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This study investigates the use of hemp/glass fiber reinforced epoxy composites for designing automotive front bumper beams, focusing on crashworthiness and pedestrian safety. The composite bumper beam model is evaluated through low- and high-velocity crash simulations and pedestrian leg form impact tests using LS-DYNA software. Optimal stacking sequences are analyzed, with high-strength glass fibers positioned on the outer layers to bear impact loads and low-density hemp fibers in the middle. The hybrid hemp (H)/glass (G) fiber composite laminate can absorb up to 90 % of the impact energy absorbed by a glass fiber composite, with a ± 45° fiber orientation, showing exceptional energy absorption capabilities. The [G(±45°) 4 , H(±45°) 4 ] S composite bumper beam offers superior impact performance, safety, and a weight reduction of 49.2 % compared to a commercial steel bumper beam. This study highlights the potential of natural fiber composites as sustainable alternatives in automotive design. [ABSTRACT FROM AUTHOR]

• The baking soda abrasive jetting method as a new surface material stripping method for glass fiber reinforced materials (GFRP) was studied. • The jetting effects of different abrasives were compared, and the advantage of low damage of baking soda abrasives was highlighted. • Chemical stripping method was used to compare cleanliness. • The surface material of GFRP stripping process was simulated using LS-DYNA. Glass fiber reinforced composites (GFRP) working in a specific environment require regular inspection and maintenance. It is necessary to remove the surface material of fiber reinforced composites to check the fracture of fibers and the damage to matrix that binds fibers in this process. In this paper, the baking soda abrasive jetting was utilized to strip the surface material of glass fiber reinforced epoxy resin (GFREP). The stripping effects of baking soda abrasive jetting technology under different jetting parameters (fiber orientation, jet angle, jet pressure) were explored, and the optimum stripping conditions were determined as parallel to the fiber, 30°, 0.4 MPa. Compared with the chemical stripping method (phenol-dichloromethane), baking soda abrasive jetting can better retain epoxy resin between glass fibers. The LS-DYNA was applied to simulate the erosion process of a single abrasive particle under the optimum stripping condition. The plastic deformation of the matrix and the slight bending deformation of the glass fiber under abrasive impact were observed. [ABSTRACT FROM AUTHOR]

• Mode I fracture process is characterized for GFRP-steel bi-material interface. • Double-cantilever beam experiments supplemented by detailed DIC measurement. • Accurate modeling of crack initiation, fiber bridging and propagation by new CZM. • Four-linear traction-separation law derived from DIC measurements and iterative FEA. Debonding is characterized as the governing failure mode in the innovative wrapped composite joints made with glass fiber composite material wrapped around steel hollow sections without welding. The prerequisite for predicting debonding failure of wrapped composite joints is to obtain fracture behavior of the composite-steel bonded interface. The mode I fracture behavior of the bonded interface was experimentally investigated using glass fiber composite-steel double cantilever beam (DCB) specimens. The crack length a and the crack tip opening displacement (CTOD) during the test were accurately measured by analyzing the digital image correlation (DIC) data while the strain energy release rate (SERR) was calculated through the extended global method (EGM). The cohesive zone modeling (CZM) was utilized in the finite element model with the proposal of a four-linear traction-separation law to simulate the mode I fracture process. An approach is introduced to determine the critical stages of the proposed four-linear cohesive law by combining accurate measurements of crack length a and CTOD, along with SERR values. The validity of the four-linear cohesive law and the introduced approach to determine the critical stages were confirmed by good agreement in both global and local behavior between the testing and the FEA results. [ABSTRACT FROM AUTHOR]

• Custom-built 3D weaving machine was used to weave 3D spacer glass fiber fabrics. • PU foaming was directly performed in the vacancies of 3D woven I-beam composites. • Up to 43 % compressive modulus increase was obtained via in-situ PU foaming. • Energy absorption was increased in LD-PUFFIC by 173 % under three-point bending. • Post-mortem mechanical test samples were monitored by fractography. 3D weaving of I-beam structures can potentially create delamination- and joint-free structures, expanding their use in engineering applications compared to metal or traditional laminated composite beams. In addition, polymeric foams can be utilized to fill the vacancies between the web and the flanges of I beams, improving the mechanical characteristics and the structural integrity with little to no weight penalty. Moreover, interposing an adhesive layer between the I beam and the foam structure can result in a more effective bonding which intensifies the structure's robustness. In this study, high-performance I-beam composites were produced by combining polymeric foams with 3D woven glass fiber composites. Low- and high-density polyurethane foams were successfully inserted between the web and the flanges of 3D woven glass fiber composites manufactured by the vacuum infusion process using the free-rise foaming method. Samples with adhesive films were also produced to assess and compare their effectiveness with the composites made solely of polyurethane foam and I beam. The increases in energy absorption capacity and compressive and flexural properties were analyzed under compressive and flexural (three-point bending) loading. The obtained results indicate that structural integrity under bending can be substantially improved with the in-situ foaming supported by adhesive layers. [ABSTRACT FROM AUTHOR]

High performance shape-adjustable structural batteries with both excellent electrochemical performances and mechanical properties, and compatible with conventional batteries and composite processing techniques, are highly attractive for next generation electrical vehicles and electrical aircrafts. Herein, a high-performance structural lithium-ion battery composite (SLBC) is developed by encapsulating commercial-available battery core materials with hybrid fiber reinforced epoxy composite laminate shells, which can be assembled into desired irregular shapes with the conventional vacuum bagging technique. Firstly, the laminate shell layout with the combination of glass fiber woven fabric (GFWF) and carbon fiber woven fabric (CFWF) is designed and optimized. Meanwhile, a PET film is employed to wrap the battery core materials, which enables processing of the SLBC with liquid electrolyte in ambient condition. The SLBC obtained demonstrates both prominent mechanical (flexural strength of 211.7 MPa and flexural modulus of 7.7 GPa) and electrochemical properties (an initial discharge capacity of 98.5 mAh/g at 0.2C, a high energy density of 314.5 Wh kg−1, and a good cycling performance) owing to the hybrid design of CFWF and GFWF as well as a sealed environment to guarantee the battery operate well. Impressively, the in-situ mechano-electrochemical measurements are assessed under the out-of-plane compressive stress and the flexural stress conditions. These results show that the SLBC under loading can maintain stable electrochemical performance even at a high out-of-plane compressive stress of 20 MPa and a high flexural stress of 150 MPa. Furthermore, the SLBC can also maintain the excellent discharge capacity when subjected to a high impact energy, which is promising in next generation electrical vehicles. Finally, the wave-like SLBC fabricated demonstrates the effectiveness in withstanding loads and driving electric fan simultaneously, which is promising in next generation electrical vehicles.. [ABSTRACT FROM AUTHOR]

