Dynamic behaviour of composites reinforced with needles from fir trees

In this paper we build some composite materials reinforced with needles from fir trees. In order to build the samples, we have firstly created some strips in this way: we put the pines, continuously, on a sheet of paper where we apply a thin layer of resin (we have used epoxy and polyester ones). We have made 10 strips and we have glued them together by using the same synthetic resins (epoxy and polyester). In the end we have obtained some composites reinforced with strips from fir trees needles and paper sheet, and the matrix is made from epoxy and polyester resins. From the obtained plate, we have cut some samples in order to study their free vibrations. We have placed an accelerometer at about 10 mm from the free edge and we have clamped the samples on several free lengths. The accelerometer is connected to a signal conditioner NEXUS which is also connected to a data acquisition system SPIDER 8. The data acquisition system is connected to a notebook through USB port. From the samples free vibrations, we have determined: the eigenfrequency, the damping factor per unit mass, damping factor per unit length, dynamic stiffness, dynamic Young modulus and loss factor.

Download Full-text

Researches about the Dynamic Behavior of Green Composites Reinforced with Rush and Bulrush

Advanced Engineering Forum ◽

10.4028/www.scientific.net/aef.42.24 ◽

2021 ◽

Vol 42 ◽

pp. 24-29

Author(s):

Alexandru Ioan Rădoi ◽

Cosmin Mihai Miriţoiu ◽

Mihaela Bogdan ◽

Marius Marinel Stănescu ◽

Dumitru Bolcu ◽

...

Keyword(s):

Data Acquisition System ◽

Dynamic Mechanical Properties ◽

Free Vibrations ◽

Acquisition System ◽

Unit Mass ◽

Damping Factor ◽

Dynamic Parameters ◽

Green Composites ◽

Experimental Parameters ◽

The Matrix

The paper presents some researches about the dynamic mechanical properties for some green composites made as follows: the reinforcement is made from rush and bulrush and the matrix is from epoxy resin Resoltech 1050 with its hardener Resoltech 1055. The dynamic parameters were determined from the bars free vibrations. In the first part of the paper, there are presented the mathematical calculus formulas used for the dynamic parameters determination based on the experimental recordings for the free vibrations. The next experimental montage was used: the bars were clamped at one end and were left free at the other end. At the free end, a Bruel&Kjaer accelerometer with 0.04 pC/ms-2 sensitivity was placed in order to record the beams dynamic response. A force was applied at the free end to bend the beams and after bending, the force was cancelled and the beams were left to freely vibrate. The accelerometer was connected to a signal conditioner Nexus and the signal conditioner was connected to a data acquisition system SPIDER 8 made by Hottinger Baldwin Messtec. The acquisition system was connected to a notebook ant the experimental parameters were obtained through CATMAN EASY software. From the free vibrations recording, the following mechanical parameters were determined: the eigenfrequency of the first eigenmode and the damping factors per unit mass. With these values, we have determined some direct calculus formulas for the damping factor per unit mass.

Download Full-text

About the Dynamic Behaviour of Composite Bars Reinforced with Cotton or Hemp Fibers

Annals of Dunarea de Jos University of Galati Fascicle XII Welding Equipment and Technology ◽

10.35219/awet.2020.07 ◽

2020 ◽

Vol 31 ◽

pp. 49-54

Author(s):

A. I. Radoi ◽

C. M. Miritoiu

Keyword(s):

Epoxy Resin ◽

Unit Length ◽

Young Modulus ◽

Free Vibrations ◽

Acquisition System ◽

Cotton Fibers ◽

Mass Unit ◽

Hemp Fibers ◽

Beam Dynamic ◽

The Matrix

In this paper, the authors designed several green composites with natural reinforcements (hemp and cotton fibers) and the matrix is a synthetic resin (epoxy resin). On having produced the samples, the authors determined the dynamic mechanical characteristics. The dynamic parameters were determined from the bar free vibrations. The next experimental rig was used: the bars were clamped at one end and left free at the other end. At the free end, a Bruel&Kjaer accelerometer with 0.04 pC/ms-2 sensitivity was placed, in order to record the beam dynamic response. A force was applied at the free end to bend the beams, and after bending, the force was cancelled and the beams were left to vibrate freely. The accelerometer was connected to a Nexus signal conditioner, and the signal conditioner was connected to a SPIDER 8 data acquisition system made by Hottinger Baldwin Messtec. The acquisition system was connected to a notebook and the experimental parameters were obtained through the CATMAN EASY software. From the free vibrations recording, the next mechanical parameters were determined: the eigenfrequency of the first eigenmode, the damping factors per mass unit and per unit length, the loss factor and the dynamic Young modulus and stiffness. From the results obtained, it can be concluded that the materials with epoxy resin reinforced with hemp have better vibration damping properties as compared to the composites made from epoxy reinforced with cotton fibers.

Download Full-text