Preliminary Review of Physically Based Methodologies for Predicting the Strength of Visibly Damaged Composite Laminates

2010 ◽  
Vol 654-656 ◽  
pp. 2587-2591 ◽  
Author(s):  
Alex Harman ◽  
Andrew Litchfield ◽  
Rodney Thomson
Keyword(s):  
Residual Strength ◽  
Composite Laminates ◽  
Composite Structures ◽  
Prediction Method ◽  
Cost Effective ◽  
Preliminary Review ◽  
Management Guidelines ◽  
Compression After Impact ◽  
Physically Based

Approaches to detect, assess, monitor and repair damage in critical aircraft components fabricated from composite materials are essential for safe and cost effective operation. In metallic aircraft structures, it is common to leave some fractures in situ for a prescribed period until it is convenient to repair, provided strict inspection and verification processes are in place. Under current military aircraft structural management guidelines, visible damage to critical composite components requires either immediate repair or replacement. Much has been learnt about the behaviour of damaged composite structures, but further investigation is required to develop validated residual strength and life prediction tools. A preliminary review of an early physically based, residual strength prediction method was conducted. The accuracy of this method for use in predicting the strength of composite following a complex damage was tested by comparing the results with compression-after-impact test data for a composite laminate representative of F/A 18 fracture critical structure.

scholarly journals Improvement of the Impact Properties of Composite Laminates by Means of Nano-Modification of the Matrix—A Review

2018 ◽  
Vol 8 (12) ◽  
pp. 2406 ◽  
Author(s):  
Hamed Saghafi ◽  
Mohamad Fotouhi ◽  
Giangiacomo Minak
Keyword(s):  
Composite Laminates ◽  
Cost Effective ◽  
Careful Consideration ◽  
Impact Performance ◽  
Compression After Impact ◽  
The Matrix ◽  
The Right ◽  
2D And 3D ◽  
The Impact ◽  
Selection Of

This paper reviews recent works on the application of nanofibers and nanoparticle reinforcements to enhance the interlaminar fracture toughness, to reduce the impact induced damage and to improve the compression after impact performance of fiber reinforced composites with brittle thermosetting resins. The nanofibers have been mainly used as mats embedded between plies of laminated composites, whereas the nanoparticles have been used in 0D, 1D, 2D, and 3D dimensional patterns to reinforce the matrix and consequently the composite. The reinforcement mechanisms are presented, and a comparison is done between the different papers in the literature. This review shows that in order to have an efficient reinforcement effect, careful consideration is required in the manufacturing, materials selection and reinforcement content and percentage. The selection of the right parameters can provide a tough and impact resistant composite with cost effective reinforcements.

scholarly journals Effect of Thermal Ageing on the Impact Damage Resistance and Tolerance of Carbon-Fibre-Reinforced Epoxy Laminates

Polymers ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 160 ◽  
Author(s):  
Irene García-Moreno ◽  
Miguel Caminero ◽  
Gloria Rodríguez ◽  
Juan López-Cela
Keyword(s):  
Carbon Fibre ◽  
Residual Strength ◽  
Composite Structures ◽  
Impact Resistance ◽  
Thermal Ageing ◽  
Low Velocity Impact ◽  
Impact Tests ◽  
Compression After Impact ◽  
Structural Applications ◽  
The Impact

Composite structures are particularly vulnerable to impact, which drastically reduces their residual strength, in particular, at high temperatures. The glass-transition temperature (Tg) of a polymer is a critical factor that can modify the mechanical properties of the material, affecting its density, hardness and rigidity. In this work, the influence of thermal ageing on the low-velocity impact resistance and tolerance of composites is investigated by means of compression after impact (CAI) tests. Carbon-fibre-reinforced polymer (CFRP) laminates with a Tg of 195 °C were manufactured and subjected to thermal ageing treatments at 190 and 210 °C for 10 and 20 days. Drop-weight impact tests were carried out to determine the impact response of the different composite laminates. Compression after impact tests were performed in a non-standard CAI device in order to obtain the compression residual strength. Ultrasonic C-scanning of impacted samples were examined to assess the failure mechanisms of the different configurations as a function of temperature. It was observed that damage tolerance decreases as temperature increases. Nevertheless, a post-curing process was found at temperatures below the Tg that enhances the adhesion between matrix and fibres and improves the impact resistance. Finally, the results obtained demonstrate that temperature can cause significant changes to the impact behaviour of composites and must be taken to account when designing for structural applications.

