Compression Properties Of Composites Research Articles

Effect of heat‐treatment on compressive response of 3D printed continuous carbon fiber reinforced composites under different loading directions

AbstractThis paper investigated the effects of heat‐treatment and loading directions on compressive properties of 3D printed continuous carbon fiber reinforced composites (CCFRC). After heat‐treatment at different conditions, specimens with different stacking sequences were compressed under different loading directions. The effect of heat‐treatment on the porosity and crystallinity of composites was investigated. The porosity of short carbon fiber reinforced composites decreased but that of CCFRC increased after heat‐treatment at 200°C. The compressive properties of specimens were investigated in combination with changes in porosity and crystallinity. It was found that the compressive properties of composites usually increased with decreasing porosity induced by heat‐treatment. While the fiber direction was parallel to the applied loading direction, the yield strength of C‐CCFRC and S‐CCFRC increased from 208.1 to 281.6 MPa and from 218.5 to 264.4 MPa, respectively, though the porosity increased. After heat‐treatment at 100°C for 4 h, the crack initiation of CCFRCs was delayed during compressive tests. Besides, heat‐treatment could change failure modes of CCFRC after heat‐treatment at 200°C for 4 h. More specifically, heat‐treatment at 200°C for 4 h could result in delamination and a decrease in energy absorption of C‐CCFRC (from 7.23 to 4.05 J).

Numerical simulation on mechanical properties and damage behavior of CFRP with self-healing microvascular channels

In this study, 3D representative volume element models with microchannels were established based on measured data. And the periodic boundary conditions were moderately modified to adapt to the actual constraints of the studied object. The effects of different microvascular parameters on the tensile and compressive properties of composites were studied. And the damage pattern of carbon fiber as the main load-bearing phase under the force was analyzed. The models were verified by tensile testing and micromorphology experiments. The research results are of application to the design and analysis of CFRP laminates containing similar microchannel structures.

A review on manufacturing defects and their detection of fiber reinforced resin matrix composites

Fiber reinforced resin matrix composites are more and more widely used in aerospace and automobile manufacturing industries. However, the probability of manufacturing defects in composites is very high due to the complex physical and chemical properties of component materials and molding processes. Therefore, the research on the manufacturing defects and their detection of composites becomes important in evaluating the quality of composites. First, the formation mechanism of residual stresses, void defects and resin-rich defects in the matrix of composites are summarized. Especially, the curing of thermosetting resin and thermoplastic resin, the resin infiltration process in hot pressing, resin transfer molding and 3D printing, and resin-rich defects in molding process are described in this article. Second, the forming mechanism of fiber reinforcement defects such as fiber wrinkle and waviness in composites is introduced, and the influence of such defects on the bending and compression properties of composites is analyzed, which shows that fiber misalignment defects will seriously reduce the modulus, strength and stability of the supporting structures. Third, formation mechanism, damage causes and optimization methods of interfacial defects such as delamination and debonding in the interface between reinforcements and matrix are elaborated. Fourth, machining defects such as drilling and cutting defects are revealed. The main manifestations are delamination, tearing, and burrs, which will seriously affect the strength and reliability of the connection between components. Finally, the non-contact detection of defects in composites are shown in the article. Different detection methods can be used to measure defects of different scales to predict composite damage and life in advance. This review analyzes manufacturing defects in laminated, woven, braided, and additive manufactured composites, and summarizes common defect detection methods, also presents an outlook for composite manufacturing.

A Novel Lightweight Polyurethane Composite for Application on Ultra-High-Voltage Insulator Core Filler.

