Detection of Voids in Carbon/Epoxy Laminates and Their Influence on Mechanical Properties

2017 ◽  
Vol 25 (5) ◽  
pp. 371-380 ◽  
Author(s):  
Luca Di Landro ◽  
Aurelio Montalto ◽  
Paolo Bettini ◽  
Stefania Guerra ◽  
Fabrizio Montagnoli ◽  
...  
Keyword(s):  
Composite Laminates ◽  
Mechanical Performance ◽  
Thermal Analyses ◽  
Void Content ◽  
Processing Conditions ◽  
Micro Computed Tomography ◽  
Sem Image ◽  
Beam Shear ◽  
Mechanical Performances ◽  
Curing Cycle

Defects, such as voids and delaminations, may significantly reduce the mechanical performance of components made of composite laminates. Distributed voids and porosity are generated during composite processing and are influenced by prepreg characteristics as well as by curing cycle parameters. On the basis of rheological and thermal analyses, as well as observations of laminates produced by different processing conditions, curing pressure appears the most influent factor affecting the void content. This work compares different methods for void analysis and quantitative evaluation (ultrasonic scan, micro-computed tomography, acid digestion, SEM image analysis) evidencing their applicative limitations. Carbon/epoxy laminates were produced in autoclave or oven by vacuum bag technique, using different processing conditions, so that void contents ranging from 0% to 7% volume were obtained. Effects of porosity over laminates mechanical performances are analysed. The results of tensile and compressive tests are discussed, considering the effect that different curing cycles have over void content as well as over fibre/resin fraction. Interlaminar strength, as measured by short beam shear tests, which is a matrix-dominated property, exhibits a reduction of failure strength up to 25% in laminates with the highest void content, compared to laminates with no porosity.

scholarly journals The effect of processing on the microstructure of hoop-wound composite cylinders

2020 ◽  
Vol 54 (26) ◽  
pp. 3981-3997 ◽  
Author(s):  
Kaspar Lasn ◽  
Mats Mulelid
Keyword(s):  
Mechanical Performance ◽  
Pressure Vessels ◽  
Void Content ◽  
Cylinder Wall ◽  
Process Innovations ◽  
Short Beam ◽  
Beam Shear ◽  
Composite Microstructure ◽  
The Difference ◽  
Composite Cylinders

Fibre-reinforced polymer composites are increasingly used to make pipes and pressure vessels. The relationship between wet-winding manufacturing, composite microstructure, and the mechanical performance is complex due to many process parameters and material properties involved. Efficient manufacturing aspirations however drive process innovations that include new, radically different tow impregnation methods. In this work, the process–property–performance relationship is experimentally construed for hoop-wound carbon fibre/epoxy composite cylinders. The difference between cylinders produced by a new tow impregnation system and cylinders from the reference impregnation system was investigated. Winding speed and cylinder wall thickness were considered as two additional variables. The results indicate that, within current scope, composite microstructure is relatively insensitive to the winding speed and to final cylinder thickness. Meanwhile, un-optimized changes for tow impregnation affect the void content, the size distribution of voids and the interlaminar failure mode in short beam shear.

Mechanical Performance of Carbon/Epoxy Composites with Embedded Polymeric Films

2007 ◽  
Vol 334-335 ◽  
pp. 469-472 ◽  
Author(s):  
Ben Qi ◽  
Michael Bannister
Keyword(s):  
Composite Laminates ◽  
Mechanical Performance ◽  
Polymeric Films ◽  
Epoxy Composites ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Lap Shear ◽  
Short Beam ◽  
Monitoring Applications ◽  
Beam Shear

This paper presents experimental results on the mechanical performance of advanced carbon/epoxy composites with embedded polymeric films. The composite laminates with polymeric films, which are potentially used as a sensor/actuator carrier for structural health monitoring applications, were investigated under various mechanical loadings including low velocity impact, single lap shear and short beam shear. The preliminary work showed that embedment of those polymeric films does not degrade, but could significantly improve, the mechanical properties of the composite laminates.

scholarly journals Analysis of void morphology in composite laminates using micro-computed tomography

2018 ◽  
Vol 406 ◽  
pp. 012010 ◽  
Author(s):  
Mahoor Mehdikhani ◽  
Nghi Q Nguyen ◽  
Ilya Straumit ◽  
Larissa Gorbatikh ◽  
Stepan V Lomov
Keyword(s):  
Computed Tomography ◽  
Composite Laminates ◽  
Micro Computed Tomography

Quantitative Prediction of Mechanical Performance of Polymer Products directly from Processing Conditions

