Ply Structure Research Articles

Effect of triaxial woven fabric on bending properties of unidirectional composites

AbstractThis study investigates the impact of incorporating a triaxial woven fabric (TWF) into a unidirectional ply structure on the bending performance of the structure. The failure processes of the different ply structures were recorded using video analysis and acoustic emission. The experimental results indicated that incorporating a layer of carbon fiber TWF between the second and third layers (GGTGG) or between the third and fourth layers (GGGTG) of the four‐layer unidirectional fabric significantly improved the flexural strengths by 79.5% and 213.7%, respectively, and the flexural toughness by 480.3% and 324.8%, respectively. In addition, the incorporation of TWF in the structure resulted in a shift in the overall failure mode from brittle to ductile. When the TWF was closer to the lower surface of the sample, the crack was more uniform and the distribution range was wider. In contrast when the TWF was in the middle, the range of cracks generated by the sample was narrower. However, some of these cracks affected the stability of the material structure. Furthermore, the damage process was confirmed using images of crack growth and acoustic emission during the destruction process. This study provides valuable insights into enhancing the bending performance of unidirectional fiber layup in the non‐load direction.

Effect of ply structure on mechanical hysteresis behavior in 3D needle-punched C/SiC composites

For 3D needle-punch C/SiC composite, four ply structures were adopted to fabricate the composite using the chemical vapor deposition (CVD) and reactive infiltration (RI) methods. Effects of ply structure on the mechanical hysteresis behavior of the 3D NP C/SiC composites were analyzed. The hysteresis-based damage parameters (i.e., unloading/reloading inverse tangent modulus (UITM/RITM), interface slip parameter, and hysteresis width) were analytically derived from the hysteresis theory. Evolution of the hysteresis-based damage parameters with increasing peak stress was analyzed. Comparison analysis of the mechanical hysteresis behavior between the 3D NP-C/SiC with four ply structures were conducted. The hysteresis-based damage parameters reflect the internal damages under cyclic loading. The higher the values of hysteresis-based damage parameters, the more seriously of the damages occurred in the composite.

Effect of ply orientation and laminate thickness on carbon fibre reinforced polymers under low‐velocity impact

AbstractComposite materials, which have gained prominence in the aerospace industry due to their high strength‐to‐weight ratio, are vulnerable to delamination damage when struck by low‐speed projectiles due to their low through‐thickness strength. This paper presents the experimental evaluation of a composite plate subjected to low‐velocity impact. The plates under discussion were constructed using a carbon fibre reinforced polymer laminate with a quasi‐isotropic ply structure. Experiments were carried out using a conical‐shaped impactor on carbon/epoxy laminated plates with three different orientations ([0/0] 4 s, [0/90] 2 s, and [45/0–45/90] s) that were put through two distinct impact energies (7 J and 14 J). Impact response is determined using drop‐weight impact tests. The techniques of ultrasonic C‐scan, field emission scanning electron microscopy (FESEM), and surface micrographs were integrated to provide a new and in‐depth understanding of damage evolution and failure mechanisms in composite laminates. Damage resistance appears to decrease as impact energy increases. Furthermore, thicker laminates have lower absorbed energy but, on the other hand, more widespread delamination due to increased bending stiffness. Furthermore, quasi‐isotropic laminates outperform in terms of damage resistance and increased energy absorption rates by 8 % to 15 %. The efficacy and logic of the suggested model were shown by a strong connection between experimental results.

Dry Fibre Placement: The Influence of Process Parameters on Mechanical Laminate Properties and Infusion Behaviour.

Within the dry fibre placement (DFP) process, spread and pre-bindered carbon fibre rovings are automatically processed into dry textile preforms using 2-D and 3-D laying systems. The aim was to automate existing hand lay-up processes, reducing the complexity, increasing robustness, and facilitating the handling of the DFP technology. Process reliability, low waste rates, and flexible production are demonstrated. In this publication, the influences of the process parameters, 2 mm wide gaps and the percentage of 90° plies in the laminate, are investigated with regard to the mechanical properties, the permeability, and the infusion times in the preform z-direction (thickness). The effects on stiffness and strength are compared for several use cases. An approach to determine the infusion times as a function of the laminate thickness, the ply structure, and 2 mm wide gaps is demonstrated and analysed using vacuum-assisted process (VAP) infusion tests. The investigations are performed with carbon fibre tows (24 k), a reactive epoxy-based binder system, and a thermoset infusion resin system.

