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. 2017 Dec:103:314-326.
doi: 10.1016/j.compositesa.2017.09.011. Epub 2017 Sep 22.

Interaction of delaminations and matrix cracks in a CFRP plate, Part I: A test method for model validation

Mark McElroy  1 , Wade Jackson  1 , Robin Olsson  2 , Peter Hellström  2 , Spyros Tsampas  2 , Mark Pankow  3
Affiliations

Interaction of delaminations and matrix cracks in a CFRP plate, Part I: A test method for model validation

Mark McElroy et al. Compos Part A Appl Sci Manuf. 2017 Dec.

Abstract

Isolating and observing the damage mechanisms associated with low-velocity impact in composites using traditional experiments can be challenging, due to damage process complexity and high strain rates. In this work, a new test method is presented that provides a means to study, in detail, the interaction of common impact damage mechanisms, namely delamination, matrix cracking, and delamination-migration, in a context less challenging than a real impact event. Carbon fiber reinforced polymer specimens containing a thin insert in one region were loaded in a biaxial-bending state of deformation. As a result, three-dimensional damage processes, involving delaminations at no more than three different interfaces that interact with one another via transverse matrix cracks, were observed and documented using ultrasonic testing and x-ray computed tomography. The data generated by the test is intended for use in numerical model validation. Simulations of this test are included in Part II of this paper.

Keywords: A. Laminates; B. Delamination; C. Transverse cracking; D. Mechanical testing.

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Figures

Figure 1:
Figure 1:
Typical low-velocity impact damage in a composite plate.
Figure 2:
Figure 2:
Test schematic.
Figure 3:
Figure 3:
Biaxial-bending test specimen.
Figure 4:
Figure 4:
Quasi-static test setup.
Figure 5:
Figure 5:
Impact test details.
Figure 6:
Figure 6:
Multiple load cycles and summary force-displacement curve for specimen XP3-2.
Figure 7:
Figure 7:
Quasi-static force-displacement data.
Figure 8:
Figure 8:
UT scans of damage in Layup 1.
Figure 9:
Figure 9:
Illustration of delamination migration in a [0/90/0] layup.
Figure 10:
Figure 10:
Delamination growth and migration detail (CT images from specimen XP3-6).
Figure 11:
Figure 11:
CT images of transverse matrix cracks forming incrementally before delamination growth initiation (specimen XP3-6).
Figure 12:
Figure 12:
UT scans of damage in Layup 2.
Figure 13:
Figure 13:
CT scans showing “staggered” and simple migration in Layup 2.
Figure 14:
Figure 14:
UT scans of damage in Layup 3.
Figure 15:
Figure 15:
Delamination area versus specimen deflection for all quasi-static tests.
Figure 16:
Figure 16:
Low-velocity impact force-displacement data.
Figure 17:
Figure 17:
Representative UT scans of damage in impact and quasi-static tests.
Figure 18:
Figure 18:
Energy required for initiation of delamination in the quasi-static and impact tests.
Figure 19:
Figure 19:
Investigation on error in force-displacement data from impact tests.
Figure 20:
Figure 20:
Measured forces from hammer and impact test load cells for centered and off centered load conditions. Data points are fit with a solid linear trendline to aid in comparison with the dashed line.
Figure 21:
Figure 21:
SEM images showing cusp orientation.
Figure 22:
Figure 22:
SEM images showing transverse matrix crack face (Layup 2).
See this image and copyright information in PMC

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