Mechanical testing of pultruded composite materials

Newspultruded composite, pultruded materialsSaimex

Giu 2015

Pultruded materials present remarkable features. Even though Saimex Srl is already operating under certified conditions, it was decided to further test the capacity of their product. Therefore, flexural and pull tests were commissioned to the Technical University of Milan and performed by a technology bearing the company’s logo: Deck System, a special deck in composite material, which is light and extremely versatile. Its applications range from pedestrian bridge to pedestrian paths.

Flexural test

It was performed on sampled panels Deck System HD supplied by Saimex Srl. The single elements had the following sizes: 501.9 mm x 1,800 mm x 40 mm (Figure 2).

The promotion campaign has planned to perform three flexural load-controlled tests in a four-point static scheme and a clear distance between the supports of 1,500 mm (Figure 3). The purpose of this test is to verify if the elements are shifted towards the mid-span using the working load.

Test no. 1:

– maximum deflection limit per working load Pe = 3.10 kN kept for 10 minutes: 7 mm;

– maximum load applied: Pu = 20 kN

Results:

no breakage or failure due to Pu;
minimum residual deformation of post-discharge (u = 0.940 mm).

Test no. 2:

– maximum deflection limit per working load P_e = 3.10 kN kept for 10 minutes: 7 mm;

– maximum load applied: P_u = 25 kN

Results:

no breakage or failure due to P_u;
minimum residual deformation of post-discharge (u = 1.759 mm).

Test no. 3:

– maximum deflection limit per working load P_e = 3.10 kN kept for 10 minutes: 7 mm;

– maximum load applied: P_u = 25 kN

Results:

no breakage or failure due to P_u;
minimum residual deformation of post-discharge (u = 1.790 mm).

The maximum arrows were reached at mid-span for a maximum load applied respectively in all the three tests and are, as follows:

Test no.	f_mid-span [mm]
1	5,221
2	5,015
3	5,562

Table 1: maximum mid-span deflection of the samples

Therefore the tests give evidence to the considerable ability of Pultruded composite materials produced by Saimex Srl, which not only confirm, but also overcome by far the expectations of the Technical University of Milan and of the company and the values prescribed by the current regulations relating to composite materials (UNI EN 13706).

[Coming up the second part of ‘Mechanical testing of pultruded composite materials’]

Behaviour of pultruded FRP fiberglass profiles – part 2

Newsfiberglass profilesSaimex

Mag 2015

[To be continued…]

The overall mechanical behavior shows elastic-brittle features until reaching an ultimate strength and, therefore, a sudden collapse without further deformative contributions.

Figure 1 – A comparative stress-strain graph (www.saimex.it)

Features and advantages:

lightness;
high mechanical resistance;
thermal insulation/thermal break;
fire-resistant;
recommended maximum operating temperature 60°÷90° (using high-performance resins);
maximum temperature range – 40°C ÷ 180°C;
corrosion resistance;
maintenance-free;
radiolucent;
profiles based on customer’s drawings.

If the temperature range is low, the pultruded material doesn’t show any decay of mechanical performance; on the contrary it is possible observe an increase in the strength parameters.
The material leaves a wide margin of designing in relation to its thermal and electrical properties; the longitudinal extension in the direction of fibers is limited, whereas the same doesn’t happen along the two transverse directions. The material takes on a similar behaviour, even when the thermal conductivity is concerned with small changes depending on the fiber used. The response to electromagnetic stresses is on the whole good, although it is rather moderate against the carbon fiber composite materials.
Hereunder you find a comparative table of the key features of Pultruded Materials and of the major competitive materials:

Properties	Pultruded Material	Steel	Aluminium	PVC
Density [g/cm³]	1.8	7.8	2.8	1.4
Tensile strength [MPa]	350 – 400	370 – 500	200 – 400	40 – 60
Pull elongation [%]	1.5 – 2.0	13 – 35	5 – 35	10 – 80
Flexural strength [MPa]	400 – 450	330 – 500	200 – 400	70 – 100
Elastic modulus [10³ MPa]	25 – 30	210	70	2.8 – 3.3
Flexural modulus

[10³ MPa]15 – 20210702.8 – 3.3Impact resistance [MPa/m²]20040020085 – 95Thermal conductivity [W/m°C]0.25 – 0.35100 – 230100 – 2300.15 – 0.25Coefficient of thermal expansion [10⁶ MPa/m°C]5 – 2010 – 1420 – 2550-100Dielectric capacity [KV/mm]5 – 15–40 – 50Volume resistivity [wcm]10¹⁰ – 10¹⁴0.2 – 0.80.028> 10¹⁶

Table 1 – comparative table of mechanical features of materials under consideration (www.saimex.it)

[Coming up ‘Tests performed at the Technical University of Milan’]

Behaviour of pultruded FRP fiberglass profiles

NewsSaimex

Mag 2015

Fibers usually used for structural elements in FRP profiles are made of long continuous fiber glass. It is noted that fibers having a tensile strength show the same elasto-brittle behavior, without any impact on work hardening and softening sections. On the contrary, if they are compressed, the response is inadequate against the previous one. It exhibits a homogeneous and symmetric behavior (isotropic) compared to steel.

FRP production methods

Newspultruded profiles, pultrusionSaimex

Mar 2015

[to be continued ‘production methods’]

SMC (Sheet Molding Compound)

a molding composition, is much more similar to automated and continuous processes. It is characterized by medium-high production rates, a stable section and precise and codified tolerances. It originates from a resin impregnated mat (prepregs) formed of short free-fall fibers. The composite is placed inside an aluminium mold under forming press. In this way it undergoes a process of polymerization (‘curing’) that changes the physicality of the material. Therefore a controlled and repetitive process is generated, by which it is always possible to obtain the same result. Then the mold is closed and sealed under pressure and air is drawn in during the curing. It is destined for the production of medium sized elements.