Short beam shear damage analysis of GLARE laminates based on digital image correlation and finite element analysis

The short beam shear performance of GLARE 3A-3/2 laminates with adhesive layers was investigated by combining the short beam test and the digital image correlation technique. The failure behavior was further analyzed based on finite element simulation and micro failure morphology. The results show an 8% and 58% difference in the short beam strength and bending displacement at failure of laminates along two orthogonal directions; The damage behavior of laminates is determined by the bottom unidirectional glass fiber reinforced plastic (GFRP) layers. The two typical failure modes are matrix and fiber fracture in the GFRP layer caused by local bending deformation, and interlaminar delamination between GFRP layers; The distribution of surface strain [Formula: see text] indicates the damage initiation and evolution process. The simulation result of the finite element model established in ABAQUS/Explicit shows consistency with digital image correlation analysis, which provides an effective method to predict the damage behavior of specimens with different ply structures.

Analysis and modeling of the Z‐pin insertion in prepreg based on contact mechanism

AbstractZ‐pinning is increasingly applied to improve the fracture toughness in fiber‐reinforced laminated composites. Force modeling during Z‐pin insertion into prepreg is crucial for the manufacturing technology of Z‐pinned laminates. In this paper, the effect of lay‐up sequence on the Z‐pin insertion force is investigated. Experimental testing reveals that the change of ply structure can result in two main force‐displacement relationships in the compression phase, namely linear growth and nonlinear growth. Through analyzing the contact mechanism, the force‐displacement relationship depends highly on the contact area between Z‐pin and prepreg, which is validated by insertion experiments with different conical tipped Z‐pins. Two models based on different contact modes of Z‐pin insertion are proposed: the analytical model for the unidirectional prepreg and the finite element model for the cross‐ply prepreg. The advantage of this approach is its ability to capture the contact behavior during the insertion process, thus predicting the insertion force more accurately. The analysis results are in good agreement with experiments.

Effect of carbon/Kevlar asymmetric hybridization ratio on the low-velocity impact response of plain woven laminates

The ply structure has a significant effect on the impact resistance and failure behavior of composite laminates. In this paper, carbon/Kevlar hybrid fabric reinforcements were prepared with different Kevlar ratio (0%, 25%, 50%, 75%, 100%) by replacing carbon fabric plies on the non-impact side by Kevlar plies. The low-velocity impact tests for all configurations were carried out under 15 J and 25 J energy respectively. The results show that the maximum deflection, impact duration, impact absorption energy and absorption energy efficiency of hybrid laminates increased with the Kevlar hybrid ratio, whereas the peak force presented a decreasing trend, which indicates that the adding of Kevlar layer makes the laminates more ductile than non-hybrid carbon structure. The damage mechanism of the carbon fiber ply was brittle fiber fracture, resin cracking and resin shedding, while the fibers pull-out and tows splitting was found in Kevlar ply. The critical structural damages start from the non-impact side and evolve to the impact side. And the rules of internal crack volume distribution with Kevlar plies are consistent with the trend of external damage area on the non-impact side. It is suggested that in order to take into account the peak strength and excellent structural resilience, Kevlar asymmetric-hybrid ratio of 25% is the most appropriate. The reason is that an appropriate small ratio of Kevlar cushion ply can not only effectively avoid the tensile fracture at non-impact side happened in the non-hybrid carbon structure, but also withstand enough impact load by maintaining a high carbon fiber content.

Study the Wicking Phenomena of Cotton Woven Fabrics and its Constituent Yarns: Relation between Fabric Wicking and Yarn Wicking

ABSTRACT In this present paper, the wicking effect of cotton woven fabrics in different directions and wicking effect of its constituent yarns has been studied. Two different types of weaves have been examined to study the wicking performance. Increased fineness in yarns of ply and single structure shows lower wickability individually. However, when used in plain and twill weave samples, improvement of wicking occurs with an initial increase in yarn fineness, but further increase in fineness deteriorates the wickability of fabrics except the diagonal direction of twill design. The regression analysis has been done to show the relationship between fabric wicking and its constituent yarn wicking. Highly positive correlations between fabric and constituent yarns are observed in relation to wicking irrespective of fineness of yarns and direction of test. However, twill weave shows stronger relationship compared to plain weave.

