The bamboo structure can be generally viewed as a Functionally Graded COMPOSITE MATERIAL constituted by long and aligned cellulose fibres embedded in a lignin matrix. Analysing the transversal section of a bamboo culm, one can observe that the fibre distribution is variable through its thickness. The non-uniform distribution of fibres prevents the direct application of equations used to model the behaviour of COMPOSITE MATERIALs, as the rule of mixtures equations for strength and modulus of elasticity. These equations assume, besides the perfect bonding between fibre and matrix, uniform distribution of the fibres in the matrix. In bamboo, the fibre distribution follows an organized pattern with a higher concentration of fibres on the outer surface of the culm. Establishing how this variation occurs, the basic equations from the COMPOSITE MATERIALs approach can be modified in order to model the mechanical behaviour of bamboo. This paper presents the meso-structure analyses of bamboo culms through Digital Image Analysis. The variation of the volume fraction of the cellulose fibres across the transversal section of the bamboo is established. The developed methodology is successfully applied to study the volume fraction variation of fibres in two different samples of bamboo species Phyllostachys heterocycla pubenscens, commonly know as "Moso".      

In this article, an innovative method for filling the aircraft wings, farmes with rezin (using VARTM) is presented. This method is a suitable alternative for manual methods. Certain parts are made using both methods and their mechanical properties, speed of their production, and their cost have been compared. The ones made by VARTM have less bubbles and thus more volume fraction. This leads to better mechanical properties. Also, by optimizing the effective properties in VARTM, the production speed is increased compared to the manual method.

A micromechanical model is presented to analyze the fracture response of unidirectional COMPOSITE MATERIALs considering the nonlinear behavior of matrix MATERIAL under loading more than the yield strength as well as the fiber-matrix debonding and matrix cracking. The COMPOSITE microstructure is characterized with repeating unit cell with regular or random fiber-packing patterns. The micromechanical model is employed for COMPOSITE MATERIAL with aluminum matrix and carbon fibers. The high rigidity fibers are modeled as linear isotropic elastic MATERIAL, while matrix MATERIAL is characterized with elastic-plastic model. The damage initiation stage in matrix MATERIAL is described by principal strain criterion accompanied with damage evolution considering stiffness degradation up to crack formation. The bonding between fiber and matrix is modeled using cohesive model, in which damage initiation criterion depends on the normal and shear strength of the cohesive zone. The micromechanical model is employed to study the effects of fiber distribution, fiber volume fraction, fiber-matrix bonding strength on the crack propagation through the microstructure as well as the stress-stain graph up to microstructure fracture.

With the advent of high strength geogrids, the interest of civil engineers in using geosynthetics as reinforcement MATERIAL in pavement construction has increased. An experimental study is carried out at IIT Delhi to understand the effect of geogrid in unpaved roads. Behavior of COMPOSITE MATERIAL, which comprises of Yamuna sand as subgrade and Water Bound Macadam (WBM) as base course is studied with and without geogrid reinforcement under drained conditions. A geogrid is used as reinforcing MATERIAL. Drained triaxial tests were performed at three different confining pressures of 50, 100 and 200 kPa on both unreinforced COMPOSITE and reinforced COMPOSITE MATERIALs of specimen size 100mm diameter and 200mm height. Hierarchical single surface (HISS) model developed by Desai and co-workers is used to model the unreinforced and reinforced COMPOSITE MATERIAL. A computer program PARA6 is used to calculate the various parameters and to back predict the stress-strain-volume change behavior of unreinforced and reinforced COMPOSITE MATERIALs. The predicted results match closely with the observed results.

Failures in COMPOSITE MATERIALs occur mainly due to interlaminar fracture, also called delamination, between laminates. This indicates that characterizing interlaminar fracture toughness is the most effective factor in the fracture of COMPOSITE MATERIALs. This study reports investigation on mixed-mode interlaminar fracture behaviour in woven carbon fibre/polyetherimide (CF/FEI) thermoplastic COMPOSITE MATERIAL based on experimental and numerical analyses.Experiments were conducted using the special test loading device. By varying the loading angle,α from 0º to 90º, pure mode-I, pure mode-II and a wide range of mixed-mode data were obtained experimentally. Using the finite-element results, geometrical factors were applied to the specimen. Based on experimentally measured critical loads, mixed-mode interlaminar fracture toughness for the COMPOSITE under consideration determined. The fracture surfaces were examined by scanning electron microscopy to gain insight into the failure responses.