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Quality Control and Characterization
Published in B. T. Åström, Manufacturing of Polymer Composites, 2018
With either type of specimen and whether a support jig is used or not, the specimen dimensions are measured at a minimum of three locations. The specimen is then inserted in jig or fixture and carefully aligned before it is loaded at a crosshead speed of 0.5-1.0 mm/min until failure. In compression testing, deformation is normally measured with a compressometer (an extensometer for compressive testing) attached to the specimen or possibly to the testing machine heads, although strain gages may also be used. The stress-strain curves are then plotted and moduli, Poisson’s ratios, strengths, and ultimate strains are determined in the same fashion as for a tensile test. Determination of Poisson’s ratios requires strain gages bonded to the specimen (cf. Section 6.2.2.1).
Testing of Composites and Their Constituents
Published in Manoj Kumar Buragohain, Composite Structures, 2017
ASTM D695 gives a standard test method for the evaluation of compressive properties of neat cast resin [26]. The commonly used specimen is a short cylinder or prism, typical sizes being 12.7 mm (diameter) × 25 mm (height) for a cylinder and 12.7 mm (side) × 12.7 mm (side) × 25 mm (height) for a prism. A compression tool, consisting of two hardened, ground and flat plates, is used for holding the test specimen. Care must be taken to ensure that the end faces of the specimen are parallel to the faces of the compression tool plates. Further, the axis of the compression tool must be aligned with the center line of the plunger of the testing machine. The specimen is tested by applying compressive force under constant cross-head rate of 1.3 mm/min till the yield point is reached. After the yield point, the cross-head speed is increased to 5–6 mm/min and loading is continued till failure. The compressive strength is calculated by dividing the maximum compressive force by the original minimum cross-sectional area of the specimen. When stress–strain data are required, a compressometer is attached to the specimen for recording and plotting a force–displacement curve. The modulus of elasticity is calculated from a tangent drawn to the initial linear portion of this curve.
Residual compressive strength of plain and fiber reinforced concrete after exposure to different heating and cooling regimes
Published in European Journal of Environmental and Civil Engineering, 2022
Aref Abadel, Hussein Elsanadedy, Tarek Almusallam, Abdulaziz Alaskar, Husain Abbas, Yousef Al-Salloum
In order to ensure that the cylinders are completely flat under the compression testing machine, the top surface was capped using sulphur. In order to measure the axial strain during the compression test, a compressometer comprising of two LVDTs (180° apart) attached to the specimen was utilised. Cylinders were exposed to uniform uniaxial compression up to failure and the concrete compressive strength was measured as per the procedure of ASTM C39 (ASTM, 2010).