Residual Strength and Fracture Path for Drilled Epoxy-Glass Composites

2009 ◽  
Vol 65 ◽  
pp. 89-96 ◽  
Author(s):  
Mauricio Torres ◽  
Jorge Luis Gonzalez ◽  
Hilario Hernandez
Keyword(s):  
Residual Strength ◽  
Fiber Orientation ◽  
Composite Laminates ◽  
Composite Structures ◽  
Width Ratio ◽  
Fracture Path ◽  
Stress Criterion ◽  
Glass Composites ◽  
Failure Predictions ◽  
Fractographic Examination

Aircraft composite structures are mostly joined by mechanical fasteners like bolts, pins or screws. However, the effect of the presence of holes in the remaining strength of the composite structures is still being studied extensively. In this work, epoxy/glass laminates with drilled holes of different sizes were tensile tested and from these results, the residual strength was plotted. Strength vs. hole’s diameter at different fiber orientation was obtained. The fracture path and failure mechanism were identified by fractographic examination. The Point Stress Criterion (PSC) was used, in order to establish the stress intensification due to the presence of a drilled hole. A numerical model by Finite Element Method was carried out to verify the experimental results and the analytic failure predictions. A reduction of 50% in laminate strength was observed when diameter-width ratio was 0.12. The principal fracture mechanism observed in composite laminates was interface breakup. FEM results and analytic results by PSC show accuracy of 90% for predicting the damage in drilled composites.

scholarly journals Design and Validation of a Modified Compression-After-Impact Testing Device for Thin-Walled Composite Plates

2020 ◽  
Vol 4 (3) ◽  
pp. 126 ◽  
Author(s):  
Markus Linke ◽  
Felix Flügge ◽  
Aurelio Jose Olivares-Ferrer
Keyword(s):  
Residual Strength ◽  
Composite Structures ◽  
Composite Plates ◽  
Impact Testing ◽  
Testing Device ◽  
Testing Procedures ◽  
New Device ◽  
Compression After Impact ◽  
Thin Walled ◽  
Impact Damages

Thin-walled fibre reinforced composites like carbon fibre reinforced plastics are very susceptible to strength reductions due to low-velocity impact damages. In aerospace engineering, the dominating failure mechanisms of impact damaged composite structures are usually investigated based on the compression after impact (CAI) test procedure. This enables the determination of the influence of impact damages on the static residual compressive strength. CAI testing procedures are typically applicable to composite plates with thicknesses larger than 3–4 mm. If thinner panels are used, they typically fail near one of the loaded edges of the CAI device, in particular the area of the free edge (which is needed for compressing the panel) and not within the free measuring area. As a consequence, the investigated samples cannot be used as valid tests for the evaluation of the residual strength in CAI testing. In order to enable an investigation of the residual strength of thin-walled plates in CAI testing, a CAI testing device is developed based on an available CAI fixture and a standardized one. For comparability reasons, this new device exhibits the same dimensions as standardized fixtures. It shows a significant improvement with respect to standardized devices concerning the measurement of mechanical behaviour during CAI testing.

Modelling damage evolution and CAI strength of composite laminates under biaxial compression

2021 ◽  
pp. 002199832199842
Author(s):  
Bin Yang ◽  
Kunkun Fu ◽  
Yan Li
Keyword(s):  
Residual Strength ◽  
Composite Laminates ◽  
Failure Modes ◽  
Compressive Loading ◽  
Element Model ◽  
Low Velocity Impact ◽  
Biaxial Compression ◽  
Low Velocity ◽  
Damage Initiation ◽  
Compression After Impact

