This paper deals with the development of a numerical simulation methodology for estimating damages in LAMINATE COMPOSITE MATERIALS caused by a low-speed impact. Experimental tests were performed on LAMINATE plates reinforced with woven carbon fibers and epoxy resin. Three thickness plates were evaluated. The impact loads were transversal and punctual. Two lamina failure criteria were evaluated. The first is the maximum stress. The second is a proposed modification of the Hashin failure criterion. Four lamina degradation criteria were evaluated too. The numerical contact loads between the plate and impactor were well represented. The numerical damaged areas and lengths were similar or greater than the experimental results.

In this paper, the buckling load and buckling modes of FML panel, using first order shear deformation theory, has been studied, based on the Reddy's numerical solution. Because of various applications of FML shells, GLARE panel was considered. The effects of geometry, lay-up, and MVF were determined. Boundary conditions were simply supported and the panel was axially loaded. The results for Glare panel are presented and discussed. Reducing the number of metal layers at a constant MVF increases the Buckling load. The results from the finite element model were found to be in general agreements with the other references.

COMPOSITE MATERIALS are used frequently in industrial structures such as airplane and space vehicles. Strength and probability of failure is an important challenge for designer engineers. In this paper a practical method to determine ultimate strength of a COMPOSITE LAMINATE is explained, this method based on reliability prediction. Strength of each layers and total strength is calculated using First Order Reliability Method and failures sequence is determined by Branch & bound method. In this study two modes for failure are assumed: fiber fracture and matrix fracture. At first step, stress distribution is calculated by FE software (ANSYS Package) then according to failure mode and first order reliability method, reliability index is determined. At the second step, probability of failures mode in all layers are determined. At the end, the important sequences for the failures are determined using branch and bound method.Comparison of this method result with Monte Carlo simulation shows accuracy of this method to predict failure mode and probability of COMPOSITE LAMINATE failure.

In this work, transient dynamic stress concentration in a hybrid COMPOSITE LAMINATE subjected to a sudden internal crack is examined. It is assumed that all fibers lie in one direction and the applied load acts along the direction of fibers. Two types of arrangements are considered for the fiber; square and hexagonal. Using the shear lag model, equilibrium equations are deduced, and upon proper application of initial and boundary conditions, the complete field equations are obtained using finite difference method. The results of the dynamic effect of fiber breakage on stress concentration are well examined in the presence of a second fiber type. These results are compared to those of their static values in both models. The effect of surface cracks on stress concentration, as a result of fiber breakage, is also examined. The values of dynamic stress concentrations are deduced and compared to those of a lamina. Also, the peak stress concentration during transition time for fibers to reach static equilibrium is calculated and compared with those of static values.

Nowadays, low-velocity impact resistance and damage tolerance have become very important in the design of COMPOSITE structures, especially in the aerospace industry, and have led researchers to evaluate the low velocity impact response in the design of COMPOSITEs. In this research, a numerical model for low velocity impact (LVI) of carbon /epoxy COMPOSITE LAMINATE is proposed. This 3D damage model is based on continuum damage mechanics with subroutine development (UMAT) in Abaqus/Explicit. In this model, the interlaminar and intralaminar damage is considered and the nonlinear shear behavior is applied to consider the plasticity in the matrix. To evaluate the results obtained from the numerical model, impact testing was performed at three levels of impact energy (10 J, 15 J and 20 J). In addition, in order to verify the failure mechanisms and the amount of damage caused by the impact, delamination area was measured using radiology technique. By comparing the response of the impact behavior, a good correlation was obtained between the experimental test results and the simulation, which shows that the failure model used is well able to predict the behavior of the COMPOSITE in this process.