3D Reinforcement Research Articles

Fast GPU simulation of reinforced concrete at the scale of reinforcement ribs by the discrete element method

The paper presents the development of the GPU-based discrete element method (DEM) code for simulating damage and fracture of cohesive solids with application to reinforced concrete at the scale of reinforcement ribs. The solid volume of concrete and steel is modelled by bonded spherical particles. Very fine discretization, containing more than million particles, is applied to describe the 3D reinforcement bar geometry at the scale of ribs and to investigate cracking behaviour of concrete near the reinforcement bar. The numerical model is validated by using experimental results of the double pull-out test. Influence of the discretization scale to the numerical solution is evaluated by using the reinforcement strain profiles and the cracking patterns. The developed GPU-based DEM algorithm efficiently handles interaction of particles, does not require any atomic operation and allows performing fast damage and fracture simulations with large number of particles. The performance measured on GPU is compared with that attained on different CPUs for varying number of particles. The high value of the Cundall number (particle number multiplied by time steps computed per second) equal to 4.3E+07 is measured on NVIDIA® Tesla™ P100 GPU in the case of 1858560 particles.

BIM, STRUCTURAL ANALYSIS AND COMMUNICATION USING COMMON DATA ENVIRONMENT (CDE) IN THE FIELD OF WATER MANAGEMENT

Abstract. Presentation consists of three parts, which are interconnected:BIM application for plants treatment and other complicated structures in the field of water managementStatics of water management structures in the BIM environmentApplication of Common Data Environment (CDE) for water managementTwo areas – statics and water management technology – are crucial for water management structures. Speaking of statics, we mean the statics of reinforced concrete structures. In our company AQUA PROCON s.r.o. we deal with this area comprehensively, ie. from the initial design in the BIM architectural and construction software, through transferring a load-bearing model to BIM software for 3D reinforcement modelling to evaluating model in static design software. All communication is held in Common Data Environment (CDE). Within this environment, a three-way communication is carried out by the designer, contractor and contracting authority. Part of our performance is also above-standard support for reinforced concrete contractors. We provide models of reinforced concrete structures in LOD 400. The use of Common Data Environment (CDE) does not concern only statics, but also the work of all other professions and project participants. Our activities and workflows are based on the philosophy of OPENBIM and IFC.

Multi-Task Deep Reinforcement Learning with PopArt

The reinforcement learning (RL) community has made great strides in designing algorithms capable of exceeding human performance on specific tasks. These algorithms are mostly trained one task at the time, each new task requiring to train a brand new agent instance. This means the learning algorithm is general, but each solution is not; each agent can only solve the one task it was trained on. In this work, we study the problem of learning to master not one but multiple sequentialdecision tasks at once. A general issue in multi-task learning is that a balance must be found between the needs of multiple tasks competing for the limited resources of a single learning system. Many learning algorithms can get distracted by certain tasks in the set of tasks to solve. Such tasks appear more salient to the learning process, for instance because of the density or magnitude of the in-task rewards. This causes the algorithm to focus on those salient tasks at the expense of generality. We propose to automatically adapt the contribution of each task to the agent’s updates, so that all tasks have a similar impact on the learning dynamics. This resulted in state of the art performance on learning to play all games in a set of 57 diverse Atari games. Excitingly, our method learned a single trained policy - with a single set of weights - that exceeds median human performance. To our knowledge, this was the first time a single agent surpassed human-level performance on this multi-task domain. The same approach also demonstrated state of the art performance on a set of 30 tasks in the 3D reinforcement learning platform DeepMind Lab.

Lightweight Potential of 3D Endless Fiber Reinforcement of Polyurethane Foam Cores with Spacer Fabrics in Hybrid Sandwich Structures with Fiber Reinforced Thermoplastic Facings

Sandwich structures consisting of fibre-reinforced plastic (FRP) facings and core are ideally suited as substitution materials for reducing component masses. The endless fibre reinforcement has the greatest performance potential. Both thermoset and thermoplastics are already being processed into endless fibre-reinforced sandwich facings according to the state of the art. The 3D endless fibre reinforcement of cores is a current research topic. This paper describes the development of a hybrid sandwich consisting of thermoplastic composite facings and an innovative core composite. This is made of polyurethane (PUR) rigid or flexible foam, which is reinforced with spacer fabric. The sandwich manufacturing in Reaction Injection Moulding (RIM) includes the original forming of the core and the simultaneous bonding of the facings. This efficient process offers the potential for the production of such complex structures in medium or large series. The sandwich structures and their individual components were characterised in the standardised compression and bending test. The lightweight potential of spacer fabric reinforcement is demonstrated by comparing the specific mechanical properties of sandwich structures with and without core reinforcement. In comparison to reinforced and unreinforced foams, the effect of sandwich design is also shown.