This study aimed to prepare a new lightweight ultra-high-voltage insulator core filler composite, which can solve the problem of bulkiness. In this study, rigid polyurethane foam pellets with different densities are used as lightweight fillers and polyurethane resins to compound lightweight composite materials. On accounting for working conditions, the density, insulation, heat resistance, water absorption and mechanical properties are tested. The compressive properties of composites are determined by a foam skeleton and a process. Among three kinds of composites, in which the composites with the best comprehensive performance are materials filled with pellets to a density of 0.15g·cm−3. The density, surface resistance, volume resistance, leakage current, initial decomposition temperature, water absorption, force, rupture displacement and limiting oxygen index (LOI) of composites are 0.665 g·cm−3, 1.17 × 1014 Ω, 9.68 × 1014 Ω·cm, 0.079 mA, 208 °C, 0.047%, 2262 N, 2.54 mm, and 23.3%, respectively. The ultra-high-voltage insulator core filler in this study can reduce the weight of the solid core insulator crossarm for Ultra-High Voltage (UHV) by 50–75%.

Study on the damage behavior of carbon fiber composite after low‐velocity impact under hygrothermal aging

AbstractIn this article, T800 carbon fiber/epoxy resin composite was subjected to hygrothermal aging. By analyzing the mass change, surface morphology before and after aging, infrared spectra, and dynamic mechanical properties, the effect of hygrothermal aging on the composite properties was studied. The hygrothermal aging of the composite after low‐velocity impact, the effects of environmental factors on the damaged area, and the post‐impact compression properties of composites were studied. The results showed that the saturation moisture absorption rate of the composite after aging (71°C constant temperature) was 0.88%. Upon increasing the impact energy, an indentation appeared before the inflection point at 35 J. When the impact energy was less than 15 J, aging did not affect invisible damage. Above this, the damaged area and number of internal cracks and defects in the composite were increased. After aging, the compressive strength of composite laminates with impact damage decreased obviously. During the aging stage, the residual compressive strength of the sample was the lowest in the moisture saturated state, and hygrothermal aging had little effect on the compression failure mode after impact.

Influence of polyurethane adhesives on tensile and compressive properties of ground rubber composites

Rubber from End-of-Life Tires (ELT) is often used as secondary raw material for composites. Polyurethane adhesives are widely employed in such formulations, since they bind to rubber particles effectively. In this study Ground Tire Rubber of passenger car ELT and truck tire tread buffings were used as feedstock. Toluene diisocyanate was used as a hardener for polyether-based prepolymer resin. Hardener amounts, curing durations and temperatures were varied to produce composite sheets. Scanning electron microscopy showed differences in the type of voids within the sheet and suggested that the amount of adhesive, surface wetting and curing regime could affect the composite structure significantly. Tensile and compressive properties of the composites were more dependent on the adhesive amount than curing temperature variation below 60°C. Better understanding how to control physical and mechanical properties of such composites will significantly contribute to value-added utilization of ELT as well as environmental and societal benefits.

Temperature effects on the compression behavior and failure of 3-D MWK glass fabric-reinforced epoxy composites

This article reports the temperature effects on the in-plane and out-of-plane compression behavior and failure of 3-D multiaxial warp-knitted glass fabric-reinforced epoxy composites. The damage and fracture morphology are observed from macroscopic and microscopic views, and the failure mechanism is demonstrated. The results show that the temperature has significant effect on in-plane and out-of-plane compression properties, the stress versus strain curves decline, and the properties decrease significantly with increasing the temperature. The temperature of 75°C is a key point, at which change in compression properties occurs, and at 150°C, the materials become plastic. Moreover, fiber architecture and loading modes are also important factors on compression properties of composites. The results also show that the damage and failure patterns vary with temperature, fiber architecture, and loading modes. Under in-plane compression, material A shows local 0° fiber layers delaminating and becomes softening and plasticity with increasing temperature. Material B shows delaminating between 0°, 90°, +45°, and −45° fiber layers along 45° angle and exhibits multiple delaminating at elevated temperatures. Under out-of-plane compression, material A shows multiple local shear fracture with 45° angle and experiences softening, roughness, and expansion at elevated temperatures. Material B exhibits shear brittle failure clearly, and delaminating dominates the main failure with increasing the temperature.

