本論文研究了自增強聚對苯二甲酸乙二酯複合材料（srPET）的蠕變行為和應力/應變集中效應。該複合材料以高強度 PET 纖維作為補強材，共聚改質之低熔點 PET 作為基材，以雙包繞紗結構紡織成 2/2 平紋織物並透過疊層熱壓法製備成複合材料成品。高分子材料由於其黏彈性質導致在持續施予定應力的環境下應變值會隨時間緩慢增長，是謂蠕變現象。此現象為長期承受高載荷的應用下的熱塑性複合材料之重要性能。本論文分別通過動態機械分析儀(DMA)及拉伸試驗機研究了不同中心鑽孔孔徑（0-8 mm）的 srPET 之撓曲及拉伸蠕變特性。
並結合 Findley 模型與 Burgers 四元素模型擬合實驗數據。而後使用 Arrhenius 型時間-溫度疊加原理(TTSP)以預測 srPET 的長期蠕變行為與孔洞帶來的影響。此外，由於使用機械式拉伸系統（MTS）無法準確測量由幾何不連續性而引起的局部高應變值，本論文將數位影像相關法（DIC）應用於拉伸蠕變測試中以提高其對壽命預測的準確性。由結果得知，在未開孔的情況下兩方法的結果相近。但在開孔的情況下，由 DIC 所預測的 mastercurve 隨時間呈指數增長，而 MTS卻保持線性成長。此結果表明若僅使用 MTS 方法對開孔材料預測蠕變壽命則結果並不準確，需使用 DIC 才能有效分析孔洞對蠕變特性造成之影響。
在應力/應變集中效應的研究中，對開孔 srPET 進行了拉伸破壞測試並通過DIC 進行分析。結果表明，srPET 的超韌特性會導致其應力/應變集中因子隨局部降伏現象的發生而產生變化。而應力/應變集中因子變化的曲線可以使用 DIC配合 Neuber’s rule進行繪製。透過此曲線，將能定義 srPET 材料之局部降伏起始點、全域降伏點和破斷觸發點。在加入橢圓孔洞試片後，DIC 則被應用以分析一特殊現象，即橢圓孔 srPET 會比圓孔 srPET 具有更好的拉伸性能。利用應變/應力集中係數以及應變區分佈的結果。可以得知橢圓孔的幾何形狀會抑制孔洞周圍集中區域的擴張。由於此現象使得橢圓孔 srPET 在降伏後可以支撐更長的時間。而當接近斷裂點時，橢圓孔在孔邊緣處會具有更大的應變值。最終導致橢圓孔具有比圓形孔更好的拉伸性能。

This thesis examines the creep behavior and stress/strain concentration effect of self-reinforced polyethylene terephthalate composites (srPET), which were produced by film stacking from fabrics composed of double covered uncommingled yarns with recycled PET homopolymer filaments (serving as the reinforcements) and copolymerized PET (mPET) filaments (serving as the matrix). Creep deformation of polymers results from their inherent viscoelastic nature that changes polymer’s shape with time. Creep response represents an important property of thermoplastic composites that affects their dimensional stability, especially in applications requiring the material ability to support relatively high loads for long periods. The short-term flexural and tensile creep behavior of centrally drilled srPET with different hole diameters (0 - 8 mm) was studied by dynamic mechanical analysis and tensile machine, respectively. The obtained data were analyzed using the Findley viscoelastic and Burgers four-element models. The long-term creep behavior of srPET specimens with and without open circular holes was described using an Arrhenius-type time–temperature superposition principle. Furthermore, digital image correlation method (DIC) was utilized to improve the accuracy of strain measurements in open-hole tensile creep tests. Conventional measurements that use mechanical tensile systems (MTS) cannot accurately measure local strains caused by geometric discontinuities. When holes were introduced, the DIC curve increased exponentially with time, while the MTS
remained linear. The results demonstrated that the MTS method estimates lower creep strain compared to DIC. The modulus retention (MR) term and master curve was used to evaluate the creep behavior and to define a “failure time”. In a DIC analysis of hole effects, the creep strain increased with increasing hole size, whereas the order of the failure time decreased. The results show that an MR of 70% may serve as a creep failure indicator for lifetime predictions of srPET composites.
For studies on stress/strain concentration effect, the tensile experiment was applied on open-hole srPET and investigated by DIC. The results indicated that the non-linear stress-strain relationship of srPET caused the concentration factor varied with the local yielding phenomenon. The curve of the stress concentration factor can be plotted by using the Neuber's rule. The local yielding initiation point, the overall yielding point and the catastrophe trigger point can be defined on this curve. In final section, DIC was applied to analyze an incredible phenomenon that the srPET with a central drilled elliptical hole has better tensile properties than srPET with circular hole. Results of strain/stress concentration factor, line/plane strain distribution were discussed. These
results explained that the elliptical hole suppressed the high concentration area around the edge of the hole. Due to this effect, the specimens with elliptical hole can support a longer period of time after starting to bear stress. When approaching the breaking point, the far area of the elliptical hole has greater strain at the hole edge. As a result, the elliptical hole has a better tensile strength than the circular hole.

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