Effects of Crimp and Textile Architecture on the Stiffness and Strength of Composites with 3D Reinforcement

The aim of this study is to experimentally determine how the weave architecture and yarn crimp affect the measured tensile stiffness and strength of composites containing 3D textile reinforcement. It is shown that both the stiffness and strength decrease nonlinearly with increasing 3D crimp. The ultimate strength of specimens containing nominally straight yarns and specimens containing crimped yarns can differ more than a factor of 3, and the stress causing onset of damage can be affected even more. Adding nominally straight stuffer yarns into a 3D-woven reinforcement significantly increases the fibre volume fraction, the stiffness, and the strength of the composite. However, since the stuffer yarns are virtually straight and thus stiffer than the warp yarns, they attract the load and reach their strength at relatively lower strain than the warp yarns. The reinforcement architecture varies between the surfaces and the interior of the studied textiles, which has corresponding influence on the local stiffness. The onset of failure is predicted satisfactorily accurate with relatively simple estimations. The ultimate strength is a result of extensive damage progression and thus more dubious to predict.

Formability Behaviour of 3D Woven Solid Structures with Varying Stuffer Binder Ratio

Abstract In this study formability of three different Multilayer E-Glass 3D orthogonal woven preforms with varying stuffer (warp yarns) and binder (through thickness yarn) ratio is experimentaly investigated. 3D orthogonal woven reinforcements were developed using a in house fabricated mutibeam rigidrappier weaving machine. Formability behaviour of all structures were analysed using a fabricated formability fixure, with hemispherical pluger. Stuffer and binder yarn percenatge by mass were varied keeping same fiber volume fraction in all three structure, It is obsrved that binder percetage, Number of crossover point in a unit cell, singnificantly influence formability behaviour of the strucures.

Viscoelastic properties of architected foams based on the Schoen IWP triply periodic minimal surface

In this article, we studied the viscoelastic properties of an architected foam based on the mathematically-known Schoen IWP triply periodic minimal surface (TPMS) under both time and frequency domains. IWP-based architectures possess unique multifunctional attributes when used as a three-dimensional (3D) reinforcement in composites. The 3 D representative volume elements (RVEs) of different relative densities (i.e., the ratio of the foam’s density to the density of its solid counterpart) were generated and studied using the finite element method in order to predict the effective uniaxial, shear, and bulk viscoelastic responses of IWP-foams as a function of relative density and/or frequency. The principle of time-temperature superposition principle was used to create the master curve of the observed relative-density dependent mechanical responses (loss tangent, storage and loss moduli) in frequency domains. Reduced uniaxial, bulk, and shear stiffness-loss map results suggested that the IWP-foam possesses strongest uniaxial viscoelastic response while highest damping can be achieved under shear responses. Relaxation behavior of IWP-foam was compared with other six different types of open-cell periodic foams. It was found that IWP-foam uniaxial response is similar to simple cubic foam, bulk relaxation response is similar to primitive-foam while shear response follows the behavior of body centered cubic foam. Among these foams, we found that IWP-foam is the best candidate to use as a damper under uniaxial and hydrostatic loading conditions.

Development of a 3D reinforcement by tufting in carbon fiber/epoxy composites

Since the early development, the sectors where the composite materials are being used have been growing gradually. Nowadays, these materials have extensive application in the structural components in the aerospace, defense, transportation, civil, and energy industries. The composites, especially carbon fabric/epoxy resin, have excellent in-plane properties. However, the susceptibility to delamination from out-of-plane loads, due to the lack of fibers oriented through the thickness, is still one of the weaknesses of this kind of materials. The introduction of reinforcement through the thickness has the potential to increase out-of-plane properties of composite materials. This can be accomplished by different reinforcement methods, such as Z-pinning, stitching, and tufting. This work aimed to develop and implement a simplified method of through-the-thickness reinforcement, based on tufting reinforcement. The experimental methodology was developed in a CNC router machine where glass fiber and polyamide were used as the main reinforcement materials in different square patterns (5 × 5 and 7 × 7) and applied in laminated carbon/epoxy composites manufactured by vacuum resin transfer molding process. Then, efficiency of the reinforcement was evaluated by means of mechanical testing, i.e., tensile and end-notched flexure testing in order to evaluate the ability to improve the interlaminar fracture strength. Results showed that the presence of the reinforcements provided around 27% increase in the delamination resistance compared to the non-reinforced composites in the thickness direction.

