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High Temperature Characterization and Modelling of Thermoplastic Composites

Periodic Reporting for period 2 - HITCOMP (High Temperature Characterization and Modelling of Thermoplastic Composites)

Reporting period: 2020-10-01 to 2021-12-31

The problem addressed in this second half of the project is the development of a thermo-mechanical simulation tool for virtualizing laboratory prescribed tests on thermoplastic plane specimens when submitted to fire and mechanical load.

The overall objectives can be resumed as follows:

Within HITCOMP project a complete thermomechanical model (TMM) has been developed. Fire tests are very cumbersome and time and money consuming. The model developed can to accomplish “virtual” tests of thermoplastic composite materials of aeronautical interest submitted to mechanical load and fire or high temperature events, saving a lot of time and money to the aircraft industry.

Conclusions of the action:

A Thermal Model (TM) has been fully developed. It can provide as an output, the temperature in every point of a plane specimen at any time T(x,y,z,t) after the application of fire or high temperature events on one face of the specimen.

The thermal model has been fully validated. An accuracy between measured and simulated values in the rear face (cold), better than 5% has been achieved.

Development and validation of the Thermal Model (TM) concludes the scientific and technologic tasks of the UC3M in HITCOMP project.

The results of the Thermal Model have been used to develop and validate the thermo-mechanical model developed by INTA.

A comparison between thermoplastic and thermosetting materials under fire and load tests has been accomplished.

The manufacturing of all the thermoplastic specimens for the fire tests and material characterization tests have been satisfactorily carried out by INTA.

The thermomechanical model has been elaborated by INTA showing fair agreement with the mechanical tests.

A technique has been elaborated to measure the temperature inside the panel using fiber optic sensor. The measurements showed to be in good agreement to the theoretical values.
The global thermal model has been developed and validated by UC3M for fire tests with thermoplastic materials.

The following tasks have been carried out during this reporting period:

WP1 - Design, development and installation of an innovative ground test environment:

SENSIA developed a solution based on infrared thermal imaging technology for monitoring the thermal map of the specimens under thermal/fire test.

WP2 - Test Campaigns and Specimens manufacturing:

All the specimens necessary for the mechanical and fire tests have been manufactured. Tests in a wide temperature range from room temperature, 200ºC and 300ºC have been performed including pull out and bearing tests. Two fire test panels have been instrumented with fiber optic sensors to measure the temperature in the middle of the panel to validate the theoretical model.

UC3M has participated in the thermal characterization of the panels. UC3M, as well, has verified the homogeneity and repeatability of the thermal properties of the specimens. In addition, UC3M has compared the thermal properties of thermoplastic specimens fabricated by INTA with those fabricated by external companies (FIDAMC) in order to verify the achievement of standard fabrication.

WP3 - Analysis and correlation:

UC3M has completed the mathematical model to simulate fire tests on thermoplastic materials. Two validation tests of the thermal model have been carried out for which an error less than 5% has been measured. Also, a comparison has been made on the behavior, under fire and load application, of thermoplastic to thermosetting specimens, the last had been studied prior to HITCOMP project by UC3M.

The development of the thermo-mechanical simulation model based on the FEM tool MSC Marc has been completed by INTA. The material mechanical constitutive model was developed by correlating coupon tests and fire tests results of panels under load. The model include the thermoplastic panel and the mechanical fitting for load introduction. Different fitting designs have been simulated, finishing finally with the realistic aeronautic fitting.

Overview of the results and their exploitation and dissemination:

- A complete thermal model (TM) for virtualizing tests of thermoplastic plane specimens when submitted under fire and mechanical load has been developed. TM has been validated for Toray CETEX TC1225.
- The model is enough robust to extend it to other different composite materials.
- TM should also be extended to virtualize other types of tests of similar characteristics, even for other types of metallic fittings or mechanical loads (pullout).
- In the fire and load tests carried out on thermoplastic (TP) and thermosetting (TS) specimens, the general conclusion regarding the resistance of both materials is that, for tests with similar characteristics (load, fire, thickness of material), the time to rupture is similar for both materials.

The Thermo-mechanical-TMM model has been compared, for validation, with a fire test measuring the time-to-rupture after applying fire and mechanical load. The error in the breaking time has been 22% in excess. The expected rupture time was 135 s, 30 seconds higher than the 105 s measured in the laboratory. This result can be considered quite good since it was the first one. Further research in this line should improve the simulation results.
HITCOMP project contributes to strength the leading role of the EU to combat climate change. Ultimately, this will generate jobs and growth. And it is fully in line with the objectives of the CLEANSKY JTI.

Principal impacts of HITCOMP:

- For EU scientific knowledge

o Determination of the thermal properties of thermoplastics and their dependence of temperature from RT up to 1000 ºC by means of non-contact IR imaging techniques.
o The thermal behaviour of plane thermoplastic specimens is very different if they are heated by fire or homogeneously in ovens, even though they reach the same temperature.
o The effect of hiloks as thermal bridges through between fire and the whole sample is a key factor tending to reduce the good thermal properties of composites in their resistance to fire and load

- For Aircraft manufacturers:

o Reduction of weight.
Up to a 50% weight reduction in structural components compared to metallic solutions
Up to a 10% weight reduction compared to thermosets due to removal of autoclave process

o Lower manufacturing costs.
Parts manufactured in minutes instead of hours compared to thermosets by removing autoclave step in fabrication process
80% reduction in manufacturing cycle time

o Lower operation costs.
Assembly by welding minimizes and can even eliminate the need for fasteners

o Reduced fuel burn and environmental footprint (CO2, VOCs, noise). Compared to metallic and thermoset due to reduced weight.

- For clean sky 2:

o Safe, reliable and competitive mobility for passengers, goods and public services.
o Maintaining and extending industrial leadership.
o Minimal impact of aviation on the environment through key innovations.

- For frame ITD:

o Reduce aviation environmental footprint through product performance improvements. Fully recyclable at the end of their lifecycle
o Address future market needs with product differentiators making travel greener, more efficient and more pleasant, making aircraft globally more cost efficient.
o Materials development, virtual testing and qualification aspects such as fire resistance validated by testing carried on coupons and panels.
Fire test
IR system
Preparation for the curing process of paneles in the INTA autoclave
Fire test 2
Simulation model
Testing device for the tests between RT and 350ºC
Paneles manufactured in autoclave process
DMA tests to characterize the thermal behaviour above Tg
Test specimens for AITM1-0009 Bearing at temperature tests