Respon Polymeric Foam yang Diperkuat Serat Tandan Kosong Kelapa Sawit (TKKS) Akibat Beban Tekan Statik dan Impak (Simulasi Numerik)

Abstract

Experimental and numerical work was reported on the problem of the response of oil palm empty fruit bunch (OPEFB) fiber reinforced polymeric foam under static and impact loading conditions. In the experimental investigation, the static axial compressive test was applied on polyurethane, thermosetting resins, and OPEFB fiber reinforced polymeric foam specimens and these specimens were conducted on a servohydraulic material testing machine. The averaged stress-strain response and the fracture modes in each type of materials were derived from static test. The fracture modes in each type of materials and the collapsed cells of OPEFB fiber reinforced polymeric foam were observed by a scanning electron microscope. In the numerical simulation, the variation of the distributions of normal stresses with normalized time in OPEFB fiber reinforced polymeric foam due to static and impact wave propagation was analyzed by using a finite element method (FEM). The finite element code ANSYS and NASTRAN were used for numerical stress analysis. The obtained summaries were as followed: (1) The yield stress, the maximum stress, and the strain to failure were influenced by foams, these foams reduced the stress and decreased the strain to failure. The fracture modes were also found to be considerably different for each type of materials. Polyurethane exhibited random macroscopic fracture, thermosetting resins and OPEFB fiber reinforced polymeric foam exhibited shear dominated failure and the cells suffered progressive crushing. (2) Based on FEM computation results were found that the fracture mechanism corresponded to the regions of the static compressive stress concentration. (3) FEM computation results suggested that the propagation of incident compressive stress wave related to impact loading. (4) Based on the static axial compressive test results, the Young’s modulus and the stiffness were determined and it was found that thermosetting resins may also contributed to increased the stiffness of polyurethane.

Penelitian secara eksperimen dan numerik telah dilaporkan untuk menyelidiki permasalahan respon polymeric foam diperkuat serat tandan kosong kelapa sawit (TKKS) akibat pembebanan kondisi pembebanan statik dan impak. Di dalam penyelidikan secara eksperimen, pengujian tekan statik aksial digunakan terhadap spesimen polyurethane, resin termoset, dan polytmeric foam diperkuat serat TKKS dan pengujian spesimen tersebut dilakukan pada mesin uji material servohidraulik. Respon tegangan-regangan rata-rata dan mode kerusakan setiap material diperoleh dari uji statik. Mode kerusakan setiap material dan kehancuran rongga polymeric foam diperkuat serat TKKS diamati menggunakan scanning electron microscope. Di dalam simulasi numerik, variasi distribusi tegangan normal terhadap waktu pada polymeric foam diperkuat serat TKKS akibat beban statik dan propagasi gelombang impak akan dianalisa menggunakan metode elemen hingga (MEH). Elemen hingga dengan kode ANSYS dan NASTRAN digunakan dalam analisa tegangan secara numerik. Kesimpulan yang diperoleh dari penelitian ini sebagai berikut: (1) Tegangan yield, tegangan maksimum, dan regangan saat patah dipengaruhi oleh rongga, rongga tersebut mereduksi tegangan dan menurunkan regangan saat patah. Mode kerusakan ditemukan sangat berbeda untuk setiap jenis material. Polyurethane menunjukkan kerusakan yang acak secara makroskopik, resin termoset dan polymeric foam diperkuat serat TKKS menunjukkan dominasi kegagalan geser dan rongga-rongga mengalami kerusakan bertahap. (2) Berdasarkan hasil simulasi MEH ditemukan bahwa mekanisme kerusakan bersesuaian dengan daerah konsentrasi tegangan tekan statik. (3) Hasil komputasi FEM menyarankan bahwa propagasi gelombang tegangan insiden tekan berhubungan dengan beban impak. (4) Berdasarkan hasil uji tekan statik aksial, modulus elastisitas dan kekakuan telah ditetapkan dan ditemukan bahwa resin termoset berkontribusi meningkatkan kekakuan polyurethane.