Hard armour plates are used in body armour for protection against high-velocity threats. The strike face often consists of a single ceramic tile that is covered by a sheet material made of a high-tenacity fibre-composite material. During impact, the ceramic will fracture but at the same time cause erosion and fragmentation of the hard core of the projectile. The composite cover is there to improve the ballistic performance by partly maintaining the integrity of the fracturing ceramic. In this study, a new production method where glass fibre yarns were filament-wound around an alumina tile in a unidirectional 0°/90° lay-up, was investigated. Ballistic testing was conducted with a 7.62 mm armour piercing projectile. The new target design gave a remarkable increase in the V 50 ballistic limit velocity by as much as 16% compared to a traditional design where a glass fibre fabric was wrapped around the tile. A higher degree of fragmentation of the projectile steel core after perforation was also observed. The high degree of fibre alignment in the filament-wound composite, as opposed to the more wavy fibres in the fabric, is believed to be the main reason for the higher ballistic performance. [ABSTRACT FROM AUTHOR]

This paper describes the development of electrically insulating hybrid steel–composite cross-arm for medium-voltage overhead distribution power lines with three conductors. The main goal was to achieve substantial weight savings compared to a common steel cross-arm with three ceramic insulators widely used in the Czech Republic. The structure has been designed as a combination of two main composite components – a pultruded horizontal profile and a braided vertical conical tube. These components are connected by a steel locking component which also serves for attaching the whole cross-arm to common concrete utility poles. The hybrid cross-arm is conceived to insulate electrical current in the default configuration thanks to the properties of the glass fiber reinforced composite materials, yet additional insulating elements can be used to further increase the electrical insulation distance. The materials and components used for the construction are chosen by combining finite element simulations of mechanical and electrical behavior with experimental testing and verification of important characteristics on selected substructures. The final design of the cross-arm is then manufactured and subjected to long-term testing in real-life environmental conditions. The achieved reduction of weight exceeds 50% while maintaining the mechanical rigidity and strength of the steel solution as well as the required insulation properties. The future trend of the cross-arm development is aiming at the weight reduction and increase of manipulation capabilities resulting in lowering many additional costs. In this work the designed cross-arm has half the weight of the original one. [ABSTRACT FROM AUTHOR]

Hybrid carbon/glass fibers composites can possess pseudo-ductility of progressive failure through material design to achieve the function of load early warning. The printing design and forming thermal environment of parts have important influence on the pseudo-ductile behavior of hybrid fiber composites. In this paper, the hybrid continuous carbon/glass fibers reinforced nylon composites with progressive failure pseudo-ductility were prepared by additive manufacturing, and the effects of printing layer thickness, carbon/glass fibers layer ratio and forming thermal environment on the tensile properties and pseudo-ductility of hybrid fiber composites were investigated and characterized. The results indicate that the printing layer thickness has no significant impact on the tensile strength of hybrid fiber composites, the pseudo-ductility is obvious when the layer thickness of [G 5 C 2 G 5 ] is 0.075 mm and 0.125 mm. With the same material ratio, reducing the layers or setting the printing platform temperature (100 °C) can decrease defects generation to achieve the better pseudo-ductility. However, the pseudo-ductility immensely weakens using the annealing treatment of 120 °C for 3 h. The pseudo-ductility of the [G 5 C 2 G 5 ] 0.075 , [G 5 C 2 G 5 ] , [G 3 C 1 G 3 ] and [G 4 C 1 G 4 ] samples have been discovered successfully. [ABSTRACT FROM AUTHOR]

A fatigue constitutive model valid for the composite constituent will be presented in this paper. The composite behaviour will be obtained by means of the serial/parallel mixing theory that is also used as a constitutive equation manager. The constitutive formulation is coupled with a load advancing strategy in order to reduce the computational cost of the numerical simulations. Validation of the constitutive formulation is done on pultruded glass fiber reinforced polymer profiles. Special emphasis is made on the comparison between the experimental and the numerical failure mode. [ABSTRACT FROM AUTHOR]

• This paper proposes a damage-resistant Hybrid Fiber Reinforced Polymer Composites (HFRP) design method based on the interface properties. • The microscopic interface properties of composites are introduced into the investigation of interlayer interface properties. • The influence of different hybrid interlayer interfaces on the delamination damage behavior of composites is clarified. • The 3D printing technology was used to prepare specimens of the hybrid fiber-reinforced composites. In this work, the poor impact damage resistance of carbon fiber-reinforced plastic (CFRP) composites was improved by mixing carbon fibers with ductile fibers (glass fibers/Kevlar fibers). The damage behavior of five interfaces of the prepared hybrid fiber-reinforced plastic (HFRP) composites was investigated through mode-I and mode-II interlaminar fracture toughness tests and micro-droplet debonding tests. On this basis, a numerical model for predicting the impact damage of HFRP composites was established. Through a comprehensive evaluation of the impact damage resistance indexes obtained from the numerical simulations, the hybrid fiber type, hybrid ratio between different fibers, and hybrid lay-up sequence could be optimized. The specimens with optimized lay-ups were prepared by 3D printing, and the effectiveness of the numerical model was verified through low-velocity impact and compression after impact (CAI) tests. The results show that the introduction of glass fiber layers in CFRP composites can significantly improve the damage resistance of the composites. Compared with CFRP composites, when the volume fraction of the glass fibers is 25%, HFRP composites have a smaller delamination damage area (reduced by 74.08%), furthermore, the pit depth is reduced by 43.01%, the CAI is increased by 17.29%, and the strength retention rate is increased by 31.94%. [ABSTRACT FROM AUTHOR]

[Display omitted] Recently, methods for determining interlaminar shear properties have been continuously developed to achieve homogeneous stress states and avoid edge effects. In this regard, the torsion test on tube specimens represents a setup with many advantages. Therefore, fibre composites made by a winding of glass and flax fibres were produced at a new type of mandrel, resulting in tubes with a wall thickness between 370 µm (glass) and 640 µm (flax). A new method for determining the shear strain is described in the context of the torsion test. The results are in line with analogous investigations, proving the validity of the new methodology. [ABSTRACT FROM AUTHOR]

