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Epoxy-based thermosets are one of the most popular matrix materials in many industries, and significant environmental benefits can be obtained by developing a recyclable variant of this widely utilized material. Incorporation of a bio-based disulfide additive within a commercial epoxy system leads to a cross-linked material that can be fractionated under mild and environmentally benign conditions. The material has been analyzed by FTIR and solid-state NMR. Furthermore, modified epoxy matrices with low additive concentrations are demonstrated to have similar mechanical and thermal properties compared to commercially available benchmarks. Thus, additive formulation and fractionation based on green chemistry principles have been demonstrated, and a recyclable epoxy matrix has been developed.

Nanocomposites draw attention from many various fields and areas of usage increase with the improvement of their properties. For this purpose, nanographene particles have used to enhance the mechanical, thermal, and electrical properties. In the presented experimental study, nanocomposites were fabricated by reinforcing the epoxy matrix with nanographene particles at 0.5 and 1 wt%. The dispersion of nanofillers in epoxy matrix and the tensile properties of the nanocomposites were investigated. The tensile strength and stress at break increased with nanographene particles addition and well dispersion of nanofillers in epoxy matrix was achieved.

An epoxy resin is filled with carbon quantum dots (CQDs) leading to highly transparent and luminescent nanocomposites. The CQDs are modified to bear carboxyl groups on the surface (denoted as CQDs@COOH), which made the CQDs may participate in the curing reaction of the epoxy and homogeneously disperse in the matrix. As a result, the light scattering is avoided and transparency of the filled epoxy is enhanced. Besides, the CQDs@COOH-filled epoxy also exhibit better UV and thermal stabilities than traditional CdSe-QDs/epoxy system.

The present paper deals with the magnetoelectroelastic composites containing a doubly periodic array of multicoated fibers under anti-plane shear loads and in-plane electromagnetic loads. By introducing the generalized eigenstrain, the heterogeneous magnetoelectroelastic medium is equivalent to a homogeneous magnetoelectroelastic medium with the periodically distributed generalized eigenstrains. Then the homogeneous magnetoelectroelastic medium with the generalized eigenstrain is solved analytically under the applied load conditions, the generalized stresses and strains in the fibers, coatings and matrix are derived. Based on the average-field theory, the solutions of the generalized stresses and strains are applied to determine the anti-plane effective magnetoelectroelastic properties of the composites. Two-phase (fiber/matrix) and three-phase (fiber/coating/matrix) magnetoelectroelastic composites are examined, and the comparison between the obtained results and the existing results shows the accuracy of the proposed method. Several four-phase magnetoelectroelastic composites with epoxy matrix are studied, and the influences of the composites microstructures on the effective magnetoelectric coefficient are discussed.

Summary Micromechanics modeling, utilizing a cylindrical method of cells (CMOC) model, is employed to obtain the effective mechanical properties of an elastic transversely isotropic, isothermal material system consisting of a hollow carbon nanotube (CNT) embedded in an isotropic polymeric material matrix. It is shown that weak interfacial bonding between the CNT and polymeric matrix, which is characteristic of this type of material system, can be modeled with the CMOC. Numerical solutions of the effective independent material constants are obtained, based upon appropriate values of the properties of the carbon nanotube and epoxy matrix. The numerical results are presented graphically and compared with corresponding classical closed-form solutions. Copyright © 2015 John Wiley & Sons, Ltd.

In this study, a novel method consisting of coating carbon fibers (CF) with graphite nanoplatelets (GnP) is investigated for its ability to modify the mechanical properties in the interphase region. Coating the CF was achieved by immersing CF in a solution of GnP dispersed in an epoxy-based solution for a few seconds. The influence of the processing conditions on the properties of the coating (thickness, homogeneity, quality of the GnP dispersion) is reported. Interfacial adhesion and the associated failure modes were evaluated by the single fiber fragmentation test. The maximum value of interfacial shear strength (IFSS) was achieved when a relative GnP concentration of 7.9 wt% on CFs, which led to 45 and 34% improvements in IFSS in comparison with the non-coated CF and epoxy coated CF, respectively. POLYM. COMPOS., 37:1549–1556, 2016. © 2014 Society of Plastics Engineers

