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Abstract

This paper presents the results of the static work analysis of laminated veneer lumber (LVL) beams strengthened with carbon fabric sheets (CFRP). Tested specimens were 45mm wide, 100 mm high, and 1700 mm long. Two types of strengthening arrangements were assumed as follows: 1. One layer of sheet bonded to the bottom face; 2. U-shape half-wrapped reinforcement; both sides wrapped to half of the height of the cross-section. The reinforcement ratios were 0.22% and 0.72%, respectively. In both cases, the FRP reinforcement was bonded along the entire span of the element by means of epoxy resin. The reinforcement of the elements resulted in an increase in the bending strength by 30% and 35%, respectively, as well as an increase in the global modulus of elasticity in bending greater than 20% for both configurations (in comparison to the reference elements).

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Authors and Affiliations

M. Bakalarz
P.G. Kossakowski
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Abstract

The presented work describes the results of examination of the mechanical properties of castings made either of AlSi9Mg alloy matrix

composite reinforced with short carbon fibre or of the pure AlSi9Mg alloy. The tensile strength, the yield strength, Young’s modulus, and

the unit elongation were examined both for initial castings and for castings made of the remelted composite or AlSi9Mg alloy. After

preparing metallographic specimens, the structure of the remelted materials was assessed. A few non-metallic inclusions were observed in

the structure of the remelted composite, not occurring in the initial castings. Mechanical testing revealed that all the examined properties of

the initial composite material exceed those of the non-reinforced matrix. A decrease in mechanical properties was stated both for the metal

matrix and for the composite after the remelting process, but this decrease was so slight that it either does not preclude them from further

use or does not restrict the range of their application.

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Authors and Affiliations

Z. Konopka
M. Łągiewka
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Abstract

The paper presents the results of experimental tests on the reinforcement of bent laminated veneer lumber beams with carbon fibre reinforced polymer (CFRP) strips glued to the bottom of elements. CFRP strips (1.4×43×2800 mm) were glued to the beams by means of epoxy resin. The tests were performed on full-size components with nominal dimensions of 45×200×3400 mm. Static bending tests were performed in a static scheme of the so-called four-point bending. The increase in the load bearing capacity of the reinforced elements (maximum bending moment and loading force) was 38% when compared to reference beams. A similar increase was noted in relation to the deflection of the elements at maximum loading force. For the global stiffness coefficient in bending, the increase for reinforced beams was 21%. There was a change in the way elements were destroyed from brittle, sudden destruction for reference beams resulting from the exhaustion of tensile strength to more ductile destruction initiated in the compressive zone for reinforced beams. The presented method can be applied to existing structures.
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Authors and Affiliations

Michał Bakalarz
1
ORCID: ORCID

  1. Kielce University of Technology, Faculty of Civil Engineering and Architecture, Al. Tysiąclecia Państwa Polskiego 7, 25-314 Kielce, Poland
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Abstract

The paper describes studies on the influence of humidity on the electrical resistance of a textile sensor made of carbon fibres. The concept of the sensor refers to externally bonded fibre reinforcement commonly used for strengthening of structures, however the zig-zag arrangement of carbon fibre tow allows for measuring its strain. The sensor tests showed its high sensitivity to the temperature and humidity changes which unfavourably affects the readings and their interpretation. The influence of these factors must be compensated. Due to the size of the sensor, there is not possible electrical compensation by the combining of “dummy” sensors into the half or full Wheatstone bridge circuit. Only mathematical compensation based on known humidity resistance functions is possible. The described research is the first step to develop such relations. The tests were carried out at temperatures of 10°C, 20°C, 30°C and humidity in the range of 30-90%.

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Authors and Affiliations

Marcin Górski
Rafał Krzywoń
Sofija Kekez

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