A new approach to the application of Mori-Tanaka's theory in composite materials

Recent developments in the chemistry of halogen-free flame retardant polymers

Electrical conductivity of chemically modified multiwalled carbon nanotube/epoxy composites

A solution to the plane elasticity problem for a symmetrically laminated composite panel with spatially varying fiber orientations has been obtained. The fiber angles vary along the length of the composite laminate, resulting in stiffness properties that change as a function of location. This work presents an analysis of the stiffness variation and its effects on the elastic response of the panel. The in-plane response of a variable stiff ness panel is governed by a system of coupled elliptic partial differential equations/Solving these equations yields the displacement fields, from which the strains, stresses, and stress resultants can be subsequently calculated. A numerical solution has been obtained using an iterative collocation technique. Corresponding closed-form solutions are presented for three sets of boundary conditions, two of which have exact solutions, and therefore serve to validate the numerical model. The effects of the variable fiber orientation on the displacement fields, stress resultants, and global stiffness are analyzed.

In-plane response of laminates with spatially varying fiber orientations - Variable stiffness concept

https://web.stevens.edu/ses/documents/fileadmin/documents/pdf/Fisher-CST-2003.pdf

Fiber waviness in nanotube-reinforced polymer composites-I: Modulus predictions using effective nanotube properties

The effect of fiber waviness on the elastic moduli of flexible composites is investigated theoretically and experimentally. The flexible composites examined are composed of con tinuous fibers with sinusoidal waviness in an elastomeric matrix. Both iso-phase and random-phase fiber arrangements are used for this study. The constitutive relations for the longitudinal and transverse tensile behavior have been developed for these models. Tensile tests have been conducted to verify the constitutive relations. Carbon fiber and silicone elastomer were used for the experiments. Techniques for specimen fabrication as well as photoelastic tests are also presented. Experimental results show good agreement with the theoretical predictions.

Effect of Fiber Waviness on the Nonlinear Elastic Behavior of Flexible Composites

Changing the percolation threshold of a carbon black/polymer composite by a coupling treatment of the black

An attempt was made to study the effect of interfacial slippage on the filler reinforcement based on the boundary condition that the constituents of a particle-filled composite can slip relative to each other, but no cavities are formed at the interfaces. The elastic field satisfying these conditions is derived using the linear theory of elasticity and the effective elastic moduli of the composite are calculated. The following assumptions are made: (1) Filler particles are spherical, (2) fillers are completely dispersed, and (3) the volume fraction of fillers is sufficiently small that the interaction among fillers may be neglected. The expression for the shear modulus of the composite μ**, which is derived here, is consistent with the viscosity of a suspension which has been derived by Oldroyd. Experiments who that the increase of Young's modulus by glass beads (GB) is lower in polystyrene (PS) than in epoxy resin (Ep). The reinforcement in Ep-GB systems can be estimated by the well known formula derived assuming perfect adhesion. However, the reinforcement in PS-GB systems is in rather good agreement with the formula derived here assuming interfacial slippage.

Analysis of the effect of interfacial slippage on the elastic moduli of a particle-filled polymer

Carbon fibre/poly (ether-ether-ketone) (PEEK) composites were fabricated from plain weave cloth using the commingled yarn of carbon fibres with PEEK filaments. The undirectional specimen was made from the warp of commingled yarn and the weft of PEEK yarn, while the two-dimensional specimen was made from commingled yarns both of the warp and the weft. During the hot-pressing process, PEEK filaments melt to form the matrix of the composite. The interlaminar fracture toughness of the commingled composite was measured and compared with that of the prepreg composite. The critical strain energy release rates,/'GIcs, obtained for the commingled composites were higher than the prepreg composite. In particular, the two-dimensional composite exhibited higherGIc than the unidirectional commingled composite. Factors increasing the fracture toughness of commingled composites have also been investigated by SEM observation of the fractured surface.

Mode I interlaminar fracture toughness of commingled carbon fibre/PEEK composites

An attempt has been made to predict the thermal expansion coefficients of particle-filled polymers in which particles have various types of orienta tion distributions. The calculation is based on Eshelby's theory and a kind of self-consistent method is introduced to estimate the effect of the orien tation distribution together with the interaction among particles. The ex pression for the space random orientation of disk-shaped particles with infinitesimal aspect ratio, which is derived here, agrees with lower bound of isotropic composites predicted by Schapery. The calculated results are also compared with existing experimental data for glass particle-epoxy resin composites, and these are almost in good agreement.

Kiyohisa Takahashi

Papers

Effect of Fiber Waviness on the Nonlinear Elastic Behavior of Flexible Composites

Changing the percolation threshold of a carbon black/polymer composite by a coupling treatment of the black

Analysis of the effect of interfacial slippage on the elastic moduli of a particle-filled polymer

Mode I interlaminar fracture toughness of commingled carbon fibre/PEEK composites

Analysis of the Thermal Expansion Coefficients of Particle-Filled Polymers