Transverse loading, composites

Jadhav, P. and Mantena, P.R. (2007) Parametric optimization of grid-stiffened composite panels for maximizing their performance under transverse loading. Composite Structures, 77, 353-363. 

J. M. Whitney, Bending-Extension Coupling in Laminated Plates Under Transverse Loading, Journal of Composite Materials, January 1969, pp. 20-28. 

Pagano studied cylindrical bending of symmetric cross-ply laminated composite plates [6-21]. Each layer is orthotropic and has principal material directions aligned with the plate axes. The plate is infinitely long in the y-direction (see Figure 6-16). When subjected to a transverse load, p(x), that is, p is independent of y, the plate deforms into a cylinder ... 

The microductile/compliant layer concept stems from the early work on composite models containing spherical particles and oriented fibers (Broutman and Agarwal, 1974) in that the stress around the inclusions are functions of the shear modulus and Poisson ratio of the interlayer. A photoelastic study (Marom and Arridge, 1976) has proven that the stress concentration in the radial and transverse directions when subjected to transverse loading was substantially reduced when there was a soft interlayer introduced at the fiber-matrix interface. The soft/ductile interlayer allowed the fiber to distribute the local stresses acting on the fibers more evenly, which, in turn, enhanced the energy absorption capability of the composite (Shelton and Marks, 1988). 

Zhang, W. (1993). Compulation of stress fields in unidirectional n-phase fibrous composite under longitudinal and transverse loads. Compiit. Structures 34, 647-653. 

In cross-ply laminates, the stress-strain behavior is slightly nonlinear, as illustrated in Figure 5.123. The stress-strain behavior of a unidirectional lamina along the fiber axis is shown in the top curve, while the stress-strain behavior for transverse loading is illustrated in the bottom curve. The stress-strain curve of the cross-ply composite, in the middle, exhibits a knee, indicated by strength ajc, which corresponds to the rupture of the fibers in the 90° ply. The 0° ply then bears the load, until it too ruptures at a composite fracture strength of ct/. 

Figure 10.37 (a) A longitudinal load applied to an aligned fibre composite and (b) a transverse load applied to an aligned fibre composite... 

Transverse load on a continuous and aligned fibre composite... 

The value of the elastic modulus, often called the Reuss bound, is identical to that for transverse loading on a fibre composite, and gives a value for the elastic modulus normal to the layers. In both of these equations, E, E and Ep are the elastic moduli of the ceramic, matrix and particles, respectively, and Vc (equal to 1.0), Vm and Vp are the corresponding volume fractions. 

Compute the modulus of elasticity of a composite consisting of continuous and aligned carbon fibres of 60 % weight fraction in an epoxy resin matrix under (a) longitudinal and (b) transverse loading. The modulus of elasticity of the carbon fibres is 290 GPa and the density is 1785 kg m. The elastic modulus of the resin is 3.2 GPa and its density is 1350 kg m. ... 

The fiber composite thus has a lower modulus in transverse loading than in longitudinal loading. 

Liu, Y. J., Xu, N., and Luo, J. R, Modeling of inter phases in fiber-reinforced composites under transverse loading using the boundary element method. Journal of Applied Mechanics, 67(1), 41 9 (2000). 

Romanowicz M. (2010) Progressive failure analysis of unidirectional fibre-reinforced polymers with inhomogeneous interphase and randomly distributed fibres under transverse tensile loading. Composites-Part A Applied Science and Manufacturing, 41(12), 1829-1838. 

Figure 13. Stress-strain curve for composites under transverse loading.

The empty spaces between the fibers have to be filled with the resin as any unfilled region known as a void or dry spot can be detrimental to the mechanical performance of the composite. The interface within a composite is volume occupied by the fibers in a composite divided by the fiber diameter and multiplied by 4, approximately. As the diameter of these fibers is of the order of a few microns, the interfacial area can be very large. For example, for a part of the size of a desktop with 50% fibers, the interfacial area would be about the area of a football field [7]. To have a good interface to transfer loads to fibers and carry transverse loads, the resin must come in intimate contact with the fibers. This contact usually takes place if the resin can wet the fibers in a natural way by spreading over the fiber surface. 

Figure 2.12 The relationship between the specific modulus of boron fiber-epoxy resin composite and 0. (a) Vertical loading, (b) Transverse load.

In the present ehapter, an analytical research on the damage in composite laminates due to a concentrated transverse load is reported. Special emphasis is placed on the interlaminar delaminations below the loading point, which usually occur in the form of multiple delaminations. Figure 1 shows an ultrasonic image of a damage in a quasi-isotropic CFRP laminate created by transverse indentation. Delaminations tended to propagate radially at all interfaces, with accompanying... 

Y. Aoki, H. Suemasu, O. Majima (2001) Damage accumulation in composite laminates during quasi-static transverse loading, Adv. Compos. Mater. 10,219. 

Consider a transverse loading of unidirectional loading composite as follows ... 

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