Hideaki Kasano

Fracture behavior of CFRPs impacted by relatively high-velocity steel sphere

Abstract Carbon fiber reinforced plastics (CFRPs) of 2-mm thickness were made with different interfacial strengths, properties, and sequences of reinforcing fibers. A 5-mm diameter steel sphere was impacted upon the CFRPs at 150– 314 m / s . By energy absorption measurement and in situ morphological observation, the effects of interfacial strength and properties on the fracture behavior of the CFRPs were investigated. On impact at 150 m / s , a weak interface resulted in high energy absorption. The rear layer should consist of high-strength fiber for higher energy absorption in this velocity range.

Impact perforation of orthotropic and quasi-isotropic CFRP laminates by a steel ball projectile

This paper considers the perforation characteristics of orthotropic and quasi-isotropic carbon fiber composite laminates struck by a steel ball projectile, both analytically and experimentally. Two analytical models, which are developed on the basis of the conservation laws of momentum and/or energy, are introduced. High velocity impact tests by a steel ball projectile are also conducted on the CFRP target plates. By combining these models with the test results, simple semi-empirical expressions for estimating/predicting the perforation characteristics of these CFRP laminates are presented. The ballistic limit velocities estimated from the semi-empirical expression agree well with those obtained by applying the statistical approach to the test data. Comparison of the residual velocities also shows a fairly good agreement between those predicted from the expression and obtained from the impact tests.

Impact perforation characteristics of carbon/carbon composite laminates

An impact test system is constructed by incorporating a digital imaging system including an ultra-high speed camera into a gas gun type impact machine in order to estimate and/or predict the perforation characteristics of advanced ceramic matrix composites. High velocity impact tests are conducted on carbon/carbon cross-ply laminates and also the perforation process of the laminates struck by a steel ball projectile is observed. Combination of analytical models with impact test results and high speed photographs leads to simple semi-empirical expressions for estimating/predicting the perforation characteristics of this materials, which are found to be very successful.

Neural network localization of a steel ball in impact perforation images

The estimation of characteristics from the impact perforation process of the material by the high-speed photograph system has been studied. In this method, the characteristic of the material is estimated from the continuous images after the steel ball perforates into the material specimen. In this study, we propose to use the neural network to localize the steel ball in the continuous images.

Impact Perforation Image Processing Using a Neural Network

The evaluation of materials characteristics from the impact perforation images has been studied in the material engineering fields. In this method, the steel ball is shot into the material specimen, and the characteristic of the material is estimated from the steel balls behavior. However, the observation of steel balls behavior is often difficult because of the scattered fragments of the specimen. We have proposed to use the neural network to estimate the steel ball position in the impact perforation image. However, the miss-recognition of the steel ball was often seen because of the influence on the scattered fragments of the specimen. In this study, the preprocessing of the image with the high-pass filter is introduced to improve the performance of the recognition of the steel ball. We examine two types of filters using the Hanning window and the Blackman window

Damage analysis of CF/AF hybrid fabric reinforced plastic laminated composites with scanned image microscopy

The article presents an experimental study that has been conducted to evaluate the impact loading damage within hybrid fabric laminates-carbon and Aramid fibers. The experiments have been undertaken on a series of interply hybrid specimens with different preprags stacking sequences. Impact damage was created using an air-gun like impact device propelling spherical steel balls with diameters of 5.0mm and 10.0mm and having velocities of 113m/s and 40m/s respectively. The resulting specimen surface and internal damage (e.g., micro-cracking and debonding) was visualized nondestructively by a scanning acoustic microscope (SAM) while further interrogation of specific internal damage was visualized using a scanning electron microscope (SEM) on cross-sectioned panels.

Transverse Impact of CFRP Laminates Under Static Load of Axial Compression With Scanned Image Microscopy

The effect of an initial compressive load on the impact-induced damage of Carbon Fiber Reinforced Plastic (CFRP) laminated composites was experimentally studied. Four kinds of test specimens having laminate configurations of (06 /θ10 /06 ) were employed, wherein their ply angles (denoted as “θ”) are 30°, 45°, 60°, and 90°. The test specimens were statically loaded, and under the load, they were impacted with an air-gun type of impact apparatus. First, the impact-damaged specimens were inspected by a mechanical scanning acoustic reflection microscope (SAM). The SAM images revealed that the initially applied load gave an increase of delaminated area. Second, for obtaining detailed information on micro-fracture mechanism, vertically cross-sectioned specimens were inspected by a scanning electron microscope (SEM). The highly resolved SEM image showed that the initial load had statically suppressed the generation of the transverse cracks.Copyright

Experimental Study on Impact-Induced Damage in CFRP Laminated Composites With Scanned Image Microscopy

An objective of this article is to investigate the initiation and propagation mechanisms of the impact-induced interior damage with scanned image microscopy. Impact tests by an air-gun type of apparatus were undertaken on a series of CFRP laminated specimens having different ply orientations such as [06 /θ10 /06 ]. The tests were conducted under the conditions of the same impact velocity of 60m/s and same impact energy level of two Joule for two steel balls (i.e., impactor) of different diameters. A mechanical scanning acoustic reflection microscope (pulse-wave mode) revealed the delamination at specified interfaces. A scanning electron microscope revealed transverse cracks in the form of matrix cracking or fiber/matrix debonding at the cross-sectional area.Copyright

Application of ultrahigh-speed photography to analytical modeling of impact perforation of polymer and ceramic materials

An impact test system is developed by incorporating a digital imaging system with a gas-gun type impact machine. By using this system, impact perforation tests by a steel ball projectile traveling at high speed are conducted on polymer and ceramic materials, while, at the same time, consecutive images of the projectile perforating the target material are taken during the tests. Combination of the test results along with the ultra-high speed images leads to analytical modeling for estimating/predicting the perforation characteristics of these materials. It is concluded from the present study that, (1) the impact test system developed here is proven to be a powerful means to the end of this investigation, (2) the ultra-high speed photography allows visualization of such a high-speed mechanical process as an impact perforation of a target material by a projectile, and (3) the digital consecutive images are very helpful with the analytical modeling, from which semi-empirical expressions for estimating/predicting the major perforation characteristics of these materials are successfully obtained.

Evaluation of deformation-induced transformation and reversion processes of stainless steel by acoustic microscope

Deformation-induced martensite and reversed austenite of a metastable austenitic stainless steel sheet were evaluated by a scanning acoustic microscope with frequencies 600MHz and 800 MHz. The sheet was elongated up to 40 percent at and below the room temperature to produce martensite, followed by annealing for reversion. First martensite content was measured by a Feritscope. Next using a complex V(z) curve, leaky Rayleigh wave velocity was measured. The deformed and annealed grain structure s were observed with the frequency 800MHz and compared with those by the optical microscope. Rayleigh wave velocity is dependent on the elongation and ambient temperature in elongation and the annealing temperature, which agrees well with the one by the Feritscope. Deformed grains are more clearly observed by the scanning acoustic microscope with 800MHz. The measured value of the velocity is compared with the theoretical one which can be calculated by Youngs modulus, Poissons ratio and the density. The measured Rayleigh wave velocity is well agreement with the theoretical one.