• Hybrid continuous carbon/glass fiber composites based on different laminated design have been 3D printed. • The prepared hybrid fiber composites have excellent balance of impact resistance and tensile resistance. • The tensile strength prediction model considering hybrid effect with good applicability is established and verified. Material extrusion has been applied to the preparation of continuous fiber reinforced resin composites successfully. However, due to the limitations of the characteristics of a single fiber material, the prepared composites usually can only obtain the reinforcement of a single properties. In this study, the effects of the content ratio and arrangement mode of carbon/glass fiber layers in the 3D printed composites on tensile and impact properties were investigated, and the influence of mixed fibers was analyzed by failure morphology. The hybrid continuous carbon/glass fiber reinforced nylon composite parts with good balanced tensile and impact properties were obtained in the experiment, compared with single carbon fiber reinforced nylon composites, the impact strength increased to 250% of the original, while the tensile strength lost only 7%. Tensile strength and impact strength of the printed hybrid composites with the same fiber content and different arrangement are different by 20% and 35%, respectively. The tensile strength of 3D printed hybrid continuous fiber composites was accurately predicted by establishing a model considering hybrid effect. [ABSTRACT FROM AUTHOR]

This study aims to improve the web crippling performance of pultruded glass fibre-reinforced polymer (GFRP) C sections using fibre-reinforced epoxy composite (FEC). The strengthened GFRP C sections were subjected to two loading conditions: interior-two-flange (ITF) and exterior two-flange (ETF). The parameters considered were bearing lengths, FEC strengthening length and thicknesses. Two failure modes, namely web-flange junction failure and web buckling failure were observed for the pultruded GFRP C sections under ETF loading conditions as the bearing length changed. While the combination of the web-flange junction and FEC crushing failures were observed under ITF loading conditions at 20 mm and 50 mm bearing lengths. Furthermore, the average web crippling capacity of strengthened GFRP C sections improved by up to 426 % and 488 %, in comparison to control samples under ETF and ITF loading conditions, respectively. The average web crippling capacity of pultruded GFRP C sections increased up to 45 % when the bearing length increased from 20 mm to 50 mm. The finite element (FE) outcomes showed an agreement with experimental results in the context of failure patterns, load-displacement profiles and web crippling capacities. Finally, equations were proposed to estimate the web crippling capacity of pultruded GFRP C sections strengthened with FEC. [ABSTRACT FROM AUTHOR]

Abstract This research investigates experimentally and analytically a novel one-way slab system reinforced with either basalt fiber-reinforced polymer (BFRP) or glass fiber-reinforced polymer (GFRP) longitudinal bars embedded in fiber-reinforced concrete (FRC) incorporating basalt macro-fibers (BMF). Twelve one-way concrete slab strips were prepared and tested to failure under four-point loading configuration. The investigated parameters included the type of fiber-reinforced polymer bars (BFRP and GFRP), the longitudinal reinforcement ratio ρ f (1.4 and 2.8 ρ bf , where ρ bf is the balanced reinforcement ratio), and the volume fraction of the fibers added (0, 0.5, 1, and 2% per volume). The test results demonstrated the promise of BMF to enhance the flexural performance of the tested slab strips in terms of ductility and load-carrying capacities. The formulations of different available codes and design guidelines were used to predict the test results. Comparison between the experimental and predicted results showed the adequacy of the models to predict the flexural performance of the tested slab strips. The findings of this study demonstrated the potential of using the BMF as alternatives to conventional fibers in flexural concrete members. [ABSTRACT FROM AUTHOR]

Abstract Heated GLARE, a Fibre Metal Laminate with an integrated heater element, has a promising potential as de- or anti-icing system in aircraft structures. To investigate the long-term durability of heated GLARE previously reported thermal cycling tests up to 12,000 cycles are extended up to 144,000 cycles and moisture conditioning is included. Similar testing up to 72,000 cycles is performed on FM906 glass-fibre epoxy laminates with an integrated heater element to study the influence of the aluminium layers in GLARE. In all test results the initial decrease in interlaminar shear values from 0 to about 10,000 thermal cycles is followed by a recovery phase and a resumed decline after roughly 60,000 cycles. The decrease in ILSS is expected to be caused by internal stress relief which is counteracted by the positive effect of physical ageing due to elevated temperature exposure. Thermal cycling of conditioned samples generally resulted in slightly larger decreases in interlaminar shear strength for both heated GLARE and heated FM906 glass-fibre epoxy laminates. [ABSTRACT FROM AUTHOR]

Abstract The effect of impact load with low velocity in thin-walled plates and profiles has been investigated. The paper deals with the relation between damage propagation, size and shape as a function of boundary conditions, layer arrangements and impact energy. The structures under consideration were made of eight-layer Glass Fiber Reinforced Polymer (GFRP) laminate with a quasi-isotropic, quasi-orthotropic and angle ply arrangement of layers. The standardised plates predefined to CAI tests and channel section profiles have been subjected to impact load. Based on the performed tests, the impact characteristics have been obtained and compared with the theoretical model (one degree of freedom mass-spring system). Further, despite it not being mentioned in the ASTM 7136 standard, characteristic curves were identified. It was noted that the impacts introducing matrix damages and the partial fracture of the fibres significantly change the course of the Force-Time histories, particularly after the maximum impact force is reached. [ABSTRACT FROM AUTHOR]

Abstract This paper studies the feasibility of improving structural performance of composites in the presence of stress concentrators. Matrix grading through local deposition of additive-enhanced matrices and fibre steering by varying fibrous architecture are examined independently and in combination on a glass-fibre triaxial braided composite subjected to open hole tensile test. Stiffened and toughened matrices were incorporated through precise point-wise injections of liquid reactive resin into dry preforms (Liquid Resin Printing). Fibre steering was implemented by varying the braiding angle along the length of the braided sleeve. It has been shown that these novel forms of architecture modification enable a significant improvement in composite strength through a variety of deformation mechanisms. This includes local stiffening of composite in the direct vicinity of the stress concentrator and damage accumulation away from the stress concentrators. The experimental observations are explained by using simple finite-element models. [ABSTRACT FROM AUTHOR]

Abstract The apparent density, flexural modulus and strength of hybrid laminated composites were investigated through a full-factorial Design of Experiment (DoE) approach. Laminates were manufactured by hand lay-up using nine layers of glass fibre cross-ply fabric with an epoxy matrix phase reinforced with Portland cement microparticles. A first experiment investigated the effect of the inclusion site (particles in upper four layers, lower four layers, all layers or none), curing time (7 and 28 days) and compaction method (vacuum or uniaxial pressure). The fibre–matrix volume fraction and the particle mass fraction were fixed at 48.6/51.4% and 10% respectively. A second experiment investigated two distinct fibre–matrix volume fractions (48.6/51.4 and 29.6/70.4%) and five particle mass fractions (0, 2.5, 5.0, 7.5 and 10 wt%). Particle inclusions were restricted to the upper four layers, with 28 days of curing time and uniaxial compaction. The results were analysed via Analysis of Variance (ANOVA). A significant increase in flexural modulus and strength was observed at 28 days of curing time. Enhanced mechanical properties were obtained for laminates with particle inclusions only in the upper half of the structure, manufactured with 48.6/51.4% fibre-matrix volume fraction and uniaxial pressure. Higher flexural strength was achieved for composites manufactured with 51/49% fibre–matrix volume fraction and 2.5% of particle mass fraction. These fibrous-particulate hybrid composite laminates can be considered for future secondary structural parts in lightweight engineering applications. [ABSTRACT FROM AUTHOR]

