Composite Materials with the Coating to Detect Barely Visible Impact Based on the Retroreflective Film

A new method of indicating contact damage of composite materials, using a polymer retroreflective film (PRF) with micro-prisms, is proposed. Impact contact action leads to deformation of microprisms and with directed lighting allows seeing the place of impact in the form of a dark spot. In experimental studies, using STEF fibreglass as an example, the dependences of the spot diameter on the contact pressure up to 530 MPa were studied. An assessment of the residual strength and stiffness of a composite specimen-beam with a contact defect was obtained with three-point bending. It is shown that, during bending, the strength of STEF with contact defects decreases from 615 to 386 MPa. The data obtained allow to assess the danger of contact pressure by the known diameter of the dark spot on the PRF.

Investigation of Failure Criteria and Experimental Process of the Composite Specimen with Mechanical Joints under Tensile Loading

Generally, composite materials are used to obtain better engineering properties, including higher hardness, greater strength, lower weight, heat resistance, moisture and corrosion, which are not present in homogeneous materials such as metals, which are more commonly used in composite design. In this article, experimental study of the composite specimen with mechanical joints under tensile loading, joints of composite material structures, failure criteria in composite materials, tensile impact test is investigated. The results of research work it shows that maximum strength, the hand lay-up can be designed with [0º, 45º, 90º, -45º] s and layers with 45º fibers is very important, because these fibers in these layers have a significant role in increasing the resistance of the piecework under shear stresses due to the passage of stress lines along the hole; In other words, the maximum cut occurs at a 45º angle, and these layers resist this shear stress.

Mechanical properties and thermal and electrical conductivity of 3D printed ABS-copper ferrite composites via 3D printing technique

This study examines the effect of particulate reinforcement on the mechanical properties of 3D printed acrylonitrile–butadiene–styrene (ABS). Copper ferrite (CuFe2O4) as a reinforcer with various loadings was used to print ABS composite specimen, namely, 8, 11 and 14 wt%. Mechanical testing such as tensile test and hardness test was performed on the printed samples. Specimens with 14 wt% of CuFe2O4 showed a 135% increase in tensile strength compared to the pure ABS specimens. Specimens printed with 14 wt% of CuFe2O4 are 14% harder compared to the pure ABS specimens. Thermal conductivity increased 93% for specimen loaded with 14 wt% reinforcer. Electrical conductivity shows a one-order increase for composite specimen compared to control specimen.

Failure Law and Mechanism of the Rock-Loose Coal Composite Specimen under Combined Loading Rate

The surrounding rock deformation in the underground mining roadway increases rapidly during excavation and mining disturbance. The semirock and coal roadway, which is formed by the rock and coal composite system, will show different mechanical properties. Therefore, loading rate and anchoring or not are critical to grasp the stability law of the rock-coal combination system under different conditions. The uniaxial mechanical test under the constant loading rate and combined loading rate is carried out in the static loading range (0.01∼10 mm·min−1) of the rock-loose coal composite specimen (RCCS). The test results show that the rock and loose coal composite specimen without bolt (RCB(0) specimen) are abnormal, and the uniaxial compressive strength (UCS) and residual strength (RS) of the specimen do not increase but decrease with the increase of loading rate. In contrast, the UCS of the rock-loose coal composite specimen with the bolt (RCB(1∼2) specimen) is consistent with that of the ordinary hard and brittle rock, which increases with the increase of loading rate. To a certain extent, the initial damage and the development of microcracks in loose coal bodies are limited by bolts. Finally, the deformation mechanism and constitutive equation of the rock-loose coal composite system are discussed.