Showing papers in "Advanced Composite Materials in 2005"
TL;DR: In this paper, the authors investigated the basic mechanical properties of TEEK-L polyimide-foam of a balloon type and TEEKL filled aramid-honeycomb core material for sandwich structures and compared their mechanical properties with those of AIREX R82 and ROHACELL WF foam core-materials.
Abstract: The objectives of this study are to investigate the basic mechanical properties of TEEK-L polyimide-foam of a balloon type and TEEK-L filled aramid-honeycomb core-materials for sandwich structures and to compare their mechanical properties with those of AIREX R82 and ROHACELL WF foam core-materials. Compression, tension, and plate-shear tests provided their stress–strain relationships, elastic modulus, and strength. The test results are compared and discussed. The major results obtained are: (1) Filling the aramid honeycomb cells with TEEK-L can improve the basic mechanical properties of an aramid-honeycomb core-material, in particular making them higher than the values expected from the principle of superposition for compression tests and equal to the values expected from superposition for plate-shear tests. (2) The basic mechanical properties of the TEEK-L filled aramid honeycomb are superior to those of AIREX R82 110 and equivalent to those of ROHACELL WF 110, where the three materials have equal densi...
35 citations
TL;DR: In this article, a new preforming process was proposed to make the near-net-shaped preforms by using the conventional tubular braiding technique and deforming technique to change the configuration into the nearnet-shapes.
Abstract: Braiding is one of the useful textile techniques for fabricating near-net-shaped fiber preforms. Automated braided preform fabrication process has been improved. Triaxial braiding was evaluated as a means of reducing the cost of producing airplane framesusing automation technology. A new preforming process was proposed to make the near-net-shaped preforms by using the conventional tubular braiding technique and deforming technique to change the configuration into the near-net-shapes. The preforms were fabricated with carbon fibers by using the new performing process and molded using resin transfer molding (RTM) process with epoxy resin into I-beam frames and panels for investigating mechanical testing and production cost. Mechanical testing and cost analysis indicated that the mechanical properties of the braided composites are superior to those of aluminum materials and that the combination of the braiding and the RTM process is less costly than the hand-lay-up and autoclave process.
27 citations
TL;DR: In this paper, the fractal branch and bound method is extended to optimize multiple stacking sequences for the maximization of the buckling load of a hat-stiffened composite panel.
Abstract: Stiffened composite panels are often used as structural components in aircraft in order to avoid buckling. It is well known that stacking sequence optimizations are indispensable for laminated composite structures. Stiffened composite panels usually have more than two stacking sequences because they consist of a panel skin laminate and stiffener laminates. This means that the stacking sequences need to be jointly optimized to achieve structural optimization of the stiffened composite panel. The authors have proposed a new stacking sequence optimization method, called the fractal branch and bound method, for optimizing a single laminate. In the present study, the fractal branch and bound method is extended to optimizing multiple stacking sequences. The extended method is applied for obtaining two optimal stacking sequences for the maximization of the buckling load of a hat-stiffened composite panel. The improved method successfully provides two optimal stacking sequences determined in a short period of time.
18 citations
TL;DR: In this paper, a mechanism that brings large errors of estimation due to the shape of the delamination is detailed, and a small electric potential change method is adopted to detect delaminations.
Abstract: Detecting delaminations of carbon fiber reinforced plastic (CFRP) laminates is a difficult task for visual inspection. Delaminations cause large reductions in strength and stiffness of CFRP laminates, bringing deterioration of the structural reliability of a CFRP. Monitoring for delamination is, therefore, indispensable to maintain the reliability of a CFRP structure. In a previous study, we adopted the electric potential change method to detect delamination. This method shows good estimation performance for delamination cracks located near the edges of a specimen, but poor performance near the center where large errors that depend on the delamination shapes are created. A zigzag delamination caused by matrix cracking has a large effect on estimation performance; so the electric potential change method was not applicable to monitoring for delamination. In this paper, a mechanism that brings large errors of estimation due to the shape of the delamination is detailed. FEM analyses show a small electric curr...
16 citations
TL;DR: As president of the American Society for Composites (ASC) for 2004-2005, Professor Gibson is honored and delighted to present this paper, and he brings with him the best wishes of ASC to JSCM for a successful 30th anniversary symposium as mentioned in this paper.
