Fractographic and rheological characterizations of CF/PP-PE-copolymer composites tested in tensile

This work shows the fractographic study of fractured surfaces resulted from tensile tests of thermoplastic composites based on poly(propylene-co-ethylene) (PP-PE) and modified PP-PE copolymers reinforced with continuous carbon fibers (CF). The PP-PE matrix was modified with two agents called AM1 (based on maleic anhydride) and AM2 (containing an elastomeric agent), respectively. Three different laminates - CF/PP-PE, CF/PP-PE(AM1) and CF/PP-PE(AM2) were manufactured. The best tensile strength and elastic modulus results were determined for the CF/PP-PE(AM1) laminate (507.6 +/- 11.8 MPa and 54.7 +/- 2.4 GPa, respectively). These results show that the AM1 agent contributed to increase the physicochemical interaction between the CF and the PP-PE matrix. This condition provided a better loading transfer from matrix to the reinforcement. Scanning electron microscopy analyses of the fracture surfaces show the fractographic aspects of the samples and allow evaluating the fiber/matrix-interfacial adhesion. Poor adhesion is observed for the CF/PP-PE and CF/PP-PE(AM2) laminates with the presence of fiber impressions on the polymer rich regions and fiber surfaces totally unprotected of polymer matrix. On the other side, a more consistent adhesion is observed for the CF/PP-PE(AM1) laminate. This result is in agreement with the tensile test data and show the presence of a good interaction between the laminate constituents. The correlation of the mechanical and fractographic results with the curves of complex viscosity versus temperature of the studied polymer matrices shows that the matrix viscosity did not affect the wettability of the reinforcement.CNPqCAPES/PVNSUniv Fed Sao Paulo Unifesp, Inst Ciencia & Tecnol, Sao Jose Dos Campos, SP, BrazilITA, Div Engn Aeronaut & Mecan, Sao Jose Dos Campos, SP, BrazilUniv Fed Sao Carlos UFSCar, Ctr Ciencias Gestao & Tecnol, Sorocaba, SP, BrazilUniv Fed Sao Paulo Unifesp, Inst Ciencia & Tecnol, Sao Jose Dos Campos, SP, BrazilCNPq: 150697/2014-7CNPq: 142314/2010-2CNPq: 303287/2013-6Web of Scienc

Evaluation of mechanical properties of four different carbon/epoxy composites used in aeronautical field

Four families of carbon fiber reinforced composites (CFRC) used in aeronautical industry were evaluated by flexural and interlaminar shear tests. It is also characterized three families of non-conditioned and conditioned CFRC by compression test. The composites were obtained by hand lay-up process in autoclave by using prepregs based on epoxy matrices (F155 and F584) and carbon fiber fabric reinforcements (PW-"Plain Weave" and 8HS-"Eight Harness Satin"). The F155-epoxy matrix was cured at 121 °C and the F584-epoxy type at 177 °C. After molding, the laminates were cut in specimens attending the ASTM D790 for the flexural test, the ASTM D2344 for the interlaminar shear test (ILSS) and the ASTM D3410 for the compressive test. The compressive tests were performed for testing the specimens before and after hygrothermal conditioning. The results show that the F584-epoxy matrix laminates present higher mechanical properties when compared to the F155-epoxy ones. The shear-tested samples observed by scanning electron microscopy and that ones tested in flexural, analyzed by stereoscopy, revealed that the fractured surfaces present typical aspects. The compressive results show that the hygrothermal conditioning caused the decrease of the compressive strength in, approximately, 8-20% depending on the laminate type. The failure modes of the tested specimens were evaluated showing good agreement with the literature

Effect of the interfacial adhesion on the tensile and impact properties of carbon fiber reinforced polypropylene matrices

