板混合模型、等效均質平板模型，並分別以單層、四層與八層平放於油泥(Clay)上以子彈衝擊，並以全纖維束模型做為衝擊比較基準，觀察子彈速度歷程、油泥凹陷深度與寬度。結果顯示，當連續均質平板之元素破壞等效應變(Maximum effective strain for element failure)設為1.05時，其衝擊結果近似於全纖維束模型與混合模型，因此能代替單向纖維布模型並節省80~90%的運算時間。此外，為了解單向纖維布不同角度疊層之抗彈能力，本研究以等效均質平板建立多層單向纖維布有限元素模型，比較[0/90]24、[02/902]12、[0/902/0]12與[04/904]6四種疊層之抗彈能力，結果發現[0/90]24疊層受衝擊後油泥凹陷最淺，因此抗彈能力最佳，而[04/904]6疊層受衝擊後油泥凹陷最深，抗彈能力最差。 編織布的部分，分別建立三種編織布模型：全編織實體元素模型；接著初步簡化為混合元素模型；最後建立連續均質編織布模型，並藉由編織布單元體得到編織布材料性質。分別以單層、兩層與三層平放於油泥上以子彈衝擊，並以全編織實體元素模型做為衝擊比較基準，觀察子彈速度與油泥凹陷深度歷程。結果顯示，以低速子彈衝擊時，混合元素模型雖能節省約40%計算時間，然而衝擊結果與全編織實體元素模型有明顯差異；而連續均質編織布模型較能接近全編織實體元素模型，並節省約98%運算時間。此外，為了解單向纖維布與編織布疊層順序對抗彈能力的影響，並比較單向纖維布與編織布之抗彈能力，本研究以均質平板模型建立多層單向纖維布與編織布疊層板，比較[W]28、[0/90]18、[W4/(0/90)16]與[(0/90)16/W4]疊層之抗彈能力，結果發現，各疊層板受衝擊後油泥凹陷深度由低至高依序為[0/90]18、[W4/(0/90)16]、[(0/90)16/W4]及[W]28疊層。

This research aims to investigate ballistic impact behavior of multi-ply unidirectional fabric and woven fabric using finite element analysis (FEA). Continuous homogeneous models for unidirectional fabric was employed in order to analyze multilayer fabrics with saving compute time. For unidirectional fabrics, this research adopted three different models: all narrow strips model, narrow strips and homogenous hybrid model, and continuous homogeneous model to simulate 1-ply, 4-ply, and 8-ply impact. Bullet velocity, indent depth and indent width were investigated. A good agreement was found for all three unidirectional fabric models when the failure effective strain of the continuous homogeneous model is 1.05. Moreover, 80%~90% computational cost was reduced in continuous homogeneous model. The effect of stacking sequence on ballistic performance was examined by performing the impact simulation on the multi-ply unidirectional fabrics, i.e., [0/90]24, [02/902]12, [0/902/0]12, and [04/904]6. Results revealed that [0/90]24 fabric demonstrates lowest indent depth, while [04/904]6 fabrics showed highest indent depth. For woven fabrics, three different models have been presented. First, whole solid woven, for which is most realistic approach. Second, a solid and shell hybrid element woven was presented. Finally, a unit cell woven model was employed to observe the continuous homogeneous woven properties. 1-ply, 2-ply, and 3-ply impact simulation were presented. Bullet velocity and indent depth were investigated. For low bullet velocity impact, continuous homogeneous model showed good agreement compared to whole solid woven model, and saved 98% compute time. However, hybrid element woven model though saved 40% compute time, showed otherwise result. Ballistic performance of unidirectional fabrics, woven fabrics, and hybrid panel were examined by performing the impact simulation on the multi-ply fabrics, i.e., [0/90]18, [W]28, [W4/(0/90)16] and [(0/90)16/W4]. Results revealed that [0/90]18 unidirectional fabrics demonstrate lowest indent depth. The effect of stacking sequence on ballistic performance for hybrid panels revealed that, for woven fabric as front layer and unidirectional fabric as rear layer, i.e., [W4/(0/90)16] demonstrates lower indent depth.