Glass Vinyl Ester Research Articles

Study on friction and sliding wear behavior of woven S-glass fiber reinforced vinylester composites manufactured with different comonomers

The effect of variations in sliding velocity and applied normal load on the friction and sliding wear behavior of glass–vinylester composite (G–V) is studied by measuring the weight change and observing the surface features of worn specimens using scanning electron microscopy (SEM). The G–V composites were manufactured with Bi-directional woven S-glass fibers (65 wt%) reinforced with vinylester resin with different comonomers. Friction and wear experiments were carried at ambient conditions on a Pin on disc machine arrangement. The wear in the experiment was determined from the weight loss measured after running against steel disc at sliding velocities of 1, 2, 3, and 4 m/s and applied normal load of 10, 20, 30, and 40 N. The experimental findings show increase in specific wear rate with increase the applied load. Specific wear rate was maximum for the sample A (Styrene as Comonomer), intermediate for sample B (Methyl acrylate as comonomer), and least for sample C (Butyl acrylate as comonomer). It was also observed that increasing normal load and sliding velocity the coefficient of friction decreases. The scanning pictures show features like tendency for the matrix to adhere towards the fiber, debris formation, network of cracks, agglomeration of debris, and broken fibers depending on the load and velocity employed.

Experimental study on the axial crushing behaviour of pultruded composite tubes

This paper presents an experimental investigation on the progressive deformation behaviour of uni-directional pultruded composite tubes subjected to an axial impact load. Pultruded square and circular profiles with glass–polyester and glass–vinylester combinations were used for this study. Two types of triggering profiles were incorporated to investigate the effect of triggering on the energy absorption. All above combinations were investigated for three different impact velocities (9.3, 12.4 and 14 m/s). The crushing peak and mean load characteristics of the composite tubes with different triggering profiles and their progressive failure modes are presented. To measure the impact velocity and the impact force, a contactless method using digital image correlation technique was adopted. The effects of the geometry profile, triggering, strain rate and the type of resin on energy absorption of the composite tubes were studied in detail.

Effect of stress on the fire reaction properties of polymer composite laminates

A small-scale loading frame was used to apply tensile and compressive stresses to glass vinyl ester and glass polyester laminates in a cone calorimeter under a heat flux of 75 kW m −2. It was found, for the first time, that stress has a small but significant effect on the fire reaction properties. Increasing tensile stress increased heat release rate and smoke production while shortening the time-to-ignition. Compressive stress had the reverse effect. This was attributed to the fact that tensile stress promotes the formation of matrix microcracks, facilitating the evolution of flammable volatiles. This hypothesis is further supported by the observation that stress has the greatest effect on the early heat and smoke release peaks, with a lower effect on the final ‘run-out’ values. Stress rupture (time-to-failure) curves were produced for tension and compression. In tension, the behaviour was fibre dominated, with times-to-failure being roughly 10 times those in compression. Compressive failure involved resin dominated local fibre kinking, initiated near to the rear face of the specimen. The failure time was determined by a significant proportion of the specimen reaching its glass transition temperature.

Three-body abrasive wear behaviour of particulate-filled glass–vinyl ester composites

Abstract The incorporation of silicon carbide (SiC) and graphite fillers on three-body abrasive wear behaviour of glass–vinyl ester (G–V) composites has been investigated. Dry sand/rubber wheel abrasion tests (RWAT) were carried out at 200 rpm test speed. The tests were carried out at 22 and 32 N loads by varying the abrading distance from 270 to 1080 m in steps of 270 m. The worn surfaces were examined using scanning electron microscopy (SEM). The wear volume and specific wear rate of G–V composite reduces significantly on the addition of SiC filler. Graphite filler, however, performed poorly resulting deterioration in wear performance of SiC-filled G–V composite. The SEM studies indicate the reasons for failure of composites and influencing parameters.

Cyclic Water Absorption Behavior of Glass—Vinylester and Glass—Epoxy Composites

The cyclic water absorption behavior of vinylester (VE) and epoxy matrices and their composites with mat glass fiber is studied. The water absorption increases with the cycle. Degradation of the matrix occurs during fast drying and this leads to a very different behavior of the materials in both cycles. Epoxy-based materials absorb more water than VE-based ones due to their different hydrophilicity. The diffusion coefficient increases with temperature and it is higher in the second cycle than in the first one. The diffusion coefficients of VE composites are similar to that of the matrix, but the epoxy composites absorb water at a higher rate than the matrix. The mechanical properties decrease with immersion but the change in strength is higher than the modulus loss. The fiber—matrix interface presents good adhesion at low temperature but it decreases as temperature increases and there are more voids with the worst interface for the last cycle.

