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• Development and characterization of a composite leaf spring, with bucking working

  A. Arnáiz, E. Cañíbano, J. Romo, J. Merino

  Materiales Compuestos (2022). Vol. 04 - Comunicaciones Matcomp19 (2020), (Núm. 4 - Aplicaciones de los materiales compuestos. Nuevos procesos de fabricación y materiales compuestos avanzados.), 152

  
  

  Abstract

  For a long time, metal leaf springs have been used as elastic element, merging them with helicoidal spring for suspension applications. This type of system based on ferrous materials combined in independents plies, presents multiple problems such as interface friction, or its poor behavior in plastic state. These conditions lead to a mechanical property lost through a period of time, evoking fatige problems. Throughout this project a high strength unidirectional leaf spring based on glass fiber composite material has been developed with the purpose of solving these problems. To ensure an adequate service life, an bicomponet based material has been selected, improving its process. CRTM has been chosen for the processing of the prototypes. Finally, taking other related problems away is possible thanks to multiple CAD implementations tools. So with this as the backdrop, a one blade leaf spring under a buckling situation has been designed, solving all the existing problems found in current iron technology. Under the scope of industrial implementation and optimization, composite advantages related with flexibility and lightweight can be resourceful.

  Abstract
  For a long time, metal leaf springs have been used as elastic element, merging them with helicoidal spring for suspension applications. This type of system based on ferrous [...]

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• Study of the influence of concrete on the thermal properties of vinilester-uretane composites vs accelerated tests

  A. Navarro, E. Segovia

  Materiales Compuestos (2022). Vol. 04 - Comunicaciones Matcomp19 (2020), (Núm. 4 - Aplicaciones de los materiales compuestos. Nuevos procesos de fabricación y materiales compuestos avanzados.), 151

  
  

  Abstract

  Specifically, the use of vinyl ester resins has been studied profusely in both the maritime and industrial sectors and with less time, in the use of reinforcement in civil engineering structures and architecture as passive reinforcements. The resin used in the present work is novel, and still little used. It is vinyl ester resin of bisphenol-A segment modified with urethane. This presents a greater resistance to chemical agents such as those of the petroleum industry, alkaline agents and vapors; together with a lower exotherm that facilitates the manufacture of thick laminates. A thermal and mechanical characterization has been carried out through the techniques of Differential Scanning Calorimetry (DSC), Infrared Spectroscopy (FTIR) and Thermogravimetry (TGA) of said resin reinforced with high grammage (780 g / cm2) fiber of E glass to evaluate the degradation of the composite and its mechanical properties to the interlaminar shear and bending. The influence of the contact with self-compacting concrete (HAC) on said material, imbedded inside its matrix as a reinforcement, as if it were a passive reinforcement, as well as an accelerated aging study in solution simulating the exudation liquid of the concrete pores (LPH) through said characterization. With the obtained results, it is evaluated and compared, from the point of view of degradation-stiffening vs. mechanical properties, with the traditional Bisphenol-A (VEBA) resins, as well as its suitability for the aforementioned applications, resulting in a resin with better properties than the VEBA.

  Abstract
  Specifically, the use of vinyl ester resins has been studied profusely in both the maritime and industrial sectors and with less time, in the use of reinforcement in civil [...]

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• Delamination behavior under mode I and mode II of adhesive bonded joints for different surface treatments

  S. Sánchez, . J.Bonhomme, . V.Mollón, A. Argüelles, . J.Viña

  Materiales Compuestos (2022). Vol. 04 - Comunicaciones Matcomp19 (2020), (Núm. 4 - Aplicaciones de los materiales compuestos. Nuevos procesos de fabricación y materiales compuestos avanzados.), 150

  
  

  Abstract

  The automotive, aerospace and renewable energy generation industries have replaced significantly the use of traditional materials, such as steel and aluminum, by reinforced fiber composites. It has recognized that joints drilling and screwing joints damage the fibers introducing a higher concentration of stresses. That is why the application of structural adhesives, as a method of joining in reinforced composites, has increased in recent years. Delamination is the most critical failure mode of composite materials resulting in stiffness and structural strength losses. This works studies the behavior against delamination under mode I and mode II interlaminar fracture of adhesive bonded joints in carbon-epoxy composite materials, using structural adhesives of epoxy and acrylic bases. For the execution of the joints, different surface treatments have been employed: sanding, grit blasting and peel ply technique, allowing to make a fracture resistance comparision study. The double cantilever beam (DCB) and end notched flexure (ENF) tests configuration were used to determine stress-strain behavior and fracture toughness for mode I (GIC) and mode II (GIIC), respectively. Surface modifications have been evaluated by  contact angle measurements and scanning electron microscopy (SEM). The experimental results are shown in the same situation. The experimental results obtained show that, even if not showing the same delamination tendency for both fracture modes, the strain energy release rate are higher for an improved of wetting properties and an increase of surface roughness.

