Pore-throat structure characterization of carbon fiber reinforced resin matrix composites: Employing Micro-CT and Avizo technique

Micro-CT technique poses significant applications in characterizing the microstructure of materials. Based on the CT three-dimensional(3D) reconstruction technology and “Avizo” 3D visualization software, the microscopic pore-throat structure of porous media can be quantitatively characterized. This paper takes the carbon fiber reinforced resin matrix composites as an example to introduce the operation process of “Avizo” in details, which mainly covers the following modules: Volume Edit, Interactive Thresholding, Fill Holes, Mask, Separate Objects and Generate Pore Network Model, then further discuss the difficult problems when the “Avizo” is employed to analyze. The microstructures of carbon fiber reinforced resin matrix composites illustrate that pores in the upper part of sample are dramatically dispersed, and mainly concentrated in the lower part of sample. The porosity of adopted cuboid is 3.6%, accordingly the numbers of pores and throats reach 268 and 7, respectively. The equivalent radius of pores seems mainly distributed in the range of 0.7–0.8μm, accounting for 28.73% of the total pore number. The surface area of pore ranges from 5 to 10μm2, accounting for 14.16% of the total pore number. The pore volume concentrates in the range of 1–20μm3, accounting for 57.46% of the total pore number. In addition, the equivalent radius of throat mainly concentrates in the range of 1–5μm, the overall length of throat is distributed in the range of 37–60μm, and the equivalent area of throat is distributed non-uniformly in the range of 5–75μm2. This work provides a basis for the further investigation of fluid migration mechanism and law in the composite materials by the numerical simulation methodology.

Pemanfaatan Limbah Galvalum Sebagai Substitusi Aggregat Kasar Pada Jobmix Beton

Concrete is one of the construction materials that is widely used. Currently, variations in concrete are being studied. Galvalum waste has high tensile properties but is mild. Its lightweight properties are expected to reduce the weight of the concrete itself. The purpose of this study is to find out the value of strong press, absorption, weight type (E), degree of saturation (Sr), moisture content (Wc), and porosity of the addition of galvalume waste. The method used is a experimental method. Variations in galvalum waste substitution used are 50% and 100% of the aggregate weight is roughT the sample used in the form of a cylinder size of 15cm x 30 cm with the initial quality of fc' 18.67 Mpa. The results of the strong press test showed that the galvalum waste subtitution has not been able to exceed the initial quality of the plan. The highest test result was obtained at a percentage of 50% with a strong press score of FC' 17.94 Mpa. In the percentage, absorption test results are 0.010%, the weight of the type is 2325 kg / m3, the pore number is 0.00232%, the water content is 0.108%, and porosity is 0.00108%.Beton merupakan salah satu bahan konstruksi yang banyak dipergunakan. Saat ini, pengguanaan variasi pada beton sedang banyak diteliti. Limbah galvalum memiliki sifat tarik yang tinggi namun ringan. Sifatnya yang ringan diharapkan mampu mengurangi berat beton itu sendiri. Tujuan dari penelitian ini adalah untuk mengetahui nilai kuat tekan, absorpsi, berat jenis (Ɣ), angka pori (e),derajat kejenuhan (Sr), kadar air (Wc), dan porositas dari penambahan limbah galvalum. Metode yang digunakan merupakan metode eksperimen. Variasi pensubtitusi limbah galvalum yang digunakan yaitu 50% dan 100% dari berat agregat kasar. sampel yang digunakan berbentuk silinder ukuran 15cm x 30 cm dengan mutu awal fc’ 18.67 Mpa. Hasil uji kuat tekan menunjukkan bahwa subtitusi limbah galvalum belum mampu melebihi mutu awal rencana. Hasil uji tertinggi didapat pada prosentase 50% dengan nilai kuat tekan fc’ 17,94 Mpa. Pada prosentase tersebut, didapat hasil uji absropsi yaitu 0,010%, berat jenis yaitu 2325 kg/m3, angka pori yaitu 0,00232%, kadar air yaitu 0,108% serta porositas yaitu 0,00108%.

