Performance Of Composite Laminates Research Articles

Low‐velocity impact properties of carbon fiber/ultrahigh molecular weight polyethylene fiber hybrid composites

AbstractTo understand the hybrid fiber enhanced impact‐resistance performance of composite laminates. In particular, the effects of different parameters, such as hybrid fiber ratios and plying modes, were investigated. The effects of UHMWPE short fibers (UHMWPESFs) fiber content and ply angle changes on the impact resistance of Carbon fiber/ultra‐high molecular weight polyethylene short fiber hybrid composite (CUFHRP) laminates were investigated in this article. The impact resistance of the CUFHRP laminate was tested by the drop weight test and residual strength test after impact. The results indicated that the peak load and absorption energy of the specimen with a fiber content of 15 g/m2 were the highest, reaching 6.543 kN and 16.51 J, respectively. Specimens with different ply modes of [0/−45/45/90]2s showed the most obvious effect on the maximum load. Its maximum load was 28.93% higher than that of the original sample. The critical damage threshold load of composite laminates is improved, and the impact resistance is strengthened.Highlights Study to improve the impact resistance of the composite on the basis of the hybrid structure. Report the optimal parameters of the effects on the impact resistance of the composite, such as: hybrid fiber ratios and plying modes. Reveal the fundamental failure mode of hybrid structure composite laminates under low‐velocity impact.

Influence of distributed out-of-plane waviness defects on the mechanical behavior of CFRP laminates

One of the most common defects induced during manufacturing of laminates is out-of-plane fibre waviness. This defect significantly affects the mechanical behavior of the laminate and reduces fatigue life and the load capacity of the material. Therefore, it is important to understand the impact of fibre waviness on the performance of composite laminates. In this work, multiple out-of-plane waves have been introduced throughout a Carbon Fibre Reinforced Polymer (CFRP) laminate at different thickness positions. The specimens were tested under tensile loading and an analysis of the surface of the laminate has been carried out by means of Digital Image Correlation (DIC). The results obtained by DIC were able to predict the apparent strain of the laminate quite accurately, as well as locate up to seven undulations at different depths. It was proved that a laminate with multiple wrinkles has 16% less tensile load strength. The results were used to validate different Finite Element (FE) models of the laminate showing a good agreement. These simple models were able to predict the initiation and propagation of failure in both the matrix and the fibre.

Experimental investigation of Z-pin insertion angles on the mechanical behavior and failure mechanism of compression after impact for CFRP laminates

This paper studied the effects of Z-pin insertion angles (60°, 75° and 90°) on the behavior and failure modes of compression after impact (CAI) for composite laminates. Unpinned and different angle Z-pinned [0/90]4s and [45/0/-45/90]2s laminates were impacted at 25–60 J to introduce damage ranging from barely visible impact damage (BVID) up to penetration, then subjected to compression load until failure. The damage induced by low-velocity impact (LVI) was introduced, and the damage status after compression was inspected and evaluated by micro-CT, scanning electron microscope (SEM) techniques and visual observation of surfaces. Experimental results demonstrate that the effects of Z-pin insertion angles on CAI behavior and failure modes are related to layups and impact energies. 90° Z-pin is the most effective in improving CAI strength for both [0/90]4s and [45/0/-45/90]2s laminates by stitching delaminated sub-laminates together. Decreasing Z-pin insertion angles will reduce the enhancement of CAI strength, which is more evident for [0/90]4s laminates at relatively high impact energies. This study provides new insight into the effect of Z-pin insertion angles on the CAI failure mechanism and performance of composite laminates.

The effect of different number of layers and fiber distribution on the performance of composite laminates

Fiber-reinforced composites are widely used in world industries such as transportation vehicles, sports tools, space crafts, and more. This research investigates the influence of the number of layers and fiber distribution on the mechanical properties of woven fiber-reinforced composites by changing the number of layers or the manufacturing process. Hand lay-up and infusion processes are used to manufacture the composite plates. Three mechanical tests are conducted for all composite plates, such as Interlaminar shear stress (ILSS), ultimate tensile strength (UTS), and ultimate flexural strength (UFS). Furthermore, analyzing the microstructure of the laminates is conducted to evaluate fractal dimension (FD). It is observed that the distribution of the fibers measured by FD had an effective role in improving the mechanical properties. Also, the use of vacuum molds had an additional role in improving the mechanical properties. One could conclude that all the mechanical properties have proportional relationships with FD.

Finite Element Free Vibration Analysis of Marine Composite Laminates with Variable Stiffness

Ouyang, X., 2020. Finite element free vibration analysis of marine composite laminates with variable stiffness. In: Yang, D.F. and Wang, H. (eds.), Recent Advances in Marine Geology and Environmental Oceanography. Journal of Coastal Research, Special Issue No. 108, pp. 270–273. Coconut Creek (Florida), ISSN 0749-0208.Reinforced variable stiffness composites are commonly used in marine engineering and marine engineering structures. The free vibration behavior of composite laminates varies with varying stiffness. Classical layering theory and first-order shear deformation theory are used to model the structure. On the basis of the virtual work principle and the finite element method, the vibration equation is established. The curved fiber can improve the design performance of composite laminates, and the free vibration behavior of composite laminates with variable stiffness can be changed by changing the orientation of the fiber.

