添加奈米二氧化矽編織複合材料含中心橢圓孔平板之破壞強度探討

A Study of the Strength of Nano-Silica/Braided Composite Plates with a Central Elliptical Hole

蔡昆恊(K. H. Tsai) ； 黃宗立(C. L. Hwang) ； 邱長塤(C. H. Chiu) ； 李維平(W. P. Lee) ； 陳威穎(W. Y. Chen)

《華岡紡織期刊》 24卷1期 (2017/01) Pp. 1-7

摘要

本研究探討透過添加不同含量之奈米二氧化矽對具橢圓孔編織複合材料平板開孔強度的影響，並用金相顯微鏡觀測其經過拉伸後複材的破壞模式，再進一步利用有限元素軟體ANSYS 與點應力準則預測不同開孔半徑之編織複合材料平板的破壞強度。首先將奈米二氧化矽添加到環氧樹脂基材中進行攪拌混合，，並把碳纖維編織帶含浸改質後的環氧樹脂，以熱壓法製成編織複合材料平板。經金相實驗求得纖維紗束的高長比，並計算纖維體積含有率，帶入撰寫好的Visual Basic 程式計算編織複合材料之整體工程模數，最後將所得等效工程模數帶入有限元素軟體ANSYS 中進行拉伸分析，得開孔平板的應力分布圖，再配合點應力準則求出特徵長度，由特徵長度和孔洞長軸半徑與材料板寬度比值(2R/W)呈現乘冪關係計算不同孔徑破壞強度之預測值，並與實驗值做比較。研究結果顯示，改質過後的試片其軸向楊氏模數與破壞強度皆有所提升，其中以3 wt%的提升效果最為顯著，至於開孔強度方面，添加3 wt%之奈米二氧化矽，不論哪種孔洞尺寸破壞強度皆有提升。此外，未添加與添加3 wt%奈米二氧化矽試片的特徵長度皆會隨著孔洞半徑的增大而減小。ANSYS 分析結果顯示，本研究方法可以準確預測含中心橢圓孔編織複合材料平板之破壞強度，其誤差皆在1.39%以內。

關鍵字

奈米二氧化矽 ； 編織複合材料 ； 點應力準則 ； 特徵長度 ； 有限元素

並列摘要

In this study, we observed the effects of different percentage nano SO_2 on the braided composite plates with an central elliptical hole. And then we used ANSYS and Point Stress Criterion to calculate and predict the notched strength of braided composite plates with various aspect ratio of elliptical holes. First the pure epoxy and nano SO_2 particle were mixed using mechanical stirrer. Then carbon fiber braid was impregnated with the improved epoxy resin to make braided composite plates by hot-press method. The metallographic microscope was used to get the high length ratio of fiber yarn wave by observing the cross-section of the braided composite plate along the fiber yarn braiding direction. After the high length ratio and the fiber volume fraction were obtained, then Visual Basic was used to calculate the module of the braided composite plates. The calculations were then input into ANSYS to analyze the stress distribution around each hole. Then, a Point Stress Criterion was used to calculate the characteristic length for each hole size. Through the characteristic length composite plates with various aspect ratio of elliptical holes their strength was predicted. The result shows that, the composite plates with nano SO_2 have higher the Young's modulus and the strength. The sample with 0.3wt% nano SO_2 have the highest strength. In regard to notched strength, no matter what size the hole is, notched strength of adding 3wt% nano-silica have highest strength. Besides, whether nano-silica was added or not, the characteristic length decreases when the increasing hole sizes. ANSYS analysis shows that our method accurately predicted the notched strength of braided composite plates with a central elliptical hole with a maximum error of only 1.39%.

並列關鍵字

Nano-Silica ； Braided Composite Plates ； Point Stress Criterion ； Characteristic Lengths ； Finite Element