Abstract: As president of the American Society for Composites (ASC) for 2004–2005, Professor Gibson is honored and delighted to present this paper, and he brings with him the best wishes of ASC to JSCM for a successful 30th anniversary symposium. It has been a great pleasure for ASC to co-sponsor the Japan–US Conference on Composite Materials with JSCM over the years, and we hope that the tradition will continue for many years to come. ASC will celebrate its 20th anniversary at its 2005 conference at Drexel University in Philadelphia, and we invite you all to join us there.
14 citations
TL;DR: In this article, the influence of residual stresses on the mechanical behavior of carbon/epoxy cross-ply laminates under tensile and torsion loading was investigated using the incremental blind-hole drilling technique combined with the finite element analysis.
Abstract: Residual stresses occur during most manufacturing processes (from shrinkage of the resin, difference of thermal expansion coefficients, etc.). Residual stresses may cause local yielding and damage initiation and propagation, and can severely affect performances of a composite structure component. The aim of this work is to investigate the influence of residual stresses on the mechanical behavior of carbon/epoxy cross-ply laminates under tensile and torsion loading. The residual stresses field was determined using the incremental blind-hole drilling technique combined with the finite element analysis. The effect of various cure cycles on the residual stress level is analysed. The quantitative effect of the residual stresses on the mechanical behaviour and the damage initiation and growth is studied by using acoustic emission technique.
13 citations
TL;DR: In this paper, an extended Brinson model was proposed to clarify complicated behaviors of SMA foils and several simulations were conducted and compared with experimental results to express the thermo-mechanical behavior of the Ti-Ni SMA foil adequately.
Abstract: Ti-Ni shape memory alloy (SMA) foils are embedded into carbon fiber reinforced plastic (CFRP) cross-ply laminates in order to suppress the occurrence and progress of the transverse cracks in the laminates. When the pre-strained SMA foil is heated, the shape memory effect produces appropriate recovery compressive stress in the direction to suppress transverse cracks. However, Ti-Ni SMA foil has these specific characteristics due to the existence of a rhombohedral phase (R-phase). Thus, in this research, in order to use this SMA foil as an actuator, an extended Brinson model was proposed to clarify complicated behaviors of SMA. Then, for the determination of the parameters in the constitutive equation in this model, experimental tests were performed for the SMA foils. Using this model, several simulations were conducted and compared with experimental results. The agreement indicated that this model could express the thermo-mechanical behavior of the Ti-Ni SMA foil adequately. Finally, the behavior of the SM...
8 citations
TL;DR: The difference between the nominal and actual value of the winding tension is due both to the typology of the wound trajectory that has been set and to the agents that are external to the technological process and consequently hardly controllable as discussed by the authors.
Abstract: Winding tension is a very critical parameter to be controlled during the manufacturing of composite parts by robotized filament winding technology. In fact, the winding tension influences directly the defects and the mechanical properties of composite parts.The nominal value of the winding tension that has been set in order to obtain a good roving alignment and compactness inside the composite part is not equal to the actual value acting on roving during the winding. The difference between the nominal and actual value of the winding tension is due both to the typology of the winding trajectory that has been set and to the agents that are external to the technological process and consequently hardly controllable. Therefore, once the value of the nominal winding tension has been set and the geometry of the part to be wound has been fixed, it is necessary to act on the geometric parameters of the winding trajectory in order to guarantee that tension acting on the roving during the winding is as near as possi...
8 citations
TL;DR: In this article, a foam type of phenolic resins and glass fibers were used as the matrix and reinforcement, respectively, for the new phenolic foam composite and examined its mechanical properties and thermal conductivity.
Abstract: Phenolic resin has the excellent properties of fire resistance, low smoke production during burning, and a good balance between its cost and mechanical properties compared with other types of resin used in fire-resistant polymers (FRPs). If phenolic resin can be employed as a matrix of FRP, such FRP can have a higher fire safety factor which will be a desirable property in the structures of vessels and railway carriages. However, for the case of the resole type of phenolic resin, water formed from the condensation reaction remains in the matrix, and this water evaporates resulting in the formation of voids during the curing process. In order to develop a new type of phenolic composite that can overcome this weakness, we used a foam type of phenolic resin and glass fibers as the matrix and the reinforcement, respectively. We, then, developed a new pultrusion technique for the new phenolic foam composite and examined its mechanical properties and thermal conductivity.In this paper, we report a new technique...
8 citations
TL;DR: In this article, the authors used optical microscopy to identify matrix cracks that lead to delamination in cross-ply glass-fibre-reinforced polymers under transverse loading and to provide evidence on the associated damage evolvement procedure.