Thermoplastic composites have been applied in a wide variety of industrial products, showing recently a great potential to be used in aeronautical field. The objectives of this work were to evaluate the fiber/matrix interface of carbon fiber reinforced polypropylene-based matrices after tensile and impact tests and also to compare the mechanical test results of the manufactured laminates. The laminates were prepared by stacking carbon fiber fabric style Plain Weave (CF) and films of four different polypropylene matrices, described as (a) polypropylene-PP, (b) polypropylene-polyethylene copolymer-PP-PE, (c) PP-PE with an interfacial compatibilizer-AM1 and (d) PP-PE containing an elastomeric modifier-AM2. The composites were processed using hot compression molding. The mechanical testing results showed that the CF-AM1 laminate family presented the lowest impact strength and the highest tensile strength values when compared to the other laminates. SEM analysis observations of both tensile and impact fractured specimens of the CF-PP/PE-AM1 specimens revealed a stronger fiber/matrix interface. The CF-PP/PE-AM2 laminate showed a lower tensile strength and higher impact strength values when compared to the CF-PP/PE-AM1 one. PP-PE and PP laminates presented the lowest impact strength values

Mechanical and morphological characterizations of carbon fiber fabric reinforced epoxy composites used in aeronautical field

Carbon fiber reinforced composites (CFRC) have been used in aeronautical industry in the manufacture of different aircraft components that must attend tight mechanical requirements. This paper shows a study involving mechanical (flexural, shear, tensile and compressive tests) and morphological characterizations of four different laminates based on 2 epoxy resin systems (8552TM and F584TM) and 2 carbon fiber fabric reinforcements (Plain Weave (PW) and Eight Harness Satin (8HS)). All laminates were obtained by handing lay-up of prepregs plies (0º/90º) and consolidation in an autoclave following an appropriate curing cycle with vacuum and pressure. The results show that the F584-epoxy matrix laminates present better mechanical properties in the tensile and compressive tests than 8552 composites. It is also observed that PW laminates for both matrices show better flexural and interlaminar shear properties

Ionized-air-treated curaua fibers as reinforcement for phenolic matrices

Curaua fibers were treated with ionized air to improve the fiber/phenolic matrix adhesion.The treatment with ionized air did not change the thermal stability of the fibers. The impact strength increased with increase in the fiber treatment time. SEM micrographs of the fibers showed that the ionized air treatment led to separation of the fiber bundles. Treatment for 12 h also caused a partial degradation of the fibers, which prompted the matrix to transfer the load to a poorer reinforcing agent during impact, thereby decreasing the impact strength of the related composite. The composites reinforced with fibers treated with ionized air absorbed less water than those reinforced with untreated fibers

Recycling scrap automotive heat shield insulation material

Automotive heat shields are usually composed of two metal sheets enclosing an insulating material with a paper-like texture that contains refractory ceramic particles. This article discusses the results achieved by recycling the scrap automotive insulation that is discarded in landfills, using the same concept as paper recycling. For comparison with the original product, tests of thickness, bulk density, weight loss on ignition, tensile strength, compressibility, and recovery were performed on recycled materials produced in a so-called "manual" process (involving little automation and performed in adapted facilities) without pressing, and pressed once, twice, and four times. Materials recycled in a so-called "industrial" process (in a paper recycling plant) without pressing, and pressed once were also tested. The recycled materials can be considered approved with respect to the main requirement, thermal insulation, since they dissipated the under-hood temperature by more than 300 A degrees C (like the original product). Like the heat insulation tests, the thermogravimetric analysis suggested that the recycled materials showed higher stability than the original product. Thermogravimetric, microscopy, and energy dispersive spectroscopy analyses indicated that the structural and compositional characteristics of the original product were preserved after recycling

Structural carbon/epoxy prepregs properties comparison by thermal and rheological analyses

Two different carbon/epoxy prepreg materials were characterized and compared using thermal (DSC, TGA, and DMA) and rheological analyses. A prepreg system (carbon fiber preimpregnated with epoxy resin F584) that is currently used in the commercial airplane industry was compared with a prepreg system that is a prospective candidate for the same applications (carbon fiber prepreg/epoxy resin 8552). The differences in the curing kinetics mechanisms of both prepreg systems were identified through the DSC, TGA, DMA, and rheological analyses. Based on these thermal analysis techniques, it was verified that the curing of both epoxy resin systems follow a cure kinetic of n order. Even though their reaction heats were found to be slightly different, the kinetics of these systems were nevertheless very similar. The activation energies for both prepreg systems were determined by DSC analysis, using Arrhenius's method, and were found to be quite similar. DMA measurements of the cured prepregs demonstrated that they exhibited similar degrees of cure and different glass transition temperatures. Furthermore, the use of the rheological analysis revealed small differences in the gel temperatures of the two prepreg systems that were examined