Proceedings in Applied Mathematics and Mechanics, 8 January 2015
∗Corresponding author: e-mail [email protected], phone +213 21 36 18 50, fax +213 21 36 18 50
∗∗ Second author footnote.
Effects of a circular defect size and position on the damage progression in hybrid laminates under compressive loading
Nacer TALA-IGHIL1 1,*, Ahcene MOKHTARI1,**
Welding and NDT Research Center (CSC). BP 64 CHERAGA -ALGERIA
The effects of a circular defect size and position on the post-damage response of the FMLs laminates under compressive loading have been studied. Compression tests are performed on composite plates comprising a hole having different diameters (8 mm, 12 mm and 18 mm) and located at different positions (25%, 50% and 75%) in the loading direction. A numerical analysis using the finite element method FEM has permits the identification of the initiation zones and the description of the damage evolution in these laminates. The results of the numerical simulation are in good agreement with the experimental results. The FEM has well predicted the critical damage zones.
Copyright line will be provided by the publisher
1 Introduction
The composite structures made from glass fiber reinforced with polymer matrices have resistance to compression considerably lower when holes (defects) are present. The hardness of the polymer matrix, the properties of the interface matrix/fiber and fiber stability are the main factors that affect the resistance to compression of notched laminates. The importance of these factors results in complex damage modes which involve the matrix cracking, delamination, local buckling and shear failure. The importance of the damage tolerance analysis of composite materials was shown by many authors [1]. An approach was presented by Wang [2] related to the delamination problem of the composite laminates edges. Davis and Jones [3] have examined the effect of manufacturing defects on the fracture of composite structures. An experimental and numerical study on the residual stresses in the composite laminates subjected to an impact loading was done by the authors [4]. The progressive evolution of the damage in the laminates under compressive loading containing a circular hole has been studied experimentally [5], it was observed that the rupture was initiated at the instability localized at the surface of the hole edge. In this paper, the damage has been Modelled by the combined use of the Cohesive Zone Model [6] (CZM) and the Linde mechanical model [7].
2 Experiment and results
The composite structures are made from glass fiber “roving” reinforced with polymer matrices. The fiberglass has an elastic modulus of 52.3 GPa and a rupture strain to tensile of 3.4%. The laminates are composed of four layers. The mechanical properties of the fiber and the epoxy matrices are resumed in Table 1.
Table 1. Mechanical properties of the glass fibers and epoxy matrices. Proprieties Epoxy Fiber Tensile strength (GPa) 0.11 3.40 Young modulus (GPA) 4.10 52.30 Rupture strain (%) 4.60 4.80 Poisson coefficient 0.30 0.20
Three types of specimens were produced and adopted for the study of the effects of the defect's size and position on the mechanical behavior. These specimens designated A, B and C contain layers of aluminum and composite glass/epoxy with stacking sequences [Al/(0°/90°)2S/Al]. The fiber orientation angles are shown in figure 1. After testing, the laminate plates were inspected nondestructively using an ultrasonic scanning method. The