In this work, the static and dynamic mechanical properties of glass fiber reinforced polypropylene (GRPP) laminated self-reinforced polypropylene (SRPP) composite structure were studied, which includes the influences of the SG (SRPP/GRPP) internal and external positions (with two SG positions which are S/G/S, G/S/G) and the SG thickness ratios (with three SG ratios which are 1: 1, 1: 2, 1: 3). Results show that the tensile modulus improvement of laminates was obvious compared with SRPP. A hypothesis is constructed based on the elementary flexural beam theory. The flexural responses of S/G/S and G/S/G are highly similar to SRPP and GRPP respectively, the flexural strength and modulus of S/G/S are less than 50% of G/S/G. The flexural modulus of G/S/G- SG1: 3 is 111 % of GRPP. The impact responses of S/G/S and G/S/G are similar to GRPP and SRPP respectively, but more energy was absorbed in S/G/S. With the increase of SG ratio, less damage and deformation were shown in two structures, which their modes converge. [ABSTRACT FROM AUTHOR]

The knowledge of impact behaviour of heat exposed composites is very limited, even though this could be one of the critical issues for many practical applications. Therefore, the current study was conducted to investigate the effect of preheating on the impact performance of glass and flax fibre reinforced composite laminates by a comprehensive set of experiments. The composite laminates were partially damaged by heat convection (using a fan assisted furnace) and their impact properties, such as force and energy absorption, were measured under a low velocity (1.85 m/s) impact loading situation. The impact test results showed that the heat exposure at 300 °C increased the energy absorption of the glass fibre composites but reduced those of the flax fibre composites. Furthermore, an addition of ammonium polyphosphate, as a flame retardant, also incremented the absorbed energy of the heat exposed composites and significantly reduced the heat release rate, resulting in an acceptable vertical burning behaviour, that meets the aviation standard requirements. [ABSTRACT FROM AUTHOR]

An unstructured mesh Galerkin finite element method is used to obtain estimates of the viscoelastic moduli of short glass fiber reinforced polymer composites. Periodic Monte Carlo models with 125 identical inclusions are studied. Both spheroidal and spherocylindrical inclusions are considered. The estimates are compared against predictions of the dilute approximation, Mori-Tanaka (MT) and self-consistent (SC) models. It is shown that at small fiber fractions, the dilute approximation (Eshelby) model is exact. However, for the axial stiffness the dilute regime is limited to fiber volume loadings of a few tens of a percent while typical short glass fiber polymer composites have fiber loadings from 10 to 20 percent. It is found that in this concentrated regime, both MT and SC models give excellent predictions for all but the axial stiffness modulus. To assess the feasibility of reliable stiffness and vibration damping design of composite structures from short fiber reinforced polymers, Monte Carlo models with various fiber orientation distribution (FOD) states are studied. It is shown that the quick Voigt (constant strain) orientation averaging procedure gives excellent viscoelastic stiffness predictions provided that the finite element estimates are used for the required moduli of the basis FOD state with fully aligned fibers. [ABSTRACT FROM AUTHOR]

Combined with GFRP composites stress corrosion experiments, the traditional virtual crack closure technique (VCCT) is improved, and a new WDN-VCCT method is proposed to calculate the stress intensity factor (SIF) at the crack tip of GFRP composites. Its calculation formula makes up for the deficiency of the traditional VCCT method. The calculation results of the WDN-VCCT method and the calculation results of the stress extrapolation method (SEM) are compared and analyzed, and the actual accuracy of the two methods is fully evaluated. The results show that the calculation accuracy of the WDN-VCCT method is higher than that of the SEM method, the calculation efficiency is faster, and the calculation results are closer to the real value. [ABSTRACT FROM AUTHOR]

Fiber Reinforced Mortars (FRM) represents a promising technique for the in-plane and out-of-plane reinforcement of existing masonry buildings, coupling effectiveness with compatibility needs. The paper focuses on a technique consisting in the application on the masonry surface of a 30 mm thick mortar coating with Glass Fiber-Reinforced Polymers (GFRP) meshes embedded, presenting and discussing the results of several characterization tests (pull-out, lap-splice, bond and tensile tests) performed so to investigate on the tensile properties and bond performances of the strengthening system, useful for correct design procedures and suitable also for numerical modeling. The main aspects that has to be taken into account in the design of characterization tests are evidenced and the influence of some fundamental parameters (as the clamping system, the anchorage length, the boundary conditions and the sample dimensions) is discussed. Moreover, proper characterization tests permitted the estimation of the anchorage length to make effective the reinforcement and the definition of the stress-strain curve of the reinforced material subjected to tensile force. [ABSTRACT FROM AUTHOR]

Advances in new applications for composite materials create a difficult environment for an effective nondestructive evaluation as the complexity of the components increases with time. For the first time in this study, a nondestructive testing technique known as the electromechanical impedance (EMI) method is used to identify two different damage types in a composite structure. Since the EMI method is a non-model method that relies on the variations in the impedance signature that is quantified using a statistical method, data alone is insufficient to distinguish between different damage types as any changes in the structure cause the signature to change. A different method of attaching the piezoelectric transducer is combined with an averaging technique to differentiate the crack damage case from a debonding case. The study is concluded by conducting an experiment involving both damage types where the threshold values were defined for a successful damage identification process. [ABSTRACT FROM AUTHOR]

Based on a Finite Elements Analysis homogenization technique which uses a Representative Volume Element with a random distribution of the fibers, this article presents the adequate characteristics to obtain a mesoscopic model which predicts the mechanical behavior of a unidirectional glass fiber-reinforced polymer composite under monotonic transverse traction. A parametric study is made and finally an appropriate model was chosen to present the comparison between experimental and numerical results. The mesh and the RVE size/fibers size ratio are the most sensitives attributes. Considering the numerical model is in the framework of elasticity and elasto-plasticity, it is in good agreement with the macroscopic response. To improve the accuracy of the model, a further study accounting the interface and damage phenomenons as matrix cracking and fiber/matrix debonding is suggested. [ABSTRACT FROM AUTHOR]