We reported a facile approach to fabricate graphene nanoplatelets (GNPs)/epoxy composites with a novel blend method. The influence of GNPs on the thermal and electrical properties was investigated. Compounds with different GNPs content (0-8 wt%) were mixed with a Flacktek speedmixer at a speed of 3000 rpm for 5 min. The thermal conductivity of the epoxy composites with 8 wt% GNPs was 1.181 W/m K, which is increased by 627% compared with those of the neat epoxy. It is found that the thermal stability and electrical property also have a certain degree of improvement. Scanning electron microscopy images demonstrate that the structures of the composites have a closed relationship with their properties. In addition, the incorporation of GNPs in epoxy matrix indicated excellent Vickers hardness at the low weight fractions of GNPs. POLYM. COMPOS. 36:556-565, 2015. (c) 2014 Society of Plastics Engineers

Epoxy composites filled with copper particles with sizes of the order of 100 μm are studied with the aim of analyzing the particle–matrix interphase. Two matrixes are used: diglycidyl ether of bisphenol A resin (DGEBA)–anhydride catalyzed using a tertiary amine, and uncatalyzed DGEBA–anhydride. The surface of both types of composites was analyzed using scanning electron microscopy, X-ray photoelectron spectroscopy, and instrumented nanoindentation. The formation of Cu(I) and Cu(II) complexes is revealed using X-ray photoelectron spectroscopy, while instrumented nanoindentation measurements allow us to determine regions with different mechanical properties in the uncatalyzed composite. The influence of anhydride and the type of curing reaction on the formation of copper complexes is analyzed. The main results point out that copper particles can interact strongly with the epoxy, depending on the chemistry and kinetics of the curing reaction, to modify the composite. Fil: Tognana, Sebastian Alberto. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física de Materiales; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Tandil. Sede Tandil del Centro de Investigaciones En Fisica E Ingenieria del Centro de la Provincia de Buenos Aires.; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina Fil: Salgueiro, Walter Alberto. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física de Materiales; Argentina. Universidad nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Centro de Investigaciones En Física E Ingeniería del Centro de la Provincia de Buenos Aires; Argentina Fil: Valcarce, María Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentina Fil: Schreiner, Wido H.. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física de Materiales; Argentina. Universidade Federal do Paraná; Brasil Fil: Montecinos Espinoza, Susana de Los Angeles. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Física de Materiales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina

This study is focused on the investigation of the effect of thermal shock cycling on the mechanical properties of cellulose based reinforced polymer composites. Polymer composites reinforced with olive pits powder at different filler-volume fractions were manufactured. An increase in the bending modulus on the order of 48% was achieved. On the other hand, results showed that the bending strength remained almost unaffected from the amount of filler introduced. Next, the effect of thermal shock cycling on the mechanical behaviour of the thus manufactured composites was investigated. Theoretical predictions for both the properties variation with number of thermal shock cycles applied as well as with filler-volume fraction were derived using the residual properties model (RPM) and the modulus predictive model (MPM), respectively. Predicted values were compared with respective experimental results. In all cases, a fair agreement between experimental findings and theoretical predictions was found. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Dielectric properties of hollow Al2O3 nanoparticle-dispersed epoxy matrix composites in a frequency range from 18 to 30 GHz have been studied. Hollow Al2O3 nanoparticle-dispersed composites show lower dielectric properties compared with those of solid α-Al2O3 nanoparticle-dispersed ones. The hollow part inside the nanoparticle reduces the effective dielectric constant of Al2O3 nanoparticle-dispersed composites. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1069–1072, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25099

The bisphenol-F type flexible epoxy resin, having a good flexibility, was combined with an organo- and slurry-clay. The clay dispersions in the obtained epoxy/clay systems are significantly different depending on the type of clay. Particularly, the epoxy/slurry-clay system showed a high clay dispersibility into the epoxy matrix and was transparent in spite of the addition of 10 wt % clay. This result means that the swelling of the clay with formamide is effective for the expansion of the basal spacing of the clay. The slurry-clay nanocomposite (clay content: 5 wt %) showed a 4 times higher fracture energy than the neat epoxy system in the tensile test, though the organo-clay system (clay content: 5 wt %) was 1.5 times higher. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

More interestingly, it has been confirmedthat the nanonecklaces have an unusual reinforcing effect forepoxy due to the mechanical interlocking between beads andpolymer matrix, which in turn enhances the interfacial bondbetween the fillers and the epoxy matrix. Epoxy with only0.5wt % nanonecklaces showed an increase in the elasticmodulus value by 32.3% and nanoindentation hardness by61.9% when compared to the neat epoxy. The reinforcementeffect of this kind of nanonecklaces in epoxy nanocomposites iseven better than normal carbon nanotubes.

