Kekakuan dan Kekuatan Lentur Maksimum Balok Glulam dan Utuh Kayu Akasia

Abstract

Abstrak. Glulam merupakan salah satu metoda mengatasi keterbatasan dimensi bahan dasar kayu yang tersedia. Dengan mempersiapkan lamina-lamina dan menyusunnya serta melakukan proses perekatan antar permukaan lamina dapat menghasilkan dimensi balok sesuai kebutuhan. Tujuan dari penelitian ini adalah mendapatkan nilai kekakuan dan kekuatan lentur maksimum balok glulam dengan ketebalan lamina yang berbeda serta membandingkannya terhadap balok utuh. Kekakuan dinyatakan dalam MOE (modulus of elastcity), dan kekuatan lentur maksimum dinyatakan dalam MOR (modulus of rupture). Penelitian ini menggunakan kayu Akasia (Acacia mangium) termasuk kayu dengan kerapatan menengah. Balok glulam dibagi menjadi 3 (tiga) kelompok ketebalan lamina, masing-masing 20 mm, 15 mm and 10 mm. Selain balok glulam disiapkan pula balok utuh. Penampang melintang balok glulam maupun balok utuh adalah 60 mm x 60 mm. Perekat yang digunakan adalah Polyurethane merupakan Water Based Polymer Isocyanate. Perekat terdiri dari dua bagian; begian pertama adalah PI 3100 sebagai cairan resin, dan H7 sebagai cairan pengeras. Berat labur perekat diaplikasikan sebesar 280 g/m2 pada kedua permukaan rekatan. Prosedur pengujian dilaboratorium dilakukan berdasarkan ASTM D143-05, Standard Test Methods for Small Clear Specimen of Wood. Hasil penelitian menunjukkan bahwa konfigurasi penampang melintang balok glulam mempengaruhi nilai MOE dan MOR-nya; semakin tipis ketebalan lamina mempunyai tendensi semakin tinggi MOE dan MOR-nya; nilai MOE dan MOR balok glulam tidak berbeda nyata dengan balok utuh, dan kedua nilai tersebut dipengaruhi oleh tipe kerusakan balok.

Abstract. Glued Laminated Beam represents one method in overcoming limited dimension of available raw material of wood. By stacking sequence of several timber layers to be bonded with glue perfectly, the dimension which was required could be obtained. The objectives of this research were to determine the stiffness and maximum bending strength of glued laminated beam (glulam) with different thickness of lamina; it was compared to solid beam. The stiffness was represented as MOE (modulus of elasticity), and maximum bending strength as MOR (modulus of rupture). This research used Acacia (Acacia mangium) as a medium density wood. Glulam beam was divided into 3 (three) groups based on the thickness of lamina, 20 mm, 15 mm and 10 mm respectively. Solid beam was also prepared besides glulam beam. The cross section of glulam and solid beam was 60 mm x 60 mm. The adhesive, Polyurethane was used as Water Based Polymer Isocyanate. It consisted of two parts; the first part of the adhesive was PI 3100 as a liquid resin, and H7 as a liquid hardener. The two parts were mixed in the ratio of 100:15 by weight. The glue spread of adhesive was applied 280 g/m2 in a double spread. The procedure of investigation in the laboratory was tested in accordance with ASTM D143-05, Standard Test Methods for Small Clear Specimen of Wood. The result showed that the cross section configuration of glulam beam influenced in the value of MOE and MOR; the lesser the thickness of lamina the higher MOE and MOR value tendency were; the MOE and MOR of glulam beam were not significant different with solid beam, and it were influenced by the type of failure.