Beban Kerut pada Pelat Sandwich Anisotropik

Sari. Suatu metode baru untuk menganalisis kegagalan kerut pada struktur pelat sandwich komposit yang bersifat anisotropic dibahas, baik untuk moda simetri maupun moda tidak simetri. Untuk mendapatkan modus kegagalan ini, modulus geser dan normal transversal bagian inti dimasukkan ke dalam analisis. Pertama-tama, energi regangan total yang terjadi dalam sistem ini akan dihitung, dan dengan menggunakan metode Rayleigh-Ritz, sistem eigen yang didapat akan dipecahkan. Dari hasil yang diperoleh dapat disimpulkan bahwa beban kritis kerut dapat terjadi jauh di bawah beban kritis Euler, sehingga menjadi beban kritis yang lebih berbahaya dibandingkan dengan beban Euler. Beban kerut ini juga terjadi pada panjang gelombang yang jauh lebih pendek daripada beban Euler, sehingga bersifat katastropik. Hasil yang didapat juga menunjukkan bahwa analisis baru ini bersifat umum, yang dapat dipakai untuk menghitung beban kritis Euler maupun beban kritis kerut untuk pelat sandwich komposit anisotropik secara simultan. The Wrinkling of Anisotropic Sandwich PanelsAbstract. A new method to analyze the wrinkling failure of anisotropic sandwich panels was discussed, for both symmetrical and asymmetrical wrinkling. To calculate the wrinkling loads, both shear and transverse normal modulus of the core were included in the analysis. First, the total energy of the system was calculated, and then using the Rayleigh-Ritz method, the eigen-system was solved to get the critical buckling loads. The results show that wrinkling could occur far below their corresponding Euler loads, that make them more dangerous. Wrinkling also contain shorter waves, that may lead to catastrophic failures. The results also show that the new method presented in this article is so general and can be used to calculate both Euler buckling and wrinkling loads of anisotropic sandwich panels simultaneously

PENYERAPAN UAP AIR PADA BAHAN KOMPOSIT CARBON / EPOXY

In this paper, moisture absorption process in composite material was analytically and experimentally studied. The environmental condition was 72o C and 85 % RH. During a fixed interval time, the composite specimens were taken out from the experimental chamber and weighted. The weight gain showed that the absorption isoterm proï¬le followed Fick Law andthere was a good agreement between the analytical and experimental results. The average maximum moisture absorption was 0.84 %

Finite element procedure to simulate sandwich structure with an auxetic core under impact loading using ABAQUS/Explicit

<p>A sandwich structure with an auxetic core is promising in improving the performance of a sandwich structure by implying an auxetic core as its core to combine the advantages of the two structures, e.g., sandwich structure's superior ability in flexural and shear resistance, auxetic structure in localizing damage, and densification phenomena. This paper discusses a finite element modeling procedure to simulate a sandwich structure with a heterogeneous re-entrant auxetic core. The material of the face is a unidirectional carbon fiber reinforced polymer (UD CFRP) and the core is polylactic acid (PLA). The model is subjected to a low-velocity impact loading and is run through the ABAQUS/Explicit software. We found that the model we developed here could simulate up to the elastic region and identify which element had failed. However, it could not fully resemble and represent the model from reference, where fracture or damage does not occur. This model can be further improved in its material modeling strategy, especially in the fracture modeling of the composite face with compatible material properties in all required sectors, especially damaged sections, which are strictly necessary.</p&gt

Alternative dental impression fillers made of nanorod glutinous rice flour particles through precipitation

In this work, nanorod particles were synthesized from a locally available source, glutinous rice flour, using sodium hydroxide (NaOH) through a simple precipitation process. The synthesized nanofillers were then presented as an alternative organic filler for dental impression application to support the making of a diagnostic and working model. Dynamic Light Scattering, Scanning Electron Microscope, Fourier Transform Infrared Spectroscopy, x-ray Diffraction, Energy Dispersive Spectroscopy, Thermogravimetric Analysis, and Differential Scanning Colorimeter were used to characterize the fillers. The particle size measurement, morphology interaction, and composition of glutinous rice flour nanorod particles were also investigated. The cell viability using 3T3L1 cells was assessed to determine the safety of nanorod particles using the MTT assay and trypan blue solution. All treated samples exhibit a change in particle morphology from polyhedral to rod. Additionally, a decrease in crystallinity, dehydration, and gelatinization temperature was observed. The functional group interacting with sodium hydroxide also changes slightly after size reduction. The samples treated with 3000 centrifugation speed without surfactant addition showed changes from the control sample’s 3931.71 nm to the smallest average width particle size of 73.26 nm with an average length of 865.15 nm. All of the treated samples with NaOH and NaOH-surfactant additions met the non-cytotoxicity acceptance criteria in the range of 73.54%–99.58%, according to the cell viability results. The incorporation of 15 wt% of the synthesized nanorod fillers resulted in a 20 μ m continuous line as the impression materials specimen, yielding a satisfactory detail reproduction test result. In conclusion, nanorod particles with biocompatible properties have been successfully manufactured and can potentially be used in the future as an alternative dental impression filler materials

<strong>Centrifugation effect on size distribution of organic dental filler made from glutinous rice flour</strong>

ABSTRACT Introduction: Organic fillers made from the green-synthesis process can be utilized in dental treatment due to their non-toxic characteristic of the oral environment. Dental fillers must be smaller to improve their mechanical, physical, and biological properties. Material processing and centrifugation contribute to the size of processed materials. This study evaluates the effect of different centrifugation speeds on the size and distribution of glutinous rice flour as organic dental filler. Methods: This experimental study uses glutinous rice flour suspended in water and then centrifuged at different speeds of 3000 and 6000 rpm compared to untreated glutinous rice flour as control. The particle size was examined using Scanning Electron Microscope (SEM) and Dynamic Light Scattering (DLS). Next, Fourier Transform Infra Spectroscopy (FTIR) and X-ray Diffraction (XRD) were performed to evaluate whether there were structure and crystallinity changes. Finally, the cytocompatibility of fillers was examined by a cell viability test. Results: Centrifugation of glutinous rice flour at 3000 rpm resulted in smaller average size particles, evenly distributed, and higher crystallinity than other groups. There were no changes in functional groups, as shown by FTIR spectra. However, the processed samples were more amorphous compared to the control. Importantly, the processed samples appeared to be non-toxic, with a range of cell viability of 82.75-86.67% after 24 h incubation. Conclusion: Centrifugation speed of 3000 rpm has decreased in size, and a more homogenous particle size of organic filler made from glutinous rice flour. Importantly, it improved the cytocompatibility of particles compared to untreated control. Altogether, we proposed this organic material as a new potential material in the dental application that can be further investigated.  Keywords: centrifugation speed; size distribution; organic dental filler; glutinous rice flou