In this paper, a finite element model (FEM) was developed to investigate failure mechanism and compression after impact (CAI) strength of woven carbon fibre reinforced polymer (CFRP) after low-velocity impact (LVI) subjected to biaxial compressive loading. A built-in VUMAT user-defined material subroutine was adopted to take into account the in-plane damage and intralaminar delamination under LVI loading and in-plane compression. The LVI response, failure pattern, and residual mechanical properties under uniaxial compression were compared to the available experimental data to verify the numerical model. The damage initiation, subsequent evolution, final failure modes, and residual strength of the composite laminates with LVI damages subjected to biaxial compressive loading are presented by numerical methods, and the effects of impact energy and impactor diameter on the residual strength of the laminates are discussed.

scholarly journals Influence of cure parameters in polymer matrix composites using embedded optical fibers

2020 ◽  
Vol 54 (19) ◽  
pp. 2611-2621
Author(s):  
Daniel A Drake ◽  
Rani W Sullivan ◽  
Jonathan E Spowart ◽  
Katie Thorp
Keyword(s):  
Optical Fibers ◽  
Composite Laminates ◽  
Composite Structures ◽  
Polymer Matrix Composites ◽  
Processing Parameters ◽  
Internal Strain ◽  
Matrix Composites ◽  
Molding Process

The influence of cure processing parameters was investigated using strain distributions from embedded optical fibers. The determination of optimized cure parameters is often needed to achieve material properties which meet aerospace industry design requirements. Optical fibers were embedded near the midplane of thin (5 mm; [0/90/90/0]3s) composite laminates to monitor the internal strain during cure for two different cure cycles (manufacturer-recommended and an alternative two-step cure). Each laminate was fabricated using a vacuum-assisted resin transfer molding process. The internal strain with respect to the spatial position and time were monitored. During cure, greater variations in the strain near the vicinity of the laminate edges were observed. However, a two-step cure cycle revealed that the variation of strain near the laminate edges is reduced. The results demonstrate the capability of high-spatial resolution optical fibers to measure the in-situ cure and residual strain during the processing of composite structures.

Development of a mathematical model to analyze residual strength of composites after low-velocity impact

2018 ◽  
Vol 53 (8) ◽  
pp. 738-745 ◽  
Author(s):  
Camila Medeiros Dantas de Azevedo ◽  
Rayane Dantas da Cunha ◽  
Raimundo Carlos Silverio Freire Junior ◽  
Wanderley Ferreira de Amorim Junior
Keyword(s):  
Residual Strength ◽  
Composite Laminates ◽  
Repair Process ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Velocity Impact ◽  
Three Point Bending ◽  
Compression After Impact ◽  
Strength And Stiffness ◽  
The Impact

This study aimed to develop a model to analyze the residual strength of composites after low-velocity impact, using three-point bending and compression after impact tests. Two types of composite laminates with an orthophthalic polymer matrix were used: one reinforced with bidirectional E-glass fabric and the other reinforced with bidirectional Kevlar-49 fabric. To that end, an equation was developed to assess loss of strength and stiffness after impact at different distances from the impact point, and this equation was not found in any previously searched article. The results demonstrate that the laminate based in glass fiber is more appropriate for the repair process.

scholarly journals Applications of Fiber Bragg Grating Sensors in the Composite Industry

MRS Bulletin ◽  
2002 ◽  
Vol 27 (5) ◽  
pp. 400-407 ◽  
Author(s):  
Pierre Ferdinand ◽  
Sylvain Magne ◽  
Véronique Dewynter-Marty ◽  
Stéphane Rougeault ◽  
Laurent Maurin
Keyword(s):  
Electromagnetic Interference ◽  
Composite Structures ◽  
Civil Engineering ◽  
Cost Effective ◽  
Industrial Applications ◽  
Fiber Sensors ◽  
Impact Detection ◽  
Remote Measurements ◽  
Temperature Strain

