ISO 14125:1998 download free.Fibre-reinforced plastic composites Determination of flexural properties.
1.1 ISO 14125 specifies a method for determining the flexuraf properties of fibre- reinforced plastic cornposlles under ttwee-point (Method A) and four-point (Method B) loading. Standard test specimens are defined but parameters included for alternative specimen sizes for use where appropriate. A range of test speeds is included.
1.2 The method is not suitable for the determination of design parameters. but may be used for screening materials, or as a quality-control test.
NOTE — For example, me flexural modulus is only an appropriate value of the tensile Young’s modulus of elasticity as the test Is not for the additional deflection due to the shear stress which leads to a lower value of the flexural modulus but uses test span/specimen thickness ratios that minimise this effect. Differences between tensile and flexural properties are also caused by the material structure/lay-up.
1.3 The method is suitable for fibre-reinforced thermoplastic and thermosethng plastic composites.
Unreinforced and particle-filled plastics and plastics reinforced with short (i.e. less than 1 mm length) ftres are covered by ISO 178.
1.4 The method is performed using specimens which may be rnoulded to the chosen dimensions. machined from the central portion of the standard multi-purpose lest specimen (see ISO 3167) or machined from semi-finished or finished products such as mouldings or laminates.
1.5 The method specifies preferred dimensions for the specimen. Tests which are carried out on specimens of other dimensions, or on specimens which are prepared under different conditions, may produce results which are not comparable. Other factors, such as the speed of testing and the conditioning of the specimens can influence the results. For materials which are not homogeneous through the section, or above the linear-eLastic response region, the result applies only to the thickness and structure tested. Consequently, when comparative data are required, these factors must be carefully controlled and recorded.
6.2.3 Long-fibre-reinforced plastic materials
Specimens shall be machined from a panel prepared In accordance with ISO 1268 or another specified
or agreed•upon procedure. Guidance on machining of plastics is given In ISO 2818.
6.3 Checking the test specimens
The specimens shall be free of twist and shall have mutually perpendicular pairs of parallel surfaces. The surfaces and edges shall be free from scratches, pits, sink marks and flashes. The specimens shall be checked for conformity with these requirements by visual observation against straight-edges. squares and flat plates, and by rneasunng with micrometer callipers, Specimens showing measurable or observable departure from one or more of these requirements shall be rejected or machined to the required size and shape before testing.
7 Number of test specimens
7.1 At least five test specimens giving valid failures shall be tested. The number of measurements may be more than five if greater precision of the mean value is required.
It is possible to evaluate this by means of the confidence interval (95% probability, see ISO 2602).
7.2 The results from lest specimens that rupture outside the central one-third in three-point tests and outside the central portion in four-point tests shall be discarded and new specimens tested in their place.
8 ConditIoning
Where applicable, condition the test specimens as specified in the standard for the material under test. In the absence of this information, select the most appropriate conctions from ISO 291, unless agreed otherwise by the interested parties (e.g. for testing at elevated or low teneratures).
9 Procedure
9.1 Where applicable conduct the test in the atmosphere specified in the standard for the material under test. In the absence of this information, select the most appropriate conditions from ISO 291, unless agreed otherwise by the interested parties (e.g. for testing at elevated or low temperatures).
9.2 Measure the width band the thickness h to the nearest I % in the centre of each test specimen. Discard any specimen with a thickness exceeding the tolerance of ± 2% of the mean value and replace it by another one, selected at random. Calculate the mean thickness h of the set of specimens.
Report it specimens are used that do not meet this thickness tolerance requirement.
Adjust the span L to within 1 % of the calculated value, to oompty with the test span/mean specimen thickness ratio LIh given in tables 3 and 4 for preferred specimen sizes, and measure the resulting span to better than 0,2% of the calculated value.
Tables 3 and 4 shall be used unless unacceptable faitures modes (e.g interlaminar shear) are obtained (see figure 6). In this case, a higher value of L/hshall be used. Acceptable ratios are. in order, 16/1, 20/1,4011 and 6011.
12 Test report
The test report shah include the following information:
a) a reference to ISO 14125, Indicating the test method, malerial dass and test speed:
b) complete dentif,cation of the material tested, including type. source, manufacturer’s code number, form and previous history, where these are known;
c) for sheets, the thickness of the sheet and, it applicable, the direction of the mapr axes of the specimens in retation to some feature on the sheet;
d) the date of measurement;
e) the shape and dimensions of the test specimens (note if the specimens do not meet the thickness tolerance in 92);
f) the method of preparing the specimens:
g) the test conditions and conditioning procedures, if applicable:
h) the number of specimens tested;
i) the nominal length of the span used:
j) the speed of testing:
k) the accuracy grading of the test machine (see ISO 5893);
l) the face of the specimen in contact with the loading member(s):
m) the type, material and thickness of the cushion material, it used;
n) the equation used:
o) the test results;
p) the individual measurements, including sttess (force) – strain (displacement) diagrams, if required:
q) the type ol failure obtained:
r) the standard deviation and the 95 % confidence intervals of the mean values, if required.