Research on intralaminar load reversal damage modeling for predicting composite laminates’ low velocity impact responses

Despite abundant finite element analysis (FEA) of low velocity impact (LVI) performance of composite laminates, the questions regarding the effects of different load reversal damage laws on predicted impact responses of composite laminates and which one is preferred for more physically-sound simulation of laminate LVI responses remain unresolved. In this paper, an elasto-plastic progressive damage model based on three load reversal damage laws including coupled tension-compression law, semi-stiffness recovery law and full-stiffness recovery law, were numerically implemented in predicting laminate LVI responses. By comparisons between simulations and available experimental data, the influences of different load reversal damage laws on predicted delamination threshold load, impact force, laminate central deformation, dissipated impact energy as well as damage status were analyzed. More accurately predicting laminates’ LVI responses, the semi-stiffness recovery law was concluded as the preferred intralaminar load reversal damage law.

Effect of enhancement of interface performance on mechanical properties of shape memory alloy hybrid composites

Effect of enhancement of interface performance on mechanical properties of shape memory alloy hybrid composites (SMAHCs) was investigated in this work. Composite laminates without Ni-Ti shape memory alloy (SMA) fibers, with Ni-Ti SMA fibers polished, corroded and modified by silane coupling agent KH550 were taken into comparison to investigate the effect of surface treatments. Surface morphology of Ni-Ti fibers under different treatments were observed with scanning electron microscope. The mechanical performance of specimens without Ni-Ti fibers and with Ni-Ti fibers under different treatments were investigated through tensile, three-point bending and low-velocity experiments. The morphology and micromorphology were observed to study the effect of different surface treatment methods. The conclusion shows that embedded Ni-Ti SMA fibers can enhance the mechanical performance of composite laminates. However, the performance of Ni-Ti SMA fibers was restrained by the poor interface performance. After surface treatments, SMAHCs illustrate better mechanical performance owing to the enhanced interface performance. Among all the surface treatment methods, modification with silane coupling agent KH550 shows the best effect.

Design optimization of CFRP stacking sequence using a multi-island genetic algorithms under low-velocity impact loads

A method to improve the low-velocity impact performance of composite laminate is proposed, and a multi-island genetic algorithm is used for the optimization of composite laminate stacking sequence under low-velocity impact loads based on a 2D dynamic impact finite element analysis. Low-velocity impact tests and compression-after impact (CAI) tests have been conducted to verify the effectiveness of optimization method. Experimental results show that the impact damage areas of the optimized laminate have been reduced by 42.1% compared to the baseline specimen, and the residual compression strength has been increased by 10.79%, from baseline specimen 156.97 MPa to optimized 173.91 MPa. The tests result shows that optimization method can effectively enhance the impact performances of the laminate.

Effect of Specimen Thickness on High Strain Rate Properties of Kevlar/Polypropylene Composite

Characterization of Kevlar-Polypropylene based composite material system under high strain rate loading has been investigated using Split Hopkinson Pressure Bar (SHPB) test for varying specimen aspect ratios. Flat laminates of 16, 24 and 30 layered Kevlar composite were compression molded and laser machining to get cylindrical specimensof desired aspect ratios. Based on SHPB experiments, stress-strain plots were obtained and analysed to reveal compressive material behaviour as function of growing strain rate. The peak stress, strain and toughness exhibited considerable increase with growing strain rate of loading. With increasing strain rates peak specimen stress increased by 90%, for lowest thickness composite. The aspect ratio studies suggests application of thin laminates for better performance of composite laminates.

Investigation of two finite element modelling approaches for ballistic impact response of composite laminates

ABSTRACTWe evaluated two numerical modelling methods based on different modelling scales in simulating the ballistic performance of composite laminates. An orthogonal continuous material model was developed and used to establish an equivalent macro-scale impact model of a projectile/composite target (uniform model). Combining the Chang–Chang failure model and tiebreak contact algorithm, the corresponding computational model for the cross-plied microstructure of composite laminates was constructed layer by layer (layered model). Using the two modelling methods mentioned earlier, a series of ballistic impact simulations were carried out for Kevlar/epoxy composite laminates, and the simulation results were compared with the corresponding experimental results. The computational capacities of the two methods were compared in terms of damage pattern, ballistic limit, residual velocity and computational efficiency. The results indicate that the uniform model can simulate the main ballistic impact behaviour of composite materials, whereas the layered model can simulate more detailed features of composite damage. Moreover, the predictive capability of the uniform model for ballistic limit and residual velocity is equivalent to that of the layered model, and the uniform model exhibits a higher computational efficiency than the layered model.

