About the impact behavior of woven-ply carbon fiber-reinforced thermoplastic- and thermosetting-composites: A comparative study

This study is aimed at comparing the response of TS-based (epoxy) and TP-based (PPS or PEEK) laminates subjected to low velocity impacts. C-scan inspections showed that impact led to diamond-shaped damage resulting from different failure mechanisms: fiber breakages in warp and weft directions, more or less inter-laminar and intra-ply damage, and extensive delamination in C/PEEK and C/epoxy laminates. The permanent indentation can be ascribed to specific mechanisms which mainly depend on many factors including the ultimate out-of-plane shear strength, and the interlaminar fracture toughness in modes I–II–III. In TP-based laminates, the matrix plasticization seems to play an important role in matrix-rich areas by locally promoting permanent deformations. Fiber-bridging also prevents the plies from opening in mode I, and slows down the propagation of interlaminar and intralaminar cracks in modes II–III. Both mechanisms seem to reduce the extension of damages, in particular, the subsequent delamination for a given impact energy. In epoxy-based laminates, the debris of broken fibers and matrix get stuck in the cracks and the adjacent layers, and create a sort of blocking system that prevents the cracks and delamination from closing after impact

Influence of matrix toughness and ductility on the compression-after-impact behavior of woven-ply thermoplastic- and thermosetting-composites: A comparative study

This study was aimed at comparing the residual compressive strength and behavior of TS-based (epoxy) and TP-based (PPS or PEEK) laminates initially subjected to low velocity impacts. Provided that the impact energy is not too low, the permanent indentation is instrumental in initiating laminates local buckling under compressive loadings. CAI tests revealed that matrix toughness is not the primary parameter ruling the damage tolerance of the studied materials. However, matrix ductility seems to slow down the propagation of transverse cracks during compression thanks to plastic micro-buckling which preferentially takes place at the crimps in woven-ply laminates. It could therefore justify why the matrix toughness of TP-based laminates does not result in significantly higher CAI residual strengths. Finally, the compressive failure mechanisms of impacted laminates are discussed depending on matrix nature, with a particular attention paid to the damage scenario (buckling and propagation of 0° fibers failure)

Influence of temperature on the impact behavior and damage tolerance of hybrid woven-ply thermoplastic laminates for aeronautical applications

Impact damage tolerance of hybrid carbon and glass fibers woven-ply reinforced PolyEther Ether Ketone(PEEK) thermoplastic (TP) laminates obtained by consolidation process is investigated. Service temperature being one of the most important parameters to screen TP or thermosetting matrix for aeronautical purposes, impact testing at room temperature (RT) and near the glass transition temperature (Tg) has been conducted. From the results, it turns out that temperature has little influence on the impact behavior in terms of maximum force developed or maximum deflection, though it reduces the dissipated energy especially at lower impact energy. However, temperature has a strong effect on the internal and external damages caused to the plate, as it increases the permanent indentation and it limits the projected delaminated area. As for the influence of temperature on the compressive residual strength of the laminates, it also appears that the classical experimental set-up for CAI tests is not completely appropriate to draw a clear cut conclusion. At last the obtained results show that the considered TP-based laminates are characterized by a very good impact behavior and a high-degree of damage tolerance

De la contribution de la visco-élasto-plasticité au comportement en fatigue de composites à matrice thermoplastique et thermodurcissable