In the paper, effect of quartz additions on the durability of a polymer composite was investigated. The tested material was based on a resin MC-DUR 1200VK with two layers of E-type glass fiber reinforcement of an area density 300 g/m2 with an emulsion binder. The quartz was added in form of powder of fraction 0.1–0.3 mm in different proportions. Durability was measured in terms of specific wear work obtained from the novel tribological tester TT-4. Its important feature was the application of friction belt instead of disc or plate, which made it possible to avoid undesirable impact of the used friction surface and wear debris on the measurement results. Apart from that, standard measurements of flexural strength, shear strength between the layers, tensile strength, proof resilience, and microhardness were performed. It was found that the examined polymer composite increased its wear resistance when it contained 1% of the quartz powder. Similarly, the best results were achieved for the composite with 1% addition of quartz for the shear strength and proof resilience. However, further increase of the addition content caused decrease of the wear resistance. On the other hand, in comparison to the composite with no quartz powder, all other properties worsened after the quartz powder was added in any proportion. Despite no clear trends in characteristics after quartz addition was present, important finding was that it was disadvantageous to increase above 1% addition of quartz powder in the composite of resin MC-DUR 1200VK reinforced with two layers of E-type glass fiber of a weight 300 g/m2 with an emulsion binder. Initial researches also demonstrated that quartz additions might have different effect on the similar composite with other sort of reinforcement. [ABSTRACT FROM AUTHOR]

This study presents experimental investigation and formulation of a new anisotropic nonlinear thermo-viscoelastic constitutive model to understand the time-dependent multi-axial responses of polyamide composites subjected to various histories of mechanical loading at several isothermal temperatures: 20 °C-100 °C. The composites were tested under uniaxial tension along 0° and 90° injection molding directions and the axial and lateral responses of the specimens were recorded. Experimental results indicate that composites exhibit pronounced time-dependent responses, even at low temperatures, and mechanical loadings, even at relatively low strain levels, cause permanent deformations and hysteretic responses. A new constitutive model that accounts for continuous microstructural changes under thermo-mechanical stimuli was formulated to describe the macroscopic anisotropic responses of the composites. The model was derived based on a multi-network approach and the microstructural changes are governed by the deformations of the composites. Elevated temperatures soften the polymers, making it easier to deform the composites, and thus accelerate the microstructural changes. The model is shown capable of describing mechanical responses of polyamide composites under various loading conditions, loading histories, and temperatures. [ABSTRACT FROM AUTHOR]

High tolerance requirements during fibre placement bear specific challenges, such as long process times for the global process, caused by fibre preparation and matrix-curing. To ensure highest quality composites, a new production process for an economic production of large structures is proposed. Therefore, the bonding of unidirectional, pre-consolidated fibre tows to a load-specific global structure is investigated. With this approach, the fibre embedding is temporary decoupled from the fibre layup process. By producing a structure from optimally aligned fibres and with a hedged bonding process, an increase of the manufacturing-rate and quality is possible. To prove a general suitability of this approach, initial basic investigations are carried out. Those demonstrate if an adhesively fixed prepreg structure can compete with a pure prepreg structure. In a first sample series, reference samples of pure prepreg and adhesively fixed prepreg samples with different adhesives are investigated. For a second sample series, the prepreg-surfaces of the adhesively fixed samples have been pretreated with different methods before bonding. Finally, pressure-tests, 4-point-flexure tests and interlaminar-shear-strength test have been carried out with all samples. All test results have been compared with the reference sample. Investigations led to initial promising results and motivate to further pursue this approach. [ABSTRACT FROM AUTHOR]

Fibre Metal Laminates have been manufactured by liquid moulding. Flow paths have been drilled to enable the impregnation through the aluminium sheets. The effect of these holes on the low velocity impact behaviour has been studied. Damage mechanisms, dissipated energy and peak force of drilled samples have been compared to those of reference samples without holes. Results show that the presence of the holes has no effect on the performance of the plate and that the internal damage is confined to the surrounding of the impact zone. When the holes are inside the impact contact zone cracks in aluminium sheets propagate through the holes, but their effect is mitigated by the fibre bridging mechanism. Holes located out of the impact contact zone have no effect in the damage mechanisms. [ABSTRACT FROM AUTHOR]

The design of glass fibre reinforced polymer (GFRP) pultruded members is often governed by deformability and buckling phenomena, preventing the full exploitation of the material potential. Hybridization – the partial replacement of the glass reinforcement with (stiffer) carbon fibres – is a possible approach to improve the performance of GFRP thin-walled profiles. This paper presents an experimental study on the structural behaviour of I-section hybrid fibre reinforced polymer (FRP) pultruded columns made of glass and carbon fibres (GF and CF) embedded in a polyester resin. A bare GFRP reference profile and four series of hybrid C-GFRP profiles, with different types and architectures of CF reinforcement, were designed, manufactured and tested under compression in three different lengths – short, intermediate and long. Particular attention was given to the buckling behaviour of the columns and to the delamination at the interface between GFRP and CFRP layers. In terms of serviceability performance, results obtained confirm the hybridization’s effectiveness in increasing the axial stiffness of GFRP compressive members. In terms of ultimate limit states behaviour, hybridization increased the load carrying capacity of the long columns, which exhibited global buckling. In opposition, for the short and intermediate columns, which failed respectively due to local buckling and a combination of global and local buckling, the load carrying capacity of the hybrid columns was lower than that of the reference profile; such worse performance seems to have been caused by the delamination of the CF layers, owing to the relatively high axial strains that developed in those columns. In a companion paper (Part 2), the experimental data presented and discussed herein is compared with predictions from numerical models and analytical formulae, which also provide further information about the delamination and progressive failure of the hybrid columns. [ABSTRACT FROM AUTHOR]

Thirty-six, four-point flexure tests on simply supported pultruded glass fibre reinforced polymer composite (GFRP) Wide Flange (WF) beams with mid-span bolted splice joints are described. The joints were fabricated with two and six pultruded GFRP splice plates. Three splice plate lengths were investigated and two bolt torques were used to tighten the bolts. Each of the twelve splice joint combinations was subjected to three repeat tests up to the serviceability deflection limit. Their load versus deformation responses were shown to be linear and repeatable. During each test loads, support rotations, splice joint end rotations and mid-span surface strains were recorded for each mid-span deflection increment. The beams’ transverse stiffnesses and splice joints’ rotational stiffnesses were derived from the test data. The variation of the stiffnesses with splice plate length, number of splice plates and bolt torque was also quantified. A simple analysis was developed for splice-jointed beams and was used to predict the transverse and rotational stiffnesses determined from the test data. It was shown that the transverse stiffnesses could be predicted to within 10%, provided a rigid-body rotational correction was applied. The correction also provided an estimate of the splice joint’s slip displacement. [ABSTRACT FROM AUTHOR]