A Mechanistic Approach to Matrix Cracking Coupled with Fiber–Matrix Debonding in Short-Fiber Composites

A micro–macro mechanistic approach to damage in short-fiber composites is developed in this paper. At the microscale, a reference aligned fiber composite is considered for the analysis of the damage mechanisms such as matrix cracking and fiber–matrix debonding using the modified Mori–Tanaka model. The associated damage variables are defined, and the stiffness reduction law dependent on these variables is established. The stiffness of a random fiber composite containing random matrix microcracks and imperfect interfaces is then obtained from that of the reference composite, which is averaged over all possible orientations and weighted by an orientation distribution function. The macroscopic response is determined using a continuum damage mechanics approach and finite element analysis. Final failure resulting from saturation of matrix microcracks, fiber pull-out and breakage is modeled by a vanishing element technique. The model is validated using the experimental results found in literature as well as the results obtained for a random chopped fiber glass–vinyl ester system. Acoustic emission techniques were used to quantify the amount and type of damage during quasi-static testing.

Comparison of MCT Failure Prediction Techniques and Experimental Verification for Biaxially Loaded Glass Fabric-reinforced Composite Laminates

The inability to accurately predict the onset of failure in modern fabric-reinforced composite materials has hindered the implementation of these materials into the mainstream applications. Excessive qualification and structural testing must be performed on composite members as a result of uncertainty in the performance of the material, resulting in significantly higher expenses associated with these materials. This situation can only be improved through the rigorous development of both improved failure and material response prediction capabilities and improved experimental verification. The current study addresses these issues, as well as explores recent developments in numerical predictions and experimental techniques. A combined numerical investigation of damage initiation mechanics and experimental verification of predicted results for a woven glass–vinyl ester composite material is performed. More specifically, 18-oz biased (5 warp/4 fill rovings) plain weave E-glass–vinyl ester laminate with warp rovings oriented in [0/90]s and [0/90/±45]s configurations are investigated. Experimental data for the E-glass–vinyl ester [0/90]s laminate is summarized in a two-dimensional biaxial failure envelope. The feasibility of using thickness-tapered cruciform specimens for generating the experimental biaxial test data is also addressed. Finally, numerical predictions of failure of the fabric-reinforced laminate are developed and compared against the experimental failure envelope for the cross-ply laminate.

Failure analysis of woven laminated glass–vinylester composites with pin-loaded hole

This study deals with the bearing strength, failure mode and failure load in a woven laminated glass–vinylester composite plate with circular hole subjected to a traction force by a rigid pin. These are investigated for two variables; the distance from the free edge of the plate-to-the diameter of the hole ( E/D) ratio (1, 2, 3, 4, 5), and the width of rectangular plate-to-the diameter of the hole ( W/D) ratio (2, 3, 4, 5), numerically and experimentally. The numerical study is performed by using 3D FEM with assistance of LUSAS 13.4 finite element analysis program. Hashin failure criteria is used in the failure analysis. The woven glass–vinylester composite material is produced and the mechanical properties of the composite material are obtained from standard tests. Experimental results concerning damage progression and ultimate strength of the joint are obtained and compared with predictions. A good agreement is obtained between experimental results and numerical predictions.

Collapse of clamped and simply supported composite sandwich beams in three-point bending

Composite sandwich beams, comprising glass–vinylester face sheets and a PVC foam core, have been manufactured and tested quasi-statically. Clamped and simply supported beams were tested in three-point bending in order to investigate the initial collapse modes, the mechanisms that govern the post-yield deformation and parameters that set the ultimate strength of these beams. Initial collapse is by three competing mechanisms: face microbuckling, core shear and indentation. Simple formulae for the initial collapse loads of clamped and simply supported beams along with analytical expressions for the finite deflection behaviour of clamped beams are presented. The simply supported beams display a softening post-yield response, while the clamped beams exhibit hardening behaviour due to membrane stretching of the face sheets. Good agreement is found between the measured, analytical and finite element predictions of the load versus deflection response of the simply supported and clamped beams. Collapse mechanism maps with contours of initial collapse load and energy absorption are plotted. These maps are used to determine the minimum mass designs of sandwich beams comprising woven glass face sheets and a PVC foam core.

Effects of Hygrothermal Cycling on Properties of Glass–Vinyl Ester Composite

Hygrothermal freeze–thaw cycling exposures were performed on glass–vinyl ester composite to simulate harsh temperature and moisture conditions that the composite might encounter during their lifetime in services. The cycling conditions used were 80°C/saturated steam/48h⇔−17.8°C/dry/24 h. A characteristic moisture absorption behavior observed was that each time when the composite was taken out of the warm and humid environment and put into freezer, it exhibited a fast absorption of moisture, while the composite underwent an obvious desorption when moved from freezer to a warm humidity chamber. After the desorption at the very beginning of the thaw process, the composite showed a moderate absorption in the saturated steam at 80°C. This phenomenon was explained by the difference in thermal expansion rates of the fibers and the resin. Compression tests were conducted to investigate hygrothermal cycling effects on mechanical properties of the composite. The results showed that the degradation in compression strength for hygrothermally cycled composites was less significant than that of samples simply experienced isothermal holding at the same temperature and with the same exposure duration. Thermal analysis results indicated that glass transition temperature of the composite increased with an increase in hygrothermal cycling duration and leveled off after about 1000 h of the exposure, while thermal decomposition temperature of the composite was only slightly influenced by the hygrothermal exposures.