Non-destructive evaluation of through-thickness permeability in 3D woven fabrics for composite fan blade applications

In this study, we propose a non-destructive modeling framework, with an ability to obtain computational models for numerical prediction of resin flow through 3D fabrics (commonly used in engine fan blade applications) at multiple fiber volume fractions using a single experiment. The work involves extracting real-time geometrical features of two types of 3D reinforcements during an in-situ compaction experiment using micro CT. The 3D image slices obtained at four different thicknesses were converted to computational models. The fiber tows and inter-tow gaps were modeled as distinct phases. The gap analysis and geometrical measurements revealed significant differences in the preform microstructure investigated at different thicknesses. This was followed by a detailed flow analysis using two different commercial software packages. The exported mesh was analyzed in GeoDict® and Ansys Fluent® for through-thickness permeability computations. The governing fluid dynamics equations were solved to obtain the flow field within the inter-tow gaps for representative volume elements. The predicted through-thickness permeability values were in very good agreement with the experimental data.

Development of composites, reinforced by novel 3D woven orthogonal fabrics with enhanced auxeticity

Auxetic materials are under great attention of researchers due to their excellent mechanical response under certain conditions. Previous works have been carried out in knitted or uni-stretch woven fabrics. In the present study, three-dimensional (3D) woven structures were produced and the effect of float length of ground weave and binding yarn on auxeticity of the fabric was investigated. Eight different 3D orthogonal woven structures/reinforcements were produced on rapier dobby loom by changing the float length in ground weave and binding yarns. Hand layup technique was used for composite fabrication, while green epoxy resin was used as a matrix. For investigating the auxeticity, 3D reinforcement samples were subjected to tensile loading and change in their thickness was measured. The results showed that 3D woven reinforcements with equal and maximum float length of ground weave and binding yarn showed greater auxetic behavior, because both weaves support each other and room for opening of structure increases. As the difference between the float length of ground weave and binding yarns increases, the auxeticity of reinforcement decreases because the ground weave and binding yarn cancel out the effect of each other. Moreover, the impact energy absorption of the developed composites was found to increase with the increase in float length, justifying that the structures are auxetic in nature.

Experimental assessment of the mechanical behaviour of 3D woven composite T-joints

To understand the influence of the fibre architecture of 3D woven composite T-joints on mechanical performance, as well as the benefits that 3D woven T-joints can offer over the equivalent 2D laminates, experimental testing is performed on two types of 3D woven T-joint with only weave variation at the junction, and one type of 2D woven laminate T-joint. A quasi-static tensile pull-off loading is selected in this work as this out-of-plane load case is one of the typical loading conditions for such T-joint structures. The significant advantages of 3D woven composite T-joints in terms of ultimate strength and damage tolerance over the 2D alternative were identified in the testing. More importantly, this work showed that variation in the fibre architecture can considerably enhance properties such as delamination resistance and total energy absorption to failure, as well as increasing slightly the stiffness and initial failure load. This experimental assessment has demonstrated that using 3D woven reinforcements is an effective way to improve the load-bearing capability of composite T-joints over laminates, and also that this improvement could be optimised with regard to fibre architecture.

Delamination toughening and healing performance of woven composites with hybrid z-fibre reinforcement

This paper presents an investigation of a novel three-dimensional (3D) hybrid fibre-polymer composite material that has the unique combination of properties to both resist the growth and self-heal delamination cracks. This hybrid fibre composite contains two types of through-the-thickness z-binders made of carbon fibre tows (for high delamination resistance) and thermoplastic filaments (for self-healing). The performance of this hybrid 3D composite is compared with 3D composites reinforced in the through-thickness direction with either carbon tows or thermoplastic filaments. The results show that the hybrid 3D reinforcements substantially improve the mode I interlaminar fracture toughness (∼1200%) and self-reparability of the composite. To understand the toughening mechanism of the hybrid z-binders, a finite element analysis is conducted to simulate the crack growth resistance behaviour and the fracture properties of the composite materials in the as-manufactured and healed conditions. The model is able to predict with good accuracy the fracture toughness and healing properties, and is used to further study the effects of hybridization ratio of the carbon and thermoplastic z-binders on the fracture toughness and healing properties of the 3D reinforced composites.