AbstractOptical-fiber sensors based on fiber Bragg gratings (FBGs) provide accurate, nonintrusive, and reliable remote measurements of temperature, strain, and pressure, and they are immune to electromagnetic interference. FBGs are extensively used in telecommunications, and their manufacture is now cost-effective. As sensors, FBGs find many industrial applications in composite structures used in the civil engineering, aeronautics, train transportation, space, and naval sectors. Tiny FBG sensors embedded in a composite material can provide in situ information about polymer curing (strain, temperature, refractive index) in an elegant and nonintrusive way. Great improvements in composite manufacturing processes such as resin transfer molding (RTM) and resin film infusion (RFI) have been obtained through the use of these sensors. They can also be used in monitoring the “health” of a composite structure and in impact detection to evaluate, for example, the airworthiness of aircraft. Finally, FBGs may be used in instrumentation as composite extensometers or strain rosettes, primarily in civil engineering applications.

scholarly journals An Experimental Study of the Cyclic Compression after Impact Behavior of CFRP Composites

2021 ◽  
Vol 5 (11) ◽  
pp. 296
Author(s):  
Raffael Bogenfeld ◽  
Christopher Gorsky
Keyword(s):  
Composite Laminates ◽  
Composite Structures ◽  
Impact Behavior ◽  
Damage Growth ◽  
Compression Load ◽  
Kink Bands ◽  
Cyclic Compression ◽  
Compression After Impact ◽  
Ultimate Failure ◽  
Damage Tolerant

The behavior of impact damaged composite laminates under cyclic load is crucial to achieve a damage tolerant design of composite structures. A sufficient residual strength has to be ensured throughout the entire structural service life. In this study, a set of 27 impacted coupon specimens is subjected to quasi-static and cyclic compression load. After long intervals without detectable damage growth, the specimens fail through the sudden lateral propagation of delamination and fiber kink bands within few load cycles. Ultrasonic inspections were used to reveal the damage size after certain cycle intervals. Through continuous dent depth measurements during the cyclic tests, the evolution of the dent visibility was monitored. These measurements revealed a relaxation of the indentation of up to 90% before ultimate failure occurs. Due to the distinct relaxation and the short growth interval before ultimate failure, this study confirms the no-growth design approach as the preferred method to account for the damage tolerance of stiffened, compression-loaded composite laminates.

Effect of ethanol on the mold filling-time and mechanical properties of woven glass fiber reinforced epoxy filled with TiO2 nanoparticles

2020 ◽  
pp. 152808372097134
Author(s):  
Sherif M Youssef ◽  
M Megahed ◽  
Soliman S Ali-Eldin ◽  
MA Agwa
Keyword(s):  
Mechanical Properties ◽  
Composite Laminates ◽  
Cost Effective ◽  
Mold Filling ◽  
High Viscosity ◽  
Ansys Fluent ◽  
Glass Fiber Reinforced ◽  
Filling Time ◽  
Ethanol Addition ◽  
Woven Glass Fiber

Vacuum resin infusion (VRI) is a promising technique for manufacturing complicated structural laminates. This high viscosity of nanofilled resin increases the filling time and leads to an incomplete mold filling. The mold filling time can be reduced either by making the fiber dimensions smaller than the mold (gaps around the fibers) or by adding ethanol to nanofilled epoxy. However, ethanol addition influences the mechanical properties of composite laminates. In this study, different amounts of ethanol (0.5 wt. % and 1 wt. %) were used as a diluent to both neat epoxy and epoxy filled with (0.25 wt. %) of titanium dioxide (TiO2) nanoparticles. From results, it was found that ethanol addition saves the time for neat and nanofilled epoxy by 47.1% and 24.1%, respectively. It was found that adding 0.5 wt. % of ethanol to 0.25wt. % of TiO2 nanoparticles (GT0.25E0.5) enhances the tensile and flexural strength by 30.8% and 55.9%, respectively compared with neat specimens. Furthermore, the tensile and flexural moduli increased by 62% and 72.3%, respectively. Furthermore, the mold filling time was investigated experimentally and validated numerically using ANSYS FLUENT software. The mold filling time prediction using ANSYS FLUENT can be used to avoid resin gelation before the incomplete mold filling and thus can be considered a cost-effective methodology. The results showed that the gaps around the fibers reduce the time by 178% without affecting the mechanical properties.

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