曲形界面應用於複合材料單搭接膠合試片剪切強度提升之方法與數值分析

Abstract

複合材料因具有輕巧及堅韌的特性，被廣泛運用至許多產業，如：汽車工業、造船工業、航太工業以及風力發電等。膠合法(Adhesively Bonded Method)為連結複合材料的主要方法，許多學者也致力於研究如何提升膠合接點的強度，近年來，改變膠合接點的外型(如：波浪形試片、試片導角)也成為一研究方向。本研究提出一可增強玻璃纖維複合材料單搭接膠合試片強度之實驗方法，應用複合材料Seemann真空灌注製程(Seemann Composite Resin Infusion Molding Process, SCRIMP)，在欲疊層的纖維下方埋入具有硬度的線材，此線材可以在真空製程中被大氣壓力壓抑成一曲形表面，注入樹脂後熱硬化形成一具有曲形表面的複合材料。本研究參照美國材料試驗學會(American Society for Testing and Materials, ASTM)所制定的複合材料膠合試片測試標準ASTM D5868-01製作單搭接膠合試片。為確認此方法可確實提升膠合接點強度，由同一塊複合材料版中取材，製作出具平坦膠合介面的傳統膠合接點，以及具有曲形介面的改良接點，以拉伸試驗測試接點的剪切強度，實驗結果顯示本研究所提出的實驗方法可提生複合材料單搭接接點的強度。另一方面，本研究亦建立有限元素分析模型，模擬試片受外力拉伸下的力學行為，進行收斂性分析確認模型的正確性，並且紀錄收斂性分析時遇到的問題以提供給後人參考。也進行膠合區中心線的應力分析，並且進行不同參數改變如：埋設材料種類、直徑大小、距邊界長度以及排列方式探討，討論出可降低最多剝離應力峰值的試片外型。最後將實驗與模擬具相同情況的結果互相討論，分析其中出現差異的原因，整合為本研究之結論。本研究所提出之製作曲形表面方法不需特別訂作模具，且可以直接應用於現有模具上，具有其便利性且有利於推廣至應用複合材料的相關產業。

The composite material has been widely applied in different engineering fields like automobiles, naval architectures, aerospace, and wind power due to its lightweight and strength. Many researchers have investigated the means for enhancing the strength of the bonded joint of composite material. Specifically, the investigators have focused on the change the surface geometry (e.g. wavy, taper, fillet) of the composite to improve the tensile strength and decrease stress concentration of the bonded area. In this research, a method capable of improving the tensile strength of the adhesively bonded single-lap joint is introduced. The enhanced material was embedded into the glass fiber in the Seemann Composite Resin Infused Molding Process (SCRIMP) and formed a wrinkled surface composite material. The composite single-lap joint specimens were fabricated by following the ASTM D5868 01 standard and subjected to the tensile test to compare the strength of the conventional single-lap joint and the improved wrinkled surfaced single-lap joint. The test results have suggested that the wrinkled interface formed by the embedded material could successfully improve the strength. Simultaneously, the finite element models of these two geometries of single-lap joints were established to analyze the stress distribution within the bonded area. Parametric study such as changing embedded materials, distance from the overlap boundary, and arrangement of embedded material has been done. In addition, differences between the experiment and simulation are discussed and concluded. Moreover, this research, which the common composite material fabrication process, SCRIMP, is applied to make wrinkled surface without a special mold is easier to promote to the industry.