A study on the robustness of unidirectional S-2 glass and T700S carbon fibre reinforced epoxy hybrid composites under flexural loading is presented in this paper. The flexural strengths of various stacking configurations are computed using the Classic Lamination Theory (CLT), and the computed data are fitted to a regression model. With the aid of the developed regression model, robust indices are developed for both flexural strength and specific flexural strength. The concept of robust strength is introduced to address both the strength and robustness criteria, with which a design guideline for robust hybrid composites is given. Simulation studies are conducted to demonstrate the validity of the proposed method. [ABSTRACT FROM AUTHOR]

In recent years, natural fiber as a green and renewable resources have attracted much attention to be used as reinforcement in composites. The aim of this work is to assess mechanical properties and durability in harsh environments of epoxy-based flax and glass bio-hybrid fiber reinforced plastics (bio-HFRP) composites. With the same fiber mixing ratio, the flexural and dynamic mechanical properties of the bio-HFRP composites were studied by changing the stacking order. The pure flax FRP and bio-HFRP composites were exposed to hygrothermal at 20 °C, 40 °C, and 60 °C for 28 days, respectively. The water absorption and diffusion capacity, the bending and shear properties were analyzed. Compared with the pure flax FRP, the flexural strength of G 2 F 2 s group sample was increased by 2.2 times. When exposed to the hygrothermal environment, flexural strength loss rate of the G 2 F 2 s group sample is only reduced by 4.35%, 9.00% and 11.51%, and its flexural modulus decreases 15.48%, 15.90% and 23.89%. It shown that the addition of glass fiber effectively improves the water absorption of flax fiber composites. Hybridization of flax fibers with glass fibers was a practical approach to enhance FRP laminates in hygrothermal environmental conditions after synthesizing the stacking sequence, mechanical properties and aging resistance. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and modelling study that determined the influence of thickness on the softening-rate, composite damage initiation and propagation, and structural survivability of composite structures in fire. Fire-under-compression load tests were conducted using glass fibre reinforced vinyl-ester laminates of varying thicknesses to quantify the influence of thickness on fire structural survivability. The matrix softening and degradation rates decreased as the composite thickness increased. The laminate thickness variations had a strong influence on the fire-under-compression load performance and failure mode. The analysis reveals complex multi-mode failure mechanisms involving global buckling and transitioning into shear dominated failure as the composite thickness increased. A thermal–mechanical model that can predict the time-to-failure of glass fibre reinforced composite subjected to a combined compression and fire load was developed and its validity was assessed by comparing the theoretical predictions to the experimental data. [ABSTRACT FROM AUTHOR]

Composite materials provide high strength and stiffness-to-weight ratios and adjustable directional material properties. As a result, a growing application of composite materials in weight-relevant and complex-loaded structures is noticeable, especially, for the production of high-speed rotors. However, their material complexity, their parameter scatter and unpredictable impact events contribute to the prediction uncertainty of the operational capability. The in situ measurement of damage-sensitive features can provide information for reliable simulation models. Such models are a prerequisite for the analysis of the damage behaviour in practice-relevant loading scenarios. For this purpose, a novel optical measurement system is introduced measuring the rotor deformation. The system offers a measurement rate of 1.6 kHz with an 7 μm error independent on the rotational speed. Furthermore, the rotor vibration response was identified using a combined excitement-measurement system for different rotational speeds. Both measurement systems were successfully applied on a glass fibre-reinforced composite rotor. Based on the experimental results, a simulation model was adjusted using an advanced mixed numerical–experimental technique. A good compliance between experimental and simulation results was identified for rotor-typical stress states. In addition, the rotor temperature is shown to have a significant influence on the model accuracy and has to be incorporated in future models. [ABSTRACT FROM AUTHOR]

Repairs made with composite patches on impact damaged fiber reinforced composite pipes offer distinct advantages over traditional repairs in addition to reduced cost. In this study, effects of number of patch layers on the burst pressure of low velocity impact damaged tubes that have been repaired with composite patches were investigated. The tubes were pressurized up to 32 bar prior to impact. The pre-stressed glass fiber reinforced plastic tubes were damaged by applying low velocity impacts at different energy levels (5, 10 and 15 J). The damaged areas of the affected tubes were repaired with 2, 4 and 6 layers of glass/epoxy fabrics. The repaired tubes were then failed catastrophically by being subjected to monotonic internal burst tests based on ASTM D 1599–99 standards. Changes in the tubes’ burst pressures were recorded and the resulting damages on the tubes were studied. It was found that, for all the energy levels employed in this study, a six-layered patch repairing is suitable for the retrofitting of impact damaged tubes. [ABSTRACT FROM AUTHOR]

Pultruded glass fibre reinforced polymer (GFRP) composite wide flange (WF) beams were fabricated with mid-span splice joints. The joints comprised: two or six GFRP plates bolted to the flanges. The bolts were torqued to 3, 20 and 30 Nm. The 2.9 m span simply supported spliced beams were tested in symmetric three-point flexure. Each beam was subjected to three load – unload cycles and loads, mid-span deflections, support rotations and splice plate surface strains were shown to be linear and repeatable. Spliced beam transverse stiffnesses were quantified as functions of bolt torque for both splice plate configurations and were shown to increase linearly as the bolt torque increased. Transverse stiffnesses of unspliced and six-plate bolted/bonded splice jointed beams were compared and the stiffness of the splice bonded beam was shown to be about 47% stiffer than the splice bolted beam with a bolt torque of 3 Nm. [ABSTRACT FROM AUTHOR]

Fiber reinforced polymer composites have great potential to replace steel for bridge cables, underground oil extraction and ocean engineering owing to light weight, high strength and desirable corrosion and fatigue resistances. How to reduce the material cost and improve the durability through the reasonable material design is significant to promote the engineering application. In the present paper, two kinds of carbon/glass fiber hybrid plates were developed including the fiber random hybrid (RH) and core–shell hybrid (CH) modes. The exposure of sustained bending loading and water immersion as long as 360 days was conducted to investigate the effect of fiber hybrid mode and bending loading on the mechanical properties. The results showed the synergetic effects between the carbon and glass fibers can be fully developed through the random fiber hybrid mode. Furthermore, the incongruous bearing behavior and stress concentration of carbon/glass fiber/resin interface were largely relieved, which contributed to higher mechanical properties. Compared to CH plate, the maximum increase percentages of tensile and flexural strength for RH plate after 360 days were 51.3% and 39.7%, respectively. Higher bending loading level resulted in the fast formation of microcracks, which provided more storage space for the water molecule and accelerated the resin hydrolysis and interface debonding of fiber/resin. Finally, the long-term life prediction of hybrid plate in three typical bridge service environments showed the RH plate has superior corrosive resistance compared to CH plate. The retentions of tensile and flexural strength for the service time of five years were close to 30–40% and 50–60%, which provided the durability guideline based on fiber hybrid design for the engineering applications. [ABSTRACT FROM AUTHOR]

