Transverse Compressive Properties

Source Muraki, C., et. al.. Journal of the Textile Institute, 81,12-ofthe Textile Institute, 81,432-447, 1990. -21, 1994. Kawabata, S., Journal 

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Kelly PA, Bickerton S, Cheng J. Transverse compression properties of textile materials. Advanced Materials Research, 2011 332-334 697-701. EX)I 10.4028/ www.scientific.net/AMR.332-334.697. 

In addition to longitudinal compressive properties, transverse compressive properties also are important. Fibers in composites need have sufficient transverse compressive modulus and strength since the external force sometimes is applied in the transverse direction to the fiber axis (Figure 15.27B). In both woven and nonwoven fabrics, fibers also may experience transverse compressive forces while in use. 

The lamina s transverse compressive/tensile properties are determined from a hoop wound (90°) cylinder loaded in axial compression and/or tension. The test methods have been standardized under ASTM D5450 and D5449. The tube geometry and manufacturing procedures are similar to those used in the lamina s in-plane shear tests. 

Efforts to improve the compressive properties of rigid-rod polymer fibers have involved introduction of cross-linking in the transverse direction (Bhattacharya, 1989 Spillman et al, 1993) and coating the fiber surface with a thin layer of a high modulus material (McGarry and Moalli, 1991,1992). 

In practice, it is often useful to evaluate the influence of moisture on a fiber assembly directly. This is particularly meaningful when the performance of the product depends on several mechanical properties (such as transverse compression, tensile, bending, and torsional characteristics, etc.) of the constituent fibers at once. 

Fibers and films possess anisotropic mechanical properties. Hence a discussion of this subject should include tensile and compression properties in at least two different directions, viz. in longitudinal and transverse direction to the filament axis. However, in general little is known of the transverse properties of fibers and films. 

The matrix material has several duties to perform it transfers load between the fibres, it protects the notch sensitive fibres from abrasion and it forms a protective barrier between the fibres and the environment. As a protective barrier it prevents attack from moisture, chemicals and oxidation. It also plays the dominant role in providing shear, transverse tensile and compression properties to the composite. The behaviour of the composite under the effects of temperature is also governed by the matrix performance. 

These values are for individual lamina or for a unidirectional composite, and they represent the theoretical maximum (for that fiber volume) for longitudinal in-plane properties. Transverse, shear, and compression properties will show maximums at different fiber volumes and for different fibers, depending on how the matrix and fiber interact. These properties are not reflected in strand data. These values may also be used to calculate the properties of a laminate that has fibers oriented in several directions. Using the techniques shown in Sec. 4.5.1, the methods of description for ply orientation must be introduced. 

Figure 8.12 Transverse fibre compression apparatus. (Reproduced from Kotani, T, Sweeney, J. and Ward, I.M. (1994) The measurement of transverse mechanical properties of polymer fibres. J. Mater. Sci., 29, 5551. Copyright (1994) Springer Science and Business Media.)...

Madhukar, M.S. and Drzal, L.T., Fiber-matrix adhesion and its effect on composite mechanical properties, II. Longitudinal (0°) and transverse (90°) tensile and flexure behavior of graphite/epoxy composites. J. Compos. Mater., 25, 958-991 (1991). Madhukar, M.S. and Drzal, L.T., Fiber-matrix adhesion and its effect on composite mechanical properties. III. Longitudinal (0°) compressive properties of graphite/epoxy composites. J. Compos. Mater., 26, 310-333 (1992). 

Some fibres, e.g. organic and carbon ones, are anisotropic in their behaviour. The transverse, compressive and shear properties of such materials, as well as thermal and electrical properties, have to be estimated by measuring the appropriate parameter for a well-made composite and then using a model which fits the data to obtain the appropriate fibre properties. 

Notes The first subscript 1 or t refers to directions longitudinal and transverse to the fibre. The second subscript, t, f or c, refers to tensile, flexural and compressive properties. For example, is the transverse tensile modulus. 

The carbon fibres used are from the separate sources and cover all the grades listed in Table 3.1. Measurements were made at room temperature and all the matrices except one are epoxies. The use of bismaleimide resin makes little difference to properties apart from the relatively low transverse strain-to-failure. The large gaps in information especially for transverse, compressive and shear properties are clear. The anisotropy of unidirectional materials can be seen by comparing longitudinal and transverse tensile or shear moduli and strengths. 

It is interesting to compare the efficiency of the reinforcement for AS4 fibre in PPS and PEEK. In the former case the values are 92% and 63% for modulus and strength respectively and in the latter 99% and 87% respectively. Modulus uptake is excellent in both cases and strength in the second. The poorer strength result for PPS may be due to reduced compatibility between the fibre surface and matrix. This is supported by the lower ILSS value for PPS carbon fibre composite. Compressive properties are notably lower than tensile ones, while transverse tensile properties are similar to those of thermosetting polymer matrix materials. 

The measured elastic properties for a range of fibres, determined by the ultrasonic immersion method, are given in Table 6.8. It is particularly notable that is greater than 0.5, a result that is in accordance with the fact that, in highly oriented fibres, the high axial stiffness means that transverse compression becomes close to pure shear in the transverse plane. 

In addition to chemical analysis a number of physical and mechanical properties are employed to determine cemented carbide quaUty. Standard test methods employed by the iadustry for abrasive wear resistance, apparent grain size, apparent porosity, coercive force, compressive strength, density, fracture toughness, hardness, linear thermal expansion, magnetic permeabiUty, microstmcture, Poisson s ratio, transverse mpture strength, and Young s modulus are set forth by ASTM/ANSI and the ISO. 

It is critical that surface treatment conditions be optimized to composite properties since overtreatment as well as undertreatment will degrade composite properties. Typically composite interlaminar shear strength (ILSS), in-plane shear, and transverse tension ate used to assess the effectiveness of surface treatment. More recently damage tolerance properties such as edge delamination strength, open hole compression, and compression after impact have become more important in evaluating the toughness of composite parts. 

Predicted results for E2 are plotted in Figure 3-10 for three values of the fiber-to-matrix-modulus ratio. Note that if Vj = 1, the modulus predicted is that of the fibers. However, recognize that a perfect bond between fibers is then implied if a tensile <32 is applied. No such bond is implied if a compressive 02 is applied. Observe also that more than 50% by volume of fibers is required to raise the transverse modulus E2 to twice the matrix modulus even if E, = 10 x E ,l That is, the fibers do not contribute much to the transverse modulus unless the percentage of fibers is impractically high. Thus, the composite material property E2 is matrix-dominated. 

Factors influencing jet breakup may include (a) flow rates, velocities and turbulence of liquid jet and co-flowing gas, (b) nozzle design features, (c) physical properties and thermodynamic states of both liquid and gas, (d) transverse gas flow,[239] (e) dynamic change of surface tension, 1151[2401 (f) swirlj241 242 (g) vaporization and gas compressibility,[243] (h) shock waves,[244] etc. 

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