Microwave Dynamic Dielectric Analysis of Curing Neat Resins

1992 ◽  
Vol 269 ◽  
Author(s):  
Ray J. King ◽  
Michael J. Werner ◽  
Guillermo D. Mayorga
Keyword(s):  
Polymer Matrix Composites ◽  
Mechanical Analysis ◽  
Matrix Composites ◽  
Dielectric Analysis ◽  
Scanning Calorimetry ◽  
Strongly Coupled ◽  
Analysis Techniques ◽  
Noninvasive Sensors ◽  
Prototype Software

ABSTRACTMicrowave reflection resonator sensors have been developed to monitor the dynamic, in situ real and imaginary dielectric components (ε′, ε″) of thermoset polymer matrix composites and thermoplastics. These reusable and noninvasive sensors are conformably mounted in the autoclave mold in such a manner that the EM fields are strongly coupled to the resin. Tracking of (ε′, ε″) during the cure provides information about the chemical kinetics such as timing the point of minimum viscosity and monitoring the relative cure index. The sensor is readily adjustable for optimum coupling to the type of material being tested and is rated for temperatures up to 250°C (480*F). The technique is complementary to other analysis techniques such as Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). A prototype software and electronics package has been developed to support the sensor.

Viscoelastic properties of woody hemp core

Holzforschung ◽  
2011 ◽  
Vol 65 (2) ◽  
Author(s):  
Rahime Bag ◽  
Johnny Beaugrand ◽  
Patrice Dole ◽  
Bernard Kurek
Keyword(s):  
Cell Wall ◽  
Viscoelastic Properties ◽  
Specific Effect ◽  
Mechanical Analysis ◽  
Low Molecular Weight ◽  
Dielectric Analysis ◽  
Technological Transformation ◽  
Chain Mobility ◽  
Cell Wall Polymers

Abstract The aim of this study was to determine the effect of removing extractives from the woody core of hemp (chènevotte) on the chain mobility of hemicelluloses and lignins, which can react during technological transformation such as de-fibering and/or composite materials production. Extractives are molecules with low molecular weight, which are present in the cell wall matrix and can be readily removed by solvents. In the present paper, the nature and amounts of extractives, removed under different conditions and with solvents of different polarities, were determined. The mobility and structural relaxations of lignins and hemicelluloses were stu-died in situ by dynamic mechanical analysis and dielectric analysis under controlled moisture content. Extractions at low temperature led to rigidification of lignins and plasticizing of hemicelluloses, probably due to local changes by the selective removal of molecules interacting with the polymers. Probably, the accessibility of hemicelluloses to plasticizing water was increased at controlled humidity. In contrast, hot extractions including water induced rigidification of the hemi-celluloses and plasticizing of lignins. This could be related to a combination of molecule extractions and chemical modi-fications of both polymers. This interpretation is supported by the variation of activation energy for relaxation of hemi-celluloses. It can be concluded that each type of extraction has a clear specific effect on the relaxation properties of the amorphous cell wall polymers.

scholarly journals Viscoelastic Characterization of Short Fibres Reinforced Thermoplastic in Tension and Shearing

2010 ◽  
Vol 24-25 ◽  
pp. 419-423 ◽  
Author(s):  
A. Andriyana ◽  
Luisa Silva ◽  
Noelle Billon
Keyword(s):  
Mechanical Response ◽  
Polymer Matrix Composites ◽  
Mechanical Analysis ◽  
Integrated Modelling ◽  
Matrix Composites ◽  
Moulding Process ◽  
Permanent Strain ◽  
Mould Filling ◽  
Injection Moulding Process

The present work can be regarded as a first step toward an integrated modelling of mould filling during injection moulding process of polymer matrix composites and the resulting material behaviour under service loading conditions. More precisely, the emphasis of the present research is laid on the development of a mechanical model which takes into account the processing-induced microstructure and is capable to predict the mechanical response of the material. In the Part I, a set of experiments which captures the mechanical behaviour of an injection moulded short fibre reinforced under different strain histories is described. Three mechanical testing are conducted: Dynamic Mechanical Analysis (DMA), uniaxial tension and simple shear. Tests show that the material exhibits complex responses mainly due to non-linearity, anisotropy, time/rate-dependence, hysteresis and permanent strain. Moreover, the relaxed state of the material is characterized by the existence of a so-called anisotropic equilibrium hysteresis independently of the prescribed strain rate.

Embedded optical nanosensors for monitoring the processing and performance of polymer matrix composites

2019 ◽  
Vol 7 (46) ◽  
pp. 14471-14492
Author(s):  
David B. Lioi ◽  
Vikas Varshney ◽  
Sarah Izor ◽  
Gregory Neher ◽  
W. Joshua Kennedy
Keyword(s):  
Spatial Resolution ◽  
Polymer Matrix ◽  
Polymer Matrix Composites ◽  
Matrix Composites ◽  
Responsive Materials ◽  
Material State ◽  
Optical Nanosensors ◽  
And Performance ◽  
Structural Polymer

We provide a broad review of optically responsive materials with potential for in situ monitoring of material state properties in structural polymer-based materials with nanoscale spatial resolution.

