Overlap Length Research Articles

Optimisation of bonded and hybrid step lap joints of thick carbon fibre/epoxy panels used in aircraft structures

The use of composite materials is widely spread across the Aerospace sector. Scarf and step lap joints are amongst the most commonly used methods for flush joint repairs; they restore original stiffness and nearly original strength. Prior investigations conducted by the authors have shown that bonded and hybrid step lap joints have superior static strength capabilities than bolted joints. Hybrid step lap joints have shown the highest fatigue resistance than its bolted and bonded counterparts. This investigation aims at optimising the previous step lap joint design containing five steps with a 90 mm long overlap length in order to improve joint efficiency. Four new step lap joint configurations are considered based on a parametric study conducted using Abaqus; two of which contain seven steps and a 130 mm long overlap (bonded and hybrid) whilst the other two contain six steps and a 105 mm long overlap (bonded and hybrid) with a tapered outer step region. Experimental tests right through to numerical modelling using three-dimensional (3D) finite element (FE) models have been investigated. Adhesive non-linear material properties, fastener contacts and friction forces were all included in the 3D FE models. The Multicontinuum Theory (MCT) is used to simulate the progressive failure process and determine the stress states in the four configurations. Overall the FE models are able to accurately predict the bonded and hybrid joint strengths and highlights the importance of not only optimising the number of steps and their lengths but also the individual step heights. This is a parameter which has often been overlooked by fellow researchers. Experimental results showed that all four step lap joint configurations have significant improvement under static and fatigue load cases; the greatest improvement is seen in the two bonded step lap joint configurations. Overall the hybrid joint configuration consistently outperformed the bonded joint configurations. The presence of fasteners supress crack propagation, minimise peak peeling stresses at the ends of the overlap and increase the durability of the joint. This enables early crack detection which can assist composite joint repair certification.

The effects of using intermittent metal part reinforcement and countersink on the strength of adhesively bonded joints

This study investigates the impact of two innovative methods, namely, intermittent metal part reinforcement and countersinking, on the strength of single lap joints (SLJs). In the former method, metal inserts are strategically integrated within the adhesive layer, while the latter involves the application of countersinks on the adherends to create conical depressions for adhesive application. The metal inserts and countersink samples were fabricated using a 5-axis CNC milling machine. Subsequently, the joints were produced by subjecting the samples to 0.15 MPa pressure and 70 °C temperature for 120 min with the aid of a hot press. Tensile tests were conducted on single lap joints (SLJs) featuring five different configurations of intermittent metal part reinforcement joints (IMRJs) with varying sizes and positions of reinforcements, as well as six countersunk reinforced joints (CRJs) with different orientations of countersinks, all while keeping the width and overlap length constant. A two-dimensional finite element (FE) model of the IMRJ was constructed using ABAQUS software, incorporating cohesive zone elements to simulate the behavior of the adhesive layer (DP 460). The model's accuracy was confirmed through experimental verification. Additionally, fractographic analysis of the failure surfaces of both types of joints was carried out. The inclusion of IMRJs and CRJs in the SLJs increased their load-carrying capacity by more than 10 % and 30 %, respectively.

Hybrid grouted joints: Load bearing and failure behaviour under static, axial loading

The hybrid grout joint is a new type of joint to structurally connect circular hollow sections (CHS). It combines the two joining processes adhesive bonding and mineral grouting. While the adhesive bonding process is performed under controlled environmental conditions, the grouting is conducted on-site. Of particular interest is its ability to compensate tolerances, which makes it very interesting in various areas of steel construction. In the present paper, the influence of different factors on the load-bearing behaviour under quasi-static, axial loading is investigated. In general, the connection is characterised by high stiffness and load-bearing capacity. With increasing overlap length, the capacity increases, although because of the stress concentrations average shear strength decreases. The radial stiffness of the adherends is identified as a second considerable influence factor for the load-bearing capacity. With increasing radial stiffness (decreasing diameter/thickness ratio), bond strength increases. The load capacity under compression is about 10% lower than under tension. Two investigated imperfections, misalignment and eccentricity, exerted no negative influence on the load-bearing behaviour. While changing the adhesive influences the load-bearing behaviour, a change of grout has negligible influence. Additional tests on hybrid grouted joints with reinforced grout layer show, that reinforcing the grout layer is not necessary.