Graphite nanoplatelet/rubbery epoxy composites as adhesives and pads for thermal interface applications

Composites of graphite nanoplatelets (GNPs) and rubbery epoxy (RE) resins as adhesives and pads are evaluated as thermal interface materials (TIM). GNP-15 and GNP-5 (15 and 5 µm across, respectively) were loaded in RE by 3-roll milling to produce GNP/RE composites. The role of composite processing techniques on the texture, thermal and electrical conductivities and compression properties of composites was studied and compared. Scanning electron microscopy revealed uniform dispersion of GNPs in RE, regardless of loading and X-ray diffraction texture measurement showed less platelet alignment in the composites at low loadings. Thermal conductivities of 20 wt% GNP-15/RE (3.29 W/m K) and 35 wt% GNP-5/RE composite (2.36 W/m K) were both significantly higher than pure RE (0.17 W/m K). GNP/RE retained good compliance, compressive moduli at 20 wt% loading being comparable to commercial BN/silicone TIM. Although thermal contact resistance of GNP/RE was higher than for commercial paste, its interfacial thermal transport outperformed GNP/silicone (due to RE’s strongly adhesive nature) and, across thick bond lines, outperformed reported GNP-pastes. The 20 wt% GNP-15/RE thermal pad had significantly lower thermal contact resistance than other GNP/RE pads. This decreased with increasing applied pressure, being comparable to commercial BN/silicone pad. GNP/RE composites are thus promising candidates for thermal interface adhesives and pads.

Effect of Needle Punching Direction on Nonwoven Fiber Mat to the Mechanical Properties of Kenaf Reinforced Epoxy Composites Produced by Vacuum Assisted Resin Transfer Molding

This study evaluates the performance of nonwoven kenaf mat reinforced epoxy that was fabricated by vacuum resin transfer molding method. Kenaf mats were formed by carding and needle punching technique at 50 cm2 sticthing density and 1.5 cm penetration depth. The specimens were prepared from different volume fraction of kenaf mat and epoxy resin, which consist of 18% kenaf mat/ 82% epoxy resin and 27% kenaf / 73% epoxy resin. Tensile and compression properties were studied at 0o, 45o and 90o needle punching direction. The tensile properties increased with the increase of composites volume fraction and were decreased with the increase of needle punching direction degree. On the other hand, the compression properties of composites were reduced with the increase of volume fraction and needle punching direction degree. The composites properties were affected by the orientation and interlocking of fiber caused by needle penetration in direction of depth and movement direction.

Influence of cement stiffness and bone morphology on the compressive properties of bone–cement composites in simulated vertebroplasty

Vertebroplasty is widely used to treat vertebral compression fractures. Little is known about the influence of morphological parameters of the bone on the properties of the bone-cement composite. Furthermore, although generic finite element (FE) models have been suggested as a way to compute the values of these properties, their accuracy has not been established. In the experimental part of this study, we tested bovine cancellous bone and three different polymethylmethacrylate bone cements and determined six quasi-static uniaxial compressive properties of bone-cement composite specimens and 10 morphological parameters of the bone. For the FE work, we used two simulations, one being μFE and the other unit cell FE. In conclusion, we found that (1) for composite specimens, that relative contribution of the cement to the overall response of the composite increases with increasing cement stiffness; (2) the anisotropy ratio is the bone morphological property that exerts the most significant influence on the experimentally obtained compressive properties of the bone-cement composites determined; (3) the accuracy of the computed compressive properties of the composites ranged from low to high, depending on simulation method used. The largest errors, however, can partially be explained by difference in boundary conditions between the experimental testing and the simulation techniques. The lattermost finding points to the potential for simplified FE models being incorporated into automatic material mapping schemes in whole bone vertebra FE simulations.

Thermal, dielectric and compressive properties of hollow glass microsphere filled epoxy-matrix composites