The effects of room temperature aging on the cure kinetics of a bismaleimide (BMI) matrix prepreg have been characterized by different time and storage conditions. The study has focused on the stability of BMI matrix carbon fiber prepregs, when exposed to controlled environmental conditions before being used in composite manufacturing. The effects of aging on reactivity, glass transition temperature, and process window have been investigated by differential scanning calorimetrer through dynamic and isothermal tests. A theoretical kinetic model for epoxy matrix prepregs, developed in previous studies, has been applied to the cure of both aged and virgin BMI matrix. The model is able to satisfactorily describe the effect of processing variables such as temperature and degree of cure during the curing of the composite under different conditions (curing temperature and heating rate). The effects of diffusion-controlled phenomena on the cure kinetics, associated with changes in glass transition temperature as a function of the degree of cure, have been taken into account in the formulation of an nth-order kinetic model. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

A nonautoclave vacuum bag process using atmospheric pressure alone that eliminates the need for external pressure supplied normally by an autoclave or a press is an attractive method for composite fabrication. This type of process does not require large capital expenditures for tooling and processing equipment. The traditional single-vacuum-bag (SVB) process is best suited for molding epoxy matrix-based composites because of their superior flow and the absence of reaction byproducts or other volatiles. This is not the case for other classes of materials such as polyimides and phenolics. Polyimides and phenolics are cured by condensation reactions which generate water as a reaction byproduct. In addition, these materials are commonly synthesized as oligomers using solvents to facilitate processability. Volatiles (solvents and reaction byproducts) management therefore becomes a critical issue. SVB molding, without additional pressure, normally fails to yield void-free quality composites for these classes of resin systems. A double-vacuum-bag (DVB) process for volatile management in composite fabrication using common molding equipment was designed and built at the NASA Langley Research Center. This experimental DVB process affords superior volatiles management compared with the traditional SVB process. Void-free composites are consistently fabricated as measured by C-scan and optical photomicroscopy for high-performance polyimide and phenolic resins. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

Frontal polymerization (FP) has been successfully applied, for the first time, to obtain polymeric nanocomposites containing polyhedral oligomeric silsesquioxanes (POSS) in an amine-cured epoxy matrix. Variations of maximum temperature ( T max ) and front velocity ( V f ) have been studied. A comparison of these products with the corresponding materials, obtained by the classical batch polymerization technique, demonstrated that FP allows a higher degree of conversion than batch polymerization. The products have been characterized in terms of their thermal behavior with DSC analysis. SEM and X-ray analyses revealed the morphology and the structures of the nanocomposites. The nanocomposites obtained by FP have the same characteristics of those synthesized, in much longer times, by batch polymerization.

The influence of incorporated 300 nm TiO2 (4 vol %), graphite (7 vol %), or combination of both fillers on the tribological performance of an epoxy resin was studied under various sliding load (10–40 N) and velocity conditions (0.2–3.0 m/s). Mechanical measurements indicated that the incorporation of TiO2 significantly enhanced the flexural and impact strength of the neat epoxy and the graphite including epoxy. Tribological tests were conducted with a cylinder-on-flat testing rig. The incorporation of nano-TiO2 significantly improved the wear resistance of the neat epoxy under mild sliding conditions; however, this effect was markedly diminished under severe sliding conditions (high velocity and normal load). Nano-TiO2 reduced the coefficient of friction only under severe sliding conditions. Graphite showed a beneficial effect in reducing the wear rate and the coefficient of friction of the neat epoxy. Compared to the nano-TiO2-filled epoxy, the graphite-filled epoxy showed more stable wear performance with the variation of the sliding conditions, especially the normal load. A synergistic effect was found for the combination of nano-TiO2 and graphite, which led to the lowest wear rate and coefficient of friction under the whole investigated conditions. The synergistic effect was attributed to the effective transfer films formed on sliding pair surfaces and the reinforcing effect of the nanoparticles. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2391–2400, 2006