  Abstract
  The automotive, aerospace and renewable energy generation industries have replaced significantly the use of traditional materials, such as steel and aluminum, by reinforced [...]

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• FE Mechanical properties prediction of CFRP considering different carbon fiber surface treatments

  C. Valero, M. Laspalas, F. Serrano, . C.Sáenz, A. Chiminelli

  Materiales Compuestos (2022). Vol. 04 - Comunicaciones Matcomp19 (2020), (Núm. 4 - Aplicaciones de los materiales compuestos. Nuevos procesos de fabricación y materiales compuestos avanzados.), 149

  
  

  Abstract

  Reinforcement/matrix interaction is recognized as a key issue in polymeric composite materials. From the mechanical point of view, being the link between the fibres and the polymer, a proper load transfer is ensured only if a good enough interphase exists. This is particularly critical in carbon fibre (CF) composites since, due to the non-polar characteristics and chemical inertness of carbon, sometimes they exhibit weak interfacial adhesion. In this sense, various surface treatments for CFs are currently being investigated, in order to improve their interaction with the polymeric matrices: wet chemical or electrochemical methods, chemically or physically activated oxidation procedures, application of thin coatings and plasma treatments. This is precisely one of the challenges addressed in the MODCOMP project. This paper describes part of the work carried out within the mentioned project in order to estimate the improvement of properties that can be achieved through enhancements of the CF/epoxy interphases. The study covers both elastic engineering constants and strengths predictions, and it has been performed using finite element models of RVEs of UD fibres and introducing cohesive elements to take into account the interfacial failure mode. The results obtained allow identifying which range of CF/epoxy interphase properties enhancement should be achieved in order to get significant effects in the composites mechanical response.

  Abstract
  Reinforcement/matrix interaction is recognized as a key issue in polymeric composite materials. From the mechanical point of view, being the link between the fibres and the [...]

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• Simulation of a pultrusion process of composite material profiles reinforced with carbon fiber for aeronautical applications

  J. Bayo, I. Gracia, C. Mellado

  Materiales Compuestos (2022). Vol. 04 - Comunicaciones Matcomp19 (2020), (Núm. 4 - Aplicaciones de los materiales compuestos. Nuevos procesos de fabricación y materiales compuestos avanzados.), 148

  
  

  Abstract

  The manufacture by means of a pultrusion process allows to obtain structural profiles of composite materials, avoiding discontinuous processes that need the use of an autoclave to cure the material. This process usually uses fiberglass as reinforcement, not reaching the necessary qualities in structural aeronautical applications. The present work develops a numerical simulation of the pultrusion with composite materials reinforced with carbon fiber for aeronautical structural applications. In order to obtain high quality materials, a product development is required where the process parameters are studied. In this sense, a complete study of the pultrusion process has been carried out through the development of numerical simulations using the software ABAQUS and NASTRAN / PATRAN from the point of view of the material manufactured and the pultrusion mold used. These two approaches have been developed by generating finite element models. In the first place, models that simulate and predict the physical-chemical properties of the material, such as the glass transition temperature and the degree of final curing of the material before processes with different temperature settings, draft speeds and geometries. Second, the pultrusion mold was simulated to obtain the expansions and loads applied to the fabricated profile to evaluate the influence of this on the pultrusion process and the quality of the obtained profile. The results obtained have been correlated by mechanical and physical-chemical tests as well as manufacturing tests that obtained the simulated profiles in order to introduce the technology and the parts manufactured in future aeronautical structures.

  Abstract
  The manufacture by means of a pultrusion process allows to obtain structural profiles of composite materials, avoiding discontinuous processes that need the use of an autoclave [...]

