Browsing by Author "Reis, P.N.B."
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- 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.
- Effect of adherends and environment on static and transverse impact response of adhesive lap jointsPublication . Reis, P.N.B.; Soares, J.R.L.; Pereira, António; Ferreira, J.A.M.Impact response of adhesive joints has received limited attention compared to quasi-static loading. On the other hand, there are very few studies combining moisture and its effect on the impact strength. Therefore, the present paper aims to study the effect of moisture on the tensile and impact strength of single lap joints with different adherends (high limit elastic steel and a commercial composite). It was possible to conclude that adhesive joints with steel adherends are very sensitive to the environment and exposure time. For adhesive joints with composite adherends, the water showed a marginal effect. A marked hygrothermal effect was observed for all joints. For impact loads the environment effect is similar, but much more severe than that observed in tensile tests. For both tests, adhesive failures occurred for adhesive joints with steel adherends and delaminations for joints involving composite.
- Effects of external patch configuration on repaired composite laminates subjected to multi-impactsPublication . Coelho, S.R.M.; Reis, P.N.B.; Ferreira, J.A.M.; Pereira, AntónioThis work intends to study the impact performance of repaired composites by the overlap patch technique and, for this purpose, experimental tests were carried out on single and double-patch specimens. In order to evaluate the impact fatigue strength, both configurations were submitted to multi-impacts, until the full perforation occurs. It was possible to conclude that the double-patch geometry supports higher maximum loads, lower displacements and promotes higher elastic energies. Relatively to the impact energy of 6 J, for example, the maximum load and the elastic energy is 97.1% and 51.2% higher, respectively, but the maximum displacement is about 50% lower than the values obtained with the single-patch geometry. Higher impact fatigue life was also observed, as consequence of its higher stiffness. The impact bending stiffness confirms the difference of stiffness between them, and shows to be a parameter able to monitor the damage progression.
- Fatigue behaviour of epoxy-steel single lap joints under variable frequencyPublication . Reis, P.N.B.; Monteiro, J.F.R.; Pereira, António; Ferreira, J.F.R.; J.D.M. CostaThis work investigates the loading frequency effects on the fatigue behaviour of adhesively-bonded steel lap joints. S-N diagrams of fatigue tests, under constant amplitude loading, were obtained for frequencies ranging between 2 and 40 Hz. The fatigue life for variable frequency tests was estimated based on constant frequency S-N curves, using a linear cumulative damage rule. It is possible to conclude that, for the higher shear stresses, the frequency presents only a marginal effect on fatigue life. On the other hand, for the lower shear stresses, the fatigue life of the adhesive joints is very dependant on the frequency level. Good correlations were obtained between fatigue life predictions and experimental results. © 2015 Elsevier Ltd. All rights reserved.