This article addresses the experimental characterization of the mechanical properties of three types of woven fabric composites taking into account the effects of hygrothermal and hygrothermomechanical aging. Characterization was carried out using the mode I, double cantilever beam (DCB) and the mode II, end notched flexural (ENF) interlaminar fracture tests in order to determine the loss in crack propagation resistance. The materials used were two types of woven (2/2 Twill, 8-Harness Satin) glass fiber, and 8-Harness Satin carbon fiber. The matrix was polyetherimide (PEI). The critical values of the energy release rate in mode I and mode II were calculated using the corrected beam theory. The material reinforced with 8-Harness Satin glass fiber presented the best behavior in mode I and mode II. The decrease in fracture strength is more important in the material reinforced with carbon fiber.
In the present study, the effect of moisture on the interlaminar fracture toughness of two woven fabric composite materials has been investigated. The composites used are made of a woven fabric 8H Satin glass fiber and 8H Satin carbon fiber. The matrix is a polyetherimide (PEI). The composites are used in aeronautical and aerospace applications. The interlaminar fracture behavior is analyzed using the mode I, double cantilever beam (DCB) test, and the mode II, end notched flexure (ENF), in order to determine the energy required for the initiation and growth of an artificial crack. The composites are subjected to a relative humidity (95%) and a constant temperature (70 C) in a climatic chamber for 30, 60, 120, and 180 days. The delamination energies are calculated using the corrected beam, Berry theories, and the experimental calibration method at the characteristic points. The result shows that the decrease in the fracture behavior is more important in the material CD342 8H Satin weave. The fracture mechanism was also analyzed by means of scanning electron microscopy.
The present paper deals with the strain energy release rate of three woven fabric reinforced thermoplastic composites. The interlaminar fracture behavior was studied using the mode I, double cantilever beam test and the mode II, end notched flexure test, in order to determine the energy required for the initiation and growth of an artificial crack. The materials used were made of two types of glass fiber weave (2∕2 Twill, 8H Satin) and a carbon fiber (8H Satin). The matrix was polyetherimide. The delamination energy of these two materials was compared in order to study the effect of weave and reinforcement on mechanical properties. The fracture mechanism was also analyzed by means of scanning electron microscopy.
The main purpose of the present investigation was to determine the damages generated by the low velocities with the help of the experimental method (Impact by a drop test) and the finite element method. The commercial transient finite element package LS-dyna used to model the effect of slug impactor and circular notch induced damage in composite material
IntroductionThe fibrous composites are being increasingly used in load bearing structures due to number of advantages over conventional materials: high specific strength and stiffness, good fatigue performance and corrosion resistance. A serious obstacle to more widespread use is their sensitivity to impact and static loads in the thickness direction. As composites have demonstrated to be very venerable to out of plane impact, which cause barely visible impact damage (BVID) reportedly contributes up to 60 % loss in structures' compressive strength and major reason of catastrophic failures. The energy absorbed during impact is mainly dissipated by a combination of matrix damage, fibre fracture and fibre-matrix de-bonding, which leads to significant reductions in the resistance. In ballistic impacts the damage is localized and clearly visible by external inspection, while low velocity impact involves long contact time between impactor and target, which produces global structure deformation with undetected internal damage at points far from the contact region. Low velocity impact is often simulated by simple static indentation-flexure tests, neglecting the influence of dynamic effects. It is also suggested the complete model to take into account the full dynamic behavior of the laminates. Abrate et al. [1] have investigated the delamination of two laminated composite graphite/PEEK and graphite/BMI under low velocity impact. The range number of layers varies from 9 to 95 plies. The obtained result shown a higher delamination threshold load and higher damage resistance. The resulting damage is not normally visible on the specimen surface nor is easily detected and grows rapidly during normal service. The area has been under active research for a quite some time. Some of the relevant articles addressing this issue found in the literature are presented below. The strategy of reducing the stiffness of damaged plies to a certain fraction without considering the degree of damage was used by some investigators [2,3]. Other researchers applied damage theory of continuum mechanics to address the internal damage. They initiated the stress-strain relation for the actual damaged by introducing a fourth-order damage operator to transform the compliance matrix according to the damage states. Based on this work, several investigations
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.