PENGARUH FRAKSI VOLUME SERAT TERHADAP SIFAT MEKANIS KOMPOSIT MATRIKS POLIMER POLYESTER DIPERKUAT SERAT PELEPAH GEBANG

Penelitian ini dilakukan untuk mengetahui vraksi volume terbaik yang dapat digunakan sebagai komposit bermatrik polyester dengan penguat serat pelepah gebang. Sifat mekanik yang dimaksudkan adalah kekuatan impak dan foto mikro permukaan patahan hasil uji impak pada komposit ini. Komposit berpenguat serat pelepah gebang dengan matrik polimer polyester ini menggunakan fraksi volume 0% (tanpa serat), 20%, 40%, dan 60% serat dalam komposit sesuai ASTM D 6110-04. Spesimen dibuat sepuluh sampel per fraksi volume untuk mengetahui rata-rata kekuatan spesimen. Selanjutnya data dianalisis menggunakan ANAVA Dari penelitian yang dilakukan diketahui bahwa nilai impak tertinggi ada pada fraksi volume serat 60% yaitu 4.495,04383 J/m3, sedangkan kekuatan impak terendah ada pada fraksi volume 0% (tanpa serat) yaitu 604,50120 J/m3. Pada fraksi volume serat 0%-60% rata-rata mengalami patah getas (brittle) dan mekanisme fiber puul out dan dikategorikan memiliki pola patahan sikat (brush fracture) pada fraksi serat 60%.Kata Kunci : brittle, gebang, impak, komposit, polyester This reserch was conducted to determine the best volume vraksi that can be used as a composite matriks Polyester with fiber amplifier gebang. Mechanical properties is meant impact strength and fracture surface micro photograph impact test results on this composite. Composite fibers gebang with polyester polymer matrix using 0 % volume fraction ( without fiber ) , 20 % , 40 % , and 60 % of the fibers in the composite according to ASTM D 6110-04. The samples speciment volume fractions to determine the average power of the specimen. Furthermore, the data were analyzed using ANAVA. From this research known that the highest impact is on the fiber volume fraction of 60 % which is 4495.04383 J / m3, while the impact strength is lowest at 0 % volume fraction ( without fiber ) is 604.50120 J / m3. In the fiber volume fraction of 0% - 60% on average brittle fracture ( brittle ), fiber puul out and categorized has a fracture pattern brush (brush fracture) on the fiber fraction of 60%.keyword : brittle, gebang, impact, komposit, polyester

Dynamic effects of single fiber break in unidirectional glass fiber-reinforced composites

In a unidirectional composite under static tensile loading, breaking of a fiber is shown to be a locally dynamic process that leads to stress concentrations in the interface, matrix and neighboring fibers that can propagate at high speed over long distances. To gain better understanding of this event, a fiber-level finite element model of a two-dimensional array of S2-glass fibers embedded in an elastic epoxy matrix with interfacial cohesive traction law is developed. The brittle fiber fracture results in release of stored strain energy as a compressive stress wave that propagates along the length of the broken fiber at speeds approaching the axial wave-speed in the fiber (6 km/s). This wave induces an axial tensile wave with a dynamic tensile stress concentration in adjacent fibers that diminishes with distance. Moreover, dynamic interfacial failure is predicted where debonding initiates, propagates and arrests at longer distances than predicted by models that assume quasi-static fiber breakage. In the case of higher strength fibers breaks, unstable debond growth is predicted. A stability criterion to define the threshold fiber break strength is derived based on an energy balance between the release of fiber elastic energy and energy absorption associated with interfacial debonding. A contour map of peak dynamic stress concentrations is generated at various break stresses to quantify the zone-of-influence of dynamic failure. The dynamic results are shown to envelop a much larger volume of the microstructure than the quasi-static results. The implications of dynamic fiber fracture on damage evolution in the composite are discussed.

Numerical Analysis of Masonry Enhanced by Fiber Reinforced Lime-Based Render

Out of plane load bearing capacity of a masonry structure enhanced by surface render made of high performance lime-based mortar is investigated by numerical simulations using the finite element method (FEM). The response of the wall is simulated firstly without render (as a reference) then with surface render consisting of conventional lime mortar with increased tensile strength (by addition of the metakaolin) without fibers and finally with the proposed lime-metakaolin mortar reinforced with PVA fibers. The thickness of the surface render is considered in two configurations (20 mm and 40 mm). Material parameters of masonry units (bricks), joints (mortar between bricks) and conventional plain render are chosen with regard to investigations of historic structures (reported in the literature), material characteristics of fiber reinforced render are evaluated based on experiments or numerical simulations of these experiments. Using these parameters and characteristics, the numerical simulations of masonry wall subjected to out of plane bending are performed. The results allow us to identify influence of the thickness and the material of render on load-bearing and deformation capacity, failure mode and amount and width of cracks. The results show that the conventional plain mortar improves load-bearing capacity and deformation capacity proportionately to the thickness of render, but the response remains brittle. Fiber reinforced mortar significantly increases the deformation capacity and load-bearing capacity and the amount of absorbed energy is significantly improved.

A Statistical Constitutive Model for the Strength of Brittle Fiber at Different Strain Rates

A statistical constitutive model, which takes account the effect of strain rate, was presented to describe the stress-strain relationship of brittle fiber bundles. To verify its reliability, tensile tests on two kinds of brittle fibers: glass fiber and SiC fiber, were carried out at different strain rates, and the stress-strain curves were obtained. It was found that the modulus E, the strength and the fracture strain of these fiber bundles all increase with increasing strain rate. The simulated stress-strain curves, derived from the constitutive model, fit the tested results well, which indicates that the model is valid and reliable.

Effect of Fiber-Matrix Integration on the Fracture Behavior of Aluminosilicate Fiber Reinforced Clay-Kaolin Matrix Composites

Different amounts of fiber added samples were prepared by standard ceramic processing routes and sintered at different temperatures. Although powder packing characteristics of the matrix material were negatively affected with increasing fiber content; certain improvements were observed for the density, MOR and water absorption values both for green and sintered states. Fracture surfaces of the samples after three-point bending test were investigated via detailed SEM observations and phase analyses were performed by XRD measurements. It is found that phase transformation controlled fiber-matrix integration starts with increasing sintering temperature and degree of bonding between fiber/matrix interfaces can be arranged by selecting optimum sintering temperature. Aluminosilicate fiber addition was found efficient for improving mechanical properties of clay-kaolin matrix and the mechanism of the improvement can be grouped into two categories i.e. (1) brittle fiber – brittle matrix interactions via well known pulled-out, crack deflection and bridging mechanisms prior to fiber-matrix integration (2) further densification via phase transformation controlled fiber-matrix integration after high sintering temperatures.