PSI - Issue 16

Róbert Beleznai et al. / Procedia Structural Integrity 16 (2019) 59–66 Róbert Beleznai et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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possess improved properties (mechanical and thermal) as compared to the traditional structural elements. To fulfill all these requirements, the focus is more on the composites. The objective of the study is to develop a composite bridging element that can be eligible for the new requirements: withstand the mechanical load, good thermal insulation properties, and producibility with lower CO 2 emission. After having many variants of different materials combined, the biomass reinforced polyurethane foam was selected as a potential composite. The biomass is a natural component of the composite having relatively large compression strength. The polyurethane foam provides support for the biomass and has low density and good sound, as well as thermal insulation properties. The mechanical and thermal behaviour of the composite bridging element with three different volume ratios of biomass were analyzed using numerical modeling. Due to the lack of guideline or standard for composite lintel design, the results of the analyses are compared with the results for the equivalent wooden bridging element. The composite bridging element with the higher volume ratio of biomass withstands the applied mechanical load and provides the basis for further investigation.

Nomenclature a

length of the square side of the wooden bridging element (mm)

E I x L q K x

Young’s modulus (MPa) Moment of inertia (mm 4 ) Section modulus (mm 3 )

length of the loaded part of the bridging element (mm)

average heat flux (W/m 2 )

s

thickness of the composite bridging element (m)

W

distributed load (N/mm)

λ σ Δ

thermal conductivity of the composite bridging element (W/mK)

bending stress (MPa)

maximum value of the deflection (mm)

Δ T

temperature difference (K)

2. Composite material and its properties

The matrix material of the composite is polyurethane foam reinforced with the equal length cane fibres (Phragmites australis). The geometry properties of the cane fibres are shown in Table 1 based on data by Borók (2016) and Balázs (2017). The cane fibres are defined in the model as cylindrical beam elements with ring cross section.

Table 1. Geometry properties of the cane. Geometry property

Size [mm]

Average outer diameter Average inner diameter

6.45 4.76

Average thickness

0.845

The material properties, applied by Wang et al. (2013), Kawasaki et al. (2016), Shaikh et al. (2016), Tymiński et al. (2012), of the components of the composite for the simulations are listed in Table 2.

Table 2. Properties of the components of the composite. Properties Cane

Polyurethane

Young modulus [MPa]

19820

4000 0.375

Poisson’s ratio

0.25