2008 ◽  
Author(s):  
T. A. P. Engels ◽  
L. E. Govaert ◽  
H. E. H. Meijer ◽  
Albert Co ◽  
Gary L. Leal ◽  
...  
Keyword(s):  
Mechanical Performance ◽  
Quantitative Prediction ◽  
Processing Conditions

scholarly journals Mechanical Performance of Glass-Based Geopolymer Matrix Composites Reinforced with Cellulose Fibers

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2395 ◽  
Author(s):  
Gianmarco Taveri ◽  
Enrico Bernardo ◽  
Ivo Dlouhy
Keyword(s):  
Fly Ash ◽  
Mechanical Performance ◽  
Fiber Surface ◽  
Cellulose Fiber ◽  
Maximum Effect ◽  
Matrix Composites ◽  
Curing Conditions ◽  
Chevron Notch ◽  
Geopolymer Matrix ◽  
Mechanical Performances

Glass-based geopolymers, incorporating fly ash and borosilicate glass, were processed in conditions of high alkalinity (NaOH 10–13 M). Different formulations (fly ash and borosilicate in mixtures of 70–30 wt% and 30–70 wt%, respectively) and physical conditions (soaking time and relative humidity) were adopted. Flexural strength and fracture toughness were assessed for samples processed in optimized conditions by three-point bending and chevron notch testing, respectively. SEM was used to evaluate the fracture micromechanisms. Results showed that the geopolymerization efficiency is strongly influenced by the SiO2/Al2O3 ratio and the curing conditions, especially the air humidity. The mechanical performances of the geopolymer samples were compared with those of cellulose fiber–geopolymer matrix composites with different fiber contents (1 wt%, 2 wt%, and 3 wt%). The composites exhibited higher strength and fracture resilience, with the maximum effect observed for the fiber content of 2 wt%. A chemical modification of the cellulose fiber surface was also observed.

scholarly journals Assessments on the Performance of Asphalt Mixtures Prepared with Adhesion Promoters

2019 ◽  
Vol 8 (3S3) ◽  
pp. 332-339
Keyword(s):  
Mechanical Performance ◽  
Water Immersion ◽  
Asphalt Binder ◽  
Asphalt Mixture ◽  
Asphalt Mixtures ◽  
Adhesion Promoters ◽  
Modified Asphalt ◽  
Service Characteristics ◽  
Bonding Properties ◽  
Mechanical Performances

Asphalt pavement is typically susceptible to moisture damage. However, it could be improved with the incorporation of additives or modifiers through binder modifications. The objective of the study is to assess the effect of adhesion promoters, namely PBL and M5000, onto the Hot Mix Asphalt (HMA). The performance of asphalt mixture has been assessed in terms of the service characteristics, the bonding properties, and mechanical performances. The service characteristics were assessed through the Workability Index (WI) and Compaction Energy Index (CEI) to evaluate the ease of asphalt mixture during the mixing and compaction stage. The bonding properties of the modified asphalt mixtures were determined using the boiling water test and static water immersion test to signify the degree of coating after undergoing specific conditioning period and temperature. The mechanical performances of the modified asphalt mixture were evaluated via Marshall stability, semi-circular bending, and modified Lottman tests. All specimens were prepared by incorporating adhesion promoters at the dosage rates of 0.5% and 1.0% by weight of asphalt binder. From the investigation, the bonding properties significantly improved for the modified asphalt mixture compared to the control mixture. The WI of the modified asphalt mixture increased while the CEI decreased in comparison to the control specimen. This implies the workability of modified asphalt mixture is better and requires less energy to be compacted. Modified asphalt mixture generally had better mechanical performance. Therefore, it can be deduced that the asphalt mixture with adhesion promoters have better overall performance than the control mixture.

Numerical and experimental evaluation of mechanical performance of the multifunctional energy storage composites

2021 ◽  
pp. 002199832110495
Author(s):  
Yinan Wang ◽  
Fu-Kuo Chang
Keyword(s):  
Energy Storage ◽  
Carbon Fiber ◽  
Composite Laminates ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Fiber Composite ◽  
Mechanical Damage ◽  
Experimental Tests ◽  
Structural Element ◽  
Carbon Fiber Composite

This work presents numerical simulation methods to model the mechanical behavior of the multifunctional energy storage composites (MESCs), which consist of a stack of multiple thin battery layers reinforced with through-the-hole polymer rivets and embedded inside carbon fiber composite laminates. MESC has been demonstrated through earlier experiments on its exceptional behavior as a structural element as well as a battery. However, the inherent complex infrastructure of the MESC design has created significant challenges in simulation and modeling. A novel homogenization technique was adopted to characterize the multi-layer properties of battery material using physics-based constitutive equations combined with nonlinear deformation theories to handle the interface between the battery layers. Second, mechanical damage and failure modes among battery materials, polymer reinforcements, and carbon fiber-polymer interfaces were characterized through appropriate models and experiments. The model of MESCs has been implemented in a commercial finite element code in ABAQUS. A comparison of structural response and failure modes from numerical simulations and experimental tests are presented. The results of the study showed that the predictions of elastic and damage responses of MESCs at various loading conditions agreed well with the experimental data. © 2021