Structural Design and Mechanical Performance Analysis of Carbon Fiber Closed Fixtures for UHV Transmission Lines

The closed clamp is a standard tool for the insulator replacement in ultrahigh voltage (UHV) transmission lines, which is mainly made of titanium alloy material and weighs more than 27 kg that greatly reduces the working efficiency for operators. Due to the lightweight demand, carbon fiber composite materials are applied to design a new type of clamp, in which mechanical properties of new fixtures need to be fulfilled while considering poor impact resistance and low interlaminar shear strength of carbon fiber composite materials. To excavate a high-strength ply structure, finite element progressive damage strength analysis is employed to evaluate the mechanical properties of three different ply angles of the carbon fiber closed fixture, in which Tsai–Wu strength theory is thought as the strength judgment basis for carbon fiber composite materials. After comparison with the displacement-load curves, the three different ply angles fail to meet the strength requirements. So, a carbon fiber laminate structure with an outer cladding for carbon fiber closed fixtures is raised and verified. The analysis results show that the laminate structure meets the strength requirements. Destructive test of the new closed clamp is conducted to verify the correctness of the proposed method, and the weight is reduced by 36.46%.

Parametric study on interply tracking in multilayer composites by analytic-signal technology

Recently, researchers proposed the use of ultrasound combined with analytic-signal concepts for the reconstruction of the internal ply structure of composites. Optimal parameters for the pulse-echo mode ultrasonic testing are determined by modeling the analytic-signal response. The internal structure can be reconstructed by instantaneous metrics based on the interaction of the multilayer structure and the ultrasonic wave. However, there are certain drawbacks associated with the use of instantaneous metrics. The phase-derived interply track tends to be sensitive to the inspection conditions. This paper analytically studies the errors of the interply tracking for a wide range of parameters, including (i) signal-to-noise ratio, (ii) bandwidth, (iii) interply thickness, and (iv) attenuation, amongst others. It provides a guideline on how to improve the performance of the interply tracking procedure in real measurements. An experimental study combining the analytic-signal procedure with a standard log-Gabor filter in the frequency domain is performed to derive the interply tracks of a 24-layer composite laminate in a robust way. The bandpass filter selects the appropriate frequency band of the analytic-signal response from the composite. It shows a good ability for frequency and bandwidth selection, and can efficiently cope with noise features. The reconstructed ply tracks in A-scan, B-scan, and C-scan modes are analyzed to verify the performance of this procedure.

Micro-XCT Characterization and Numerical Analysis of Bending Damage Mechanism in Carbon Fiber Plain, Twill and Winding Composite Tubes

Transverse bending damage morphologies of carbon fiber composite tubes with different ply structures were investigated by the micro-XCT characterization. Structural effects of the plain, twill and winding on the damage mechanism were analyzed. The experimental results present fiber-resin cracking, interlayer delamination and fiber tows breakage with structural deformation from the peak load to final catastrophic failure. Woven fabric plies in the plain and twill composite tubes cannot be effectively slipped because of their tight interlaced structures, which makes the load propagate along the warp and weft fiber tows, resulting in more fiber tows breakage under bending-induced stretching. There is no interlaced effect on the failure mechanism for the winding tubes, resulting in a fact that the bending load can only be transferred from the fiber-resin or the layer-to-layer interface, with more interlaminar slippage and obvious springback behaviors under in-plane shear. For investigating the interlaced effect on failure mechanism, plain and winding models under transverse bending were established using continuous shell elements, and different constitutive description were used to simulate interlayer failure and intra-layer failure behaviors. By comparing the numerical results with the experimental ones, the influence of the fabric structure on the failure behavior of the tube were analyzed.

Enhancement of Mechanical Properties of Flax-Epoxy Composite with Carbon Fibre Hybridisation for Lightweight Applications.