• Hygrothermal environment has a significant effect on the strength of glass fiber composites. • Hygrothermal environment has little effect on the tensile stiffness of glass fiber composites. • Hygrothermal environment shortens the damage process of glass fiber composites under tension. • Hygrothermal environment changes the failure diagram of glass fiber composites under tension. In this paper, a progressive damage model considering hygrothermal effect is established. Taking high strength glass fiber composite plate as an example, the progressive damage model of open-hole composite plate is established, and the ultimate tensile and compressive strength at room temperature, dry state and hygrothermal environment are predicted. The model was verified by comparing with the experimental results. The results of numerical simulation and experiment show that the hygrothermal environment has a significant effect on the ultimate strength of open-hole composite plate. The tensile ultimate strength of open-hole composite plate decreases about 39% and the compressive ultimate strength decreases about 35% at 70 °C and equilibrium moisture absorption. The results show that hygrothermal environment has little effect on the tensile stiffness of open-hole composite plate, and the tensile modulus decreases by 6% at 70 °C and equilibrium moisture absorption. According to the numerical results, the hygrothermal environment can shorten the damage propagation process of the open-hole composite plate under tensile load, but does not affect the damage propagation process under compression load. The hygrothermal environment can change the macro failure diagram of the open-hole composite plate under tension from "X" to "I", but does not affect the macro failure diagram of the open-hole composite plate under compression. [ABSTRACT FROM AUTHOR]

This work examines the influence of kerosene flame exposure on the residual mechanical behavior (tension and compression) of hybrid quasi-isotropic composite laminates consisting of carbon/glass fibers and a PEEK thermoplastic matrix. The influence of a kerosene flame exposure (116 kW/m2 and 1100 °C), on the composites structural integrity was examined as a function of exposure time (5–10-15 min). The changes in the tensile and compressive properties (axial stiffness and strength) were compared with respect to the virgin materials (experiencing no prior flame exposure). The discussions on fire- and mechanically-induced damage mechanisms are supported by fractographic analysis of specimens. It is therefore possible to better understand how the fire-induced damages within the laminates micro- and meso-structures modify the mechanical behavior of flame-exposed laminates. Regardless the exposure time, the kerosene flame exposure involves in-plane and through-thickness temperature gradients, which ultimately create two well defined areas within the laminates: an extensively delaminated one (the one close to the exposed surface) and a relatively well preserved one (close to the back surface). From the present work, it is possible to conclude that the mechanical properties in tension are severely affected (-50% in stiffness and −70% in strength) by prolonged exposures to kerosene flame (15 min) with respect to as-received specimens. When compared to the 5 min case, flame exposure time (ranging from 5 to 15 min) seems to have little very influence on tensile properties and the effect is moderate on compressive properties. The barrier formed by an extensive thermally-induced delamination contributes to relatively preserve the structural integrity of the plies close to the back surface. The mechanical loading is taken up by the 0° fibers in non-delaminated areas of the specimens, resulting in preserving the residual mechanical in tension and in compression. [ABSTRACT FROM AUTHOR]

Abstract: Liquefied natural gas (LNG) is mainly carried by membrane type LNG ships, whose cargo containment system is composed of dual tightness barriers and two insulation boards. The insulation board should have not only cryogenic reliability against thermal load, but also high thermal insulation performance for safe and efficient transportation of LNG. Although polyurethane foam (PUF) has been widely used for the insulation board due to its low production cost and relatively good thermal and mechanical properties, the cryogenic reliability of PUF is a remaining concern in marine fields due to its brittleness at cryogenic temperatures. In this work, the PUF was reinforced with chopped E-glass fiber because of its good dispersion and distribution characteristics. The compression, tension and the fracture toughness test were conducted with respect to the amount of the chopped E-glass fiber both at the room (25°C) and cryogenic (−150°C) temperatures. From the experimental results, it was found that the chopped E-glass fiber reinforcement increased the fracture toughness of the PUF much, especially at the cryogenic temperature. Therefore, the PUF reinforced with chopped glass fibers will improve much the reliability of the LNG cryogenic containment system during the voyage of LNG ships. [Copyright &y& Elsevier]

Abstract: A multiaxial fatigue damage model for fibre reinforced polymer composite materials is presented. The model combines (i) fatigue-induced fibre strength and modulus degradation, (ii) irrecoverable cyclic strain effects and (iii) inter-fibre fatigue. The inter-fibre fatigue aspect is based on a fatigue-modified version of the Puck multiaxial failure criterion for static failure. The model is implemented in a user material finite element subroutine and calibrated against fatigue test data for unidirectional glass fibre epoxy. A programme of uniaxial fatigue tests on quasi-isotropic glass fibre epoxy laminates is presented for validation of the novel fatigue damage methodology. The latter is successfully validated across a range of stress levels. [Copyright &y& Elsevier]

Computational micromechanics analysis of short fiber reinforced polymer (SFRP) composites is of great significance to provide an understanding of the relationship between microstructures and complex mechanical behaviors of the materials. In this study, an innovative computational framework is proposed for the analysis of SFRP composites considering multiple constituents and different failure modes. Firstly, a unit cell model composed of fiber, matrix and interface is built up to analyze the nonuniform stress distribution around a fiber. Secondly, a reconstruction algorithm is proposed to provide geometrical information of fiber distributions with arbitrary orientation state and a wide range of fiber length and fiber volume fraction. With the help of embedded element method (EEM) and MATLAB script, RVE models embedded with numerous unit cells are established. The predicted properties of the RVE models of short glass fiber reinforced polypropylene (SGFRPP) are verified by an orientation average method and a modified rule of mixture, respectively. The progressive damage procedure of the material is predicted and the damage initiation and evolution are for the first time quantitatively characterized by the extent variables of different failure modes. An in situ microtomography tensile test are performed to prove the feasibility and accuracy of the proposed framework. [ABSTRACT FROM AUTHOR]