The effects of oxidation and particle shape on critical volume fractions of silver-coated copper powders in conductive adhesives are investigated. Silver-coated copper powders with spherical and flake-shaped particles were oxidized at temperatures of 30°C, 175°C and 240°C for two hours and dispersed in an epoxy matrix. As silver-coated copper powders are oxidized at 30°C and 175°C, the critical volume fractions of the conductive adhesives are slightly affected by oxidation and particle shape at these temperatures. As the oxidation temperature approaches 240°C, the critical volume fractions of the conductive adhesives are strongly affected by oxidation temperature and particle shape, owing to the formation of oxides such as Cu2O on the surface of silver-coated copper powder—Cu diffuses from the interior to the surface of silver-coated copper powder and reacts with the oxygen in the air. Silver-coated copper powder with flake-shaped particles shows lower critical volume fractions in conductive adhesives than silver-coated copper powder with spherically shaped particles. Polym. Eng. Sci. 44:2075–2082, 2004. © 2004 Society of Plastics Engineers.

Solutions of rare earth modifier (RES) and epoxy chloropropane (ECP) grafting modification method were used for the surface treatment of aramid fiber. Tensile properties of both the aramid/epoxy composites and single fibers were tested. The effects of RES concentration on tensile properties of aramid/epoxy composites were investigated in detail to explore an optimum amount of rare earth elements in solution for modifying aramid fiber. The fracture surface morphologies of tensile specimens were observed and analyzed with the aid of SEM. The experimental results show that rare earth treatment is superior to ECP grafting treatment in promoting interfacial adhesion between the aramid fiber and epoxy matrix. Meanwhile, the tensile strengths of single fibers were almost not affected by RES treatment. The optimum performance is obtained when the content of rare earth elements is 0.5 wt %. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1037–1041, 2004

An experimental study was conducted to investigate the effect of coal used as a new type of filler in epoxy networks. For this purpose two series of epoxy composites with different coal weight fraction were studied and their thermo-mechanical properties were characterized. The work demonstrated that coal-filled epoxy networks show a typical behavior of a particulate filled material and follows the theoretical models already used.

The interlaminar shear strength (ILSS) of a composite containing glass rovings in a polycarbonate-toughened epoxy matrix was determined. The variation of ILSS with glass rovings and polycarbonate content was studied. For a given content of polycarbonate in the matrix, the ILSS increased with volume fraction of the glass rovings. For a given rovings content, the ILSS decreased with increasing polycarbonate content. However, the ILSS of the composites with epoxy alone as the matrix is found to be higher than that of the epoxy/polycarbonate blend and this was attributed to better bonding between epoxy and reinforcement than that between epoxy/polycarbonate blend and reinforcement. This was further confirmed by scanning electron micrographs of ILSS fractured samples. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 373–377, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10064

The reactivity and processability of prepregs for high performance composites have been investigated as a function of time and storing conditions. The study has been focused on the stability of epoxy matrix carbon fiber prepregs, affected by exposure to controlled environmental conditions before their use in composite manufacturing. Effects of the aging on glass transition temperature, reactivity and processability have been investigated by calorimetry. Dynamic, isothermal and cure simulating tests have been performed to this aim. Results on toughened TGDDM-DDS epoxy matrix prepregs are reported. A theoretical kinetic model proposed for the unaged system has been adapted for aged prepregs, by properly evaluating the variations of kinetic parameters with the aging time.

This paper reports some further studies on the tensile properties of plain weft knitted DuPont Kevlar fiber fabric reinforced epoxy matrix composites. One aim of this work is to investigate systematically the anisotropy of knitted fabric composites. Tensile tests were conducted at different off-axial angles (0°, 30°, 45°, 60° and 90°) with respect to the wale direction. Fracture modes corresponding to this off-axial variation were clearly identified. The elastic modulus and tensile strength were found to be the highest in the wale direction (0°), but decreased gradually towards the course direction (90°). This anisotropic study was carried out on both single layered and multilayered (four layered) knitted fabric composites. Another aim is to study the effect of specimen width (or number of loops per specimen width) on the tensile properties. This study indicated an optimum number of loops per sample width required to obtain meaningful tensile test results. Further, edge effect on the tensile properties of the knitted fabric composites was also investigated in the paper. This was achieved through comparative studies on cut and uncut four layered specimens. In the cut specimens the continuity of the yarns is lost at the cut edges, which show a marginal variation in the properties compared with the uncut specimens where the yarns are continuous throughout the specimen. Finally, a study was also carried out to investigate the effect of loop size (or stitch density) on the tensile strength and stiffness of the single layered composites.