Fire Retardancy of Fiber Reinforced Polymer Composites Coated with POSS/Clay/MWCNTs Hybrid Buckypaper

A hybrid buckypaper consisting of multi-walled carbon nanotubes(MWCNTs),clay and polyhedral oligomeric silsesquioxane(POSS) was fabricated through vacuum filtration method. The as-prepared buckypaper(or hybrid buckypaper) can be incorporated onto the surface of fiber reinforced polymer composite as surface fire shields. The morphology and pore size distribution of the MWCNTs buckypaper were characterized with field emission scanning electron microscope(FESEM) and Barret-Joyner-Halenda(BJH) method. The fire retardant performance of composite laminates coated with(or without) the buckypaper was thoroughly evaluated by cone calorimeter testing at a radiant heat flux of 50 kW/m2. Compared with the contral composite,the peak heat release rate(PHRR) of composite surface coated MWCNTs buckypaper or the hybrid buckypaper reduced more than 20.2% and 35%,respectively. The CO production rate and the smoke production rate reduced obviously. The formation of compact char material can be observed on the surface of the composite residues and analyzed by FESEM,the fire retardant property of composite can be improved by surface coated hybrid buckypaper.

Compressive Strength of CCF300/QY8911 Composite Laminates with LVI Damage

A series of low-velocity impact tests and residual compressive strength tests after impacts on CCF300/QY8911 composite materials were carried out to study the mechanism of compression failure of the laminates after low-velocity impact. The curves of impact energy verse dent depth and impact energy verse the damage area was obtained. And the residual compressive strength and stiffness after impact verse damage parameters were analyzed. The results showed that when the impact energy exceeded the inflection point, as the impact energy increased, the dent depth on the impacted surface of the laminates notably increased while the damage area of the internal layers merely increased slowly. If the impact energy was continued to increase, the expansion of the laminates' internal damage mainly consisted of fiber breaks. The main reason for the decrease in compressive performance of composite laminates was inside delamination between layers, while in the case in which impact energy exceeded the inflection point, there were no obvious changes in delamination damage area for different energy, so the residual compressive performance kept almost stable.

Experimental study of the effect of automated fiber placement induced defects on performance of composite laminates

The Automated Fiber placement (AFP) process shows great potential for efficient manufacturing of large composite structures. However, uncertainties exist on mechanical performance of final product that are associated with the process induced defects. This experimental work investigates the effect of four principal defect types, namely gap, overlap, half gap/overlap and twisted tow on the ultimate strengths. Tests are executed at the lamina level (fiber tension, fiber compression and in-plane shear), as well as at the laminate level (open hole tension and open hole compression). Then each test is compared with a baseline configuration exempt from defects. Tests have revealed the minimal effects of a single and isolated defects on mechanical performance especially at the lamina level (around 5%) compared to the laminate level (up to 13%).

Electromagnetic interference shielding properties of carbon nanotube buckypapercomposites

Preformed carbon nanotube thin films (10–20 µm), or buckypapers (BPs), consist of dense and entangled nanotube networks, whichdemonstrate high electrical conductivity and provide potential lightweight electromagneticinterference (EMI) solutions for composite structures. Nanocomposite laminates consistingof various proportions of single-walled and multi-walled carbon nanotubes, having differentconductivity, and with different stacking structures, were studied. Single-layer BPcomposites showed shielding effectiveness (SE) of 20–60 dB, depending on the BPconductivity within a 2–18 GHz frequency range. The effects on EMI SE performance ofcomposite laminate structures made with BPs of different conductivity values and epoxyor polyethylene insulating layer stacking sequences were studied. The resultswere also compared against the predictions from a modified EMI SE model. Thepredicted trends of SE value and frequency dependence were consistent with theexperimental results, revealing that adjusting the number of BP layers and appropriatearrangement of the BP conducting layers and insulators can increase the EMI SE from45 dB to close to 100 dB owing to the utilization of the double-shielding effect.

Static and Dynamic Mode II Strain Energy Release Rates in Toughened Thermosetting Composite Laminates

In this work, the static and dynamic Mode II fracture properties of several thermosetting resin-based composite laminates are presented. Two classes of materials are explored. These are homogeneous thermosetting resins and toughened, multiphase, thermosetting resin systems. A new dynamic Mode II test is presented for composite laminates based on an end-notched flexure (ENF) specimen geometry. The specimen is impacted in three-point bending with an instrumented impact tower. Fracture initiation and propagation energies under static and dynamic conditions are determined analytically and experimentally. The test results show that the toughened systems provide superior fracture initiation and higher resistance to propagation under dynamic conditions. The results indicate that static fracture testing is inadequate for determining the fracture performance of composite laminates subjected to conditions such as low velocity impact. A good correlation between the basic Mode II dynamic fracture properties and the performance in a combined material/structural compression after impact (CAI) test is found. The results underscore the importance of examining rate-dependent behavior for determining the longevity of structures manufactured from composite materials.