La présente étude vise à comprendre l'influence du comportement visco-élasto-plastique d'une matrice TP (PPS) et TD (Epoxy) sur le comportement en fatigue à haute température de composite tissés à fibres de carbone. Une analyse fractographique a permis de révéler le rôle déterminant des zones riches en matrice au niveau des plis à +-45 dans la chronologie d'endommagement et sur le comportement en fatigue de stratifiés à plis croisés et quasi-isotropes. Afin d'évaluer la contribution de la viscoélasticité et de la viscoplasticité de la matriceTP au comportement thermomécanique des stratifiés C/TP à T>Tg, un modèle viscoélastique de Norton généralisé ont été implémentés dans le code Eléments Finis Cast3m. Une technique de corrélation d images numériques (CIN) a été mise œuvre pour tester la capacité du modèle à prédire la réponse du stratifié dans le cas de structures à forts gradients de contraintes.The present work was aimed at investigating the influence of the matrix visco-elastoplasticbehavior on the high-temperature fatigue behaviour of carbon woven-ply TP (PPS)-and TS (Epoxy)-based laminates. A fractography analysis showed that matrix-rich areas at the vicinity +-45 plies proved to be instrumental in modifiyng the damage chronology and the fatigue behaviour of angle-ply and quasi-isotropic laminates.In order to evaluate the contribution of viscoelasticity and viscoplasticity to the thermo-mechanical response of C/TP laminates at T>Tg, a linear spectral viscoelastic model and a generalized Norton-type viscoplastic model have been implemented int the Finite Elements code Cast3m. A digital image correlation technique has been used to validate the model's ability to predict the response of high gradient structures to various loading.ROUEN-INSA Madrillet (765752301) / SudocSudocFranceF

Etude expérimentale du comportement en fluage/recouvrement de composites C/TP et évaluation du modèle de Schapery

L'objectif de cette étude est d'appréhender expérimentalement le comportement en fluage/recouvrement de composites C/Thermoplastique (PPS) par des essais à différents niveaux de chargements et à une température supérieure à la Tg du C/PPS. Afin d'évaluer la capacité du modèle de Schapery à rendre compte du comportement en fluage-recouvrement de composites C/TP, le logiciel LAMKIT (EADS) a été exploité en première approche. Ce dernier dispose d'un module basé sur ce modèle, dont les paramètres sont identifiés à partir des essais expérimentaux

High temperature translaminar fracture of woven-ply thermoplastic laminates in tension and in compression

PEEK reinforced by a woven carbon fibers obtained by consolidation process, has been studied by means of Compact Tension (CT) and Compact Compression (CC) tests. An orthotropic laminate and two quasi-isotropic laminates, have been tested at room temperature (RT) and at 150 ◦C (i.e. for a temperature slightly higher than the glass transition temperature Tg), with the purpose of evaluation the influence of the stacking sequence and the temperature on the damage mechanisms. The CT type tests show that the temperature influence on the overall mechanical response remains low. In contrast, the CC type tests show a decrease in the mechanical resistance and an augmentation in the global ductile behavior. By means of the 2D Digital Image Correlation and the implementation of a algorithm based on the sigma indicator (confidence interval in the area of interest), the crack propagation was measured during loading, then the G-R curves have been obtained from the compliance method. In tension, there is an increase in the translaminar fracture toughness with the laminate thickness and a slight improvement in this one due to the influence of temperature. In compression, the temperature strongly decreases the translaminar fracture toughness

Prediction of the ultimate strength of quasi-isotropic TP-based laminates structures from tensile and compressive fracture toughness at high temperature

This paper is intended to test the capacity of a simple model based on fracture mechanics concepts to predict the ultimate strength of notched hybrid carbon and glass fibers woven-ply reinforced PolyEther Ether Ketone (PEEK) thermoplastic (TP) quasi-isotropic (QI) laminates under different temperature conditions. In such materials, translaminar failure is the primary failure mode driven by the breakage of 0° and 45° oriented fibers in tension as well as the formation of kink-band in compression. Single-Edge-Notched Bending (SENB), Open-Hole-Tensile (OHT) and Open-Hole- Compression (OHC) specimens have been conducted at room temperature (RT) and at a temperature higher than the glass transition temperature (Tg). The Critical Damage Growth model derived from the Average Stress Criterion and Linear Elastic Fracture Mechanics (LEFM) have been applied to open-hole specimens to determine the critical damage zone from which the fracture toughness in tension (0° and 45° fibers breakage) KIc-tension and in compression (kink-band formation) KIc_comp. are estimated. In Single Edge Notched Bending (SENB) specimens experience simultaneous tension/compression. From the estimation of KIc-tension and KIc_comp., the ultimate strength of SENB specimens can be predicted. LEFM equations combined with the critical fracture toughness in tension give relatively accurate results, suggesting that failure is driven by fibers bundles breakage in tension