Underfill is the material used in a flip-chip device to dramatically enhance its reliability as compared to a nonunderfilled device. Current underfills are mainly epoxy-based materials that are not reworkable after curing, which is an obstacle in flip-chip technology developments, where unknown bad die is a concern. Reworkable underfill is the key to address the nonreworkability of the flip-chip devices. The ultimate goal of this study is to develop epoxy-based thermally reworkable underfills. Our previous work showed that when incorporated into epoxy matrix, special additives could provide the epoxy formulation with die-removal capability around solder reflow temperature. The additive-epoxy interactions were studied and the results show that the additives do not adversely affect the epoxy properties. Moreover, when the additive decomposition temperature is reached, the decomposition of the additive causes a microexplosion within the epoxy matrix. Subsequently, the adhesion of the epoxy matrix is greatly reduced. Among the four additives studied, Additivel and Additive2 may be used in reworkable underfills that can be reworked around solder reflow temperature, Additive3 cannot be used in underfill because it greatly reduces the shelf life of the underfill, and Additive4 may be used to develop reworkable underfill that withstands multiple reflows.

In previous papers the photo-chemical degradation of a bisphenol A epoxy resin cross-linked with the hardener methyltetrahydrophthalic anhydride was studied by ATR FT-IR spectrophotometry and by X-ray analysis. The analyses confirmed the presence of a thin photo-oxidation layer at the surface of the material. After the establishment period, the layer and the ablation of the organic matrix evolve spatially at a constant rate. From these results and from the IR absorbency evolution of a ν (O—H) vibration measured through thin films, the spatial distribution of the bond corresponding to this vibration was calculated as a contribution to the evolution analysis of the photo-oxidation layer during photo-ageing. In fruheren Arbeiten wurde der Photoabbau eines mit Methyltetrahydrophthalsaureanhydrid vernetzten Bisphenol A Epoxidharzes mit ATR-FTIR-Spektroskopie und Rontgenanalyse untersucht. Die Analysen zeigten eine dunne Photooxidationsschicht auf der Oberflache des Materials. Das Wachstum dieser Schicht und die Ablation der organischen Matrix laufen mit konstanter Geschwindigkeit ab. Aufgrund dieser Ergebnisse und der Intensitatsanderung einer ν (O—H)-Schwingung im IR-Spektrum wurde die raumliche Verteilung der dieser Schwingung entsprechenden Bindung, als Beitrag zu einer Entwicklungsanalyse der Photooxidationsschicht wahrend der Photoalterung berechnet.

Die hohe Vernetzungsdichte der in vielen hochwertigen Anwendungen eingesetzten Epoxidharze mit hoher Glasubergangstemperatur, hohen Festigkeiten etc. bedingt die unerwunschte Sprodigkeit dieser Werkstoffe, verbunden mit dem Aufbau von Eigenspannungen. Zur Optimierung ihrer Eigenschaften wurden cycloaliphatische Epoxidharze mit elastomerem Silicon versetzt, wobei zwei verschiedene Modifizierungskonzepte, namlich die ,,Dispersions-" und die ,,Mischungs-"Variante, mit Hilfe mechanischer Versuche, dynamisch-mechanischer Analyse und rasterelektronenmikroskopischer Untersuchungen sowie Messungen von Ausdehnungskoeffizient und Schwindung charakterisiert und bewertet wurden. Die Modifizierung mit Silicon fuhrt allgemein zu einer Erniedrigung des E-Moduls der Harzformstoffe; die Bruchzahigkeit wird gesteigert. Bei den ,,Dispersions-"Formstoffen wird aufgrund ihrer Zweiphasigkeit die Glasubergangstemperatur der Epoxidmatrix praktisch nicht gesenkt, und die Neigung zur Ausbildung von Spannungen ist geringer als bei der ,,Mischungsvariante". The high crosslink density of epoxy resins with high glass transition temperature, high strength, etc., used in many high-performance applications, causes the undesired brittleness of these materials and, hence, internal stress. For the optimization of their properties, cycloaliphatic epoxy resins were modified with elastomeric silicone. Two different modifying concepts, i. e. dispersion and mixing, were characterized using mechanical testing, dynamic-mechanical analysis and scanning electron microscopic studies as well as measurement of the expansion coefficient and the shrinkage. The modification with silicone, in general, reduces the modulus and improves the fracture toughness of the resins. Due to the two-phase structure of the resins prepared by the dispersion method, the glass transition temperature of the epoxy matrix is practically not depressed, and the tendency to enhance stress is less marked compared to the mixing method.

