聚丙烯發泡材料之撞擊能量吸收特性

聚丙烯發泡材料(EPP)擁有良好的耐衝擊性能、能量吸收效果極佳且具有優異的耐熱性，所以其用途非常廣泛，常用於製造汽車的零部件如保險桿，或是用在包裝工業保護貴重物品。在大部分之使用場合，緩衝材料通常會承受一次以上的重複撞擊，然而多數研究文獻都只對材料進行單次撞擊的實驗與分析，所以本文除了進行不同發泡倍率、不同厚度聚丙烯發泡材料在一系列不同撞擊能量下的單次撞擊實驗外，也會對材料做重複多次的落下撞擊測試，以觀察EPP材料的應力應變曲線以及能量吸收性能在重複動態撞擊下的變化。相較於多數研究文獻都使用兩種以上之儀器設備來分別量測材料撞擊過程的變形量以及承受的撞擊力量，得到應變及應力值。本實驗則使用單一量測儀器加速度規來量測撞擊過程的加速度值，再將加速度值轉換成材料變形量及承受力量，以畫出材料動態撞擊之應力應變曲線。並延伸出能量吸收曲線與效率曲線來觀察與評估材料的能量吸收性能。從動態撞擊實驗結果可以得知不同發泡倍率也就是密度不同的聚丙烯發泡材料在應力應變曲線以及能量吸收性能上有著極大的差異，整體來看，密度較高者具有較佳的能量吸收效能。而EPP材料在重複撞擊下，材料各次撞擊曲線間的差異會隨著撞擊次數增加而漸漸縮小進而使曲線達到一定值狀態，也就是材料之撞擊特性與能量吸收特性已經不會因為繼續的重複撞擊而發生大幅變化。

關鍵字

聚丙烯發泡材料；動態撞擊實驗；重複撞擊實驗；應力應變曲線；能量吸收曲線；能量效率曲線

並列摘要

Expanded polypropylene foams(EPP) are widely used in many application such as bumper beam in the automotive industry or packaging of valuable products due to their good impact resistance, thermal stability and their great capacity of absorbing energy. In most of the actual service, the foam components could be reloaded for several times. However, most of the relevant literature only characterize the single impact test of the foam materials. So the present study not only executes the single impact test on foams which have different densities and thicknesses, but also performs multiple dynamic impact tests to investigate the successive changes of the energy-absorption capability of the EPP foams. In the dynamic impact tests of many relevant researches, the impact force and the deformation of the foam were measured by two kind of different measuring instruments. But, this study only uses accelerometer to get the acceleration values which could be able to calculate the impact force and the foam deformation. Then, the stress-strain curve, energy-absorption diagram and efficiency diagram can be determined by the calculating data to evaluate the mechanical properties, the energy-absorption characteristics of the EPP foams. From the single dynamic test results, it indicates that high-density specimens have better energy-absorption capability than low-density specimens. With the results of multiple impact tests, it can be concluded that the energy-absorption capability is significantly reduced after the foam sample experiences the first dynamic loading, and that if the specimens experience sufficient number of impacts, the energy-absorption characteristics of the specimens will have little changes.

並列關鍵字

expanded polypropylene foam ； dynamic impact test；multiple impact test ； stress-strain curve ； energy-absorption diagram ； efficiency diagram

參考文獻

[19] 江瑞琪，以EPP緩衝包材包覆之液晶單元落下試驗與數值模擬，國立台灣大學土木工程研究所碩士論文，2007。

[2] A. K. Maji, H. L. Schreyer, S. Donald, Q. ZUO, D. Satpathi. Mechanical properties of polyurethanefoam impact limiters. Journal of Engineering Mechanics 1995 Vol. 121. No.4. April.

[4] P. Viot, F. Beani, J. L. Lataillade. Polymeric foam behavior under dynamic compressive loading. Journal of Materials Science 2005;40:5829–37.

[5] S. Ouellet, D. Cronin, M. Worswick. Compressive response of polymeric foams under quasi-static, medium and high strain rate conditions. Polymer Testing 2006;25:731–43.

[6] L. Sorrentino, M. Aurilia, S. Iannace. A simple method to predict high strain rates mechanical behavior of low interconnected cell foams. Polymer Testing 2007;26:878-85.

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聚丙烯發泡材料之撞擊能量吸收特性

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