Investigation of In0.7Ga0.3As/Ga0.5As0.5Sb-Based Heterojunction TFET with Ferroelectric Gate Dielectric for Performance and Reliability

This paper investigates In[Formula: see text]Ga[Formula: see text]As/Ga[Formula: see text]As[Formula: see text]Sb-based Heterojunction Tunnel Field Effect Transistor with ferroelectric dielectric as stack layer, namely Ferroelectric Dual Material Stacked Double Gate Heterojunction TFET (FDMSDG-HJTFET) for the first time for performance and reliability. Ferroelectric gate dielectric has been inculcated in the device design in addition to the doping of Ga[Formula: see text]As[Formula: see text]Sb in the source region and In[Formula: see text]Ga[Formula: see text]As in the drain region, respectively. The performance of the proposed device is quantified in terms of DC electrical parameters and short channel parameters. The reliability analysis of the proposed device has been carried out in terms of influence of variations of interface trap charges, gate-source overlap length and temperature on the device transfer characteristics. From the simulation results, it can be manifested that the proposed device presents superior DC electrical characteristic and reduced short channel effects as compared to the GaSb/Si Dual Material Stacked Double Gate Heterojunction TFET (GaSb/Si DMSDG-HJTFET), under the influence of group III–V materials and ferroelectric gate dielectric. In addition to this, the proposed device depicts elevated immunity to presence of interface trap charges at the interface, variations in gate-source overlap length and temperature variations as well. The implication of TiO2 as dielectric stack over SiO2 provides exceptional capacitive coupling at the interface and thus assists in the improvement of electrical characteristics of the device by enhancing the electric field. The outcome of the simulation results presents that Ga[Formula: see text]As[Formula: see text]Sb/In[Formula: see text]Ga[Formula: see text]As-based Ferroelectric Dual Material Stacked Double Gate Heterojunction TFET (FDMSDG-HJTFET) can prove to be a competitive alternative for high performance applications with improved reliability. The design and simulation of the proposed device structure has been executed using technology computer-aided design (TCAD) tool.

Numerical and experimental study of the residual strength of CFRP laminate single-lap joint after transverse impact

The adhesive joint is one of the efficient joining method in the composite structures, and it is important to comprehend the behavior of adhesive joints during impact in order to design stronger and safer structures. This paper investigates the residual strength of CFRP single-lap joints (SLJs) after transverse impact using both finite element analysis (FEA) and experimental methods. The impact damage FEA model and static tensile strength FEA model are established using the Hashin failure criterion and cohesive zone model. The impact damage results of the SLJs are transferred to static tensile strength FEA model using the restart analysis method. The CFRP single-lap joint models with different impact energies and lap lengths are analyzed. According to the research requirements, a total of 24 SLJ specimens with [45/0/-45/90]s lamination are manufactured, and the impact test and tensile strength test are conducted sequentially. For the SLJs with a 20 mm overlap length but different impact energies (1 J, 2 J, and 4 J), the maximum and minimum residual strength errors are 12.6 % and 6.2 % respectively. The results show that the tensile strength of the joint decreases significantly after impact. Specifically, the residual strength of the SLJ after a 4 J impact is 2902 N, whereas the strength of the non-impact SLJ is 4088 N. When considering the 20 mm, 30 mm, and 40 mm overlap length SLJs with a 4 J impact energy, the errors in the residual strength coefficients between FEA and experiment are all within 3 %. Additionally, the residual strength coefficient of a 40 mm overlap length increases by approximately 10 % compared to a 20 mm overlap length. These results demonstrate that the proposed FEA model can accurately simulate the impact and residual strength of SLJs with reasonable accuracy.

Experimental and numerical investigation of adhesively bonded kfrp/steel double strap joints incorporating eggshell powder-toughened epoxy adhesive