Transformation acoustics opens a new avenue towards the fabrication of a new class of sonic composites with scatterers made of auxetic materials embedded in the epoxy matrix. The design of the acoustic scatterers is based on the property of Helmoltz equations to be invariant under coordinate transformations, i.e. a specific spatial compression is equivalent to a variation of the material parameters in the original space. In this paper, the noise suppression for a wide full band-gap of frequencies is discussed for spherical shell scatterers made of auxetic materials. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)

Strong adhesion in the superdrawn polyoxymethylene (POM) fiber/epoxy matrix system was achieved with surface treatments, 2H-hexafluoro-2-propanol (HFP) treatment, and surface phenolation of the fiber. HFP produced micropits for mechanical interlocking with the matrix. Surface phenolation formed active layers leading to interfacial miscibility. © 1996 John Wiley & Sons, Inc.

Raman spectroscopy is shown to be a very powerfull method for the study of stress transfer in epoxy composite materials reinforced with high-performance polyethylene (PE) fibers. We found that the stress transfer length as determined by Raman spectroscopy is subtancially shorter for a plasma-treated fiber than for an untreated one. A shorter stress transfer length indicates stronger interactions between fiber and matrix. Furthermore, the stress transfer length was higher for a PE fiber/epoxy matrix cured at a higher temperature

The effect of adding fortifiers to an epoxy matrix on the response to impact and compression-after-impact properties of carbon fabric/epoxy laminates was investigated. The experimental work included determining laminate compression strength, absorbed energy from impact, damage area and compression-after-impact strength for an impact energy level of 21 joules per centimeter of thickness. This paper presents the results from this investigation and discusses the relationship between neat resin properties (with and without fortifiers) and the laminate properties.

An investigation was carried out into the effects of graphite fiber and epoxy matrix physical properties on the temperature profile in their laminates during cure. An accurate prediction of the temperature profile within a composite is of paramount importance in determining the processing conditions. In this study, a model for the temperature profile was established first. Then, three physical parameters of composites that change during cure, namely, density, heat capacity, and thermal conductivity, were varied in magnitude, and the ensuing effect on the temperature profile was examined. The range of their variation was based upon the values measured in the laboratory as well as those reported in the literature. Changes in the neat resin thermal conductivity were found to significantly influence the temperature profile. 17 refs.

Die Schwingfestigkeit eines Faserverbundwerkstoffes aus Carbon-HT Faser und Epoxyd-Matrix bei Ein- und Mehrstufenbelastung sowie statische Zug- und Druckfestigkeiten wurden experimentell ermittelt. Die Versuche wurden an ungekerbten tallierten Proben aus multidirektionalem CFK mit 0°, ± 45° und 90° Schichten durchgefuhrt. Die Ergebnisse von Einstufenversuchen bei den Spannungsverhaltnissen R = + 0,1; −0,5 −1,0; −1,66 und −5,0 liegen im Bereich von N = 103 bis N = 107 Lastspielen vor. Die Mehrstufenversuche wurden mit einem fur den Flugelwurzelbereich eines Jagdflugzeuges typischen Lastablaufes gefahren. Die Lebensdauer fur die Belastung wurde auch rechnerisch ermittelt und mit den Versuchsergebnissen verglichen. Auch der Einflus der anderung der Belastung im Bereich der hochsten und kleinsten Lasten des Kollektives wurde untersucht. Das Schwingfestigkeitsverhalten des Faserverbundwerkstoffes wird dem der Metalle gegenubergestellt. Fatigue Strength of Components of Fibre Reinforced Materials The constant and variable amplitude fatigue strength as well as the tensile and compressive strength of a composite material with carbon/HT fibre and epoxy matrix were experimentally determined. Unnotched dogbone shaped specimens of multidirectional CFRP with 0°, ± 45° and 90° layers were used for the tests. The results of constant amplitude testing with the stress ratios R = +0.1; −0.5; −1.0; −1.66; and −5.0 are presented. The variable amplitude testing was done using a flight-by-flight loading sequence which is typical for the wing root area of a fighter airplane. The life was also calculated and the outcome was compared with the test result. The influence of loading modifications regarding the high- and the low load-cycle ranges of the load spectrum was also examined. The fatigue behaviour of the composite material was compared with the fatigue behaviour of metals.