Four types of hollow glass microspheres, having the density of 0.125–0.60 g/cm3, were filled into epoxy-matrix, and volume fraction of hollow glass microsphere was varied from 0% to 60%. The thermal, dielectric and compressive properties of the composites were investigated. The results show that the thermal conductivity, dielectric constant (Dk) and loss (Df) and compressive modulus and strength of the composites show decreased trend with increasing hollow glass microsphere content or decreasing hollow glass microsphere density, which indicates that the properties of the composites are mainly dependent on the characteristics of hollow glass microsphere. By comparing the experimental data and theoretical predictions, it is found that the properties of the composites, especially for thermal conductivity, are also related to the voids in epoxy-matrix. To conveniently predict thermal conductivity and Dk in the investigated materials system, theoretical models reported in the literature are analyzed and compared with the experimental data. Finally, suitable models are recommended. In addition, the thermal conductivity and dielectric properties of the composites were investigated as a function of testing temperature. This work indicates that thermal, dielectric and compressive properties of epoxy-matrix composites can be tailored by adjusting hollow glass microsphere content and density, which makes hollow glass microsphere filled composites a promising candidate in related fields.

Dynamic Compressive Response and Failure Behavior of Basalt Fibers Polymer Functional Composites Embedded with ZnO Whiskers

A type of basalt fibers polymer functional composites embedded with ZnO whiskers was prepared. The as-prepared composites exhibited good microwave absorption properties after the dispersion of ZnO whiskers in resin. The dynamic compressive properties of composites were investigated by the split Hopkinson pressure bar (SHPB) system. The macro- and micro-fracture morphology of composites was obtained by the scanning electron microscope (SEM). The experimental results showed that the as-prepared composites have excellent mechanical properties, and the compressive properties could be significantly affected by the strain rates in the in-plane direction, as well as in the normal direction. As the strain rate increased, the higher strength and elastic modulus are obtained. Under the dynamic compressive load in the normal direction, the main failure mode of composites is pure compression. On the other hand, longitudinal splitting and delamination of composites could be induced when loaded in the in-plane direction. The micro- interfacial crack, fiber fracture and plastic deformation of resin could be observed from the morphology of fractured composites.

Microstructure and compressive properties of in situ synthesized Nd 2O 3/Ti–6Si (wt.%) alloy composites

In situ Nd 2O 3/Ti–6Si (wt.%) alloy composites were synthesized utilizing the reaction from Ti, Si, Nd and SiO 2 through homogeneously melting in a non-consumable vacuum arc melting furnace. The XRD results show that the composites clearly contain α-Ti, β-Ti, Ti 5Si 3 and the in situ synthesized Nd 2O 3 reinforcements. The continuous and quasi-continuous network-shape Ti 5Si 3 + Ti eutectic cells abundantly exist, and Nd 2O 3 grows from near-equiaxed shape to dendritic shape with increase of Nd content in the composites. From the investigations on compressive properties of composites, it is deduced that the significant improvement in modulus and strength can be attributed to the presence of abundant Nd 2O 3 in the composites.

Tensile and Compressive Properties of FRP Composites with Localised Fire Damage

The effect of localised fire damage on the tensile and compressive properties of fibre-reinforced polymer (FRP) composites is investigated. A simple model based on rule-of-mixtures is presented for determining reductions to the tensile stiffness, tensile strength, compressive stiffness and compressive strength of composite panels with localised fire damage of any shape and size. The validity of the model is rigorously tested against experimental tension and compression property data for a glass/polyester composite with localised fire damage in the shape of a circle, oval, square, diamond or in a irregular shape. The model is found to accurately predict the tension and compression properties of composites with localised fire damage of any shape, and is expected to be a useful model for estimating the residual structural integrity of fire-damaged composite panels.

Mechanical properties of GRP composites with localised thermal damage

The effect of thermal damage on the mechanical properties of glass-reinforced polyester (GRP) composites is investigated. GRP panels underwent surface heating to high temperature (750-800° C) in a cone calorimeter to create localised regions of thermal damage having a circular, oval, square, diamond or irregular shape. The size of the heat-affected region ranged from 10% to 100% of the panel width. The heat damage consisted mostly of char from combustion of the polyester matrix and delamination cracks. After heating in the cone calorimeter, the GRP was cooled to room temperature and then the residual tension and compression properties were determined. Increasing the size and depth of the fire damage zone caused reductions to the stiffness and strength of the GRP. It was found that the shape of the heat-damaged region did not affect the mechanical properties. A model is presented for accurately determining the tension and compression properties of composites with localised heat damage of any shape.