Due to the environmental concerns, the application of natural FRPs to replace synthetic fibre as a strengthening material has increased. Kenaf fibre-reinforced polymer (KFRP) has comparable specific strength with glass fibre-reinforced polymer (GFRP). Moreover, epoxy resin is widely used as a matrix of composites and adhesives; however, it has low shear strength. Improvement of epoxy properties is therefore required, for example, by incorporating biofiller such as eggshells from household waste, which contain calcite, to improve its shear strength. Testing series includes variations of KFRP bond length, KFRP thickness and eggshell filler volume fractions. All the DSJ specimens underwent a two-stage testing process, experimentally and numerically. In Stage 1, experimental work was performed on the specimens through quasi-static tensile tests, following the ASTM D3528–96. In Stage 2, numerical studies were conducted to predict the strength using the extended finite element method (XFEM) within ABAQUS CAE. Subsequently, the strength prediction from developed 2-D FEA models was validated by the experimental datasets. All testing specimens exhibited KFRP rupture mode. For all the studied overlap lengths, the joint strength increased with the increase of the studied composite's adherend thickness (1 - 4 mm); however, the overlap length reached the optimum at the overlap length of 80 mm, where beyond that overlap length, the joint strength tended to decrease. The maximum joint strength is achieved with a combination of 80 mm bond length and 4 mm KFRP thickness, resulting in a 226.5% enhancement compared to the baseline (composite thickness of 1 mm, with adhesive without filler). Moreover, it was found that volume fraction of 5% eggshell was the optimum. The strength prediction was performed using an extended finite element method (XFEM), In general, there were good agreements in both experimental datasets and XFEM models, with discrepancies of less than 16.1% (averaging less than 8%). The FEA modelling approaches are promising for predicting the joint strength of KFRP/steel DSJ.

Effects of Sheared Edge and Overlap Length on Reduction in Tensile Fatigue Limit before and after Hydrogen Embrittlement of Resistance Spot-Welded Ultra-High-Strength Steel Sheets

The effects of a sheared edge and overlap length on the reduction in the tensile fatigue limit before and after hydrogen embrittlement of resistance spot-welded ultra-high-strength steel sheets were investigated. Ultra-high-strength steel sheets with sheared and laser-cut edges were subjected to resistance spot welding followed by hydrogen embrittlement via cathodic hydrogen charging and subjected to static tensile shear and fatigue tests. The distance between the resistance spot weld and the sheared and laser-cut edges was changed by changing the overlap length, and the influence of the weld position was investigated. In the tensile shear test, the maximum load decreased with decreasing overlap length and the maximum load decreased with hydrogen embrittlement, but the effect of hydrogen embrittlement was smaller than that in the fatigue test. In the fatigue test, the fatigue mode changed from the width direction to the sheared edge direction with the increase in the repeated load. Even if the overlap length was reduced, the fracture changed to the sheared edge direction. In the specimens with sheared edges, the effect of fatigue limit reduction due to hydrogen embrittlement was greater than in the specimens with laser surfaces. In particular, the effect was greatest when the fatigue mode was changed via hydrogen embrittlement.

Accelerating environmental ageing effects of adhesively bonded aluminium joints by using smaller bonding areas

ABSTRACT In all areas of application, adhesive joints are exposed to environmental conditions, which can weaken the joint. To verify the functionality of the joints for a certain service life, accelerated ageing tests are used. To assess the mechanical performance of aged joints, single lap joints (SLJ) are often used. The influence of various geometries of SLJ on the strength and stress behaviour is known. The various ageing processes in bonded joints are not yet sufficiently known. Thus, the influence of the specimen geometry on the ageing behaviour cannot be reliably estimated and is therefore investigated in this work. SLJ with different geometries made of an AlMgSi alloy and a one-component epoxy-hybrid adhesive were artificially aged. T dimensions of the SLJ were varied in width, overlap length, adhesive thickness or joint design. Similar ageing results were seen in a significant shorter time with narrower samples or shorter overlap length. A SLJ with a bonding area of 6.3 mm x 6.3 mm was derived from these results. After 4–5 weeks of ageing, this shows comparable results to the standard test SLJ after 8 weeks. This allows to speed up industrial ageing tests nearly by factor two without changing ageing mechanisms.

Parametric cohesive zone analysis of bi-adhesive single-step joints

The industry has advanced in replacing traditional joining methods, such as screwing/riveting and welding, especially the aeronautical and automotive industries, which have adopted the adhesive bonding method. This method has the advantages of simplifying the process, improving performance in terms of fatigue load, and improving the union between dissimilar materials. In addition, the development of computational numerical methods, with greater precision, has contributed to the dimensioning of joints, as well as the prediction of the resistance of these joints, which has contributed to more reliable simulations of different adhesive bonding solutions and their industrial implementation. Different modifications to the conventional designs are addressed in the literature to achieve the best results, including geometrical and material modifications. In the present research, the strength of single-step single-adhesive joints and bi-adhesive joints (BAJ) manufactured with AW 6082-T651 aluminium adherends is experimentally and numerically studied for different overlap lengths (LO). Three commercial adhesives were studied, from brittle to ductile, along with different adhesive combinations in the BAJ technique. The experimental work was mainly used for numerical model validation. The numerical analysis took advantage of triangular cohesive zone models (CZM) and included the study of peel and shear stresses, strength, and energy to failure. It was possible to validate the CZM accuracy by comparison with the experimental data. The analysis carried out showed that the BAJ technique did not reveal significant increases in strength compared to single-adhesive joints. However, when damage tolerance and dissipated energy are analysed, a noticeable increase in performance is observed, especially in joints with larger LO.

