Detecting microscopic defects in aged thermoplastic using thermoelastic technique
An experimental investigation into the thermoelastic technique applied on a thermoplastic material is presented. The TSA response in PEEK polymer after it has been exposed to methane at elevated temperatures was used to establish whether microscopic defects in the PEEK material can be detected using thermoelastic measurement. Utilising a combination of high resolution lenses and sensitivity of the detectors, the TSA method was able to detect and sizing of surface damage. The size of the defect was approximately 300 μm. However the subsurface damage was untraceable by the technique.
Thermal imaging and Thermoelastic Stress Analysis of impact damage of composite materials
Abstract The infrared thermography, together with Thermoelastic Stress Analysis and Pulse heating thermography, is used in evaluation of impact damage in fiberglass composite materials. The controlled impact of fiberglass specimen was recorded by a high frame rate infrared thermal camera. The elastic deformation, together with the damage, was evaluated and compared with the post-impact analysis performed by methods of Thermoelastic Stress Analysis and Pulse heating thermography. The applicability and limitations of presented infrared based methods were addressed. Combination of both methods, Thermoelastic Stress Analysis and Pulse heating thermography, is suggested as appropriate for detecting damage including fiber fractures and delamination.
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.