Effect of impact face damage on strength of sandwich composites

Research output: Book/ReportReport

Abstract

A low energy impact face defect is likely to decrease the face buckling load of a sandwich composite to. P = Po (1--Wom/Wm) t. where P0 is the buckling load without initial damage, and wOm and wm are theinitial and failure values of displaceme nt amplitude at the centre of the defect. This expression represents the critical lateral face load incompression, and is essentially unchanged regardless whether the structure is asandwich panel or a strut on elastic foundation. Experimental studies suggest that the diameter of the impact delaminationdefect du ~IN where ~is the impact energy and N is the number of equal impacts. This corresponds to the critical energy criterion for fatigue. If w0m ~l, where 21 is the wavelength of the initial irregularities, and l du, then wOm ~. This would agree with both the equation (1) and the experimentally fitted equation. P = Po · (1 ~'JN/K). where K is a constant for similar composites. If the wavelength is proportional to the diameter of the impact damage, then wOm dU2. However, a relation wOm du3 is suggested by another experimentally fitted equation. P = Po · [1 (1.5 · dU/b)3]. where b is the effective width under loading. The observed correlation 'between defect size and strength loss is somewhat worse with the last equation. However, in practice using the measured defect size du from NDT inspections is more attractive than the usually unknown impact energy in the evaluation of strength loss due to impacts.
Original languageEnglish
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Number of pages25
ISBN (Print)951-38-4246-0
Publication statusPublished - 1993
MoE publication typeNot Eligible

Publication series

SeriesVTT Publications
Number128
ISSN1235-0621

Fingerprint

Defects
Composite materials
Buckling
Wavelength
Struts
Nondestructive examination
Inspection
Fatigue of materials

Keywords

  • sandwich structures
  • composite materials
  • impact
  • damage
  • defects
  • impact strength
  • mechancal properties
  • composite structures
  • performance evaluation methods
  • loads (forces)
  • buckling
  • bending
  • tests
  • struts
  • structural members
  • panels
  • fatigue (materials)

Cite this

Auerkari, P. (1993). Effect of impact face damage on strength of sandwich composites. Espoo: VTT Technical Research Centre of Finland. VTT Publications, No. 128
Auerkari, Pertti. / Effect of impact face damage on strength of sandwich composites. Espoo : VTT Technical Research Centre of Finland, 1993. 25 p. (VTT Publications; No. 128).
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abstract = "A low energy impact face defect is likely to decrease the face buckling load of a sandwich composite to. P = Po (1--Wom/Wm) t. where P0 is the buckling load without initial damage, and wOm and wm are theinitial and failure values of displaceme nt amplitude at the centre of the defect. This expression represents the critical lateral face load incompression, and is essentially unchanged regardless whether the structure is asandwich panel or a strut on elastic foundation. Experimental studies suggest that the diameter of the impact delaminationdefect du ~IN where ~is the impact energy and N is the number of equal impacts. This corresponds to the critical energy criterion for fatigue. If w0m ~l, where 21 is the wavelength of the initial irregularities, and l du, then wOm ~. This would agree with both the equation (1) and the experimentally fitted equation. P = Po · (1 ~'JN/K). where K is a constant for similar composites. If the wavelength is proportional to the diameter of the impact damage, then wOm dU2. However, a relation wOm du3 is suggested by another experimentally fitted equation. P = Po · [1 (1.5 · dU/b)3]. where b is the effective width under loading. The observed correlation 'between defect size and strength loss is somewhat worse with the last equation. However, in practice using the measured defect size du from NDT inspections is more attractive than the usually unknown impact energy in the evaluation of strength loss due to impacts.",
keywords = "sandwich structures, composite materials, impact, damage, defects, impact strength, mechancal properties, composite structures, performance evaluation methods, loads (forces), buckling, bending, tests, struts, structural members, panels, fatigue (materials)",
author = "Pertti Auerkari",
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publisher = "VTT Technical Research Centre of Finland",
number = "128",
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}

Auerkari, P 1993, Effect of impact face damage on strength of sandwich composites. VTT Publications, no. 128, VTT Technical Research Centre of Finland, Espoo.

Effect of impact face damage on strength of sandwich composites. / Auerkari, Pertti.

Espoo : VTT Technical Research Centre of Finland, 1993. 25 p. (VTT Publications; No. 128).

Research output: Book/ReportReport

TY - BOOK

T1 - Effect of impact face damage on strength of sandwich composites

AU - Auerkari, Pertti

N1 - Project code: MET7025

PY - 1993

Y1 - 1993

N2 - A low energy impact face defect is likely to decrease the face buckling load of a sandwich composite to. P = Po (1--Wom/Wm) t. where P0 is the buckling load without initial damage, and wOm and wm are theinitial and failure values of displaceme nt amplitude at the centre of the defect. This expression represents the critical lateral face load incompression, and is essentially unchanged regardless whether the structure is asandwich panel or a strut on elastic foundation. Experimental studies suggest that the diameter of the impact delaminationdefect du ~IN where ~is the impact energy and N is the number of equal impacts. This corresponds to the critical energy criterion for fatigue. If w0m ~l, where 21 is the wavelength of the initial irregularities, and l du, then wOm ~. This would agree with both the equation (1) and the experimentally fitted equation. P = Po · (1 ~'JN/K). where K is a constant for similar composites. If the wavelength is proportional to the diameter of the impact damage, then wOm dU2. However, a relation wOm du3 is suggested by another experimentally fitted equation. P = Po · [1 (1.5 · dU/b)3]. where b is the effective width under loading. The observed correlation 'between defect size and strength loss is somewhat worse with the last equation. However, in practice using the measured defect size du from NDT inspections is more attractive than the usually unknown impact energy in the evaluation of strength loss due to impacts.

AB - A low energy impact face defect is likely to decrease the face buckling load of a sandwich composite to. P = Po (1--Wom/Wm) t. where P0 is the buckling load without initial damage, and wOm and wm are theinitial and failure values of displaceme nt amplitude at the centre of the defect. This expression represents the critical lateral face load incompression, and is essentially unchanged regardless whether the structure is asandwich panel or a strut on elastic foundation. Experimental studies suggest that the diameter of the impact delaminationdefect du ~IN where ~is the impact energy and N is the number of equal impacts. This corresponds to the critical energy criterion for fatigue. If w0m ~l, where 21 is the wavelength of the initial irregularities, and l du, then wOm ~. This would agree with both the equation (1) and the experimentally fitted equation. P = Po · (1 ~'JN/K). where K is a constant for similar composites. If the wavelength is proportional to the diameter of the impact damage, then wOm dU2. However, a relation wOm du3 is suggested by another experimentally fitted equation. P = Po · [1 (1.5 · dU/b)3]. where b is the effective width under loading. The observed correlation 'between defect size and strength loss is somewhat worse with the last equation. However, in practice using the measured defect size du from NDT inspections is more attractive than the usually unknown impact energy in the evaluation of strength loss due to impacts.

KW - sandwich structures

KW - composite materials

KW - impact

KW - damage

KW - defects

KW - impact strength

KW - mechancal properties

KW - composite structures

KW - performance evaluation methods

KW - loads (forces)

KW - buckling

KW - bending

KW - tests

KW - struts

KW - structural members

KW - panels

KW - fatigue (materials)

M3 - Report

SN - 951-38-4246-0

T3 - VTT Publications

BT - Effect of impact face damage on strength of sandwich composites

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -

Auerkari P. Effect of impact face damage on strength of sandwich composites. Espoo: VTT Technical Research Centre of Finland, 1993. 25 p. (VTT Publications; No. 128).