Failure Analysis of Hybrid FREP Composites Laminated Bonded Tubular Lap Joints

Fibre-reinforced polymer composites have found extensive applications in the oil, gas industries. The use of interlayer Hybrid composite pipes are used in several engineering applications is increasing due to their superior properties such as high specific strength, high chemical resistance and resistance to UV rays .Hybrid composite adherends lap joints need to be explored to develop a cost-effective combination of materials to address the certain complex behavior due to hybridization . It is essential to understand the mechanical behavior of Hybrid Tubular Lap Joints (HTLJ) to provide design guidelines for safe performance of joint. In the present work Failure analysis of the adhesively bonded HTLJ is performed. Stress distributions within the joint region are estimated under tensile load. Failure indices at critical interfaces are evaluated by using Quadratic Failure Criterion (QFC).The failure index values of HTLJ were obtained for different overlap lengths. Effective overlap length for suitable performance of the joint is determined based on the Tsai-Wu failure criterion.

Efficient design of overlapped purlins loaded by gravity

Cold-formed steel represents a competitive solution for a wide range of structural applications due to its efficient use of material and its rapid manufacturing and installation. Concerning the purlin systems, continuous Z-shaped steel purlins overlapping over the intermediate rafters are the best choice to minimise material use. The connection between two purlin segments can be achieved by overlapping the profiles over the supports. Using a finite element model validated against experimental data, an extensive study was performed to identify the parameters that influence the design of overlapped purlins loaded by gravity. The analysis is performed on a two-span continuous beam under gravity loading. To capture as much as possible the real behaviour of the purlin, the sheeting is included in the model. The design of lapped purlins was found to be primarily influenced by the length of the span and the overlap length. The detail of the lapped connection is relevant only for short overlaps. A material efficiency study was performed to determine how the overlapped purlin should be designed to minimise material use. Numerical results demonstrate that short overlaps behave poorly from a material efficiency point of view. The optimal overlap length Lp1 + Lp2 was found to be between 15 and 25 % of the length of the span. Connection details or the use of unsymmetric overlaps do not bring a significant increase in terms of material efficiency. However, the use of higher-grade steels bring great improvements.

Experimental and numerical investigation of tensile-loaded staggered bolted and hybrid pultruded composite double lap joints

On-site construction projects typically employ staggered fastener patterns. This article describes the application of Hollo Bolts (HB). It also highlights the effectiveness of using flexible epoxy adhesive to increase the load-carrying capacity of staggered connections fastened with HB. The distribution of loads between connecting elements largely determines joint performance. Pultruded glass fiber reinforced polymer (PGFRP), bolted (B), and hybrid bolted/bonded (BB) double lap joints were subjected to a typical pulling load and numerically validated in this investigation. To simulate delamination effects, a Cohesive Zone Model with a 3D progressive damage analysis was developed. In addition, a parametric study capturing the influence of various geometrical variables such as e/d, overlap length, bolt size, adherend thickness, and the number of bolts was used to compare both categories of joints in detail. The results indicate that for staggered connections fastened with HB, an efficient load transfer can be obtained in conjunction with flexible epoxy adhesive. It is anticipated that this interaction will be even more effective as the overlap length, adherend thickness, and fastener diameter increase. The present study proves that BB connections are 43.56% stronger than B connections.