Glass fiber-reinforced composites have been used as a secondary barrier structure in LNG cargo containment systems (CCS) for their excellent strength and corrosion resistance. However, during LNG transport, the tanks experience periodic thermal and bending stress because of the cryogenic environment. These conditions degrade the mechanical properties of the composites in the CCS. In this study, finite element analysis was conducted using the mechanical properties of each composite. A quasi-static tensile test was carried out, and the coefficients of thermal expansion were used to obtain the mechanical properties. To verify the reliability of the numerical analysis, modeled structural unit specimens were manufactured, and 3-axis strain gauges were attached to measure thermal strain under cryogenic conditions. Validation of the strain between experiments and computation was performed, and the finite element analysis was conducted based on the observed mechanical properties and their reliability. [ABSTRACT FROM AUTHOR]

The fiber-reinforced composite (FRP) shaft need to consider vibration performance of the transmission system to improve work efficiency, comfort, service life and safety. The fiber materials and tubes containing metal connectors are important parts of the FRP shaft so that the study on the vibration performance of these two key components is of great significance for an in-depth understanding of the vibration performance of shafts. The finite element analysis (FEA), pulse vibration excitation technique (PVET) and formula computing were used to study the effect of the vibration characteristics of shafts. This study revealed that increasing the modulus of the fiber is one of the effective methods to increase the natural frequency of the FRP tube and the damping ratio of the carbon FRP tubes were slightly smaller compared with basalt and glass fiber. The FEA of FRP tube results were not distinct from the measured and calculated results so that these FEA results were relatively reliable. The damping of the tube with metal flanges at both ends were weaken compared the FRP tube. This work will be of great significance to the optimization design of the vibration performance of FRP shafts. [ABSTRACT FROM AUTHOR]

The GRP (Glass Reinforced Polymer) composite pipes produced by filament winding technique are used in many fields such as the transmission of pressurized chemical liquids, industrial liquids, oil and natural gas transmission and construction materials. GRP composite pipes may be subjected to low velocity impacts for various reasons both during installation and service. The impact on the GRP composite pipe wall may lead to some nonvisible damages such as matrix crack, fiber damage, delamination and inter-layer separation. Composite pipes suffered strength loss due to these damages caused by impact cannot support the expected strength values during service. Pipes with three different diameters (Ø54, Ø72 and Ø96 mm) were produced to investigate the damage caused by low velocity impact and to determine the effect of these damages on the strength losses of the composite pipe. In order to investigate the influence of low velocity impact damage, the produced pipes were subjected to impacts at the velocity of 1.5, 2, 2.5 and 3 m/s according to ASTM D 7136 and preliminary damage was formed. During low velocity impact tests, Force-Time, Force-Displacement and Energy-Time graphs were obtained and dynamic behavior of the pipes were examined. With the increase in diameter; it has been observed that the effect of low velocity impact is reduced and the damage after impact transformed into delamination damage rather than multiple damage. [ABSTRACT FROM AUTHOR]

Abstract: The behaviour of structural fibre composite sandwich beams made up of glass fibre composite skins and phenolic core material was investigated under three-point short beam and asymmetrical beam shear tests. The effect of the shear span-to-depth ratio (a/D) on the strength and failure behaviour of the composite sandwich beams was examined. The results showed that with increasing a/D ratio, the failure load of the sandwich beam is decreasing. On the contrary, the coupling effect of flexural stresses increases with increasing a/D ratio. Noticeably, the fibre composite sandwich beams tested under asymmetrical beam shear exhibited higher failure load compared to beams tested under short beam shear. Analysis showed that the shear stress in the core is more dominant than flexural stress when the a/D ratio is 1 for the sandwich beams under short beam test and 1–3 for the sandwich beams tested under asymmetrical beams shear test. The proposed prediction equation which accounts for the combined effect of shear and flexural stresses due to the changing a/D ratio, presented a good agreement with the experimental results, showing that it can reasonably estimate the failure load of structural fibre composite sandwich beams. [Copyright &y& Elsevier]

Abstract: This paper presents an experimental and analytical study about the mechanical response at elevated temperature of glass fibre reinforced polymer (GFRP) pultruded profiles. The paper first describes results of DMA and DSC tests that were used to evaluate the glass transition and decomposition processes of the GFRP pultruded material. The paper then describes an extensive study about the tensile, shear and compressive responses of the GFRP material at temperatures varying from 20°C to 250°C. In these tests the mechanical responses of the GFRP material as a function of temperature were assessed, namely the load–deflection curves, the stiffness, the failure modes and the ultimate strength. Results obtained in these experiments confirmed that the mechanical performance of GFRP is severely deteriorated at moderately high temperatures, particularly when loaded in shear and compression, owing to the glass transition of the resin. The final part of this paper assesses the accuracy of different empirical models and one phenomenological model to estimate the tensile, shear and compressive strengths of GFRP pultruded material as a function of temperature. All empirical models, including a function based on Gompertz statistical distribution suggested in the present paper, provided accurate estimates of tensile, shear and compressive strengths as a function of temperature. The phenomenological model was less accurate and in general provided non conservative estimates of material strength. [Copyright &y& Elsevier]

Abstract: This paper deals with the study of water diffusion in unidirectional composite associating experimental data, analytical and numerical models. A fibre/matrix interphase with a gradient of molecular mobility is characterized by microthermal analysis. The fibre dispersion observed by optical microscopy shows an important heterogeneity and many contacts between fibres. This particular fibre distribution as well as the interphase thickness have been considered to model our composite microstructure accurately. Diffusion kinetic parameters from water absorption measurements on both the resin and the UD composite were then used in the finite element analysis of the composite. The comparison between experimental data, analytical and numerical models show the influence of fibre distribution and interphase properties on water diffusion kinetic. An average water diffusion coefficient is then identified for the interphase. [Copyright &y& Elsevier]

Abstract: In this work, unidirectional multi-scale, carbon nanostructure (CNS)–glass fiber–epoxy, composites were manufactured using a novel in-line continuous production scalable chemical vapor deposition based CNS manufacturing process. The processing parameters peculiar to the growth system, specifically growth chamber temperature, catalyst concentration and line speed, were varied to observe the effect on the CNS growth and parent filament degradation. Unidirectional tension and compression tests were conducted to measure the strength and modulus in the filament direction and failure mechanisms of the hybrid materials identified. Based on the results of tensile tests, gains in tensile strength and tensile modulus are achieved through a uniform coverage of short CNS. The greatest increases in CNS-enhanced composite compressive strength can be achieved through the combination of low weight percent CNS on the fiber and minimal parent filament environmental degradation. For stiffness governed applications, these CNS-enhanced composites may not provide the ideal solution. However, applications which demand significant deformation prior to failure or damage tolerance can benefit from the properties afforded by these CNS–fiber–epoxy composites. [Copyright &y& Elsevier]