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• Load rate influency over delamination failure in composites

  H. Zabala, L. Aretxabaleta, F. Sánchez, L. Pérez-Martínez, C. López-Taboada, G. Castillo-López

  Materiales Compuestos (2022). Vol. 04 - Comunicaciones Matcomp19 (2020), (Núm. 4 - Aplicaciones de los materiales compuestos. Nuevos procesos de fabricación y materiales compuestos avanzados.), 147

  
  

  Abstract

  Impact is one of most critical stress over a structure, so as it induces a high strain rate on the material. Under low speed transverse impacts in composites, the secuence of material degradation is: intralaminar fracture of the matrix that does not mean a load bearing capacity decrease but makes it easier the starting of the seconf failure mode: the interlaminar failure of the matrix or delamination and, finally, the intralaminar failure of fibre. Delamination is one of the most critical failure mechanisms in composites because it means an important bearing capacity loss, It is quite difficult to detect visually and it's evolution determines the subsequent failure of the component. That behaviour depends on it's interlaminar fracture toughness. Nowadays there is not a general agreement over the dependency between interlaminar fracture toughness, in Modes I&II, and the strain rate. Nevertheless several biaxial equi energy impacts show that delaminated area increases as same as load rate application, so it is clear a dependency between fracture energy and load rate. This work shows the set-up and first results of a Mode I test using a drop weigth impact tester.

  Abstract
  Impact is one of most critical stress over a structure, so as it induces a high strain rate on the material. Under low speed transverse impacts in composites, the secuence [...]

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• Compression after impact test on woven CFRP laminates: the effect of ply clustering

  P. Rodríguez-Luján, J. Artero-Guerrero, J. Pernas-Sánchez, D. Varas, J. López-Puente

  Materiales Compuestos (2022). Vol. 04 - Comunicaciones Matcomp19 (2020), (Núm. 4 - Aplicaciones de los materiales compuestos. Nuevos procesos de fabricación y materiales compuestos avanzados.), 144

  
  

  Abstract

  One of the mayor threats for FRP is the out-of-plane loading conditions such as impacts, which produce interlaminar failures, among others, decreasing drastically the material's strengths in plane. Drop weight and compression after impacts tests have been selected as the standard methodology to evaluate laminate performance under impact loadings. The present work aims to reveal the influence of the material structure in woven laminate response under impact. To this end a complete set of experiments was designed using the actual ASTM standards (D7136/D7137), including the actual monitoring capabilities to address this problem. Composite coupons, made of AGP 280-5H carbon/Epoxy satin, were manufactured using three laminate configurations to analyze the effect of ply clustering [(+-45)/(0/90)]4S, [(+-45)2/(0/90)2]2S, and [(+-45)4/(0/90)4]S). Laminates have been subjected to low velocity impact using an INSTRON-CEAST Fractovis 6875 drop weight tower while compression test has been performed using a INSTRON 250 kN. Impact tests have been recorded with two high speed video-cameras (Photron SA-Z 2100K) configured at 20000 fps in order to analyze the plate behavior during the impact. In addition, a three dimensional high velocity digital image correlation (3D-HV-DIC) analysis has been done with the VIC-3D 7 system to measure the out of plane displacement and strains evolution. Also 3D-DIC analysis has been carried out for the CAI test to check the validity of the failure modes. It has been observed that the most clustered laminates increase the perforation threshold, while it decrease the residual strength of the material, due to damage spreading effect.

  Abstract
  One of the mayor threats for FRP is the out-of-plane loading conditions such as impacts, which produce interlaminar failures, among others, decreasing drastically the material's [...]

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• Biaxial testing on CFRP laminates cruciform specimens under compressive loads

  S. Muñoz, M. Moreno

  Materiales Compuestos (2022). Vol. 04 - Comunicaciones Matcomp19 (2020), (Núm. 4 - Aplicaciones de los materiales compuestos. Nuevos procesos de fabricación y materiales compuestos avanzados.), 146

  
  

  Abstract

  A numerical and experimental study is performed on biaxial tests with cruciform specimens in which at least one direction is under compression. Continuous carbon fibre reinforced polymer matrix laminates are studied in angle-ply sequences. The high complexity of the biaxial test is analysed, highlighting the non-linear behavior of the material with pseudo-ductile response. In addition, the presence of compression loads lead to tests in which it is necessary to avoid instabilities in order to obtain adequate results. The numerical simulations based on the Finite Element Method allow to study of the initiation and evolution of the damage in the laminate. The combination of numerical techniques with experimental results, obtained by means of the test instrumentation with strain gauges and Digital Image Correlation, allows to perform a complete characterization of the behaviour of the material in order to achieve less conservative designs of composite structures.

