Electronic Theses and Dissertation

Penelitian ini bertujuan untuk memanfaatkan limbah tekstil berupa kain denim sebagai bahan penguat komposit yang diharapkan dapat menjadi alternatif material teknik yang ramah lingkungan serta menganalisis pengaruh metode manufaktur dan kondisi serat terhadap karakteristik getaran bebas material komposit. Spesimen komposit dibuat menggunakan tiga metode, yaitu cetak tekan, cetak vakum infus, dan Hand Lay-up dengan matriks resin epoksi serta menggunakan dua jenis serat, yaitu denim baru dan denim lama. Pengujian sifat dinamis dilakukan melalui uji getaran bebas untuk memperoleh nilai frekuensi natural dan rasio redaman.Hasil penelitian menunjukkan bahwa metode manufaktur dan kondisi serat berpengaruh signifikan terhadap performa komposit. Pada komposit berbahan denim baru, metode cetak tekan menghasilkan frekuensi natural sebesar 130 Hz dengan rasio redaman sebesar 0,041, metode cetak vakum infus sebesar 120 Hz dengan rasio redaman 0,040, dan metode cetak tekan menghasilkan frekuensi natural tertinggi sebesar 120 Hz dengan rasio redaman 0,041. Sementara itu, pada komposit berbahan denim lama, nilai frekuensi natural cenderung lebih rendah, yaitu masing-masing sebesar 100 Hz (cetak tekan), 115 Hz (cetak vakum infus), dan 95 Hz (Hand Lay-up), dengan rasio redaman sebesar 0,030, 0,039, dan 0,032. Penurunan frekuensi natural pada denim lama disebabkan oleh degradasi sifat mekanik serat akibat pemakaian, sedangkan peningkatan rasio redaman menunjukkan kemampuan disipasi energi yang lebih baik.

Kata kunci: komposit, denim, hand lay-up, cetak vakum infus, cetak tekan, getaran bebas, frekuensi natural, redaman.

This study aims to utilize textile waste in the form of denim fabric as a reinforcing material for composites, which is expected to become an environmentally friendly alternative engineering material, as well as to analyze the influence of manufacturing methods and fiber conditions on the free vibration characteristics of composite materials. The composite specimens were manufactured using three methods, namely compression molding, vacuum infusion molding, and hand lay-up, with an epoxy resin matrix and two types of fibers, namely new denim and used denim. Dynamic property testing was carried out through free vibration tests to obtain the values of natural frequency and damping ratio. The results showed that the manufacturing method and fiber condition significantly affected the composite performance. In composites reinforced with new denim, the compression molding method produced a natural frequency of 130 Hz with a damping ratio of 0.041, the vacuum infusion molding method produced 120 Hz with a damping ratio of 0.040, and the hand lay-up method produced the highest natural frequency of 120 Hz with a damping ratio of 0.041. Meanwhile, in composites reinforced with used denim, the natural frequency values tended to be lower, namely 100 Hz (compression molding), 115 Hz (vacuum infusion molding), and 95 Hz (hand lay-up), with damping ratios of 0.030, 0.039, and 0.032, respectively. The decrease in natural frequency in used denim composites was caused by the degradation of the mechanical properties of the fibers due to usage, while the increase in damping ratio indicated better energy dissipation capability. Keywords: composite, denim, hand lay-up, vacuum infusion molding, compression molding, free vibration, natural frequency, damping.