Electronic Theses and Dissertation

Perkembangan teknologi material dalam industri otomotif, khususnya pada struktur badan bus, menuntut penggunaan material ringan yang memiliki kinerja mekanik tinggi, ketahanan terhadap beban statik dan dinamik, serta efisiensi konsumsi bahan bakar. Material sandwich yang berbasis inti honeycomb dan lapisan muka komposit menjadi salah satu solusi yang banyak dikaji karena kemampuannya dalam meningkatkan rasio kekuatan terhadap berat. Sejalan dengan tuntutan keberlanjutan, pemanfaatan serat alam sebagai penguat komposit juga menjadi fokus penelitian untuk menggantikan serat sintetis. Penelitian ini bertujuan untuk mengkaji secara komprehensif karakteristik mekanik, fisik, dan perilaku impak material sandwich biokomposit yang menggunakan inti aluminium honeycomb dan lapisan muka komposit serat abaka dengan variasi orientasi serat.
Material sandwich yang dikembangkan terdiri atas inti aluminium honeycomb tipe AA3003 dan lapisan muka berupa komposit serat abaka–epoksi. Komposit serat abaka dibuat dengan fraksi volume 40% serat dan 60% matriks epoksi, dengan variasi orientasi serat searah, acak, dan anyaman. Sebelum proses fabrikasi, serat abaka diberi perlakuan alkali menggunakan larutan NaOH 5% selama 2 jam untuk meningkatkan ikatan antarmuka serat–matriks. Pengujian sifat mekanik komposit meliputi uji tarik dan uji tekuk yang dilakukan sesuai standar ASTM D638 dan ASTM D790, dan dengan mempertimbangkan pengaruh orientasi serat serta kondisi sebelum dan sesudah perendaman air. Pengujian sifat fisik meliputi daya serap air, perubahan ketebalan, dan massa jenis komposit yang mengacu pada standar ASTM D570 dan ASTM 792.
Selanjutnya, pengujian tekuk pada material sandwich biokomposit dilakukan berdasarkan standar ASTM D393 untuk mengevaluasi kemampuan struktur dalam menahan beban lentur. Analisis numerik dilakukan menggunakan Cohesive Zone Model (CZM) untuk memodelkan perilaku kontak dan delaminasi antarlapisan, serta divalidasi terhadap hasil eksperimen. Selain itu, simulasi numerik pengujian impak weight drop dilakukan sesuai standar ASTM D3763 dengan variasi kecepatan impaktor sebesar 1 m/s, 2 m/s, 2,43 m/s, dan 3 m/s untuk mengevaluasi respons kerusakan material berlapis.
Hasil penelitian menunjukkan bahwa komposit serat abaka dengan orientasi anyaman memiliki kekuatan tarik yang lebih tinggi dibandingkan orientasi searah dan acak, baik sebelum maupun sesudah perendaman air. Sebaliknya, komposit dengan orientasi serat acak menunjukkan kekuatan lentur yang relatif lebih tinggi pada pengujian komposit tunggal. Pada pengujian material sandwich, lapisan muka komposit serat abaka berorientasi anyaman mampu menahan beban lentur dan energi impak dengan lebih baik serta menunjukkan tingkat kerusakan yang lebih rendah. Hal ini disebabkan oleh kemampuan anyaman serat dalam mendistribusikan energi beban dan tumbukan secara lebih merata ke berbagai arah. Secara keseluruhan, hasil penelitian ini menunjukkan bahwa material berlapis biokomposit berbasis serat abaka berorientasi anyaman memiliki potensi yang signifikan sebagai material struktural ramah lingkungan untuk aplikasi otomotif.
Kata Kunci: material berlapis, aluminium honeycomb, komposit serat abaka, karakteristik mekanik, karakteristik fisik, analisa numerik.

The development of materials applied in the automotive industry, particularly for bus manufacturing, continues to receive significant attention from researchers. Comfort, safety, and fuel efficiency are critical issues in selecting materials for bus body structures. Among various candidates, material sandwich structures have emerged as a promising option due to their excellent structural and functional properties. The aims of this study are to determine the mechanical, physical and morphological characteristics of a sandwich structure biocomposite made of an aluminum honeycomb structure core made of aluminum alloy AA3003. The face sheet is made of abaka fiber composite. The abaka fiber composite consists of 40 wt% fiber and 60 wt% matrix. A 5 wt% NaOH solution treated the abaka fibers for 2 hours, then rinsed with water to remove residual NaOH and dried. The treated fibers were subsequently woven and impregnated with epoxy resin to produce woven abaka fiber composites. Mechanical and physical characterizations were performed on the abaka fiber composites with different fiber orientations. The mechanical tests included tensile testing in accordance with ASTM D638-14 and flexural testing in accordance with ASTM D790-03 standards. The results revealed that the woven abaka fiber composite exhibited higher tensile strength compared to composites with unidirectional and randomly oriented fibers. Similarly, after water immersion, the woven fiber composite maintained higher tensile strength than the others. However, before and after water immersion, the composite with randomly oriented fibers exhibited greater flexural strength compared to woven and unidirectional fiber composites. Physical tests were also conducted on the abaka fiber composites. Water absorption, thickness swelling, and density were performed according to ASTM D570-22 and ASTM D792-20 standards, respectively. The results indicated that the woven fiber composite absorbed less water than the unidirectional fiber composite. However, it exhibited greater at the edge of the specimen after immersion. The flexural strength of the sandwich structure biocomposite–aluminum honeycomb core and abaka fiber composite facesheet was evaluated according to ASTM D393-00. The results showed that the sandwich material with woven abaka fiber composite face sheets demonstrated superior bending resistance compared to those with unidirectional and randomly oriented fiber face sheets. Numerical contact model was conducted using the Cohesive Zone Model (CZM), which produced load-displacement curves consistent with the experimental results. Additionally, numerical weight drop impact test simulations, which are suitable with ASTM D3763. The numerical analysis, performed at impact velocities of 1 m/s, 2 m/s, 2.43 m/s, and 3 m/s, revealed that the sandwich material with woven abaka fiber composite face sheets experienced less damage compared to those with unidirectional and random fiber orientations. This superior performance is attributed to the ability of the woven fiber composite face sheets to distribute impact energy effectively along multiple fiber directions. Keywords: sandwich structure, Aluminum Honeycomb, Abaka Fiber composite