BMC (Bulk Molding Compound)

is similar to the previous process, in which the composite is used in the form of ‘prepreg paste mass’; it can be processed using processing methods, such as, moulding, transfer or direct injection inside the mold. This technique is also destined for the production of small-medium sized elements.

Pultrusion

a system for the continuous pull extrusion of profiles with a stable section and straight axis, with subsequent curing in the heated closed die. The use of long fibers provides resistance to the product and mechanical responses similar to those which are typical for steel, except for the isotropy of material (the Pultruded Profile is highly orthotropic). Therefore the production is steady and automated; the dies used are made of hardened steel and ensure high production rates, thanks to their very high resistance. At the end of the process the product is cut to the desired length. Examples: IPE profiles, squared profiles, round profiles and profiles with complex shapes.

[Coming up ‘Behaviour of the GFRP composite material’]

FRP production methods – composite materials

NewsSaimex

Mar 2015

It is not possible to decouple the design of materials from geometry and from the most suitable production process in the field of composite materials. Aspects to be taken into account when choosing a certain type of product are manifold:

structural performances;
costs;
morphological constraints.

FRP composites: production systems, characteristics and technology

NewsPultruded ProfileSaimex

Feb 2015

To date the use of FRP (Fiber Reinforced Polymers) for structural reinforcement and seismic retrofit of the building stock is largely spread both at national and international level.

Fiberglass pedestrian bridges

NewsSaimex

Feb 2015

After the construction of one of the most important pedestrian bridges, completely made of fiberglass (more information on fiberglass) in Prato – in Tuscany, Saimex, a leading company in the production of composite materials, has acquired a new contract to pave the pedestrian bridge at the railway station in Cesano Maderno and in Belluno.

Our social contribution

NewsSaimex

Feb 2015

In the light of enhancing its corporate social responsibility, every year Saimex chooses to fund a project, to find an association or a charity, to whom its economic contribution can be devoted.

A strong and key voluntary commitment aimed at defining the role of Saimex within its territorial community, where it operates and develops its activities; a task for dealing not only with the economic aspect, but also with promotion and social support.

Materiali compositi FRP: sistemi produttivi, caratteristiche e tecnologia

NewsSaimex

Feb 2015

Ad oggi, l’impiego degli FRP (Fiber Reinforced Polymers) per il rinforzo strutturale e post-sismico del patrimonio edilizio è ampiamente diffuso sia a livello nazionale che internazionale.

Al contrario, la considerazione delle fibre nei profili strutturali non è ancora penetrata a fondo nel campo della progettazione, anche se appare fortemente promettente. Le possibili applicazioni sono molteplici e spaziano in ogni campo dell’ingegneria:

 costruzioni edilizie;
 trasporti (copertura per treni, autobus, tram, sponde per camion ecc.);
 aeronautica;
 industria chimica (ambienti corrosivi);
 isolanti per alto voltaggio, trasformatori, ecc.;
 equipaggiamento sportivo (bastoni da hockey, frecce, prue, tende).

I materiali compositi rappresentano quindi una delle ultime innovazioni tecnologiche nel campo dell’industrializzazione del prodotto, con riscontri anche in ambito meccanico, elettrico, elettrotecnico ed altro ancora. La particolarità di questi prodotti risiede nell’unione non solo materica ma anche “caratteriale” di due componenti apparentemente molto diversi tra loro, ma in grado di solidarizzarsi nella risposta meccanica alle sollecitazioni esterne. Sono quindi caratterizzati da leggerezza, resistenza, elasticità e durabilità, ed in tal senso le attuali applicazioni principali sono rappresentate da ponti pedonali e carrabili, strutture leggere permanenti e removibili, ma anche elementi strutturali di dimensioni più o meno contenute.

In particolare, in questa sede si parlerà di Pultruso, un composito generato dall’omonimo procedimento di produzione, che vede collaboranti resine e fibre di diverso genere. Esistono diverse tipologie di Pultruso, differenziate per resina o fibra utilizzata: il processo di produzione è infatti in grado di trattare matrici termoindurenti (resina epossidica, poliestere, vinilestere, acrilico, ecc.) o termoplastiche, in unione con fibre di diverso genere quali fibre di vetro, carbonio o kevlar (aramidica); ma la combinazione più utilizzata al momento risulta essere quella relativa ad isopoliestere e fibra di vetro.

Le normative che attualmente regolano ed indirizzano l’attività dei progettisti nel campo della progettazione strutturale con profili pultrusi rinforzati fibravetro sono le seguenti:

 UNI EN 13706, “Compositi plastici rinforzati – Specifiche per profili pultrusi – Metodi di prova e requisiti generali”;
 CNR-DT 205/2007, “Istruzioni per la Progettazione, l’Esecuzione ed il Controllo”.

La settimana prossima parleremo, sempre in ambito di Materiali Compositi FRP delle Tecniche di produzione.

Saimex, i progetti per il sociale

NewsSaimex

Feb 2015

Ogni anno Saimex, in un’ottica attenta di responsabilità sociale d’impresa, sceglie un progetto da finanziare, un’associazione o Ente benefico al quale destinare il proprio contributo economico.

Un impegno volontario fortemente voluto e centrale per definire il ruolo di Saimex nella comunità territoriale nella quale lavora e si sviluppa; una funzione che non vuole essere solo economica ma anche di promozione e supporto sociale.

Yearly Archives: 2015

SMC (Sheet Molding Compound)

BMC (Bulk Molding Compound)

Pultrusion