Kajian sifat fisis, mekanis dan akustik komposit sandwich serat kenaf bermatrik polyester dengan core kayu sengon laut

DIHARJO, Kuncoro, Promotor Prof. Ir. Jamasri, Ph.D

2009 | Disertasi |

Tujuan penelitian ini adalah mengkaji pemanfaatan serat kenaf dan kayu sengon laut (KSL) untuk pembuatan panel komposit sandwich dan akustik. Penelitian panel komposit dikonsentrasikan pada sifat-sifat fisis dan mekanis, sedangkan penelitian panel akustik dikonsentrasikan pada optimasi serapan bising sel dan panel akustik. Bahan penelitian ini adalah serat kenaf, KSL, Unsaturated Polyester Resin (UPRs), hardener MEKPO dan NaOH. Serat kenaf dikenai perlakuan alkali (5% NaOH) selama 0, 2, 4, 6 dan 8 jam dan KSL dipotong pada arah melintang. Spesimen uji terdiri dari komposit skin kenaf - UPRs, komposit sandwich kenaf – UPRs - KSL dan panel akustik KSL. Variabel penelitian komposit skin meliputi jenis serat (acak, anyam), kandungan hardener, perlakuan alkali, fraksi volume serat (vf), perlakuan siklis termal dan perendaman air, sedangkan variabel penelitian komposit sandwich meliputi tebal skin dan core. Untuk penelitian akustik, variabelnya adalah stud, cavity depth, diameter lubang leher resonator dan penambahan acoustic fill serat kenaf. Pengujian pada penelitian komposit dan akustik adalah uji fisis dan mekanis, dan Noise Absorption Coefficient (NAC). Komposit skin serat acak memiliki kekuatan tarik dan bending yang lebih tinggi dibandingkan dengan komposit skin serat anyam. Pada vf = 23%, komposit skin tersebut memiliki kekuatan tarik tertinggi (40,14 MPa) pada kandungan hardener 1% (v/v). Pada berbagai variasi vf, komposit skin serat acak perlakuan alkali 2 jam memiliki kekuatan tarik tertinggi dan disusul oleh komposit serat tanpa perlakuan. Sesuai teori ROM, peningkatan vf meningkatkan kekuatan tarik dan bending, dan ketangguhan impak komposit skin. Perlakuan siklis termal dan perendaman air menurunkan kekuatan bending komposit skin. Kekuatan bending dan ketangguhan impak komposit sandwich meningkat seiring dengan peningkatan tebal skin. Namun pada tebal skin 5 mm, kekuatan bending-nya menurun karena kegagalan delaminasi. Komposit sandwich berpenguat serat perlakuan 2 jam memiliki ketangguhan impak yang lebih rendah dan penampang patahannya lebih getas dibandingkan dengan komposit sandwich berpenguat serat tanpa perlakuan. Pada variasi tebal core, komposit sandwich serat acak perlakuan alkali 2 jam memiliki nilai ss/c yang lebih tinggi dibandingkan dengan komposit sandwich serat tanpa perlakuan. Peningkatan tebal core menurunkan ketangguhan impak spesifik (KI/c). Peningkatan siklus bending dinamis menurunkan kekakuan (K) dan meningkatkan nilai d/c. Peningkatan tebal core juga menurunkan kekakuan komposit sandwich. Nilai koefisien serapan bising (NAC) yang tinggi terjadi pada sel akustik dengan stud 30 dan 40 mm; cavity depth 25 mm; diameter lubang leher resonator 6, 8 dan 10 mm; dan penambahan acoustic fill 10%. Panel akustik dengan stud 30 mm, cavity depth 25 mm, diameter lubang leher resonator 10 mm dan penambahan acoustic fill 10 % memiliki nilai serapan bising di atas 0,74 pada rentang frekuensi bising 63 – 10.000 Hz.

The objective of this research is to study the use of kenaf fiber and albizzia wood for producing sandwich composite and acoustic panels. The research of the composite panel is concentrated on the physical and mechanical properties, while the research of acoustic panel is concentrated on the optimization of noise absorption of the acoustic cell and panel. This research materials were kenaf fiber, albizzia wood, Unsaturated Polyester Resin (UPRs), MEKPO hardener and NaOH. The kenaf fiber was treated in alkali solution (5% NaOH) for 0, 2, 4, 6 and 8 hours, and the wood was cut on cross section direction. The test specimen consisted of kenaf – UPRs skin composite, kenaf – UPRs – albizzia sandwich composite, and albizzia acoustic panel. The research variables of the skin composite were fiber type (random, woven), hardener content, alkali treatment, fiber volume fraction (vf), thermal cyclic treatment and water immersion, and the research variables of sandwich composite were skin and core thickness. For acoustic research, the variables were stud, cavity depth, neck hole diameter of resonator and addition of kenaf fiber as acoustic fill. The testings on composites and acoustic research were physical and mechanical tests, and Noise Absorption Coefficient (NAC), respectively The skin composite with random fiber has higher tensile strength compared to that with woven fiber. For vf = 23%, the composite has the highest tensile strength (40.14 MPa) for 1% of hardener content (v/v). For a number of variations of vf, the skin composite with 2 hours treated fiber has the highest tensile strength and is followed by the composite with untreated fiber. According to ROM theory, the increasing of vf increases tensile and bending strength, and impact toughness of skin composite. The thermal cyclic and water immersion treatments decrease the bending strength of skin composite. The bending strength and impact toughness of sandwich composite increase with the increasing of skin thickness. However, for 5 mm of skin thickness, the bending strength decreases because of delamination failure. The sandwich composite with 2 hours treated fiber has lower impact toughness and more brittle of fracture surface compared to that with untreated fiber. For core thickness variations, the sandwich composite with 2 hours treated fiber has higher value of ss/c compared to that with untreated fiber. The increasing of core thickness decreases specific impact toughness (KI/c). The increasing of dynamic bending cycles decreases stiffness (K) of the sandwich composite and increases the value of d/c. The increasing of core thickness also decreases the stiffness of the sandwich composite. The higher NAC occurs on the acoustic cell with stud 30 and 40 mm of stud, cavity depth 25 mm, 10 mm - neck hole diameter of resonator, and addition of acoustic fill 10%. The acoustic panel with stud 30 mm, cavity depth 25 mm, 10 mm - neck hole diameter of resonator, and addition of acoustic fill 10% has more than 0,74 of NAC for 63 – 10,000 Hz.

Kata Kunci : Serat kenaf, Kayu sengon laut, Polyester, Komposit, Akustik, kenaf fiber, albizzia wood, polyester, composite, acoustic