Riassunto analitico
The present master's thesis work is the result of the internship activity performed in Dallara Automobili S.p.A., specifically in Dallara Advanced Research Center (DARC) laboratories.
After a brief introduction of the importance of Carbon Fiber Reinforced Polymers (CFRPs) in the automotive and motorsport sectors, the most widespread manufacturing techniques of these materials are described. An overview of all the relevant mechanical properties is presented, together with standard testing procedures for their characterization.
The final objective of the activity is to validate the implementation of Digital Image Correlation (DIC) technique into the standard procedure to measure interlaminar fracture toughness in mode I (G1C) for CFRPs. This properties is of critical importance for the design of these materials, due to their tendency to delaminate.
The application of a optical instrument is needed to monitor the propagation of the crack during the test and to measure its length. Among all the possible choices, DIC has the merit to operate a complete recording of the test, thus allowing the operator to measure the crack length in a more precise way once the test itself is concluded.
The experimental setup is fully described and results of the tests are shown. The procedure was applied to different types of CFRPs to evaluate possible effects on the accuracy of the results. Calculation methods proposed by the regulation were compared in detail to underline advantages and disadvantages of each of them.
Experimental results were compared to previous analysis performed with a traditional technique and to material datasheets. The correspondence was in general very good, thus confirming the potential of the implementation of DIC into the test setup.
The findings of this work might lead to a further improvement of the procedure, in particular to a complete automation of the phases of crack length measurement and fracture toughness calculation; this further step would make the results completely independent from the operator skills, that is a key factor for their quality if the test is performed with a traditional technique.
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Abstract
The present master's thesis work is the result of the internship activity performed in Dallara Automobili S.p.A., specifically in Dallara Advanced Research Center (DARC) laboratories.
After a brief introduction of the importance of Carbon Fiber Reinforced Polymers (CFRPs) in the automotive and motorsport sectors, the most widespread manufacturing techniques of these materials are described. An overview of all the relevant mechanical properties is presented, together with standard testing procedures for their characterization.
The final objective of the activity is to validate the implementation of Digital Image Correlation (DIC) technique into the standard procedure to measure interlaminar fracture toughness in mode I (G1C) for CFRPs. This properties is of critical importance for the design of these materials, due to their tendency to delaminate.
The application of a optical instrument is needed to monitor the propagation of the crack during the test and to measure its length. Among all the possible choices, DIC has the merit to operate a complete recording of the test, thus allowing the operator to measure the crack length in a more precise way once the test itself is concluded.
The experimental setup is fully described and results of the tests are shown. The procedure was applied to different types of CFRPs to evaluate possible effects on the accuracy of the results. Calculation methods proposed by the regulation were compared in detail to underline advantages and disadvantages of each of them.
Experimental results were compared to previous analysis performed with a traditional technique and to material datasheets. The correspondence was in general very good, thus confirming the potential of the implementation of DIC into the test setup.
The findings of this work might lead to a further improvement of the procedure, in particular to a complete automation of the phases of crack length measurement and fracture toughness calculation; this further step would make the results completely independent from the operator skills, that is a key factor for their quality if the test is performed with a traditional technique.
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