Abstract
The employment of composite materials in the aerospace industry has been gradually considered due to the fundamental lightweight and strength characteristics that this type of materials has. The science material and technological progress reached matched perfectly with the requirements for high-performance materials in aircraft and aerospace structures; thus, the development of primary structure elements applying composite materials became something very convenient. It is extremely important to pay attention to the failure modes that influence composite materials performances, since these failures lead to a loss of stiffness and strength of the laminate. Delamination is a failure mode present in most of the damaged structures and can be ruinous, considering that the evolution of interlaminar defects can carry the structure to a total failure followed by its collapse. The present work aims at the development of a delamination propagation model to estimate a progressive interlaminar delamination failure in laminated composite materials and to allow the prediction of material’s degradation due to delamination phenomenon. Experimental data, available at literature, was considered to determine some model parameters, like the strain energy release rate, using GFRPs laminated composites. This new delamination propagation model was implemented as subroutines in FORTRAN language (UMAT-User Material Subroutine) with formulations based on the Fracture Mechanics and Continuum Damage Mechanics. Finally, the UMAT subroutine was complemented with an intralaminar model and compiled beside the commercial Finite Element (FE) software ABAQUS™.
Highlights
Composite materials afford the unique possibility of designing the material, the manufacturing process, and the structure in one unified and concurrent procedure; having a large number of degrees of freedom available enables simultaneous material optimization for several given constraints
Engineers and structure designers must use large safety factors in order to guarantee an invulnerable performance of a composite part during its life, which leads to an overweight penalty and compromises the characteristic performance-weight ratio of laminated composite materials
At the end of the first portion of the curves, before the maximum load, all the experimental specimens present a yield zone affected by matrix crushing, which the numerical model could not represent
Summary
Composite materials afford the unique possibility of designing the material, the manufacturing process, and the structure in one unified and concurrent procedure; having a large number of degrees of freedom available enables simultaneous material optimization for several given constraints. One of the peculiarities of composite materials is the complexity of failure behavior due to the presence of three different material phases (fibers, matrix, and their interface) that compose this material and directly affect damage mechanisms. Engineers and structure designers must use large safety factors in order to guarantee an invulnerable performance of a composite part during its life, which leads to an overweight penalty and compromises the characteristic performance-weight ratio of laminated composite materials. Tita, and Vandepitte [1] proposed an intralaminar model that estimates the material degradation due to matrix and/or fiber failure for tensile or compression loads. The present work aimed at the complementation of Ribeiro’s material model by describing the delamination propagation as a means of interlaminar fracture failure. A simulation of a 3-point bending tests is performed and compared with experimental results in order to demonstrate the potentiality of the model proposed
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