Impact Resistance Of Composite Laminates Research Articles

Low‐velocity multiple impact damage characteristics and numerical simulation of carbon fiber/epoxy composite laminates

AbstractLow‐velocity impact damage is one of the main defects of composite laminates, which seriously affects the bearing capacity and service life of composite laminates. Multiple impact experiments of carbon fiber/epoxy composite laminates were carried out under different impact energies. The finite‐element model was established according to the experimental conditions. The impact damage mechanism of laminated plates was studied by means of simulated damage cloud image, water immersion ultrasonic C‐scan, and computed tomography. The results showed that the matrix damage occurred mainly during the whole impact process, and the tensile damage of the matrix was dominant. As the number of impacts increased, the impact resistance of composite laminates decreased and the damaged area increased, with the second impact having the greatest influence on the degree of damage to the laminates; multiple impacts with low energy were easy to cause delamination at the top of the laminated plate. With the increase in impact energy, the damage at the bottom of the laminated plate was more serious, and the propagation mode of delamination damage in laminates changed from top‐bottom to bottom‐up.Highlights Establishing a multiple impact finite‐element model for composites. Accurately predicting the impact mechanical response of composites. Revealing multiple impact damage evolution of composites by simulation.

Edge-on impact behaviors of helicoidal fiber arrangement of composite laminates

To improve the low-velocity edge-on impact resistance of composite laminates, a helicoidal fiber arrangement of composite laminates (HFACLs) emulated from the micro-structure of the dactyl club is proposed. A finite element method with the progressive intralaminar and interlaminar damage model is adopted for verifications and investigations. Based on the verified model, the failure behaviors and reinforcement mechanisms of the HFACLs subjected to edge-on impact load are extensively revealed. To explore the effect of the rate of variation of helix angle, three types of helicoidal configurations with different derivatives are designed, including helicoidal-Sinusoidal (HS), helicoidal-Linear (HL), and helicoidal-Exponential (HE). From the predicted results, the HFACLs have a higher resistance load and shallower penetration depth. The maximum increase in resistance load and reduction in penetration depth can reach 50.66% and 26.37%, respectively. The laminate with a slight helix angle (HS laminate) variation rate has better edge-on impact resistance. In addition, the effects of impactor ellipticity and impact kinetic energy on edge-on impact response are studied. This study deepened an understanding of the edge-on impact failure mechanisms of the composite laminates and provided a design guideline for the edge-on impact-resistant design of composite laminates.

Research on low-velocity impact characteristics of Z-pin reinforced quartz/phenolic laminates

The problem of in-plane damage caused by dynamic impact loading of composite laminates can be enhanced by implanting Z-pins. The effect of Z-pin implantation on the impact resistance of composite laminates is investigated experimentally, and the damage process is analyzed by establishing a low-velocity impact finite element model of Z-pin reinforced laminates. The test results show that the maximum impact contact force of Z-pin reinforced laminates can be increased by 8.23%, and the maximum contact force and absorbed energy of Z-pin reinforced samples both increase gradually with the increase of impact energy. The simulation results show that with the increase of impact energy, the expansion of impact damage is hindered by the Z-pin, and it reduces in-plane matrix damage. The expansion path of the interlaminar crack changes when it reaches the Z-pin enhancement area, and the shape of the interlaminar damage changes from circular to elliptical.

Impact of Al2O3 on mechanical properties of basalt/kenaf composite

Composites that make use of both natural & synthetic fibers reinforced with polymer matrix have found numerous industrial applications, thanks to their desirable properties such as high strength to weight ratio, minimal cost, higher modulus, biodegradability, and eco-friendliness. When a composite contains two or more reinforcement materials, it is categorized as a hybrid composite material. Basalt fiber hybridization with natural fiber can lower the cost and density of the composite while increasing it’s tensile, flexural, and impact strengths. Fiber-reinforced composites have received a lot of interest in material science and applications recently because they outperform more conventional materials like metals in terms of strength and stiffness to weight ratios. This research aims to investigate the effects of adding aluminum oxide (Al2O3) on the tensile, flexural, and impact resistance of composite laminates made of kenaf, epoxy, and basalt, respectively. The variation in mechanical properties is due to the different epoxy and filler weight ratios. The failure characteristics of the constructed samples are also determined and compared across different filler loadings of Al2O3.