The effect of unidirectional (UD) carbon fibre hybridisation on the tensile properties of flax fibre epoxy composite was investigated. Composites containing different fibre ply orientations were fabricated using vacuum infusion with a symmetrical ply structure of 0/+45/−45/90/90/−45/+45/0. Tensile tests were performed to characterise the tensile performance of plain flax/epoxy, carbon/flax/epoxy, and plain carbon/epoxy composite laminates. The experimental results showed that the carbon/flax fibre hybrid system exhibited significantly improved tensile properties over plain flax fibre composites, increasing the tensile strength from 68.12 MPa for plain flax/epoxy composite to 517.66 MPa (670% increase) and tensile modulus from 4.67 GPa for flax/epoxy to 18.91 GPa (305% increase) for carbon/flax hybrid composite. The failure mechanism was characterised by examining the fractured surfaces of tensile tested specimens using environmental scanning electron microscopy (E-SEM). It was evidenced that interactions between hybrid ply interfaces and strain to failure of the reinforcing fibres were the critical factors for governing tensile properties and failure modes of hybrid composites.

A review on the mechanical properties of textile structural composite T-beams

In order to review the most effective ways to improve the mechanical properties of composite T-beams and further increase their application potential, research progress on the mechanical properties of textile structural composite T-beams was summarized based on two-dimensional (2-D) ply structure composite T-beams, delamination resistance enhanced 2-D ply structure T-beams, and three-dimensional (3-D) textile structural composite T-beams; future research directions for composite T-beams were also considered. From existing literature, the research status and application bottlenecks of 2-D ply structure composite T-beams and T-beams with enhanced delamination resistance performance were described, as were the specific classification, research progress, and mechanical properties of 3-D textile structural composite T-beams. In addition, the superior mechanical properties of 3-D braided textile structural composite T-beams, specifically their application potential based on excellent delamination resistance capacity, were highlighted. Future research directions for composite T-beams, that is, the applications of high-performance raw materials, locally enhanced design, structural blending enhancement, functionality, and intelligence are presented in this review.

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 peer ply and cooling rate on the tensile properties of Al/Gf/PP laminate prepared by hot pressing

The glass fiber-reinforced polypropylene/AA2024 hybrid composite (short for Al/Gf/PP laminate) was prepared by hot pressing with anodized 2024-T3 aluminum alloy as the skin and thermoplastic glass fiber-reinforced polypropylene core as a substitute of thermosetting glass fiber-reinforced polymer (based on epoxy) in order to increase the productivity and reduce the production costs during manufacturing procedure. The effect of peel ply (release cloth) and cooling rate on the laminate was investigated elaborately in this work. The orientation of glass fiber is mainly influenced by the peel ply structure, resulting in the resin’s overflow during hot press. Moreover, different cooling rates due to various cooling methods significantly affected both the degree of crystallization of the matrix and deformation of the metal skin during the curing process. Finally, a new peel ply structure was adopted to prevent the fiber from spilling during hot press process, while bubbles were allowed to flow out normally along with partial resin. Finally, a novel cooling method to reduce the degree of polypropylene crystallization and control metal deformation was proposed.

Towards the scale up of tissue engineered intervertebral discs for clinical application

Replacement of the intervertebral disc with a viable, tissue-engineered construct that mimics native tissue structure and function is an attractive alternative to fusion or mechanical arthroplasty for the treatment of disc pathology. While a number of engineered discs have been developed, the average size of these constructs remains a fraction of the size of human intervertebral discs. In this study, we fabricated medium (3 mm height × 10 mm diameter) and large (6 mm height × 20 mm diameter) sized disc-like angle ply structures (DAPS), encompassing size scales from the rabbit lumbar spine to the human cervical spine. Maturation of these engineered discs was evaluated over 15 weeks in culture by quantifying cell viability and metabolic activity, construct biochemical content, MRI T2 values, and mechanical properties. To assess the performance of the DAPS in the in vivo space, pre-cultured DAPS were implanted subcutaneously in athymic rats for 5 weeks. Our findings show that both sized DAPS matured functionally and compositionally during in vitro culture, as evidenced by increases in mechanical properties and biochemical content over time, yet large DAPS under-performed compared to medium DAPS. Subcutaneous implantation resulted in reductions in NP cell viability and GAG content at both size scales, with little effect on AF biochemistry or metabolic activity. These findings demonstrate that engineered discs at large size scales will mature during in vitro culture, however, future work will need to address the challenges of reduced cell viability and heterogeneous matrix distribution throughout the construct. Statement of SignificanceThis work establishes, for the first time, tissue-engineered intervertebral discs for total disc replacement at large, clinically relevant length scales. Clinical translation of tissue-engineered discs will offer an alternative to mechanical disc arthroplasty and fusion procedures, and may contribute to a paradigm shift in the clinical care for patients with disc pathology and associated axial spine and neurogenic extremity pain.

