scholarly journals Use of Thermomechanical Analysis in the Design of a Composite System with a Low Coefficient of Longitudinal Thermal Expansion for End Gauges

2021 ◽  
Author(s):  
Dora Kroisová ◽  
Štěpánka Dvořáčková ◽  
Petr Kůsa
Keyword(s):  
Thermal Expansion ◽  
Composite System ◽  
Thermomechanical Analysis ◽  
End Gauges

Synthesis and properties of low coefficient of thermal expansion copolyimides derived from biphenyltetracarboxylic dianhydride with p-phenylenediamine and 4,4′-oxydialinine

e-Polymers ◽  
2016 ◽  
Vol 16 (4) ◽  
pp. 295-302 ◽  
Author(s):  
Yonglin Lei ◽  
Yuanjie Shu ◽  
Jinhua Peng ◽  
Yongjian Tang ◽  
Jichuan Huo
Keyword(s):  
Thermal Stability ◽  
Thermal Expansion ◽  
Coefficient Of Thermal Expansion ◽  
Thermomechanical Analysis ◽  
Amic Acid ◽  
Molar Ratio ◽  
Structure And Property ◽  
Property Relations ◽  
Ft Ir ◽  
Biphenyltetracarboxylic Dianhydride

AbstractA series of copolyimides were prepared by thermal imidization of poly(amic acid)s (PAAs) derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3′,3,4′-biphenyltetracarboxylic dianhydride (a-BPDA), p-phenylenediamine (PDA) and 4,4′-oxydialinine (4,4′-ODA) commonly used for the production of commercial polyimides. The flexible copolyimide films were obtained from that the molar ratio of s-BPDA, a-BPDA, PDA and 4,4′-ODA was 9:1:8:2 (Co-PIs-3), 8:2:9:1 (Co-PIs-5) and 8:2:8:2 (Co-PIs-6). These obtained copolyimide films were characterized by Fourier transform-infrared spectroscopy(FT-IR), wide angle X-ray (WAXD), Thermogravimetric (TG), dynamic mechanical thermal analysis (DMA), thermomechanical analysis (TMA), field-emission scanning electron microscopy (FE-SEM) and mechanical properties measurement. The results showed that three copolyimides remained semi-crystalline and exhibited high glass transition temperature (Tg), high thermal stability, great ultimate tensile strength and low coefficient of thermal expansion (CTE). The Co-PIs-5 had lower crystallinity, lower CTE, greater elongation at break, higher Tg and thermal stability and the greater dense extent, compared with Co-PIs-3 and Co-PIs-6. Structure and property relations of the prepared polyimides were also briefly discussed. The results revealed that the copolymerization of s-BPDA/PDA with a small number of 4,4′-ODA/a-BPDA was a useful means for enhancing flexibility without sacrificing low CTE.

Thermal Expansion of Composite System Epoxy Resin/Recycled Carbon Fibers

2020 ◽  
Vol 994 ◽  
pp. 162-169
Author(s):  
Štěpánka Dvořáčková ◽  
Dora Kroisová
Keyword(s):  
Experimental Study ◽  
Thermal Expansion ◽  
Epoxy Resin ◽  
Carbon Fibers ◽  
Composite System ◽  
Linear Thermal Expansion Coefficient ◽  
Linear Thermal Expansion ◽  
Carbon Fibres ◽  
Sample Matrix ◽  
Composite Systems

This experimental study deals with the problematics of thermal expansion α [10-6/K] of the composite systems based on recycled carbon fibres reinforced epoxy resin. The epoxy resin CHS – EPOXY 520 (EPOXY 15), cured with the hardener P11 (Districhem, s.r.o.), was chosen as a sample matrix. Recycled carbon fibres with a diameter of 7 μm and a length of 100 μm (Easy Composites Ltd.) were the filler. In the experiment, samples with the fulfilment of 10, 20, 40, 60, 80, 90 and 100 phr were prepared. The samples were being poured into silicone molds, cured at an overpressure of 0.7 MPa and a temperature of 23 ± 2 °C for 24 hours. A thermomechanical analyzer was used to determine the thermal expansion of composite systems. The addition of recycled carbon fibers to epoxy resin can reduce the coefficient of linear thermal expansion at 20°C in half, from the original α = 45 to 55 × 10-6/K for non-filled epoxy resin to α = 25 to 27 × 10-6/K for filled epoxy resin. Optimal filling is at the level of 40 phr, with higher filling there is no further reduction of the linear thermal expansion coefficient.

Thermal Expansion Behavior of the Multiphase Composite System

2004 ◽  
Vol 449-452 ◽  
pp. 765-768
Author(s):  
Chong Sung Park ◽  
Hyun Seok Hong ◽  
Myung Ho Kim ◽  
Chong Mu Lee
Keyword(s):  
Thermal Expansion ◽  
Composite System ◽  
Welding Process ◽  
High Volume ◽  
Volume Percent ◽  
New Approach ◽  
Composite Systems ◽  
Expansion Behavior ◽  
The Matrix ◽  
Multiphase Composite

A new approach for the CTE on the basis of Ashelby.s cutting and welding process was made for the analysis of the thermal expansion behaviors of Al-Si alloys and composites. In this theoretical approach, it was considered that relaxation of residual stress could create an elastoplastic zone in the matrix around a particle during cooling. A comparison of the measured CTEs with the calculated ones for the Al-Si-SiCp and Al-Si-Al2O3 composite systems was performed in terms of the volume percent and the size of reinforced phases. The calculated results revealed that the linear CTE of the both composite depends on the size of the reinforce phases, especially at the composite systems with a low volume percent of the reinforce phases. The increase in the volume percentages of Al2O3, SiCp and Si phase lowers the linear CTEs of the systems. The measured CTEs was deviated less than about ten percents from the calculated ones at composites with a high volume percent. The deviations of the CTEs of reinforced phases are about 4 - 6 vol% from real composite systems.

Synthesis and processing of nanocrystalline Ag–Fe–Ni for low thermal expansion–high conductivity thermal management applications

2001 ◽  
Vol 16 (2) ◽  
pp. 340-343 ◽  
Author(s):  
J. Stolk ◽  
M. Gross ◽  
D. Stolk ◽  
A. Manthiram
Keyword(s):  
Electrical Conductivity ◽  
Thermal Expansion ◽  
Metal Ion ◽  
Coefficient Of Thermal Expansion ◽  
Thermomechanical Analysis ◽  
Nominal Composition ◽  
Two Phase ◽  
X Ray ◽  
Fine Grained ◽  
Low Thermal Expansion

Nanocrystalline Ag–Fe–Ni powders were produced by a reduction of the aqueous metal ion solutions with sodium borohydride and then converted to fine-grained silver–Invar alloys that offer attractive thermal, electrical, and mechanical properties. The samples were characterized by x-ray diffraction, scanning electron microscopy, wavelength dispersive x-ray spectrometry, thermomechanical analysis, microhardness measurements, and electrical conductivity measurements; thermal conductivity was estimated using the Wiedemann–Franz law. Sintering of a specimen with a nominal composition of 60 wt% Ag–25.6 wt% Fe–14.4 wt.% Ni led to the formation of a two-phase silver–Invar alloy with a grain size of approximately 2 μm, a hardness of 133 HK200g, coefficient of thermal expansion of 12.44 × 10−6 / °C, and electrical conductivity of 2.13 × 105 (Ω cm) −1.

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