Mechanical Analysis of Unidirectional Fiber-Reinforced Polymers under Transverse Compression and Tension

2010 ◽  
Vol 139-141 ◽  
pp. 84-89 ◽  
Author(s):  
Hong Chang Qu ◽  
Xiao Zhou Xia ◽  
Hong Yuan Li ◽  
Zhi Qiang Xiong
Keyword(s):  
Polymer Matrix Composites ◽  
Glass Fibers ◽  
Constitutive Models ◽  
Mechanical Analysis ◽  
Interface Strength ◽  
Fiber Reinforced Polymers ◽  
Matrix Composites ◽  
Transverse Compression ◽  
Cohesive Elements ◽  
The Matrix

The mechanical behavior of polymer–matrix composites uniaxially reinforced with carbon or glass fibers subjected to compression/tension perpendicular to the fibers was studied using computational micromechanics. This is carried out using the finite element simulation of a representative volume element of the microstructure idealized as a random dispersion of parallel fibers embedded in the polymeric matrix. Two different interface strength values were chosen to explore the limiting cases of composites with strong or weak interfaces, and the actual failure mechanisms (plastic deformation of the matrix and interface decohesion) are included in the simulations through the corresponding constitutive models. Composites with either perfect or weak fiber/matrix interfaces (the latter introduced through cohesive elements) were studied to assess the influence of interface strength on the composite behavior. It was found that the composite properties under transverse compression/tension were mainly controlled by interface strength and the matrix yield strength in uniaxial compression/tension.

Reorientation of carbon nanotubes in polymer matrix composites using compressive loading

2005 ◽  
Vol 20 (4) ◽  
pp. 1026-1032 ◽  
Author(s):  
Michael J. Lance ◽  
Chun-Hway Hsueh ◽  
Ilia N. Ivanov ◽  
David B. Geohegan
Keyword(s):  
Strain Energy ◽  
Polymer Matrix Composites ◽  
Compressive Loading ◽  
Local Strain ◽  
Peak Shift ◽  
Raman Peak ◽  
Matrix Composites ◽  
Raman Peak Shift ◽  
Polarized Raman

Purified single-walled nanotubes (SWNTs) were dispersed in an epoxy polymer and subjected to uniaxial compressive loading. The orientation and stress in the nanotubes were monitored in situ using polarized Raman microscopy. At strains less than 2%, the nanotubes reorient normal to the direction of compression, thereby minimizing the local strain energy. Above 2% strain, the Raman peak shift reaches a plateau. A new analytical model, which approximates the SWNT reorientation by varying the aspect ratio of a representative spheroid, predicted the rotation behavior of nanotubes under load. The results of this model suggest that the observed plateau of the Raman peak shift is caused by both polymer yielding and interfacial debonding at the ends of nanotubes.

scholarly journals Lightweight and Durable PVDF–SSPF Composites for Photovoltaics Backsheet Applications: Thermal, Optical and Technical Properties

Materials ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2104 ◽  
Author(s):  
M. H. Alaaeddin ◽  
S. M. Sapuan ◽  
M. Y. M. Zuhri ◽  
E. S. Zainudin ◽  
Faris M. AL- Oqla
Keyword(s):  
Polyvinylidene Fluoride ◽  
Mechanical Analysis ◽  
Short Fiber ◽  
Photovoltaic Module ◽  
Scanning Calorimetry ◽  
Sugar Palm Fiber ◽  
Technical Properties ◽  
Critical Components ◽  
Thermal Mechanical Analysis

Photovoltaic module backsheets are characterized according to their thermal, optical, mechanical, and technical properties. This work introduces new fabricated backsheets for PV modules using polyvinylidene fluoride (PVDF) reinforced with short sugar palm fiber (SSPF) composites. The preparation of composites undergoes multiple phases of fabrication. Thermal, optical, and technical investigations of their properties were conducted. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, in-situ scanning probe microscopy (SPM), dynamic mechanical analysis (DMA), thermal mechanical analysis (TMA), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and prolonged technical testing were accomplished to expansively understand the complex behavior of composites under various conditions. The optical properties of PV backsheets are critical components in determining the reflectance, absorbance, and transmittance of light. The PVDF–SSPF composites exhibited exceptional compatibility and thermal stability, further revealing a homogenous composite structure with enhanced interfacial bonding between the short fiber and polymer matrix.

Mechanical properties of jute fiber–reinforced UP/PU hybrid network composites

2019 ◽  
Vol 27 (9) ◽  
pp. 546-556 ◽  
Author(s):  
Richa Singh ◽  
B Singh ◽  
Hina Tarannum
Keyword(s):  
Mechanical Properties ◽  
Unsaturated Polyester ◽  
Fiber Surface ◽  
Mechanical Analysis ◽  
Hybrid Networks ◽  
Hybrid Network ◽  
Matrix Composites ◽  
Scanning Calorimetry ◽  
Jute Fibers ◽  
Polyester Matrix

Hybrid networks (unsaturated polyester–polyurethane (UP/PU)) of UP resin and PU prepolymer were synthesized and characterized for their phase miscibility with the help of Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis (DMA), and atomic force microscopy. The existence of hydrogen bonded –NH groups, broadened glass transition region, and reduced phase domains evidenced the formation of intermixed phase when compared with the parent UP. The optimum mechanical properties of UP/PU hybrid networks were observed at ∼5 wt% PU content. The composites made from treated jute fibers and UP/PU hybrid networks were evaluated for their physico-mechanical properties. DMA curves showed that UP/PU matrix composites had ∼20% higher storage modulus and ∼17% lower tan δ than the polyester matrix composites. The tensile and flexural strengths of these composites were increased by ∼13% and ∼40%, respectively. During accelerated aging, the UP/PU matrix composites retained ∼15% more tensile strength than the polyester matrix composites. Fractographic evidence, such as resin adherence onto the pullout fiber surface, fiber breakage, and adequate adhesion between the jute fibers and the resin, supported the superior properties of UP/PU matrix composites to polyester matrix composites.

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