A Bond-Based Peridynamic Model with Matrix Plasticity for Impact Damage Analysis of Composite Materials

The prediction of damage and failure to fiber-reinforced polymer composites in extreme environments, particularly when subjected to impact loading, is a crucial issue for the application and design of protective structures. In this paper, based on the prototype microelastic brittle (PMB) model and the LaRC05 composite materials failure model, we proposed a bond-based peridynamic (BB-PD) model with the introduction of plastic hardening of the resin matrix for fiber-reinforced polymer composites. The PD constitutive relationships of the matrix bond and interlayer bond under compressive loading are considered to include two stages of linear elasticity and plastic hardening, according to the stress-strain relationship of the resin matrix in the LaRC05 failure model. The proposed PD model is employed to simulate the damage behaviors of laminated composites subjected to impact loading. The corresponding ballistic impact tests of composite laminates were carried out to observe their damage behaviors. The PD prediction results are in good agreement with the ballistic experimental results, which can verify the correctness and accuracy of the PD model developed in this study in describing the impact damage behaviors of composite materials. In addition, the characteristics and degree of damage in composite laminates are analyzed and discussed based on this PD model. The difference in the impact resistance of composite laminates with different stacking sequences is also studied using the numerical simulation results.

Low-velocity impact resistance behaviors of bionic double-helicoidal composite laminates

To improve the low-velocity impact resistance of composite laminates, a bionic double-helicoidal composite laminate (BDHCL) emulated from the micro-structure of coelacanth scales is proposed. The micro-structure is a double helicoidal Bouligand structure in which two adjacent collagen layers are arranged into an orthogonal bilayer and then rotating at a small helix angle. Three types of helicoidal configurations with different derivatives are designed, including sine rotation angle (SRA), linear rotation angle (LRA), and exponential rotation angle (ERA). The progressive intra-laminar and inter-laminar damage model is adopted to capture the failure behaviors of material. The impact behaviors of BDHCLs with several helix angles and included angles of the bilayer are studied. The results show that the double-helicoidal Bouligand structure has a higher resistance load and shallower penetration depth. The impact resistance of ERA laminate has the maximum improvement among the above three types of helix angle. A certain included angle of bilayer for the BDHCL will exhibit excellent impact resistance.

The effect of cooling rates on crystallization and low-velocity impact behaviour of carbon fibre reinforced poly(aryl ether ketone) composites

Crystallization of poly(aryl ether ketone) (PAEK) plays an important role in the impact resistance of composite laminates but it is still unclear how the cooling rate affects the performance. In this paper, carbon fibre (CF) reinforced new copolymer PAEK and commonly used poly(ether ether ketone) (PEEK) were fabricated by furnace cooling and water cooling. The effects of cooling rates on the crystallization behaviour of thermoplastics, interfacial bonding strength, interlaminar fracture toughness and low-velocity impact performance of composites were studied. Results show that the crystallization and the crystalline size of PAEK are smaller than those of PEEK at the same cooling rate. In composites, the lower crystallinity and smaller crystals of the matrix are conducive to improving the matrix ductility and interfacial bonding strength. Under the water-cooling condition, the impact damage area CF/PAEK is about 71% lower than that of CF/PEEK, while the CAI is about 14% higher.

Experimental Research on the Thermal-Consolidation Compound Forming of Thermosetting Fiber Metal Laminates Design for Complex Structures with Variable Curvature

The glass fiber-reinforced metal laminates (GLARE) cannot be used to form complex laminate structures in the aerospace industry, because there is substantial variation in the plasticity of the heterogeneous materials. Hence, a compound process for composite materials based on the thermoforming technology for aluminum alloy and fiber-reinforced metal laminates (FMLs)-forming technology was proposed; it contains solution heat treatment, thermoforming, quick cold die quenching, artificial aging integrated process (HFQ), and the thermal consolidation of fiber-reinforced metal laminates, and it is named the HFQ-FMLs forming process. In order to test and judge the effect of the heat treatment on the properties of the materials obtained by the new technology, the pure metal sheet and the three kinds of HFQ-FMLs composite laminates fabricated with the different layup method were assessed with the Vickers hardness test and the Charpy impact test at the same time, and they were labeled #1, #2, #3, #4, respectively. In the Charpy impact test, in order to obtain accurate data, the shape and fixing position of the specimen was optimized so that the gap direction was parallel to the loading direction. After the heat treatment, the properties of the aluminum alloy were improved, the hardness will affect the energy absorption of the laminates, and the relationship between the thickness, hardness and impact properties will be analyzed. The hardness test results are 39.9 HV, 37.5 HV, 37.4 HV, 37.1 HV which indicates the pure metal sheet had the greatest hardness, and the greater the thickness of fiber layer, the lower was the hardness of the HFQ-FMLs composite laminate. The impact resistance of the HFQ-FMLs composite laminates was about two times of the pure metal sheet for the same thickness, and the values are 2.3 J, 4.8 J, 4.8 J, 4.8 J, respectively. In addition, the method of laying the fiber layer had no effect on the impact resistance of the composite laminates. For the novel composite laminates subjected to different cutting processes, the scanning electron microscope (SEM) results for the incision morphology suggest that the water cutting process ensures the structural integrity of the composite laminates after the edges’ and holes’ cutting procedures, and the performance maintains continuity.

