Mechanical testing procedure

It is only in the context of the systematic variation of the properties of the adhesive and/or the adherend surface in a set of otherwise identical specimens subjected to a given mechanical testing procedure that it is reasonable to think of predicting relative interfacial strength. 

Polymer films of approximately 1000 microns wet film thickness were laid down with a bar applicator on PTFE coated glass panels and the solvent allowed to evaporate at ambient temperature for a standard period of seven days. A typical plot of solvent weight loss with time is shown in Figure 2. The thickness of the wet film was dictated by the need to have adequate mechanical strength in the dry films in order that they might be suitable for subsequent mechanical test procedures. Dry film thicknesses were approximately 300 microns as measured by micrometer. The dried polymer films were examined by dynamic mechanical thermal analysis (DMTA) (Polymer Laboratories Ltd.). Typical DMTA data for a polymer and paint are... 

Chapter 3 describes basic mechanical testing procedures. This chapter describes various structural-related factors which affect polymeric mechanical properties. 

The TS of the compacted samples was determined by transverse compression with a custom-built tensile tester. Tensile failure was observed for all the rectangular compacts when compressed between flat-faced platens at a speed ranging between 0.006 and 0.016 mm/sec. Platen speed was adjusted between materials to maintain a time constant of 15 2 seconds to account for viscoelastic differences the constant is the time between the sample break point and when the measured force equals Fbreak/e in the force versus time profile, where the denominator is the mathematical e. Specially modified punch and die sets permitted the formation of square compacts with a centrally located hole (0.11 cm diameter) that acted as a stress concentrator during tensile testing. This capability permitted the determination of a compromised compact TS and thus facilitated an assessment of the defect sensitivity of each compacted material. At least two replicate determinations were performed for each mechanical testing procedure and mean values are reported. 

Posner test This mechanical testing procedure is designed for measuring spatial-visual attention and orientation (M.L Posner et al., 1988). The test persons are required to sit in front of a computer monitor using a cross in the middle of the screen as a fixation point. A square is visible on either side of the cross. In the neutral position, a question mark is displayed as a cue 200 milliseconds before the stimulus (= asterisk) appears in one of the squares. In the valid position, the cue is an arrow... 

Other mechanical test procedures are given in BS 812, namely the aggregate crushing value, aggregate abrasion value and the polished stone value. Other tests are widely used, such as the Los Angeles test for impact resistance [8.6]. 

This chapter will first discuss fracture mechanics applications to polymer composites in aerospace, and then compile the different test methods by type of load. The industiy-specific fracture mechanics test procedures for FRP composites, such as the Airbus Industries Test Method (AITM) or Boeing Support Specification (BSS), are essentially based on test procedures developed by national or international standardization agencies. This will be followed by a section with literature data to highlight selected effects of processing and material layup and type. Further sections will discuss non-unidirectional reinforcement and testing under environmental conditions that are relevant to aerospace applications, and the chapter concludes with an outlook on materials and test development trends. 

Internal friction (IF), e.g. [102]. IF is a mechanical testing procedure which may be understood as a special technique of DMT A. The mechanical damping of the free oscillation is measured depending on the temperature at a constant frequency. The internal friction parameter is proportional to the natural logarithm of the ratio of two subsequent amplitudes of the oscillation and hence is also related to the damping factor tan (5, (see also section 12.1). 

The control of surface pretreatment procedures may be done optically, by assessment of surface wettability, by surface analytical means, or by the use of simple mechanical test procedures. (See Adhesion control .)... 

The standardization of mechanical testing procedures began around 30 years ago at a national level. However, during the past ten years serious efforts on internationalization have also been made, and the first international standard (ISO 14704 ... 

Standard mechanical testing procedures are commonly used to measure the effects of hydrogen. Test results expressed as differences or ratios of the hydrogen-affected and nonaffected specimens are compared as a measure of the hydrogen effect. 

Mechanical testing procedures in common use involve other patterns of stress history than the simple creep and relaxation experiments on which the definitions of the transient viscoelastic functions are based, and the sinusoidally varying stress which is inherent in the definitions of the so-called dynamic properties. Certain relations between the behavior under coniplicated conditions and the basic viscoelastic functions are presented here together with some related problems. They are limited to linear viscoelastic systems and hence small strains, but in some cases could be extended to describe larger deformations, especially for simple extension. 

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