Fracture mechanics of hybrid composites with ductile matrix and brittle fibers: Influence of temperature and constraint effect

The fracture behavior of hybrid carbon and glass fiber woven-ply reinforced polyether ether ketone thermoplastic quasiisotropic laminates is investigated. Single-edge-notch bending and single-edge-notch tensile tests were conducted at room temperature and at a temperature higher than the glass transition temperature (Tg) to study the influence of both the constraint effect and the temperature on the strain energy release rate in laminates with ductile polyether ether ketone matrix and brittle fibers. As failure is primarily driven by fibers breakage in tension (single-edge-notch tensile test) and in tension/compression (single-edge-notch bending), it turns out that a temperature increase has very little influence on the mode I critical translaminar fracture toughness KIc though the ductility of polyether ether ketone matrix is exacerbated at T>Tg. It also appears that the constraint effect has very little influence on KIc as single-edge-notch tensile test and single-edge-notch bending specimens have virtually the same mean value (about 45MPa. m−−√). Single-edge-notch bending specimens being characterized by a gradual failure, the G-R curves were derived from the computation of the compliance loss and the corresponding gradual crack growth in agreement with the ASTM standard E1820. From the evolution of the G-R curves at high temperature, the highly ductile behavior of the polyether ether ketone matrix at T>Tg provides a good intrinsic toughness to the material, and the bridging of translaminar crack by the glass fibers at the outer surfaces of laminates contribute to a moderate increase in its extrinsic toughness

Experimental and Finite Element Analysis of the Tensile Behavior of Architectured Cu-Al Composite Wires

The present study investigates, experimentally and numerically, the tensile behavior of copper-clad aluminum composite wires. Two fiber-matrix configurations, the conventional Alcore/ Cu-case and a so-called architectured wire with a continuous copper network across the crosssection, were considered. Two different fiber arrangements with 61 or 22 aluminum fibers were employed for the architectured samples. Experimentally, tensile tests on the two types of composites show that the flow stress of architectured configurations is markedly higher than that of the linear rule of mixtures’ prediction. Transverse stress components and processing-induced residual stresses are then studied via numerical simulations to assess their potential effect on this enhanced strength. A set of elastic-domain and elastoplastic simulations were performed to account for the influence of Young’s modulus and volume fraction of each phase on the magnitude of transverse stresses and how theses stresses contribute to the axial stress-strain behavior. Besides, residual stress fields of different magnitude with literature-based distributions expected for cold-drawn wires were defined. The findings suggest that the improved yield strength of architectured Cu-Al wires cannot be attributed to the weak transverse stresses developed during tensile testing, while there are compelling implications regarding the strengthening effect originating from the residual stress profile. Finally, the results are discussed and concluded with a focus on the role of architecture and residual stresses

Influence of impact velocity on impact behaviour of hybrid woven-fibers reinforced PEEK thermoplastic laminates

This study aims at examining the impact behavior of hybrid carbon and glass fibers woven-ply reinforced PolyEther Ether Ketone (PEEK) thermoplastic quasi-isotropic laminates. An instrumented Charpy pendulum is specifically designed to estimate its capability to perform low velocity impact tests. Through the comparison of different impact methods (Quasi-static indentation tests, Charpy and drop tower impacts), the influence of impact velocity on the impact behavior of this hybrid composite material is investigated. From the obtained results, it appears that the macroscopic impact response is similar in terms of force-displacement response. Indeed, the im- pact velocity is significantly higher (2.5 times higher) with falling weight impact testing. In PEEK-based laminates whose mechanical behaviour is time-dependent, slow loading rates (e.g. Charpy impact testing) are instrumental in ruling the dissipated energy ( + 20% at 35 and 40J) as well as in increasing the permanent indentation (1.6 times higher) that is always higher than the Barely Visible Impact Damage