Literature review of tufted reinforcement for composite structures

In order to minimize the damage caused by the 2D structures, several research have been done on more complex structures (3D-preforms) which have more interesting mechanical characteristics. Divers textile technologies are used to manufacture 3D preforms such as weaving, knitting, stitching, z-pinning, tufting… This kind of reinforcement aims to achieve a balance between the in-plane and out-of-plane properties. Recently, the tufting technology shows more opportunities to develop 3D reinforcements especially with the advances in robotics. The present paper focuses not only on the various technologies of reinforcement through the thickness but also on the mechanical behaviour of a tufted preform in a stamping process.

3D Metamorphic Stretchable Microphone Arrays

AbstractThis article describes the realization of a metamorphic microphone array. The array morphs from a concave to a planar and then to a convex shape. The morphing array enables a better (12×) sound source localization when compared to existing static and planar arrangements. To enable the realization, a novel stretchable (elongated up to 320% of the original length) printed circuit board fabrication process is reported. The fabrication process enables high‐temperature processing, alignment, and registration. Moreover, conventional and otherwise rigid surface mount devices (SMDs) can be used. The process allows the researcher to increase the number of devices (30 SMDs) and interconnects (60 in total) to the required level. As electrical connections, a polyimide‐cladded metal track design is reported; the design sustained 11 050 stretch and release cycles. Moreover, 3D reinforcement frames are reported as an effective measure to shield the SMD components from high levels of stress. The resulting products are millimeter‐thin stretchable rubber‐embedded and electrically interconnected electronic structures with mechanical rubber‐membrane‐like properties. Morphology changes involve deflation and inflation of the membrane to bulge inward or outward. Finally, the use of 3D‐shaped chaperon is discussed to provide additional shape control.

Tuning the structure of 3D woven aramid fabrics reinforced with shear thickening fluid for developing soft body armour

Soft body armour panels have been developed by tuning the structure of 3D woven orthogonal aramid fabrics and reinforcing them with shear thickening fluid (STF). Five 3D woven orthogonal aramid fabric structures were prepared by changing the ratio of stuffer (X direction) to binder (Z direction) yarns and also by changing the relative position of the latter. Two types of ballistic evaluations, namely energy absorption against low velocity (165±10 ms−1) bullets and back face signature (BFS) against high velocity (430±10 ms−1) bullets were carried out for neat and STF impregnated 3D fabrics and their panels. STF impregnation improved impact energy absorption by 3D woven aramid fabrics. Increasing the ratio of stuffer to binder yarns was found to be beneficial in terms of impact energy absorption and resistance against bullet penetration. STF impregnated 3D fabrics having 4:1 stuffer to binder ratio performed the best in ballistic evaluations. Synergistic effect of 3D woven fabric structure and reinforcement of STF was found to be the key for successful design of soft body armour.

On the use of selective stitching in stiffened composite panels to prevent skin-stringer debonding

Abstract Composite laminates are generally characterized by poor mechanical properties along the thickness direction, therefore they are highly susceptible to delaminations. A potential increase in structural efficiency may be obtained by using 3D reinforcements technologies. In this paper, an experimental/numerical study is presented focusing on the effects of a single reinforcement seam of stitches along the edge of a stringer foot, in a stiffened composite panel. Three-point bending tests have been performed on a skin-stringer configuration by considering variations of the skin thickness, the stitching technique, the pitch and the yarn diameter. Then, a Finite Element Model has been developed capable to simulate the mechanical behaviour of stiffened composite panels with selective stitching and to assist the design of more complex geometrical configurations by estimating the damage behaviour, as well as the onset and the propagation of delamination taking into account the effect of the selective stitching. The numerical results, in terms of load vs applied displacements, have been found in good agreement with the experimental data proving the effectiveness of the introduced numerical model. The numerical results have confirmed the potential beneficial effects of stitching in terms of delay of the crack initiation and growth, of smoother delamination profile, of increase in the stiffness of the structure with a reduction of the delamination area.