Fatigue of marine laminates in aqueous environments

The effect of pre-exposure in sea water on the fatigue of glass fibre composites has been investigated in fully reversed bending at constant amplitude. Stiffness monitoring during fatigue showed the usual gradual decline caused by increasing microcrack density, followed by a rapid fall due to the onset of delamination. This transition has been characterised for three resin systems and both wet and dry. Glass–polyester was the only system adversely affected by pre-exposure, which significantly reduced the number of cycles to the transition point, presumably by affecting the fibre/matrix interface. In contrast, both glass–vinyl ester and glass–phenolic resin were largely unaffected by pre-exposure. This was attributed to a superior hydrolysis resistant interface in the vinyl ester case and to a relatively poor initial interface in the case of the phenolic resin. When exposed to water over time, glass–phenolic resin and glass–polyester display rather similar fatigue performances. For polyester there was a significantly higher level of acoustic emission events in the wet samples, especially at higher numbers of cycles, indicating a greater level of ongoing damage.

Investigation on resin interphase produced near silane-treated glass fiber in vinyl ester resin

In order to investigate the reaction of silane-treated glass fiber with thermosetting resin, a set of spectra were measured near the interface between the glass fiber and vinyl ester resin using microscopic FT-IR spectroscopy. A thin-sliced sample was made from glass fiber/vinyl ester resin composite to be subjected to the spectroscopy. The spectra were obtained through a 20 × 40 μm of a mask window at each 20 μm step from the glass strand area to the matrix resin. The intensity at 1450 cm-1 of the spectra decreased from the glass strand area to the matrix resin. It was noticed, however, that the intensity kept the same value even in the matrix at a distance of 80 μm from the glass strand area. This meant that the resin in such an area was denatured by the reaction of silane to resin at the surface. This mechanism was supported by the significant size of the denatured area, which increased with amounts of silane at the surface of glass fiber.

Investigation on resin interphase produced near silane-treated glass fiber in vinyl ester resin

In order to investigate the reaction of silane-treated glass fiber with thermosetting resin, a series of spectra were measured near the interface between the glass fiber and vinyl ester resin using microscopic FT-IR spectroscopy. A thin sliced sample was made from glass fiber/vinyl ester resin composite to be subjected to the spectroscopy. The spectra were obtained through a 20 μm × 40 μm mask window at each 20 μm step from the glass strand area to the matrix resin. The spectral intensity at 1450 cm-1 decreased from the glass strand area to the matrix resin. It was noticed, however, that the intensity kept the same value even in the matrix at 80 μm distance from the glass strand area. This meant that the resin in such an area was denatured by the reaction of silane with resin at the surface. This mechanism was supported by the significant size of the denatured area which increased with amounts of silane at the surface of glass fiber.

Influence de la post-cuisson sur le comportement à long terme en fissuration sous tension dans l’eau de composites verre/vinylester

The separated and coupled effects of an hydrothermal environment and a mechanical loading on a long term behaviour of glass–vinylester composites have been studied as a function of post-curing conditions. It appears that the lack of post-curing does not affect significantly neither the water absorption nor the residual mechanical properties after a simple hydrothermal aging (even after 1000 h). On the contrary, it has been shown that a lack of post-curing turns out to be highly prejudicious for the material when subjected to the coupled effects of a same hydrothermal aging and constant mechanical loads, even low ones: lifetimes are divided by 100 because of a modification of damage processes. Moreover, it is also proved that standard hydrothermal aging tests are unable to predict the materials behaviour under hydrothermomechanical conditions (i.e. environmental stress-cracking).

LOW VELOCITY PERFORATION BEHAVIOUR OF POLYMER COMPOSITE SANDWICH PANELS

The paper describes low-velocity impact tests on square panels made from two polymer composite sandwich constructions, namely woven glass vinyl ester skins with Coremat core and woven glass epoxy pre-preg skins with honeycomb core. The impact velocity was up to 8 m s -1 with an impact mass of up to 30 kg giving a maximum impact energy of 882 J. This maximum energy gives full perforation of the panels. The panels were 0.5 m by 0.5 m with clamped but free to pull in boundary conditions. The impactor geometry considered was a 50 mm diameter hemisphere. Results are expressed in the form of energy and failure mode plots and it is shown that the energy absorbing capabilities of the panels increase with the velocity of impact. The increase in energy absorption is attributed to an increase in the core crush stress and skin failure stress at high strain rates. Some discussion is given on the influence of the energy absorbing capabilities of constituent materials on the overall energy absorption behaviour of the panel. Suggestions have also been made for increasing panel perforation energy.