Papers by Keyword: CFRP Composite

Abstract: Carbon fibre reinforced polymer (CFRP) composites a perfect structural material due to their outstanding malleable strength, great rigidity, light mass and pronounced thermal resistance. But their inferior out-of-plane properties which are controlled by the matrix–fibre interface restrict the use of CFRP composites in critical applications. Amalgamation of nanofiller in the CFRP composites has found to improve the matrix-fibre interface and there by out-of-plane response. Though matrix modification has contributed to the improvement of interface, fibre modification has a scope for higher levels of nanofiller incorporation and proper fibre nanofiller adhesion. Out of several methods available for fibre modification electrophoretic deposition (EPD) is an eye-catching method for monitoring as well for nanofiller deposition. In recent ages, Graphene has grabbed wonderful consideration Among the graphene based functionalised nanofillers Carboxyl functionalized Graphene (G-COOH) modified CFRP composites have shown better ILSS properties. This research primarily aims to fabricate a CFRP composite using G-COOH modified carbon fibres with varying nanofiller concentrations of 0.5g/ltr, 1g/ltr and 1.5g/ltr in the EPD bath and its impact on the mechanical properties of the FRP composites. The laminates thus obtained were subjected to short beam shear test for the determination of inter laminar shear strength (ILSS). Fractography of the tested samples to observe various failure modes has been carried out by using scanning electron microscope (SEM).

Abstract: Cure-induced strain is produced inevitably during the fabrication of the composite. To measure the strain, undamaged methods such as using fiber Bragg grating(FBG) sensor are employed. In this paper, nine unidirectional carbon fiber-reinforced polymer(CFRP) laminates are autoclaved produced, with FBGs embedded in different layers through the thickness (0-layer, 5-layer, 10-layer and 13-layer). The experiment measures the difference of the FBGs’ Bragg wavelengths before and after the cure which is linearly relevant to the cure-induced strain, to explore the distribution of strains through the thickness. The experimental results indicate a certain strain in neural plane of approximately 370με under the designed size of the laminates. The results also show that the cure-induced strains in different layers through the thickness are less than 1000με even including all errors, however they do not display distinct regular in thickness direction. Moreover, through the FBG sensors and the thermocouples, the cure process with the strain and temperature variations is understood well. The result verifies that the cure-induced strain is mainly generated at the end of the cure when the temperature cools down.

Abstract: The mechanics of interface delamination in CFRP composite laminates is examined using finite element method. For this purpose a 12-ply CFRP composite, with a total thickness of 2.4 mm and anti-symmetric ply sequence of [45/-45/45/0/-45/0/0/45/0/-45/45/-45] is simulated under three-point bend test setup. Each unidirectional composite lamina is treated as an equivalent elastic and orthotropic panel. Interface behavior is defined using damage, linear elastic constitutive model and employed to describe the initiation and progression of delamination during flexural loading. Complementary three-point bend test on CFRP composite specimen is performed at crosshead speed of 2 mm/min. The measured load-deflection response at mid-span location compares well with predicted values. Interface delamination accounts for up to 46.7 % reduction in flexural stiffness from the undamaged state. Delamination initiated at the center mid-span region for interfaces in the compressive laminates while edge delamination started in interfaces with tensile flexural stress in the laminates. Anti-symmetric distribution of the delaminated region is derived from the corresponding anti-symmetric ply sequence in the CFRP composite. The dissipation energy for edge delamination is greater than that for internal center delamination. In addition, delamination failure process in CFRP composite can be described by an exponential rate of fracture energy dissipation under monotonic three-point bend loading.

Abstract: The ultimate objective of the current programme of work is to detect and quantify low-velocity impact damage in structures made from composite materials. There are many situations in the use of composites where an impact does not result in perforation of the material but causes damage that may not be visible, yet still causes a substantial reduction in structural properties. Impacts that do not cause perforation are usually termed low-velocity. When a composite structure undergoes such impacts, it is important to know the type and level of damage and assess the residual strength. In this study, following a systematic series of experiments on the induction of impact damage in composite specimens, Scanning Electron Microscopy (SEM) was used to inspect the topographies of the specimens at high magnification. Matrix cracking, fibre fracture, fibre pullout and delamination were the types of damage observed in the composite laminates after the low-velocity impacts. The study also conducted a (very) preliminary correlation between the damage modes and the impact energy.

Abstract: The microstructure (i.e., fibre volume fraction, void content, and fibre misalignment) of unidirectional carbon fibre-reinforced polymer (CFRP) composites was optimised by controlling several parameters during manufacture, namely: (i) compressive pressure (0.25~1.25 MPa, in steps of 0.25 MPa), (ii) vacuum pressure (−0.15, −0.20, −0.30, −0.45, and −0.65 MPa), and (iii) holding temperature (100~140 oC, in steps of 10 oC), applied during autoclave curing with the holding time being 30 minutes for all specimens. Optical micrographs captured from cross-sectional, through-the thickness areas, and in-plane areas of the resulting composites were evaluated and analysed in order to describe their microstructural characteristics.

Abstract: Ultrasonic motors are of great interest since their operation is not affected by a magnetic field. On this work the development of a prototype of a smart ultrasonic motor and its characteristics will be presented. The stator of the motor is formed by a cantilever made of PZT ceramic plate sandwiched between two unidirectional CFRP composite sheets. The composite sheets are oriented to 45º and -45º in the longitudinal direction. By application of a sinusoidal electric field to the piezoelectric ceramic plate, it vibrates. The anisotropy of the CFRP composite sheets induces an expansion/torsion movement. This effect is transformed into rotation by friction. The study of adequate voltages and frequencies of the applied electric field allows the optimization of the rotating motor performance.