Prediction of residual strength after impact of CFRP composite structures

2014 ◽  
Vol 15 (7) ◽  
pp. 1323-1329 ◽  
Author(s):  
Jae-Mean Koo ◽  
Jung-Hun Choi ◽  
Chang-Sung Seok
Keyword(s):  
Residual Strength ◽  
Composite Structures ◽  
Cfrp Composite

scholarly journals Fatigue performance of nanoclay filled glass fiber reinforced hybrid composite laminate

2017 ◽  
Author(s):  
◽  
John Olumide Olusanya
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Glass Fiber ◽  
Residual Strength ◽  
Composite Structures ◽  
Fatigue Performance ◽  
Fiber Reinforced ◽  
Fiber Reinforced Composite ◽  
Reinforced Composite ◽  
Glass Fiber Reinforced

In this study, the fatigue life of fiber reinforced composite (FRC) materials system was investigated. A nano-filler was used to increase the service life of the composite structures under cyclical loading since such structures require improved structural integrity and longer service life. Behaviour of glass fiber reinforced composite (GFRC) enhanced with various weight percentages (1 to 5 wt. %) of Cloisite 30B montmorillonite (MMT) clay was studied under static and fatigue loading. Epoxy clay nanocomposite (ECN) and hybrid nanoclay/GFRC laminates were characterised using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The mechanical properties of neat GFRC and hybrid nanoclay/GFRC laminates were evaluated. Fatigue study of the composite laminates was conducted and presented using the following parameter; matrix crack initiation and propagation, interfacial debonding, delamination and S–N relationship. Residual strength of the materials was evaluated using DMA to determine the reliability of the hybrid nanoclay/GFRC laminates. The results showed that ECN and hybrid nanoclay/GFRC laminates exhibited substantial improvement in most tests when compared to composite without nanoclay. The toughening mechanism of the nanoclay in the GFRC up to 3 wt. % gave 17%, 24% and 56% improvement in tensile, flexural and impact properties respectively. In the fatigue performance, less crack propagations was found in the hybrid nanoclay/GFRC laminates. Fatigue life of hybrid nanoclay/GFRC laminate was increased by 625% at the nanoclay addition up to 3 wt. % when compared to neat GFRC laminate. The residual strength of the composite materials revealed that hybrid nanoclay/GFRC showed less storage modulus reduction after fatigue. Likewise, a positive shift toward the right was found in the tan delta glass transition temperature (Tg) of 3 wt. % nanoclay/GFRC laminate after fatigue. It was concluded that the application of nanoclay in the GFRC improved the performance of the material. The hybrid nanoclay/GFRC material can therefore be recommended mechanically and thermally for longer usage in structural application.

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.

scholarly journals Influence of machining damage generated during trimming of CFRP composite on the compressive strength

2019 ◽  
Vol 54 (11) ◽  
pp. 1413-1430 ◽  
Author(s):  
N Nguyen-Dinh ◽  
C Bouvet ◽  
R Zitoune
Keyword(s):  
Surface Roughness ◽  
Mechanical Behavior ◽  
Composite Structures ◽  
Compressive Loading ◽  
Machined Surface ◽  
Reinforced Plastic ◽  
Cfrp Composite ◽  
Optical Topography ◽  
Induced Defects ◽  
Machining Damage

Machining of composite materials is a challenging task due to the heterogeneity and anisotropy of composite structures. The induced defects reduce integrity of the machined surface as well as the loading capacity of the composite structure in service. Therefore, it is necessary to quantify the damage induced during trimming and correlate the quality of the machined surface to mechanical properties. The correlation of the surface roughness criteria, widely used in literature, to the mechanical behavior raise several contradictions. For this reason, new parameters for the characterization of the machined surface are proposed and correlated to the mechanical behavior under compressive loading. In this context, carbon fiber-reinforced plastic laminates are conventionally trimmed, and the machining damage is characterized using scanning electron microscope observations, X-ray tomography, and 3D optical topography. The results reveal that crater volume and maximum depth of damage quantify the machining damage more realistic compared to the classical surface roughness criteria.

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 Damage Monitoring and Analysis of the Structure Effect on Strength of Composite Laminates

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Chia-Chin Chiang ◽  
Liren Tsai ◽  
Vu Van Thuyet
Keyword(s):  
Composite Laminates ◽  
Composite Structures ◽  
Three Dimensional ◽  
Three Dimensional Model ◽  
Element Analysis ◽  
Damage Propagation ◽  
Whole Process ◽  
Initial Damage ◽  
Open Hole ◽  
Cfrp Composite

Carbon fiber reinforced polymer (CFRP) composite materials have been widely used in industries in recent years. The design of composite structures, and open-holes for joining are also widely used. Understanding of open-hole behavior is very necessary for the design of complex structures. In this paper, the initial damage, progressive damage analysis, and the effect of structure on strength of composite laminates are investigated. Based on Hashin’s criteria, three-dimensional model of composite laminates containing a central open-hole is developed. The model is conducted by finite element analysis, commercial Abaqus software to simulate the whole process of initial damage, propagation of damage, and analysis of the effect of a few structures on strength of composite laminates containing open-hole.

scholarly journals Comparative Study on Fatigue Life of CFRP Composites with Damages

2019 ◽  
Vol 2019 (11) ◽  
pp. 28-38
Author(s):  
Marta Baran ◽  
Piotr Synaszko ◽  
Janusz Lisiecki ◽  
Sylwester Kłysz
Keyword(s):  
Residual Strength ◽  
Stress Ratio ◽  
Fatigue Tests ◽  
Equivalent Diameter ◽  
Compression After Impact ◽  
Strength Tests ◽  
Cfrp Composite ◽  
Sinusoidal Shape ◽  
Weight Impact ◽  
The Impact

AbstractIn this work, the compressive residual strength tests results, Compression After Impact (CAI), are presented. The specimens were made of carbon-epoxy prepreg E722-02 UHS 130-14. Two variants of specimens were tested: samples undamaged and samples with damage that was centrally introduced by a drop-weight impact, as per the ASTM D7136/7136M standard. An impactor with potential energy equal to 15J and the type of support required by the standard were used. The size of impacted damages, defined as an area of damage on a plane perpendicular to the impact direction, and the equivalent diameter were specified using the flash thermography method.The tests were performed using the fixtures manufactured according to the ASTM D7137/7137M standard. The specimens were compressed to determine the residual strength. This value was afterwards used to specify the force levels for the fatigue tests. The fatigue tests were carried out under force control – with a sinusoidal shape, stress ratio R equal to 0.1 and frequency f 1Hz. Maximum force in a loading cycle Pmax was being increased after each thousand of cycles N until its value was close to the residual strength determined in the previously mentioned tests. In this work, the following relationships were presented: force-displacement P-δ for both static and fatigue tests and displacement-loading cycles δ-N for fatigue tests.A method of conducting the fatigue tests of CFRP composite was proposed, in which both the CAI specimens and CAI fixture were used. This allowed researchers to accelerate making initial comparisons between the two groups of specimens with damages – grouped relative to the way of conditioning.

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.

Prediction of compressive strength of CFRP composite structures using notch strength

2013 ◽  
Vol 14 (6) ◽  
pp. 1103-1108 ◽  
Author(s):  
Sang Soo Ahn ◽  
Suk Woo Hong ◽  
Jae Mean Koo ◽  
Chang Sung Seok
Keyword(s):  
Compressive Strength ◽  
Composite Structures ◽  
Cfrp Composite ◽  
Notch Strength
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