Effects of Fiber Architectures on the Impact Resistance of Composite Laminates Under Low-Velocity Impact

Effects of Fiber Architectures on the Impact Resistance of Composite Laminates Under Low-Velocity Impact

Application of genetic algorithm to optimize the impact resistance of composite laminates

The impact resistance of composite fan hood is of great significance to improve the safety of engine. Taking the fiber reinforced resin matrix composite laminate for Aeroengine fan case as the research object, the maximum loss kinetic energy of impact body as the objective function, and the fiber ply angle as the design variable, the impact resistance of the fiber reinforced composite laminate was optimized. ABAQUS finite element software is used to simulate the high velocity impact of composite laminates, and genetic algorithm is used to optimize the design, and the optimal stacking method is obtained. Through the optimization design, the impact resistance of fiber reinforced composite laminates has been greatly improved.

Low velocity impact behavior of interlayer hybrid composite laminates with carbon/glass/basalt fibres

This work investigates the effects of carbon/glass/basalt hybridization and fabric structure on the low velocity impact resistance of fibre reinforced plastic composites. Interply hybrid specimens used in the study were fabricated in a sandwich-like stacking sequence using a vacuum assisted resin infusion molding technique. Low velocity impact tests were carried out to study the effects of hybridization and fabric structure on the impact resistance of composite laminates. A continuum damage mechanical model was developed and validated for non-hybrid woven fabric laminates at different impact energy levels. Residual damage characteristics were identified using a 3D surface scanning system and an X-ray computed tomography (CT) method. On the basis of the experimental results, numerical simulation was also conducted to explore the damage mechanisms of the hybrid laminates. The study showed that: (a) hybrid laminates with carbon fibre as the core exhibited superior impact resistance for sandwich-like stacking sequence; (b) similar impact behaviors appeared for carbon laminates hybridised with either basalt or glass fibre; (c) for basalt fibre, weave fabric composite laminates exhibited better energy absorption capability and deformation resistance than cross-ply laminates reinforced in unidirectional fabrics.

Layup structure effect on the composite laminate impact resistance: experimental and finite element studies

Four kinds of sandwich laminates with different layup structures and same thickness are designed and fabricated by autoclave and heat pressing process respectively. The impact tests of four composite laminates were carried out to compare the impact resistance of composite laminates with different ply structures. The impact finite element model is established, and the impact process is simulated by the finite element method. To some extent, the impact failure mechanism of composite laminates and their impact failure results have been obtained.

Effect of Z-pinning on the impact resistance of composite laminates with different layups

The paper presents the results of an experimental investigation into the effect of Z-pinning on the impact resistance of composite laminates with different multi-directional layups. Unpinned and pinned [02/902]s, [02/±45]s and [0/±45/90]s carbon/epoxy samples were subjected to low-velocity impacts resulting in damage severities ranging from barely visible damage to full laminate penetration. The responses to impact of the laminates were characterized in terms of damage evolution, load-carrying capacity, and resistance to perforation and penetration. It was found that even though Z-pins are not capable of delaying the onset of delamination, they significantly reduce delamination size for high-energy impacts. Z-pinning improves the resistance to perforation and penetration of [02/902]s, laminates, while it does not significantly affect that of [02/±45]s and [0/±45/90]s samples. The dependence of the efficacy of Z–pins on the laminate layup is attributed to the different distribution of the delaminations through the thickness of the investigated laminates.