Abstract: Objectives of the work are to use optical microscopy to identify matrix cracks that lead to delamination in cross-ply glass-fibre-reinforced polymers (GFRP) under transverse loading and to provide evidence on the associated damage evolvement procedure. Sequence of the damage evolvement was established by examining a series of identical specimens that had been subjected to different levels of loading. The results were found to be consistent with those reported in the literature, that the transverse loading generated both bending and shear cracks in the matrix, and that it was the shear cracks that initiate the delamination. What was revealed in the current study is that delamination in the bottom half of the cross section, i.e. away from the contact surface, developed first, from shear cracks in regions of mid-thickness. Only after the load was further increased was delamination in the top half of the cross-section developed, from cracks generated by stress concentration around the contact area. The study ...
7 citations
TL;DR: In this article, the authors adopted an all-composite monocoque structure instead of a conventional aluminum skin, stringer-frame structure, which was made of several large parts in order to reduce the total number of parts.
Abstract: Two strict requirements were to be adhered to in the development of HOPE-X: to shorten the manufacturing lead-time and to reduce the fabrication cost for the lightweight prototype structure of HOPE-X. To meet these requirements, the design team adopted an all-composite monocoque structure instead of a conventional aluminum skin, stringer-frame structure. The all-composite structure was made of several large parts in order to reduce the total number of parts. These large parts were made by using the non-autoclave curing technique and assembled by bonding into a monocoque structure. The high-accuracy large lay-up tool and the custom-made oven played important roles particularly during these manufacturing processes, leading to reduction in both lead-time and cost. The structural design and the manufacturing strategy for the prototype structure are described in this paper. The development of the lay-up tool and the oven, which helped to realize low fabrication cost, is described here.
TL;DR: In this paper, the authors used T-shaped stringers made of heat resistant thermoplastic composites, CF/PIXA, for testing at room temperature and 180°C.
Abstract: Compression after impact (CAI) behavior of stiffened panels using T-shaped stringers made of heat resistant thermoplastic composites, CF/PIXA, was obtained by tests at room temperature and 180°C. Excellent impact resistance in terms of delamination area was verified for the present composite panels due to the special fusion bonding film. Room temperature CAI strengths of the stiffened panels were found to be better than CF/PEEK panels in a rough comparison, without regard to differences in stacking sequence and geometry. Relationships between temperature and CAI strengths for CF/PIXA stiffened panels were compared with the results for flat plates (SACMA) and a compatibility between flat plate and stiffened panel data was observed. It is clarified that damage tolerance properties of CF/PIXA stiffened structure are so remarkable at room temperature that compression strengths are quite insensitive to relative impact energy. Its damage tolerance capability is also excellent at high temperature for High Speed ...
TL;DR: In this paper, the authors investigated the mechanical properties of a CFRP tube under a lateral impact load using the split Hopkinson pressure bar and showed that crack propagation behavior strongly depends on the displacement rate.
Abstract: The mechanical properties of a CFRP tube, such as strength, stiffness, and energy absorption, are investigated under a lateral impact load using the split Hopkinson pressure bar. In order to obtain the load–displacement curve, a ramped wave was applied to the specimen. It was observed that the ramped incident wave can be used for evaluating the mechanical properties of a CRRP tube under a lateral impact load. The dependence of the displacement rate on the properties mentioned above is also discussed. The result indicates that crack propagation behavior strongly depends on the displacement rate.
TL;DR: In this paper, the behavior of core and core-less composite elliptical thin-walled tubes subjected to quasi-static axial crushing is examined experimentally, and two different arrangement symmetric tubes have been used.
Abstract: The behaviour of core and core-less composite elliptical thin-walled tubes subjected to quasi-static axial crushing is examined experimentally. The core-less tubes have two different arrangement sy...
TL;DR: In this paper, the Smart UAV Development program, one of the 21st Century Frontier R&D Programs funded by the Ministry of Science and Technology of Korea, was partially supported by the National Institute of Electronics and Information Technology (NIT).
Abstract: This research was partially supported by the Smart UAV Development program, one
of the 21st Century Frontier R&D Programs funded by the Ministry of Science and
Technology of Korea. The authors also acknowledge the support from the National
Research Laboratory (NRL) Program.
TL;DR: In this paper, a composite supporter with carbon fiber reinforced plastics and Nomex honeycombs is used for aerospace applications and the dynamic behaviour of the composite supporter is investigated, both numerically and experimentally, using a commercially available finite element package.