EVALUASI ELEVASI LANTAI SEKAT KANAL GOHONG NO. 9 DALAM MENAIKAN MUKA AIR TANAH MENGGUNAKAN PEMODELAN ALIRAN AIR TANAH

Penelitian ini dilakukan untuk menganalisa pengaruh MAS terhadap tinggi MAT di sekitarnya. Selanjutnya dimodelkan dan disimulasi hingga memperoleh elevasi peletakan lantai sekat kanal yang tepat untuk menaikan MAT mencapai kedalaman rata-rata ≤ 0,4 m dari permukaan tanah. Kajian dilakukan di area penelitian seluas 600m x 300m. Sekat kanal yang dimodelkan adalah sekat kanal no.9/Gohong, Desa Gohong, Kec. Jabiren Raya, Kabupaten Pulang Pisau, Provinsi Kalimantan Tengah. Gambut di lokasi penetian tergolong hemik. Angka pori berada pada angka 2,1 sd 7,7 cm3 dan porositas cukup besar yaitu antara 67 sampai 88%. Tanah tergolong bertekstur Lempung (Loam). Nilai permeabilitasnya adalah 2,76.10-4 cm/det atau setara dengan 23,85 cm/hari atau 0,994 cm/jam. Analisa MAT berdasarkan data pengukuran 9 September 2019 menunjukan kedalaman elevasi MAT lebih dari 0,4 m dari permukaan lahan. Elevasi sekat terlalu rendah sehingga tidak banyak air yang tertahan di saluran. Untuk mengefektifkan fungsi sekat yang sudah terpasang lantai sekat perlu dinaikan. Perbaikan peletakan lantai sekat kanal dengan pemodelan menggunakan aplikasi Hydrus 2D. Dari simulasi diperoleh informasi bahwa dengan memasukan nilai pressure head sebesar 98 cm akan terjadi pengaruh pressure head di rentang ketinggian 89,40 sampai dengan 7,15 cm artinya kedalaman MAT ≤ 0,4 m dari permukaan tanah dapat dicapai. Saran dari penelitian ini adalah, untuk menaikan MAT agar kedalaman rata-ratanya berada pada kedalaman ≤ 0,4 m dari permukaan tanah, maka lantai sekat kanal yang semula berada pada elevasi z=48.856 perlu dinaikan ke z=49.416. Sehingga pada saluran yang awalnya hanya tergenang setinggi 42 cm akan memiliki genangan 98 cm terjadi kenaikan MAS sebesar 56 cm. Kata Kunci: Gambut, mas, mat, sekat kanal. This research was conducted to analyze the influence of CWL on peat GWL. Furthermore, a model simulation will be made to get the appropriate elevation of the canal blocking floor that can raise the GWL to reach average depth ≤ 0,4 m from land surface. The study was conducted in a research area of 600m x 300m. The canal block is modeled by canal no.9 / Gohong, in Gohong Village, Jabiren Raya District, Pulang Pisau Regency, Central Kalimantan Province. Peat was classified as hemic. The pore number is in the range of 2.1 to 7.7 cm3 and the porosity is quite large, between 67 to 88%. The soil at the study site is classified as Clay Textured (Loam). The permeability value is ,76.10-4 cm/det or equal to 23,85 cm/day atau 0,994 cm/hour. GWL analysis based on measurement data 9 September 2019 shows the depth of elevation GWL is more than 0.4 m from the surface of the land. Elevation of canal blocking is too low so there is not much water retained in the channel, the floor needs to be increased by modeling using Hydrus 2D. From the simulation it is known that by entering a pressure head value of 98cm, pressure head effect will occur in the height range of 89.40 to 7.15 cm meaning that a depth of MAT ≤ 0.4 m from the ground surface can be achieved. the recommendation is, to raise the GWL to reach an average GWL at a depth of ≤ 0.4 m from the ground surface, the floor of canal blocking that installed at the elevation z = 48,856 needs to be increased to z = 49,416 . So the channel which was originally only flooded as high as 42 cm will have a pool of 98 cm, there will be an increase in the CWL by 56 cm. Keywords: Canal blocking, cwl, gwl, peat

Pollen morphology of Stellaria (Caryophyllaceae) from China and its systematic implications

Pollen morphology of 46 species and 11 varieties representing the 5 currently recognized sections and 10 series of Stellaria from China was investigated. Pollen grains of Stellaria are radially symmetrical, apolar, small or medium in diameter, pantoporate, spheroidal or spheroidal-polyhedral and have 8–22 pores with prominent or sunken pore membrane. The ornamentation is microechinate-punctate, microechinate-perforate or microechinate-punctate-perforate. 8 pollen types are recognized, and significant differences in shape, size, pore number and ornamentation are found. Arenaria and Cerastium were proved to be related to Stellaria, whereas Myosoton was suggested to be merged into Stellaria. The pollen morphological features indicated Stellaria was in a middle evolutionary position of the family Caryophyllaceae.

