The effect of thermal fatigue on mechanical properties of thermoset composites

The effect of thermal fatigue on mechanical properties of thermoset composites

Bruinenberg, Ingmar (TU Delft Aerospace Engineering)

Zarouchas, D. (mentor)

Delft University of Technology

Aerospace Engineering

2022-06-20

Composite structures are used more frequently in newly designed aircrafts. This results in new difficulties compared to conventional metals during operational life. Especially, the material properties of two different materials can cause side effects, which are unwanted in a structure, for example thermal stresses. Many reports have been written about the difference in damage inflicted by thermal fatigue stresses compared to mechanical fatigue stresses. However, the environmental conditions and stacking sequences used in these reports are extreme and not common in aviation. This thesis focuses on the effect of combined thermal and mechanical fatigue load on the structural integrity of a laminate, but with realistic operations mechanical and environmental loads.

In-service F-16 data has been used to get a proper indication of the order of magnitude of mechanical and thermal forces applied on an aircraft during operations. These conditions are applied to a semi-quasi isotropic coupons, which were dominant in the 0 direction, to simulate a more common laminate for an aerospace structure. The residual transverse shear strength, residual bending strength, and stiffness are measured after a mechanical and/or thermal fatigue load has been applied to test specimens.

Results show no clear reduction for any of the measured material properties. The main differences in results can be derived from size differences in test coupons. However, all results are within the scattering region of the reference values. Thus, it can be concluded that the structural integrity of a laminate will not be affected negatively by a combined thermal and mechanical fatigue load, if the conditions match the used operational circumstances.

Thermal Stresses
Thermal Fatigue
Thermoset Composite
semi-quasi isotropic laminate
Composite Material
Material Properties
Environmental Conditions
Mechanical Fatigue

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Student theses

master thesis

© 2022 Ingmar Bruinenberg