Browsing by Author "Antunes, F.V."
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- Analysis of the initial delamination size on the mode I interlaminar fracture of carbon/epoxy compositesPublication . Reis, P.N.B.; Ferreira, J.A.M.; Antunes, F.V.; Costa, J.D.M.; Capela, C.; Capela, Carlos;This paper describes an experimental study of the initial delamination length effects on the mode I fracture toughness using DCB tests. Delamination failure was also predicted using exponential cohesive model and a quite good agreement with experimental results was obtained. Numerical predictions showed a significant influence of initial delamination length on the force-displacement curves.
- Numerical modelling of the Young’s modulus of syntactic foamsPublication . Antunes, F.V.; Ferreira, J.A.M.; Capela, C.Syntactic foams are particulate composites obtained by filling a polymeric matrix with hollow solid inclusions. Numerical simulations are an important tool to predict material behaviour and optimize the mechanical properties. The aim of this work is to develop a multi-phase numerical model to predict stiffness of the syntactic foams. The numerical parameters were identified and optimized, and the numerical predictions were validated with experimental results from 3-point bending tests. Different physical parameters were then studied, namely the volume fraction and the size of the filler, the elastic properties of filler and matrix and the inclusion's thickness. A sensitivity analysis was developed to quantify the importance of these different parameters, and the rigidity of the matrix was found to be the most influent. The parametric space was scanned and a numerical interpolation procedure implemented based on shape functions of finite element method. The procedure is an interesting tool for design and was used to identify the particles having stiffness equal to the matrix.
- Study on the fatigue strength of AA 6082-T6 adhesive lap jointsPublication . Pereira, António; Ferreira, J.M.; Antunes, F.V.; Bartolo, PauloA research study on the fatigue behaviour of aluminium alloy adhesive lap joints was carried out to understand the effect of surface pre-treatment and adherends thickness on the fatigue strength of adhesive joints. The adherend material used for the experimental tests was an aluminium alloy 6082-T6 in the form of thin sheets, and the adhesive used was a high strength epoxy (Araldite 420 A/B). The surface preparation included an abrasive preparation (AP joints) and sodium dichromate-sulphuric acid etch (CSA joints). A maximum fatigue strength was obtained for the CSA surface treatment with a 1.0 mm adherends' thickness. The fastest fatigue damage was related with a high surface roughness and a high stress perpendicular to adhesive surface, which helps to promote the adhesive failure. A numerical analysis was also performed to understand the effect of the adherends thickness on the stress level. Results showed an increase of the out-of-plane peak stresses with the increase of adherends thickness.