Polymer acoustic emission

Bohse, J., Krietsch, T., Chen, J., Brunner, A.J., (2000) Acoustic Emission Analysis and Micromechanical Interpretation of Mode I Fracture Toughness Tests on Composite Materials , Proceedings ESIS Conference on Fracture of Polymers, Composites and Adhesives, ESIS Publication 27, pp. 15-26, Elsevier, Oxford. 

Brunner A.J., Nordstrom, R.A., Fliieler, P., (1997), Fracture Phenomena Characterization in FRP-Composites by Acoustic Emission , Proceedings European Conference on Macromolecular Physics Surfaces and Interfaces in Polymers and Composites, EPS Vol. 21B, pp. 83-84, European Physical Society. 

Figure 14.16. The effect of mean particle size of silica on total acoustic emission of epoxy filled with 70% silica. [Data from Ohta M, Nakamura Y, Hamada H, Maekawa Z, Polym. Polym. Composites, 2, No.4, 1994, 215-21.]...

Acoustic Emission of Polymers under Tensile Load... 

Better candidates for the study of acoustic emission are composite materials. The extremely brittle polyvinyltoluene sample which showed easily detectable acousic emission (6) was indeed to some extent such a composite material since it was a sample used for scintillation counting of nuclear radiation. The crystalline particles of the inorganic scintillator embedded in the rather rigid polymer matrix differ enough in elastic properties from those of the matrix that a substantial stress enhancement occurs on the interface between the two components. One has about twice the bulk stress on the poles and one third on the equator of a perfectly rigid spherical particle. Such a stress increase in the poles leads rather early to adhesion failure of the particle-matrix boundary and to microcrack formation. This finally makes the sample fail at small strain-to-fracture, cb = 0.5%. The microcracks act as nuclei for crazing. The opening of a fissure between the particle and the matrix is sufficiently... 

Ultrasonic analysis of polymeric materials has been carried out from vanous viewpoints. One of present authors (KM) has performed prease measurements of ultrasonic velocity under tensile stress condition and utilized an acoustic emission (AE) phenomenon to investigate the formation of microscopic cracks and the fracturing process of polymers [1] Instrumental advancements have also enabled us to conduct rapid and even two-dimensional ultrasonic analysis of polymeric materials including composite materials [2,3],... 

Very recently, in our group, enhanced self-reinforced PP composites based on commercial PP fabrics were obtained by the film stacking method followed by compression molding introducing different contents of micron-sized quartz particles in the matrix films (unpublished results). Simultaneous improvements of composite tensile strength, ductility and fracture toughness were observed from the addition of quartz to the polymer matrix (Table 14.1). Enhanced degree of consohdation was obtained for the composites with quartz as evidenced from the improved mechanical properties and by SEM observations. This was also confirmed by acoustic emission analysis in situ in tensile tests. 

When subjected to stresses sufficient to initate and propagate cracks, polymers emit sound waves with frequencies ranging from the upper acoustic hmit (ca. 10 kHz) to 10 MHz that may be detected with suitable transducers. A well-isolated acoustic emission (AE) system may used to detect deformation events including the slow to fast brittle crack transition in PMMA, fatigue in SEN samples, and crack propagation under high hydrostatic pressure [53]. 

Hamstad MA (1994) An examination of piezoelectric polymers as wideband acoustic emission displacement sensors. Progress in AE Vtl, Jap. Soc. for NDI, pp 79-86... 

V.L. Finkenstadt, C.K. Liu, PH. Cooke, L.S. Liu, and J.L. Willett, Mechanical property characterization of plasticized sugar beet pulp and poly (lactic acid) green composites using acoustic emission and confocal microscopy. /. Polym. Environm. 16(1), 19-26 (2008). 

M Takeshima, J-I Yamaki. Estimation of adhesion between fiber and matrix by the acoustic emission method. Jpn Polymer Sci Tech 6 490-503, 1977. 

AN Netravali, W Sachse. Some remarks on acoustic emission measurements and the single-fiber-composite test. Polymer Composites 12 370-373, 1991. 

The literature on NDT of polymers and PMC comprises the classes shown in Table 1. References illustrate the available range of literature or a specific topic. Omission or inclusion of a reference does not imply a rating by the authors. The amount of information available in electronic format only is steadily increasing, eg, References 2-8, and many journals feature electronic on-line editions. Electronic database searches are sensitive to spelling, eg, non-destructive yields 27, and nondestructive 384, active standards of the American Society for Testing and Materials International. Most NDT methods apply to various material classes. Those documents that explicitly mention polymers or PMC deal with effects specific to certain materials, eg, the Felicity effect in PMC (9), or with polymer products used in large quantities (10-14). Standards tend to lag behind technical developments, as discussed for acoustic emission (15), but similar arguments hold for other NDT methods. 

Locating is a prerequisite for sizing, ie, the determination of geometrical dimensions required by specified size criteria. This relates to the spatial resolution of the NDT method. For nonimaging methods, sizing may be replaced, eg, in acoustic emission by defect severity evaluation (159). Principles, limitations, and accuracy of defect location and sizing in polymers and PMC with specific NDT methods are described in (16-26). 

Izer A, Stocchi A, Bdrdny T, Pettarin V, Bernal C and Czigany T (2010) Effect of the consohdation degree on the fracture and failure behavior of self-reinforced polsqaropylene composites as assessed by acoustic emission, Polym Eng Sci 50 2106-2113. 

Roy, C., Allard,]., Maslouhi, A., Piasta, Z. (1991) Pattern recognition characterization of microfailures in composites via analytical quantitative acoustic emission, in Proc. Int. Coll. Durability of Polymer Based Composite Systems for Structural Applications , A.H. Cardon and G. Verchery eds, London Elsevier Applied Science, 312-24. 

---