High‐throughput, high‐accuracy determination of coefficient of thermal expansion of carbon fibre–epoxy composites using digital image correlation

Abstract

High-throughput, high-accuracy determination of thermal deformation and coefficient of thermal expansion (CTE) of carbon fibre-epoxy composites using 2D-digital image correlation (2D-DIC) is described. With the aid of a specially designed ultra-stable and high fidelity imaging system, which integrates a high-quality bilateral telecentric lens with monochromatic blue light illumination, surface images of multiple samples heated by a heating furnace can be captured simultaneously. The images of these samples at different temperatures are processed by advanced DIC algorithm to extract the thermal strains and the CTE of isotropic Al alloy, anisotropic unidirectional, and bidirectional carbon fibre-epoxy composites. Pure thermal expansions of these samples obtained after removing the small rigid-body rotations clearly indicate the isotropic and anisotropic expansions of these samples. The well-agreed results with literature values demonstrate the effectiveness and practicality of the proposed method for high-throughput and high-accuracy CTE measurements. KEYWORDScarbon fibre-epoxy composite, coefficient of thermal expansion, digital image correlation, high throughput, thermal strain

Tailoring thermal expansion of mechanically interlocked carbon fiber composite reinforced metal

“…Digital image correlation [ 19 ] is an effective method for full‐field strain measurement, and has been utilized to measure the thermal strains in metals, [ 12 ] films, [ 13,14 ] composites, [ 12,20 ] and polymers. [ 21 ] Analysis of the thermal strain data is not limited to CLTE calculation, [ 13 ] but also includes quantification of strain field heterogeneity [ 21 ] and residual strain of composite laminates.…”

“…[ 20 ] Recently, the bias error in DIC displacement measurements was reported to be less than 0.005 pixels, which for a gauge length of 400 pixels estimates a strain error of 12.5 microstrain. [ 22 ] When applied to (T‐DIC) over a temperature delta of 50°C, the CLTE error is [ 12 ]…”

“…[7] Non-contacting or small gap methods include optical levers, [8] interferometers, [9][10][11] and machine vision real time photographic techniques (digital image correlation [DIC]). [12][13][14] Each of the above-mentioned techniques has its own merits and challenges. Resistance strain gages possess a strain measurement resolution of 10 À7 [15] and require development of the appropriate attachment method [16] as well as determination of the critical strain gage size.…”

“…[18] Interferometry is highly suited for measuring small displacements (10 À3 m) with Fizeau interferometers commonly used for CLTE measurements of samples smaller than those typically used in quartz rod dilatometry (10 Â 10 À3 m). [10] Digital image correlation [19] is an effective method for full-field strain measurement, and has been utilized to measure the thermal strains in metals, [12] films, [13,14] composites, [12,20] and polymers. [21] Analysis of the thermal strain data is not limited to CLTE calculation, [13] but also includes quantification of strain field heterogeneity [21] and residual strain of composite laminates.…”

Improved damping and mechanical properties of carbon fibrous laminates with tailored carbon nanotube/polyurethane hybrid membranes

“…Therefore, the practical CFRPs are commonly arranged with many precisive instruments due to its dimensional stability. 3,4 Nevertheless, nowadays aerospace vehicles, for example, tend to develop in the direction of high speed, lightweight, automation and multi-function, thus, the induced vibration and noise problems become more and more noteworthy. These problems would undoubtedly not only worsen the working dynamic environment of the instruments, but also reduce the accuracy and reliability of navigation and some control electronic systems, which eventually would shorten the fatigue life and service time of CFRPs.…”