In Vitro Maturation and In Vivo Integration and Function of an Engineered Cell-Seeded Disc-like Angle Ply Structure (DAPS) for Total Disc Arthroplasty

Total disc replacement with an engineered substitute is a promising avenue for treating advanced intervertebral disc disease. Toward this goal, we developed cell-seeded disc-like angle ply structures (DAPS) and showed through in vitro studies that these constructs mature to match native disc composition, structure, and function with long-term culture. We then evaluated DAPS performance in an in vivo rat model of total disc replacement; over 5 weeks in vivo, DAPS maintained their structure, prevented intervertebral bony fusion, and matched native disc mechanical function at physiologic loads in situ. However, DAPS rapidly lost proteoglycan post-implantation and did not integrate into adjacent vertebrae. To address this, we modified the design to include polymer endplates to interface the DAPS with adjacent vertebrae, and showed that this modification mitigated in vivo proteoglycan loss while maintaining mechanical function and promoting integration. Together, these data demonstrate that cell-seeded engineered discs can replicate many characteristics of the native disc and are a viable option for total disc arthroplasty.

Flexural and interlaminar shear study of hybrid woven kenaf/recycled GFRP (rGFRP) composites subjected to bending load

Delamination known as the failure at the interface between different layers is one of critical failure mechanism for laminates composites. Hybrid laminate composites comprised of unique ply material and structure, unwanted interlaminar shear stresses may occur between ply laminate due to different material behavior and properties. The aim of this research is to study structural integrity effect of interleaf glass mat and recycled GFRP waste (rGFRP) in woven kenaf reinforcement polyester composite. The properties of composites on ILSS and flexural behavior subjected to bending load were measured by flexural and short beam test (SBT). Span length to thickness ratio varies for both tests are 16: 1 and 4: 1 for flexural test and SBT respectively. Compression molding method was selected for composite fabrication; the fiber weight percentage ratios are constant at 35% of all samples. Results revealed that the flexural stress and flexural shear measured by flexural test is comparable for kenaf and kenaf/glass composites however, kenaf/rGFRP shows significant improvement, increased in maximum flexural stress up to 47.5%. Interlaminar Shear Strength (ILSS) calculated from SBT shows comparable value for all samples with slightly increased about 10% for both hybrid composites. Failure analysis observed by Scanning Electron Microscopic (SEM) and Optical Microscope shows severe interlaminar shear failure occur on glass mat hybrid composites for both tests. From the results, it can be conclude that hybridization of glass mat and rGFRP particulate improved flexural and ILSS properties. It also can be concluded rGFRP is potential to replace glass fiber as reinforcement.

New horizons in spine research: Intervertebral disc repair and regeneration.

New horizons in spine research: Intervertebral disc repair and regeneration.

Analysis of electric current density in carbon fiber reinforced plastic laminated plates with angled plies

It is important to know the electric current distribution in a laminated carbon fiber reinforced plastics (CFRP) plates for safety analysis of lightning strikes and for damage monitoring of plates based on changes in electrical resistance. An orthotropic electric potential function has been previously proposed, which was effective for modeling of a CFRP cross-ply laminate used in beam structures. However, that method is limited to cross-ply laminates that contain no angle plies, while CFRP plate structures typically feature angle plies. In the present study, a new analysis method is proposed for laminated CFRP plates that contain angled plies. In the new method, two or three angle plies are coupled and assumed to have orthotropic conductivity of double or triple thickness. A new method to calculate the equivalent conductivity is also proposed. The new method is applied to two types of laminates containing angle ply structures. The results obtained are compared with those from a finite difference method and from experimental measurements. The new method is shown to be effective for analysis of the electric current of laminates that contain angled plies.