Enhancing stiffness and damping characteristics in nacreous composites through functionally graded tablet design

Nacreous composites offer significant potential for applications in structural damping materials, which require simultaneous high stiffness and damping properties. In this study, we propose that the incorporation of functionally graded tablets into nacreous composites can further enhance both stiffness and damping energy dissipation concurrently. Analytical formulae for the loss modulus, storage modulus, and loss factor, validated through a series of finite element analyses, were derived to investigate the effects of variations in tablet modulus, structural geometry, and constituent properties. Our analyses demonstrate that designing a parabolic modulus distribution in the tablets can yield optimal strengthening and damping results. Furthermore, the characteristic modulus variation degree, overlap length, and frequency emerged from the systematic optimization of loss and storage moduli. Additionally, numerical experiments and model predictions demonstrate that the loss modulus of functionally graded nacreous composites surpasses the predetermined design limit and is five times greater than that of existing homogeneous nacreous composites. Combining the developed theoretical model presented here with advanced 3D printing techniques would offer effective guidelines for designing and fabricating high-performance bio-inspired structural damping composites.

Performance and failure analysis of perforated CFRP/aluminum alloy bonding and self-piercing riveting hybrid joints

This paper explores the new hybrid hole-drilled bonding and self-piercing riveting (HH-BR) connection technique to enhance the strength and overall performance of carbon fiber reinforced polymer (CFRP) and dissimilar metal materials at joint interfaces. The forming quality, mechanical performance, failure modes, and fracture characteristics of the CFRP and aluminum alloy joints utilizing the HH-BR procedure were analyzed in detail and compared with the joints of the hole-less adhesive-bonding self-piercing riveting (H-BR) and self-piercing riveting (SPR). At the same time, the effects of different rivet performance levels, overlap lengths, and various fiber orientation angles on joint performance were discussed. The results show that joints made by the HH-BR technique have a substantial advantage in terms of achieving superior mechanical performance and interlocking value. Firstly, HH-BR joints with bent rivets and torn fibers have connection strengths that are noticeably higher than those with CFRP laminate delamination or rivet pullout failure. The use of the HH-BR technique for joining CFRP/aluminum alloy culminated in reduced strength loss and higher energy absorption than H-BR and SPR joints, improving the joint's overall strength. Secondly, the interlock value between the rivet and the plate, is what essentially determines the strength of HH-BR joints, especially evident in connections with 0°/90° fiber orientation and more overlap lengths. The results also show that there is a strong relationship between the height of the rivet head and the joint's mode of failure, and the height of the rivet head is affected by the rivet force. Furthermore, the interlock value's magnitude, the joint's remaining bottom thickness, and the metal material's capacity for plastic deformation are all directly correlated.

Organic Bilayer Heterostructures with Built-In Exciton Conversion for 2D Photonic Encryption.

Organic multilayer heterostructures with accurate spatial organization demonstrate strong light-matter interaction from excitonic responses and efficient carrier transfer across heterojunction interfaces, which are considered as promising candidates toward advanced optoelectronics. However, the precise regulation of the heterojunction surface area for finely adjusting exciton conversion and energy transfer is still formidable. Herein, organic bilayer heterostructures (OBHs) with controlled face-to-face heterojunction via a stepwise seeded growth strategy, which is favorable for efficient exciton propagation and conversion of optical interconnects are designed and synthesized. Notably, the relative position and overlap length ratio of component microwires (LDSA /LBPEA = 0.39-1.15) in OBHs are accurately regulated by modulating the crystallization time of seeded crystals, resulting into a tailored heterojunction surface area (R = Loverlap /LBPEA = 37.6%-65.3%). These as-prepared OBHs present the excitation position-dependent waveguide behaviors for optical outcoupling characteristics with tunable emission colors and intensities, which are applied into two-dimensional (2D) photonic barcodes. This strategy opens a versatile avenue to purposely design OBHs with tailored heterojunctions for efficient energy transfer and exciton conversion, facilitating the application possibilities of advanced integrated optoelectronics.

3D geometry and displacement transfer of an oblique relay zone on outcropping normal faults

Relay zones on normal faults accommodate transfer of displacement between adjacent fault segments. We study vertical and horizontal displacement transfer mechanisms across a relay zone adjacent to the Moab Fault at Courthouse Rock (Utah, USA). The relay zone has a reservoir scale (map overlap length ca. 750 m, separation ca. 150 m), and is bounded by two normal fault segments with maximum throw of ca. 12 m. The relay zone is exposed on multiple, sub-parallel cliff faces and intervening rock pavements. We use photogrammetry of these exposures to build a 3D virtual outcrop model of the relay-bounding faults, subordinate faults deforming the relay zone and seven faulted stratigraphic horizons. The relay-bounding faults are right-stepping in map view and contractional in cross-section, defining a relay zone oblique to bedding in 3D. Displacement is transferred both horizontally and vertically across the relay zone. Horizontal transfer of displacement is achieved by a shallow dipping (<1°) relay ramp, whereas vertical transfer is achieved by antithetic faults within the relay ramp. Our analysis demonstrates that multiple mechanisms can work in conjunction to facilitate transfer of displacement across individual relay zones.