Abstract: In this paper, modeling and vibration analysis of a composite supporter newly developed for aerospace applications are presented. The composite supporter is manufactured through hand layup process using the combination of carbon fiber reinforced plastics and Nomex honeycombs. The dynamic behaviour of the composite supporter is investigated, both numerically and experimentally, the former using a commercially available finite element package. Good agreement between the numerical results and experimental results shows that the proposed finite element modeling and analysis procedure can be used effectively to characterize the vibration behaviour of the composite supporter. The parametric investigation is also carried out using the validated FE model to show the effects of changing orthotropic properties of the core and ply orientation on the natural frequencies of the supporter. The presented results will provide a theoretical basis for a further vibration-control design of the supporter.
TL;DR: In this paper, shape memory alloy (SMA) foils were embedded into carbon fiber reinforced plastic (CFRP) cross-ply laminates to suppress the transverse cracks in the Laminates.
Abstract: In this research, shape memory alloy (SMA) foils were embedded into carbon fiber reinforced plastic (CFRP) cross-ply laminates. When the tensile pre-strained SMA foil is heated, the SMA produces appropriate compressive stress (recovery stress) to suppress the transverse cracks in the laminates. In order to investigate the damage suppression effect, tensile loading–unloading tests were conducted for the CFRP cross-ply laminates. The test results implied that the recovery stress of embedded SMA foil suppressed the occurrence and the progress of the transverse crack. Then, to confirm that the damage suppression effect was caused by the embedded SMA foil, the one-dimensional (1D) shear-lag model considering the behavior of SMA was newly derived. Using this model, the progress of transverse crack density was predicted probabilistically. The simulation results showed the same tendency as the experimental results. As a result, it was proved that the embedment of SMA foils into CFRP laminates is effective to supp...
TL;DR: In this article, the authors determined the compression-after-impact (CAI) behavior and strength of a carbon/tough-polyimide composite material, MR50K/PETI5, whose PETI5 resin has been specially developed for the next generation supersonic transport (SST) at NASA.
Abstract: This study determined the compression-after-impact (CAI) behavior and strength of a carbon/tough-polyimide composite material, MR50K/PETI5, whose PETI5 resin has been specially developed for the next generation supersonic transport (SST) at NASA. First, an impact test imposed impact damage on CAI specimens at room temperature, and the load and absorbed energy were measured; in addition, the damage was examined with an ultrasonic C-scanner and a 3D ultrasonic inspection system. Second, CAI strength and failure strain were measured at room temperature and at 180° C. Third, the damage induced by the CAI test was examined with an optical microscope. Test results were compared with those of T800H/PMR-15 carbon/polyimide composite, where PMR-15 is a typical brittle resin, and the characteristic CAI behavior and strength of a carbon fiber/highly-tough resin composite were determined.
TL;DR: In this paper, a simulation method based on fracture mechanics is investigated for skin/stiffener composite structures, which is intended to be versatile and easy to implement for commercial FEM codes.
Abstract: Skin/stiffener composite structures suffer debonding between stiffener and skin due to loading. Application of fracture mechanics to assess structural integrity is difficult because of the complexity of structural configuration and inhomogeneity of composite materials. A simulation method to assess the structural integrity that predicts the onset and growth of debonding and estimates the stiffness degradation due to debonding is needed.In this study, a simulation method based on FEM is investigated for skin/stiffener structures. The simulation method is intended to be versatile and easy to implement for commercial FEM codes. Skin/stiffener structures are modeled as coupling of shell elements. If debonding is judged by an energy criterion, the coupling is released. Debonding growth of Double Cantilever Beam (DCB) and End Loaded Split (ELS) specimens are simulated and compared with theoretical and experimental results to demonstrate the feasibility. Debonding of skin/stiffener structures is simulated succes...
TL;DR: In this article, a damping capacity concept was applied to the torsional damped oscillation of a laminated composite cylinder and a forecasting method was suggested for the damping characteristic.
Abstract: The dynamic characteristics of FRP are important for robotic arms and other applications. In this work, we applied a damping capacity concept to the torsional damped oscillation of a laminated composite cylinder. The forecasting method was suggested for the torsional damping characteristic. An experiment was conducted to verify the theory and this calculation method. Good agreement was obtained between the theoretical and the experimental values of seven types of laminated composite cylinder (unidirectional (0°, 90°) plies and cross-plies (±15°, ±30°, ±45°, ±60°, ±75°)). This demonstrates that the mathematical technique developed here is satisfactory for predicting the damping of laminated composite cylinders. Torsional damping characteristics of laminated composite cylinders vary with fiber orientation angle.