Evaluation of microdamage initiation in Z-pinned laminates by means of automated RVE computations

Z-pinning was originally designed to improve the delamination toughness and the impact resistance of composite laminates. However, there is extensive experimental evidence that this improvement is accompanied by a reduction of the in-plane properties. The main mechanisms responsible for this deterioration are the local change in fiber content, fiber distortion, and the inclusion of resin-rich regions near the Z-pin. The shape of these geometrical features strongly depends on the laminate stacking sequence and on pin parameters such as pin diameter, pin content, and initial pin inclination angle. Their shape complexity challenges analytical modelling approaches which are currently used to generate RVE geometries for simulations.A computational approach is presented to generate such geometrical models. Resin-rich regions are modelled by initially straight discretized lines which are gradually shaped by a set of geometrical operations mimicking pin insertion, pin rotation and fiber deflection. Fiber distortion is modelled in a post-processing stage in cross-sections accounting for the preservation of the amount of fibers. These models are then transformed into finite element mechanical models in order to investigate how local fiber volume fraction changes, fiber misalignment, or distortions in reinforcement due to pin rotation, affect the global stiffness and local stress concentrations.

Energy absorption of repaired composite laminates subjected to impact loading

Abstract The utility of composite materials has significantly increased in various industries, especially in aerospace industry, because of their excellent properties. Repair or reinforcement of damaged part of the structure is essential to improve its service life. In this work, the damaged area of the glass/epoxy composite is machined as elliptical steps in each layer for patch layer bonding. For ‘n’ layer laminates, ‘n + 1’ patch layers are bonded in the machined steps and free surface of the laminates. It is necessary to understand the impact resistance of composite laminates that are used in aerospace and automotive industry. The repaired composite laminates are subjected to projectile impact by a gas gun above ballistic velocity at different locations from centre of the patch. The energy absorption and impact damage of the repaired laminates are analyzed. Numerical simulations are also carried out to find out energy absorbing capability of the repaired composite laminates. The experimental results are compared with numerical results for validation.

Impact resistance of hygrothermally conditioned composite laminates with different lay-ups

Low-velocity impact testing was conducted on carbon/epoxy composite laminates exposed to hygrothermal environments. Besides normal laminates, staggered lay-up structures were made from unidirectional prepreg materials. The specimens were immersed in water at 80℃ for different durations before impact testing. Experimental data showed that moisture played a positive role by improving the impact resistance of composite laminates. Laminates with higher moisture level could behave elastically up to higher strain levels and retain their resistance to the striking impactor to larger deflections. After absorbing moisture, more of the impact energy was dissipated by the specimen through elastic deformation and less damage was induced to the laminate. Little degradation in the fiber/matrix interface was observed from SEM graphs. It is postulated that absorbed moisture improved the ductility of the epoxy resin by promoting chain segmental mobility of the polymer molecules, which eventually lead to the better impact response of laminates with higher moisture content.

Impact response of glass/epoxy laminate interleaved with nanofibrous mats

Article history: Received March 20, 2013 Received in Revised form September, 14, 2013 Accepted 16 September 2013 Available online 16 September 2013 Plain and nanofiber-interleaved glass/epoxy laminates clamped according to ASTM D7136 tested under impact loading to assess the improvement in impact resistance of composite laminates that have been interleaved by electrospun polyvinylidene fluoride (PVDF) nanofibers with two different thicknesses. Composite specimens with stacking sequence [0/90/0/90]S were impacted at impact energy of 5J. Variation of the impact characteristics such as maximum contact load, maximum deflection, maximum contact time, absorbed energy are depicted in the figures. The results showed that PVDF nanofibers are not a good choice for toughening epoxy and improving impact damage resistance of GFRP.

A Comparative Study on the Impact Resistance of Composite Laminates and Sandwich Panels

An experimental study was conducted to compare the damage resistance and energy-absorbing capabilities of graphite/bismaleimide composite laminates and foam-core sandwich panels. Two types of tests were conducted: static indentation and drop weight impact. The load-displacement response and energy absorbed were recorded for quasi-static and impact tests. The amount of core compression in sandwich panels was also measured. Damage in the laminates and sandwich panels was assessed by using ultrasonic C-scan, X-radiography, and photo-micrography. The load-displacement responses and damage area obtained from quasi-static and impact testing matched very well for the laminates. The quasi-static and impact responses for the sandwich panels have the same overall trend but differ due to the viscoelastic properties of the foam core. Test results show that the sandwich panels can absorb more energy than the laminates and undergo less deflection to absorb the same maximum energy as the laminates. Impact energy above a statically determined threshold level has been shown to cause extensive foam core damage.