Novel Analytical Model of Stress Concentration around Broken Fibers of Unidirectional Composite Plate

During the fiber fracture of unidirectional composite a distribution of stress around the neighbored fibers happens, this mechanism is called the local redistribution efforts. Referring to the "shear lag" method, the researches wanted to predict the stress concentration in the surrounding area of broken fibers as well as the longitudinal resistance of the unidirectional composite which presents a fiber breaking. The goal of this paper is to develop a new probabilistic model of unidirectional composite plate to calculate the stress concentration at the broken fibers and their neighboring fiber intact. The "shear lag" method has been generalized to see the broken fibers interference on the stress concentration factor variation of surrounding sound fibers.

Self-strengthening biphasic nanoparticle assemblies with intrinsic catch bonds

Protein–ligand complexes with catch bonds exhibit prolonged lifetimes when subject to tensile force, which is a desirable yet elusive attribute for man-made nanoparticle interfaces and assemblies. Most designs proposed so far rely on macromolecular linkers with complicated folds rather than particles exhibiting simple dynamic shapes. Here, we establish a scissor-type X-shaped particle design for achieving intrinsic catch bonding ability with tunable force-enhanced lifetimes under thermal excitations. Molecular dynamics simulations are carried out to illustrate equilibrium self-assembly and force-enhanced bond lifetime of dimers and fibers facilitated by secondary interactions that form under tensile force. The non-monotonic force dependence of the fiber breaking kinetics is well-estimated by an analytical model. Our design concepts for shape-changing particles illuminates a path towards novel nanoparticle or colloidal assemblies that have the passive ability to tune the strength of their interfaces with applied force, setting the stage for self-assembling materials with novel mechanical functions and rheological properties.

ANALISA SIFAT MEKANIK PENGARUH VARIASI PERENDAMAN DAN PENEKANAN PADA KOMPOSIT BERBAHAN SERAT BUNDUNG

This study aims to determine the effect of mechanical properties of impact, bending and tensile of bundle fiber composites with 5% NaOH variation of immersion time 0.5 hours, 1 hour and 1.5 hours. Then the blending and casting process is carried out to form a composite material with 20% fiber and 80% resin binder with a catalyst content of 1% and pressurized with press variations of 5 kg, 10 kg and 15 kg. The results of the blending and casting process are made according to the testing standard and then testing the mechanical properties. Impact, bending and tensile strength test results showed that immersion of 0.5 hours with 15 Kg concentration produced the highest value, namely Impact strength 94.89 J / mm2, bending strength 17.77 N / mm2 and tensile strength 27 N / mm2. Whereas the fracture form of the composite is the binding and fiber breaking evenly at the same point and the fiber is not pulled from the metric.

Effect of Ultraviolet C Disinfection Treatment on the Nanomechanical and Topographic Properties of N95 Respirator Filtration Microfibers

Ultraviolet germicidal irradiation (UVGI) N95 filtering facepiece respirator (FFR) treatment is considered an effective decontamination approach to address the supply shortage of N95 FFRs during the ongoing Covid-19 pandemic. In this study, we investigated the nanomechanical and topographic properties of filtration fibers that have been exposed to different doses of UVC radiation. UVC exposure was shown to decrease both Young's modulus (E), hardness (H) and fiber width, as measured on individual polypropylene (PP) fibers. Our results also show that the PP microfiber layer loses its strength when N95 respirators are exposed to an accumulated UVC dose during the process of decontamination, and the PP fiber width also exhibits a logarithmic decrease during UVC exposure. The nanoscale measurement results on individual fibers suggest that maximum cycles of UVC disinfection treatment should be limited due to excessive accumulated dose, which has the potential to decrease the fiber breaking strength.

Kaji eksperimental pengaruh ukuran dan komposisi filler komposit polyster serbuk kayu terhadap sifat mekanik dan permukaan patahan statik.