Micro-computed tomography analysis of natural fiber and bio-matrix tubular-braided composites

2019 ◽  
Vol 53 (28-30) ◽  
pp. 4003-4013 ◽  
Author(s):  
Brianna M Bruni-Bossio ◽  
Garrett W Melenka ◽  
Cagri Ayranci ◽  
Jason P Carey
Keyword(s):  
Computed Tomography ◽  
Natural Fiber ◽  
Volume Fraction ◽  
Void Content ◽  
Micro Computed Tomography ◽  
Braided Composites ◽  
Fiber Volume ◽  
Increasing Demand ◽  
Materials Used ◽  
Curing Method

There is an increasing demand for the use of “green”-based materials as reinforcement and matrix materials in composites. However, the ability of these natural-based materials to perform as consistently and reliably as conventional materials is still relatively unknown. A key importance in the viability of these materials is the evaluation of the content of voids and imperfections, which may affect the properties of the entire composite. In this study, the microstructure of tubular-braided composites manufactured from cellulose fibers and a partially bio-derived resin was studied with the use of micro-computed tomography. These methods were used to determine the effect of modifying braid angle, resin type, and curing method on fiber volume fraction, void volume, and void distribution. It was determined that the void content increased with the increase in braid angle, and vacuum-bagging reduced the total void content. The sample with the smallest braid angle produced with vacuum-bagged curing contained a void fraction of 1.5%. The results of this study proved that the materials used could be viable for further testing and development and that micro-computed tomography imaging is valuable for identifying how to improve consistency and minimize imperfections to create more accurate and reliable natural fiber-braided composites.

scholarly journals Fiber orientation quantification utilizing X-ray micro-computed tomography

2020 ◽  
pp. 002199832096255
Author(s):  
Jennifer M Sietins ◽  
Jessica C Sun ◽  
Daniel B Knorr Jr
Keyword(s):  
Computed Tomography ◽  
Fiber Orientation ◽  
Mechanical Performance ◽  
Ct Scans ◽  
Micro Computed Tomography ◽  
Orientation Data ◽  
Orientation Analysis ◽  
X Ray ◽  
Software Analysis ◽  
X Ray Computed

It is well known that the mechanical performance of composite materials is highly dependent on the fiber orientation. Several techniques have historically been used to quantify fiber orientation experimentally. Newer methods have involved 3 D X-ray computed tomography (CT) scans due to the high resolution that is now achievable within a laboratory setting. The accuracy of the analysis, however, is a function of the resulting scan image quality and the specific parameters influencing the resulting orientation analysis. This report summarizes a methodology to quantify fiber orientation from 3 D CT scans. Optimal scanning parameters are presented taking into account both the necessary resolution, geometric unsharpness, and the scan volume size. The influence of varied software analysis parameters and their effects on the resulting orientation data is discussed. The selection of software analysis parameters was independently validated with optical microscopy on a sample with only two fibers. Lastly, the orientation analysis was applied to a 0/+45/−45/90 composite to demonstrate this technique on a larger scale.

scholarly journals On the Use of Biobased Waxes to Tune Thermal and Mechanical Properties of Polyhydroxyalkanoates–Bran Biocomposites

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2615
Author(s):  
Vito Gigante ◽  
Patrizia Cinelli ◽  
Maria Cristina Righetti ◽  
Marco Sandroni ◽  
Giovanni Polacco ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Wheat Bran ◽  
Mechanical Performance ◽  
Low Cost ◽  
Impact Resistance ◽  
Mechanical Analysis ◽  
Polymeric Matrix ◽  
Flour Milling ◽  
Mechanical Performances ◽  
Analytic Models

In this work, processability and mechanical performances of bio-composites based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) containing 5, 10, and 15 wt % of bran fibers, untreated and treated with natural carnauba and bee waxes were evaluated. Wheat bran, the main byproduct of flour milling, was used as filler to reduce the final cost of the PHBV-based composites and, in the same time, to find a potential valorization to this agro-food by-product, widely available at low cost. The results showed that the wheat bran powder did not act as reinforcement, but as filler for PHBV, due to an unfavorable aspect ratio of the particles and poor adhesion with the polymeric matrix, with consequent moderate loss in mechanical properties (tensile strength and elongation at break). The surface treatment of the wheat bran particles with waxes, and in particular with beeswax, was found to improve the mechanical performance in terms of tensile properties and impact resistance of the composites, enhancing the adhesion between the PHBV-based polymeric matrix and the bran fibers, as confirmed by predictive analytic models and dynamic mechanical analysis results.

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