Modeling the viscoelastic compaction response of 3D woven fabrics for liquid composite molding processes

In liquid composite molding processes, the compaction characterization of fibrous reinforcements plays a key role in determining the thickness, fiber volume content, and part shape. This study presents detailed experimental and modeling work to study the viscoelastic compaction response of three different types of 3D woven carbon fiber reinforcements, namely, orthogonal, angle interlock, and layer-to-layer, each having a different weave style and z-binder yarn pattern. For all reinforcements, single-step, multistep and cyclic compaction experiments were conducted. A nonlinear viscoelastic model is presented that accounts for large deformations and viscous effects, to capture the response of the material under various loading histories. Model verification is also presented to capture each response with separate sets of material parameters. Parametric studies are also performed to analyze the role of model parameters on the response of different types of loadings. X-ray computed tomography analysis showed significant permanent deformation of z-binder yarns through the thickness of the reinforcements. The comparison of modeling results with the experimental data show that the model is able to capture the stress decay after multiple compaction cycles, yet needs further investigations to predict complete cyclic hysteresis. However, model results agree reasonably well with the single and multistep compaction loading.

Investigation of mechanical properties of tufted composites: Influence of tuft length through the thickness reinforcement

In the aerospace, transport and energy industries, laminated composites are widely used to manufacture thicker and more complex composite pieces. Three-dimensional (3D) fabrics have been developed to replace the multilayered reinforcements in some applications to increase performance through the thickness. The present study is dedicated to improving the understanding of the mechanical performances of 3D composite pieces reinforced by tufting. The tufting process and the equipment configuration are described in detail in the present paper. A 3D reinforcement architecture is prepared by the tufting process with varied tuft length, and then resin transfer moulding technology is used to manufacture the composite samples. Tensile tests are carried out to characterise specifically the influence of the tuft length on the tensile performance of tufting threads through the thickness of composites. The tensile results and microscopic analysis on the cross section of the 3D specimens show that the tuft length strongly influences the mechanical properties of tufted composite. Therefore, control of the tuft length is necessary to optimise the tufting process and thus improve the mechanical performance of assembled thick reinforcements and composites.

Time dependent response of architectured Neovius foams

This study presents the viscoelastic behavior of an architectured foam based on the mathematically-known Neovius (N) triply periodic minimal surface (TPMS) under both time and frequency domains. Recent computational studies showed that N-based architectures possess unique multifunctional attributes when used as a three-dimensional (3D) reinforcement in composites. Here, 3D representative volume elements (RVEs) of different relative densities (i.e., the ratio of the foam's density to the density of its solid counterpart) were generated and studied using the finite element method in order to predict the effective uniaxial, shear, and bulk viscoelastic responses of N-foams as a function of relative density and/or frequency. The principle of time-temperature superposition principle was used to create the master curve of the observed relative-density dependent mechanical responses (loss tangent, storage and loss moduli) in frequency domains. Reduced uniaxial, bulk and shear stiffness-loss map results suggested that the N-foam possesses strongest uniaxial viscoelastic response while highest damping can be achieved under shear responses. Relaxation behavior of N-foam was compared with other seven different types of open-cell periodic foams. It was found that N-foam shear response is similar to Reinforced Body Centered Cubic (RBCC) foam and possesses highest bulk and uniaxial relaxation responses. Among these foams, we found that N-foam is the best candidate to use as a damper under shear loading conditions however best to be used as light weight stiffener under uniaxial and bulk loadings.

In-plane strength enhancement of laminated composites via aligned carbon nanotube interlaminar reinforcement

Aerospace-grade unidirectional carbon fiber laminate interfaces are reinforced with high densities (>10 billion fibers per cm2) of aligned carbon nanotubes (A-CNTs) that act as nano-scale stitches. Such nano-scale fiber reinforcement of the ply interfaces has been shown to increase interlaminar fracture toughness and here we show that laminate in-plane strengths are also increased. Delamination damage modes associated with pre-ultimate failure are suppressed in the in-plane loaded laminates, significantly increasing load-carrying capability: tension-bearing (bolt pull out) critical strength by 30%, open-hole compression ultimate strength by 14%, and L-section bending energy and deflection by more than 25%. No increase in interlaminar or laminate thickness is observed due to the A-CNTs, but rather the ∼10 nm diameter carbon nanotubes interdigitate between carbon fibers in the adjacent laminae, i.e., the observed reinforcement is not due to formation of a thicker interlayer. These increases in substructural in-plane strengths are in stark contrast to degradation that typically occurs with existing 3D reinforcement approaches such as stitching, weaving and z-pinning.