Flexural behavior of wet panel-to-panel groove-and-tongue joints provided with lapped U-bars

A comprehensive experimental campaign was carried out to investigate the flexural behavior of wet joints provided with lapped U-bars connecting two precast concrete panels. Eleven assemblies were tested in 4-point bending. Nine assemblies had wet groove-and-tongue joints provided with U-bars, and different values for the overlap length, joint width, and concrete strength. As a reference, the remaining two assemblies had wet groove-and-tongue or flat joints reinforced with straight-through bars. All the assemblies but two were provided with water-stop strips. The test results show that a lap length of 15 times the bar diameter is sufficient to guarantee the same bending capacity as straight-through bars. Based on the deformations of the panels subjected to bending, a strut-and-tie model was developed to predict the flexural capacity of linear wet joints provided with lapped U-bars. The proposed model effectively predicts the flexural capacity of the assembly of two panels since the theoretical predictions and the test results differ by less than 10%.

Impact loading analysis of double-lap composite bonded joints

Currently, static modelling of adhesive joints is mostly understood, oppositely to dynamic problems, including impact. However, the literature is still scarce on the impact analysis of bonded joints, with preponderance to cohesive zone models (CZM). This work aims to predict the behaviour and strength of composite adhesively-bonded double-lap joints (DLJ) under impact loads, under different overlap lengths (LO). For this purpose, numerical simulations by the finite element method (FEM) and CZM are considered. The adhesives used for this numerical study are the Araldite® AV138 and the Sikaforce® 7752. Initially, a study was carried out with single-lap joint (SLJ) experimental data, acquired from a previous work, to validate the proposed technique to analyse impact-adhesive joints. DLJ analysis was based on elastic peel (σy) and shear (τxy) stresses, load-displacement (P-δ) curve analysis, and strength prediction. A CZM parameter-influence analysis on the DLJ strength predictions was also carried out. Validation of the proposed numerical technique was successfully accomplished to model bonded joints under impact loads. On the other hand, clear design guidelines were provided for these joints under impact.

Parametric Testing of EQTransformer’s Performance against a High-Quality, Manually Picked Catalog for Reliable and Accurate Seismic Phase Picking

Abstract This study evaluates EQTransformer, a deep learning model, for earthquake detection and phase picking using seismic data from the Southern Alps, New Zealand. Using a robust, independent dataset containing more than 85,000 manual picks from 13 stations spanning almost nine years, we assess EQTransformer’s performance and limitations in a practical application scenario. We investigate key parameters such as overlap and probability threshold and their influences on detection consistency and false positives, respectively. EQTransformer’s probability outputs show a limited correlation with pick accuracy, emphasizing the need for careful interpretation. Our analysis of illustrative signals from three seismic networks highlights challenges of consistently picking first arrivals when reflected or refracted phases are present. We find that an overlap length of 55 s balances detection consistency and computational efficiency, and that a probability threshold of 0.1 balances detection rate and false positives. Our study thus offers insights into EQTransformer’s capabilities and limitations, highlighting the importance of parameter selection for optimal results.

Influence of the architecture on the strength of a unidirectional composite with recycled discontinuous fibres

Recycled fibre composites are made of discontinuous fibres that are not of the same length. Their mechanical behaviour depends on the load transfer between fibres and in particular on the overlaps between fibres of different lengths. The objective of the study is to show the influence of the architecture on the failure of a discontinuous reinforcement composite. A numerical model was developed to simulate different overlap lengths between fibres. The influence of defects, in this study small overlap length between fibres, and of their distribution in the architecture, was thus highlighted. Experimental tests allowed to validate the model. The model makes it possible to calculate a critical overlap length, length from which the composite strength reaches its maximum. In particular, simulations showed that discontinuous fibre architectures with small overlap lengths at the edge strongly decrease the strength of the composite. On the contrary, defects in the core of the architecture are tolerable. These results open perspectives for the choice of architectures based on recycled fibre in order to optimize the final properties of the composite.