Test composites, elastic modulus

In a uniaxial tension test to determine the elastic modulus of the composite material, E, the stress and strain states will be assumed to be macroscopically uniform in consonance with the basic presumption that the composite material is macroscopically Isotropic and homogene-ous. However, on a microscopic scSeTBotFTfhe sfre and strain states will be nonuniform. In the uniaxial tension test,... 

Tensile Modulus. Tensile samples were cut from the 0.125 in. plates of the compositions according to Standard ASTM D638-68, into the dogbone shape. Samples were tested on an Instron table model TM-S 1130 with environmental chamber. Samples were tested at temperatures of -30°C, 0°C. 22°C, 50°C, 80°C, 100°C and 130°C. Samples were held at test temperature for 20 minutes, clamped into the Instron grips and tested at a strain rate of 0.02 in./min. until failure. The elastic modulus was determined by ASTM D638-68. Second order polynomial equations were fitted to the data to obtain the elastic modulus as a function of temperature for each of the compositions. 

We will see in Section 5.4.2 that the elastic modulus of a unidirectional, continuous-fiber-reinforced composite depends on whether the composite is tested along the direction of fiber orientation (parallel) or normal to the fiber direction (transverse). In fact, the elastic modulus parallel to the fibers, Ei, is given by Eq. (1.62), whereas the transverse modulus, 2, is given by Eq. (1.63). Consider a composite material that consists of 40% (by volume) continuous, uniaxially aligned, glass fibers (Ef =16 GPa) in a polyester matrix (Em = 3 GPa). 

Figure 13.5 compares the differences between the evolution of the elastic modulus and tan 8 from the DMA tests with both the kind of attached group at the atactic polypropylene and the level of grafting of the interfacial modifier present in the composites. The different effect of each interfacial agent is clearly concluded as discussed elsewhere (33,56). 

Jung et al. have developed a synthetic elastomer composed of acrylonitrile butadiene rubber copolymer [211, 212]. The properties of the copolymer can be tuned by changing its composition. Reported data for dielectric constant, elastic modulus, and strain relaxation are promising (see Table 1.2). The synthetic elastomer provides some improvement over VHB and some silicone hlms under certain conditions however, the tests were limited to low prestrain (60% radial), where the performance of VHB hlms is poor. 

High temperature mechanical characterization was performed on the PAIC compositions with Al/Si = 0.05 and 0.1. The elastic modulus has been measured in air at various temperatures between 800 and 1400°C by four point bend tests (40 X 20 mm) with a 0.2 mm min deformation rate. E has been calculated, through the standard equation valid for rectangular bars, by measuring the displacement with a LVDT. All the ceramic samples obtained by pyrolysis at 1000°C have been pre-annealed at 1400°C for 1 h in argon atmosphere, before the high temperature tests. This treatment lead to the crystallization of microcrystalline pSiC with a minor amount of aSiC. Aluminum atoms are present both as a solid solution of AI2OC in aSiC and in the residual amorphous phase. 

FIGURE 4. Relative elastic modulus versus applied strain during tensile tests on various 2D woven SiC/SiC composites reinforced with treated fibers (A) Nicalon/(PyC2o/SiC5o)io/SiC, (D) Nicalon/PyCioo/SiC, (F) Hi-Nicalon/PyCioo/SiC, (G) Hi-Nicalon/(PyC2o/SiCso)io/SiC. 

Due to the extreme difference between the matrix and fiber properties, the in-plane modulus is dominated by the fiber modulus and volume fraction. For example, the GE GEN-IV material has a modulus of 70 GPa. With 15% fiber in the loading direction and a fiber elastic modulus of 380 GPa, the stiffness due to the fibers alone is expected to be 57 GPa. The UCSB Nextel 610-based material with 33% higher fiber content likewise has roughly a 35% higher modulus. The small contribution of the matrix makes it particularly difficult to infer the elastic properties of the matrix from the composite test results [143]. As a result, and because the porous matrix materials are difficult to produce without any fiber reinforcement, their constitutive properties are not yet well characterized [145]. 

ABSTRACT It is very important to determine the thermal and mechanical parameters of mortar and concrete in mesoscopic simulation. In this paper, on the basis of the Mori-Tanaka formula of mesoscopic mechanics and the concrete is treated as a two-phase composite material constituted by aggregates and mortar, the inversion of coefficient of thermal expansion, autogenous shrinkage, elastic modulus and creep were studied. This paper proposed some inversion formulas regarding these four mechanical parameters of mortar in concrete. The accuracy of these formulas was verified by FEM numerical test and demonstrated by some examples. 

Until now, much research work has been done on the prediction of composite material coefficient of thermal expansion and elastic modulus by forefathers, and many prediction methods have been developed such as the sparse method (Guanhn Shen, et al. 2006), the Self-Consistent Method (Hill R.A. 1965), the Mori-Tanaka method (Mori T, Tanaka K. 1973) and so on. However, none of these formulas take into account the parameters variation with concrete age, and there is little research on the autogenous shrinkage and creep. In the mesoscopic simulation of concrete, thermal and mechanical parameters of mortar and aggregate (coefficient of thermal expansion, autogenous shrinkage, elasticity modulus, creep, strength) are important input parameters. In fact, there is abundant of test data on concrete, but much less data on mortar while it is one of the important components. Also parameter inversion is an essential method to obtain the data, but there are few studies on this so far. 

Influence of the amount of PEDOT-PSS on mechanical properties was studied using d3mamic mechanical anatysis in tension mode. Uniaxial tensile tests were carried out at 30 1°C with TA Q800 Dynamic Mechanic Analyzer. Elastic modulus and breaking points were measured by increasing ramp force 0.1 N/min to 18.0 N/min. Composite nanofibers were electrospun for three hours to measure mechanical properties. At least four specimens were tested for each measurement and the average values are presented. 

The nanoindentation experiments were conducted at room temperature with a Nano Indenter XP system (MTS Nanoinstruments, Knoxville, TN) using a Berkovich-type diamond tip. Before each test, the system was calibrated using a fused silica. The continuous stiffness mode (CSM) was used in the tests. Thirty randomly selected different fiber and CVI matrix locations were indented for each component of C/C composites. The method of Oliver and Pharr was employed for the elastic modulus calculations. ... 

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