Takahiro Hayashi

Quantification of the void content of composite materials using soft X-ray transmittance

Carbon fiber reinforced thermoplastics (CFRTPs) have high potential in high-cycle (1 min) molding as a weight-reducing material for the mass production of automobile components. However, residual voids in CFRTPs lead to diminished and unstable mechanical properties; therefore, the effective quantification of the void content in CFRTP products is necessary for developing an affordable system for mass production. In a previous study, we demonstrated that the X-ray attenuation coefficient decreases with increasing void content; thus, measurements of X-ray attenuation coefficients can be used to estimate the void contents of CFRTPs. In this study, we first investigated in detail the soft X-ray attenuation coefficients of completely impregnated composite materials with three different thicknesses; we observed that the attenuation coefficients decreased with increasing composite thickness, even though they should be independent of the thickness according to the Beer–Lambert law. We next demonstrated that although no correlation exists between the X-ray transmittance and the apparent attenuation coefficient of six composites with various void contents, the true attenuation coefficient modified to account for void content exhibits a good linear relationship with the X-ray transmittance, same as fully impregnated composites. Using the approximation line between the X-ray transmittance and the modified attenuation coefficient of CFRTP, we estimated the void content on the basis of the difference between the apparent and true X-ray attenuation coefficients. The average difference in void content determined by conventional hydrostatic weighing and that determined by the proposed X-ray transmittance method was 0.43%. We therefore concluded that the void content of CFRTPs of any thickness can be estimated nondestructively using soft X-rays.

Influence of void content on the flexural fracture behaviour of carbon fiber reinforced polypropylene

In order to investigate the influence of void content on the fracture behaviour of carbon fiber reinforced polypropylene (CF/PP), we investigated the relationship between the mechanical properties of carbon fiber reinforced thermoplastics and their void content using CF/PP prepreg sheet and partially impregnated sheet. Two types of flexural properties of cross-ply (CP) plates and chopped carbon fiber tape reinforced thermoplastic (CTT) plates with different void contents were measured by three-point bending tests. The flexural strength of CP specimens decreased drastically when their void content became higher than 1%, whereas the flexural strength of the CTT specimens decreased gradually with an increase in void content. Un-impregnated regions in the composites resulted in small dotted defects under loading conditions, although they were only found on the tape along the longitudinal direction in the case of CTT. In addition, a larger number of defects was observed on CP and CTT specimens with lower strengths. Therefore, cyclic loading tests were conducted to observe flexural fracture behaviour in more detail to elucidate the reason behind voids causing a decrease in strength. During these tests, the dotted defects in the CP specimens were shown to be connected along the in-plane transverse direction, while those in the CTT specimen propagated along the second layered tape.

The effect of a first-generation H1-antihistamine on postural control: a preliminary study in healthy volunteers

First-generation H1-antihistamines are known to cause fatigue and drowsiness, due to their poor receptor selectivity and their high penetration rate of the blood–brain barrier. However, little is known about the effects of first-generation H1-antihistamines on postural stability. The purpose of this study was to evaluate the effects of d-chlorpheniramine on postural stability using posturography with and without foam rubber. A double-blind study with three parallel groups was conducted. Twenty-seven healthy young volunteers (mean age 21.9xa0years) were recruited and orally administered d-chlorpheniramine, 2 or 4xa0mg, or placebo. Postural sway was measured every hour up to 8xa0h after administration. Two-legged stance tasks were performed by each subject in four conditions: eyes open or eyes closed and with or without foam rubber. Inter-group comparisons showed that the group receiving 4-mg d-chlorpheniramine showed significantly larger sway in the eyes open with foam rubber condition (visual and vestibular information available, somatosensory information reduced). Inter-subject analysis in the 4-mg d-chlorpheniramine group showed that the effect of d-chlorpheniramine on postural control was variable. Our results suggest that among the three main sensory systems responsible for postural control (visual, vestibular, and somatosensory), d-chlorpheniramine may have a larger effect on the visual and/or vestibular systems in susceptible individuals.