A Study of Keyhole Porosity in Selective Laser Melting: Single-Track Scanning With Micro-CT Analysis

Porosity is an inherent attribute in selective laser melting (SLM) and profoundly degrades the build part quality and its performance. This study attempts to understand and characterize the keyhole pores formed during single-track scanning in SLM. First, 24 single tracks were generated using different line energy density (LED) levels, ranging from 0.1 J/mm to 0.98 J/mm, by varying the laser power and the scanning speed. The samples were then scanned by micro-computed tomography to measure keyhole pores and analyze the pore characteristics. The results show a general trend that the severity of the keyhole porosity increases with the increase of the LED with exceptions of certain patterns, implying important individual contributions from the parameters. Next, by keeping the LED constant in another set of experiments, different combinations of the power and the speed were tested to investigate the individual effect. Based on the results obtained, the laser power appears to have a greater effect than the scanning speed on both the pore number and the pore volume as well as the pore depth. For the same LED, the pore number and volume increase with increasing laser power until a certain critical level, beyond which, both the pore number and volume will decrease, if the power is further increased. For the LED of 0.32 J/mm, 0.4 J/mm, and 0.48 J/mm, the critical laser power that reverses the trend is about 132 W, 140 W, and 144 W, respectively.

Species identification of European forest pathogens of the genus Milesina (Pucciniales) using urediniospore morphology and molecular barcoding including M. woodwardiana sp. nov.

Species of rust fungi of the genus Milesina (Pucciniastraceae, Pucciniales) are distributed mainly in northern temperate regions. They host-alternate between needles of fir (Abies spp.) and fronds of ferns (species of Polypodiales). Milesina species are distinguished based on host taxonomy and urediniospore morphology. In this study, 12 species of Milesina from Europe were revised. Specimens were examined by light and scanning electron microscopy for urediniospore morphology with a focus on visualising germ pores (number, size and position) and echinulation. In addition, barcode loci (ITS, nad6, 28S) were used for species delimitation and for molecular phylogenetic analyses. Barcodes of 72 Milesina specimens were provided, including 11 of the 12 species. Whereas urediniospore morphology features were sufficient to distinguish all 12 Milesina species except for 2 (M.blechni and M.kriegeriana), ITS sequences separated only 4 of 11 species. Sequencing with 28S and nad6 did not improve species resolution. Phylogenetic analysis, however, revealed four phylogenetic groups within Milesina that also correlate with specific urediniospore characters (germ pore number and position and echinulation). These groups are proposed as new sections within Milesina (sections Milesina, Vogesiacae M. Scholler & Bubner, sect. nov., Scolopendriorum M. Scholler & Bubner, sect. nov. and Carpaticae M. Scholler & Bubner, sect. nov.). In addition, Milesinawoodwardiana Buchheit & M. Scholler, sp. nov. on Woodwardiaradicans, a member of the type section Milesina, is newly described. An identification key for European Milesina species, based on urediniospore features, is provided.

PEMODELAN ANGKA PORI PADA STABILISASI TANAH GAMBUT

Methods for improving peat soils to increase soil carrying capacity and reduce environmentally sound soil compressibility, namely stabilization of the peat layer. This method uses additives such as lime, fly ash and husks. This method has been developed based laboratory by civil engineers. However, it takes a relatively long time to find out the laboratory results. Therefore, research in the field of mathematical models for stabilization of peat soil was developed to predict the laboratory results. In this study, a mathematical model was derived one of the physical properties of peat soil, that is the pore number in stabilizing peat soil. The model is derived from fluid equations through porous media based on the principle of continuum and control volume. Furthermore, the model is completed using a finite difference method, the MacCormack scheme which consists of two steps, that are predictor and corrector. After the model is simulated using matlab, it is known that there is a decrease in the soil pore value to a constant condition. This decrease in pore number is due to chemical reactions that occur by additives which make the soil pores smaller. Keywords: pore number, maccormack, stabilization of peat soil