  Abstract
  A numerical and experimental study is performed on biaxial tests with cruciform specimens in which at least one direction is under compression. Continuous carbon fibre reinforced [...]

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• Compression after impact test on woven CFRP laminates with graphene

  C. Merino, J. Artero-Guerrero, T. Blanco, A. Butragueno, R. Cuvillo, J. Pernas-Sánchez, D. Varas, S. Blanco, P. Merino, A. Reguero, E. Cholbi, B. Romero, J. López-Puente

  Materiales Compuestos (2022). Vol. 04 - Comunicaciones Matcomp19 (2020), (Núm. 4 - Aplicaciones de los materiales compuestos. Nuevos procesos de fabricación y materiales compuestos avanzados.), 141

  
  

  Abstract

  Nowadays carbon fibre reinforced epoxy laminates represent the standard material in the designing and manufacturing of aeronautical composite structures. However, advantages related to metals manufacturing could represent an important menace for the role of composite materials in this industry. Therefore, new improvements in composite structures have to be seek in order to improve their competitiveness. Graphene is a nanomaterial that possess the higher stiffness and strength ever measured. Therefore, the use of Graphene Related Material (GRM) for enhancing composite laminate materials could represent an important advance in order to reduce their impact vulnerability and to improve the performance of Resin Transfer Molding (RTM) composites.   In this work epoxy resin doped with GRM were used to manufacture carbon fiber aeronautical composites by RTM. Low velocity impacts and Compression After Impact (CAI) tests were performed. Regarding experimental methodology, ASTM standard was followed, also new measuring techniques were used as 3D High Speed Digital Image Correlations. All tests were performed on GRM enhanced material and reference material to compare their results. Under impact loads, elastic behavior, peak force or damage results do not depend on the addition of graphenic particles. Whereas, a minor improvement enhanced with GRM in compression preserving the visible damage for an impact equivalent to the tool drop (30 J). Is important to keep this effect in order to detect damages in the composites structures.

  Abstract
  Nowadays carbon fibre reinforced epoxy laminates represent the standard material in the designing and manufacturing of aeronautical composite structures. However, advantages [...]

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• The role of nanofiber veils developed by electrospinning in mechanical properties of carbon fiber composites

  A. Pérez-Márquez, J. Maudes, I. Harismendy, J. Gayoso, O. Ollo, M. Blanco, C. Monteserín, J. Vilas, I. Ocáriz, P. Venegas, M. Herrán

  Materiales Compuestos (2022). Vol. 04 - Comunicaciones Matcomp19 (2020), (Núm. 4 - Aplicaciones de los materiales compuestos. Nuevos procesos de fabricación y materiales compuestos avanzados.), 140

  
  

  Abstract

  Research on nanofiber veils used as reinforcements in composite materials began several years ago and there have been numerous works published on this topic by the research community. However, there is still a long way to go to build a solid knowledge on the behavior of nanofibers in the most common failure mode in carbon fiber composites; the delamination that happens between the tissues of the fibers and the fragile matrices that agglutinate them. The fact of inserting these thermoplastic veils in the delamination region without hardly altering the weight of the composite has proven to be an adequate method to increase the fracture toughness since the beginning of these investigations. Electrospinning is a versatile and simple technique that allows a tailor-made manufacture of nanofiber veils from a wide variety of polymers, with different morphologies in terms of grammage, nanofiber diameter, etc. One of the most important characteristics of nanofibers is their nanometric scale, which gives them a great surface-volume ratio, high porosity and excellent mechanical performance. This paper shows the influence of the grammage of veils based on polyamide 6 nanofibers and the different ways to achieve the same weight in mechanical properties of the manufactured composites. The results show an improvement in the fracture toughness and in the impact strength when these thermoplastic veils are introduced.

  Abstract
  Research on nanofiber veils used as reinforcements in composite materials began several years ago and there have been numerous works published on this topic by the research [...]

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