1,721,101 research outputs found
The Application of Double Torsion Testing to Unidirectionally Reinforced Composite Materials
No full textTo characterize the intralaminar fracture behavior of a unidirectional carbon fiber/epoxy resin composite material, two distinct sets of experiments were performed. First, the tensile mechanical properties of the lamina were determined by testing specimens with different fiber orientation at varying rates of deformation. Then, the Double Torsion technique was applied to characterize the fracture resistance of the material. The strain energy release rate vs. crack speed curve so derived is in agreement with measurements conducted by using the Double Cantilever Beam and Compact Tension techniques. The results of the research indicate that Double Torsion is an attractive technique for studying the time-dependent fracture of composite materials
Long-Term Performance of a Polymer Composite Repair System for Gas Pipelines
No full textPredictions were made of the long-term behavior of a new repair system for gas pipelines, which involves the wrapping of a polymer composite tape coated with a pressure-sensitive adhesive on the damaged pipe. The time- and temperature-dependent behavior of the tape and the adhesive was experimentally evaluated using constant strain rate tests. A theoretical model was developed for the winding, taking into account the nonisothermal viscoelastic behavior of the materials. A good agreement was found between theoretical predictions and full-scale experimental results
Fenomeni di frattura nelle tubazioni: propagazione lenta e propagazione rapida (2° parte)
No full textViscoelastic Effects on Interlaminar Fracture Behaviour of Thermoplastic Matrix Composites. I) Rate and Temperature Dependence in Unidirectional PEI/Carbon Fibre Laminates
No full textThe influence of the dependence of matrix toughness on deformation rate and temperature on the interlaminar fracture of polyetherimide (PEI)/carbon-fibre unidirectional laminates has been investigated. Fracture toughness versus crack speed data for the matrix and the composite, respectively, were determined by using the double torsion and the double cantilever beam tests. Tensile tests were also performed on the unreinforced resin. Displacement rates varying between 0.1 and 100 mm min were applied, and testing temperatures were varied between 23 and 170 °C. Fracture data reduction was achieved by means of time-temperature superposition, the shift factors being obtained from tensile tests. The toughness of PEI, by contrast with that of other thermoplastic polymers commonly used as matrices for composite materials (e.g. PEEK), showed a non-monotonic, but still moderate, sensitivity to the test conditions explored here. Interlaminar toughness of the corresponding composite increased steadily with crack speed and was always lower than that of the plain resin. This result indicates that the interlaminar structure of the composite material is not optimised as regards this particular property
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