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Y. Yuan et al.
methods for composite material gas cylinders mainly include visual inspection, radiographic inspection, and ultrasonic inspection. Among them, visual inspection mainly
performs visual inspection on the surface of the winding layer and the liner. Radiographic and ultrasonic inspections mainly detect the inside of the fiber layer and the
adhesive layer of the liner [3]. In view of the relatively few domestic applications of
Type IV gas cylinders, research on Type IV cylinders has focused on the design and
numerical simulation of gas cylinder structures [1, 2, 4–8]. Abroad, represented by
the United States, conducted acoustic emission testing research on fiber-reinforced
composite materials, and successively formulated acoustic emission testing methods
for composite pressure vessels, storage tanks, and pipelines, and included them in
ASME standards [9], but no evaluation basis was given. In order to locate the damage
source of composite materials, some researches have been done on the modal acoustic
emission of composite materials at home and abroad. Since a large amount of data
needs to be classified or clustered, the research mainly focuses on algorithms [10–20].
The above-mentioned conventional non-destructive testing methods for composite
gas cylinders cannot dynamically monitor and evaluate the internal defects of the gas
cylinders. Since modal acoustic emission can be used to identify material damage
and distinguish the signal waveforms of fiber breakage and delamination, the IV
gas cylinder can be monitored by acoustic emission detection method. However, the
collected signal cannot be judged whether it is from fiber rupture, matrix cracking
or liner rupture, and the fiber layer and liner signals need to be studied separately. In
view of the fact that the glass fiber tensile test research is very mature, and the ASME
standard also sets acoustic emission as one of the methods for detecting glass fiber
vessel, and the acoustic emission characteristics of liner high-density polyethylene
(HDPE) have not been reported. Therefore, this article takes HDPE material as the
object, conducts a tensile test, and monitors the acoustic emission during the tensile
process, so as to obtain the characteristics of the acoustic emission signal of the
HDPE material of the liner of the type IV gas cylinders. To lay the foundation for
the future research of acoustic emission detection and monitoring of Type IV gas
cylinders.
24.2 Test Materials and Methods
Figure 24.1 is a typical plastic liner composite full-wound gas cylinder (type IV gas
cylinder). The gas cylinder has a nominal working pressure of 2.1 MPa, a hydrostatic
test pressure of 3.2 MPa, and a minimum design burst pressure of 8 Mpa. Diameter
293 mm, body length 385 mm, nominal volume 18.0 L, winding layer thickness
3 mm, gas cylinders thread PZ27.8, liner material HDPE, liner blow molding, as
shown in Fig. 24.2, the liner design wall thickness 2.5 mm, liner outside Diameter
286 mm.
The HDPE material tensile process acoustic emission detection test system is
shown in Fig. 24.3, which is composed of the tensile sample, tensile testing machine,
Y. Yuan et al.
methods for composite material gas cylinders mainly include visual inspection, radiographic inspection, and ultrasonic inspection. Among them, visual inspection mainly
performs visual inspection on the surface of the winding layer and the liner. Radiographic and ultrasonic inspections mainly detect the inside of the fiber layer and the
adhesive layer of the liner [3]. In view of the relatively few domestic applications of
Type IV gas cylinders, research on Type IV cylinders has focused on the design and
numerical simulation of gas cylinder structures [1, 2, 4–8]. Abroad, represented by
the United States, conducted acoustic emission testing research on fiber-reinforced
composite materials, and successively formulated acoustic emission testing methods
for composite pressure vessels, storage tanks, and pipelines, and included them in
ASME standards [9], but no evaluation basis was given. In order to locate the damage
source of composite materials, some researches have been done on the modal acoustic
emission of composite materials at home and abroad. Since a large amount of data
needs to be classified or clustered, the research mainly focuses on algorithms [10–20].
The above-mentioned conventional non-destructive testing methods for composite
gas cylinders cannot dynamically monitor and evaluate the internal defects of the gas
cylinders. Since modal acoustic emission can be used to identify material damage
and distinguish the signal waveforms of fiber breakage and delamination, the IV
gas cylinder can be monitored by acoustic emission detection method. However, the
collected signal cannot be judged whether it is from fiber rupture, matrix cracking
or liner rupture, and the fiber layer and liner signals need to be studied separately. In
view of the fact that the glass fiber tensile test research is very mature, and the ASME
standard also sets acoustic emission as one of the methods for detecting glass fiber
vessel, and the acoustic emission characteristics of liner high-density polyethylene
(HDPE) have not been reported. Therefore, this article takes HDPE material as the
object, conducts a tensile test, and monitors the acoustic emission during the tensile
process, so as to obtain the characteristics of the acoustic emission signal of the
HDPE material of the liner of the type IV gas cylinders. To lay the foundation for
the future research of acoustic emission detection and monitoring of Type IV gas
cylinders.
24.2 Test Materials and Methods
Figure 24.1 is a typical plastic liner composite full-wound gas cylinder (type IV gas
cylinder). The gas cylinder has a nominal working pressure of 2.1 MPa, a hydrostatic
test pressure of 3.2 MPa, and a minimum design burst pressure of 8 Mpa. Diameter
293 mm, body length 385 mm, nominal volume 18.0 L, winding layer thickness
3 mm, gas cylinders thread PZ27.8, liner material HDPE, liner blow molding, as
shown in Fig. 24.2, the liner design wall thickness 2.5 mm, liner outside Diameter
286 mm.
The HDPE material tensile process acoustic emission detection test system is
shown in Fig. 24.3, which is composed of the tensile sample, tensile testing machine,