Penggunaan serat alami sebagai pengisi (filler) dan penguat (reinforcement) pada pembuatan komposit merupakan suatu paradigma untuk mengahasilkan suatu material bio-komposit yang ramah lingkungan. Serat almi yang berasal dari tumbuh-tumbuhan terdapat dalam jumlah yang sangat potensial di Indonesia yang bisa diproses menjadi serat bio-komposit berkekuatan tinggi. Penelitian ini dilakukan untuk mempelajari pengaruh komposisi dan ukuran filler serbuk kayu terhadap sifat mekanik pada pembuatan komposit polyester serbuk kayu. Material komposit dibuat dengan proses hand lay-up satu tahap .dengan memvariasikan ukuran dan komposisi filler. Filler serbuk kayu diberikan perlakuan awal untuk mendapatkan ukuran dan sifat yang seragam. Dimensi dan konsfigurasi specimen uji dibuat mengikuti standar ASTM D 79() -RI. Proses pengujian dilakukan menggunakan Universal Testing Machine dengan uji bending tiga titik untuk menentukan tegangan bending. modulus elastisitas. regangan bending dan sudut defleksi . Dart hasil penelitian diperoleh harga tegangan bending tertinggi 15.3 Pa. dan modulus elastisitas tertinggi 65.362 MPa. regangan terbesar 2.25 % dan sudut defeleksi terbesar 6. 67. Dari penelitian ini disimpulkan bahwa ukuran dan komposisi filler serbuk kayu mempengaruhi sifat mekanik komposit dimana sifat mekanik yang baik akan didapat bila filler terdistribusi secara merata di dalam matriks. Permukaan patah static menunjukkan perpatahan yang terjadi secara umum adalah patah matrik .juga terdapat gejala debonding. fiber breaking serta pengaruh voids.

KANDUNGAN ENERGI METABOLIS SEMU PAKAN DAN ENERGI METABOLIS SEMU TERKOREKSI N PADA GANDUM DENGAN SUPLEMENTASI ENZIM SEBAGAI SUBSTITUSI JAGUNG

Feed broiler is one important factor that is very supportive of other factors when broiler maintenance. One way to reduce the use of maize is to use alternative raw materials of wheat. Wheat can be obtained and the price is cheaper than corn but contains a high Non Starch Polysaccharide, while the poultry digestive tool is not able to digest such crude fiber because it has no crude fiber-breaking enzymes so it needs enzyme addition to the efficient use of nutrient feed. The research method used is the experimental method using Completely Randomized Design consisting of 4 treatments 5 replications. The treatment is as follows P0 (without wheat and xylanase); P1 (substitution of maize with 20% wheat); P2 (maize substitution with 40% wheat) and P3 (substitution of maize with 60% wheat). The observed variables are metabolic energy of pseudo-feed and metabolically correlated false energy n. Data were analyzed by analysis of variance (ANOVA) if there are differences among the treatments followed by Duncan's Test. The results showed that the use of wheat with a xylanase enzyme supplementation as a substitute corn provides highly significant effect (P<0.01) on the apparent metabolize energy of feed and apparent metabolize energy corrected N. The addition of xylanase enzymes in feed with the substitution of wheat by 20 percent produce the best feed metabolizable energy among other treatments. Keywords : Broiler, Wheat, Enzymes, Energy, Feed

Study on Cross Section Geometry of Preform for the Forming Laws of a Symmetrical Rib-Web Component

In order to reveal the forming laws，eliminate the forming defects appearing in the typical aluminum alloy web-rib parts，two types of preforms have been used in the final forging with numerical simulation software.Based on the simulation，the comparisons of metal flow，effective strain distribution are obtained between the two types of preforms applied in the final forging process，the forming laws of a symmetrical rib-web component have been obtained ,and the forming mechanism of defects often happened in web- rib parts also has been analyzed,the relationship between the fillet radius and metal flow velocity/ final load was obtain. The results show that the fiber breaking,vortex could be avoided，a high forming quality of rib-web part could be gained by the method of using the thin web-high rib preform in finish-forging.