The effect of defects in composite structures is addressed. Defects in laminates such as wrinkles, foreign particles, scratches and breaks are discussed. Effects of plygap plywaviness and machining defects are also studied

Sendeckyj, G. P.

English

NASA Technical Reports Server

EFFECTS OF DEFECTS IN COMPOSITE 
STRUCTURES 
G. P. Sendeckyj 
Structural Integrity Branch 
Flight Dynamics Laboratory 
Air Force Wright Aeronautical Laboratories 
Wright-Patterson Air Force Base, Ohio 
305 
https://ntrs.nasa.gov/search.jsp?R=19830025697 2020-03-21T03:07:35+00:00Z
DESIGN CRITERIA 
FIRST PLY FAILURE 
0 DESIGN ULTIMATE STRAIN (DUS) IS STRAIN FOR FIRST PLY FAILURE 
STATE OF THE ART 
0 DUS IS FAILURE STRAIN OF LAMINATE WITH 0.25-in. HOLE 
POSSIBLE 
0 DUS IS FAILURE STRAIN OF LAMINATE WITH LOW-ENERGY IMPACT 
DAMAGE 
l BUFFER AND SOFTENING STRIPS USED 
UPPER BOUND 
0 DUS IS FAILURE STRAIN OF LAMINATE 
0 STRESS CONCENTRATIONS DESIGNED AROUND LEAST CONSERVATIVE 
PREPREG DEFECTS 
HOLLOW FIBERS 
EXCESSIVEVARIABILITY IN FIBER PROPERTIES 
RESIN-STARVED OR FI BER-STARVED AREAS 
WRINKLES, WAVINESS, MISCOLLIMATION 
FOREIGN PARTICLES, CONTAMINATION 
PI LLS AND FUZZ BALLS 
NONUNI FORM AGGLOMERATION OF HARDENER 
PREPREG OUT OF SPECS. 
306 
DEFECTS IN LAMINATES 
HOLLOW FIBERS DELAM I NATI ONS 
FIBER BREAKS PLY GAPS 
EXCESSIVE POROSITY, VOIDS 
RES I N-R I CH AND RES I N-STARED AREAS 
FIBER WAVINESS, WRINI(LES, MISCOLLIMATION 
FOREIGN PARTICLES, CONTAMINATION, INCLUSIONS 
INCOMPLETE AND/OR VAR I ABLE CURE 
WRONG STACK I NG SEQUENCE 
DENTS, TOOL IMPRESSIONS, SCRATCHES 
LAMINATE POROSITY 
STUDIED EXTENSIVELY 
MATRIX DOMINATED PROPERTIES DEGRADED (DELAMINATION 
NOT INCLUDED) 
5% STRENGTH REDUCTION FOR 1% POROS ITY 
50% LIFE REDUCTION FOR 1% POROSITY 
FIBER-DOMINATED PROPERTIES NOT AFFECTED 
DELAMINATION GROWTH AFFECTED - NOT WELL DOCUMENTED 
MOISTURE ABSORPTION 
EQUILIBRIUM MOISTURE LEVELS INCREASED 
AGGRAVATES THERMAL SPIKE PHENOMENOM 
307 
EFFECT OF PLY GAP DEFECT 
(REF. 1) 
c(O/45/9D/-45)s12 LAMINATE 
- 16.9% STRENGTH REDUCTION FOR GAP(S) IN 90 PLIES 
- 8.7% REDUCTION FOR GAP(S) IN 0 PLIES 
C(O/45/O/-45/O)s12 LAMINATE 
- 6.5% STRENGTH REDUCTION FOR GAPS IN 0 PLIES 
(REF. 2,) 
C(O/*45/90)s12 LAMINATE 
- 12.8% STRENGTH REDUCTION FOR GAPS IN OUTER 45 PLIES 
[(D/-/45/D)S32 LAMINATE 
- 6.2% STRENGTH REDUCTION FOR GAPS IN OUTER 45 PLIES 
DEFECT CRITICALITY - BENIGN iOR DESIGN ULTIMATE STRAIN 0.7% 
EFFECT OF PLY WAVINESS DEFECT 
(REF. 3 1 
SURFACE 0 PLY WAVINESS IN [(D/45/9t+45)S12 LAMINATE 
STATIC TENSILE STRENGTH REDUCTION 
0 10% FOR SLIGHT WAVINESS 
0 25% FOR EXTREME WAV I NESS 
FATIGUE LIFE REDUCTION 
0 AT LEAST A FACTOR OF 10 
0 CONS I STENT WITH STATIC STRENGTH REDUCTION 
DEFECT CANNOT BE FOUND BY STANDARD NDE 
STRENGTH LOSS CAN BE PREDICKD BY ASSUMING LOSS OF 
LOAD CARRYING CAPACITY DUE TO THE WAVINESS 
DEFECT CRITICALITY - INSUFFICIENT DATA FOR ACCURATE ASSESSMENT 
. SHOULD BE BENIGN FOR DESIGN ULTIMATE STRAINS 0.7% 
308 
MACHINING DEFECTS 
EDGE DELAMI NATIONS EDGE NOTCHES AND SURFACE NOTCHES 
OVERSIZE HOLES HEAT-DAMAGED MACH I NED EDGES 
UNDERSIZE HOLES FIBER BREAK-OUT ON HOLE EXIT SIDE 
TILTED HOLES OUT-OF-ROUND HOLES 
TILTED COUNTERSINKS i MPROPER DEPTH OF COUNTERS INKS 
DENTS, FIBER BREAKING FROM IMPACT 
TEAROUT OR PULL-THROUGH IN COUNTERS INKS 
EFFECT OF SURFACE NOTCHES 
EXPER I MENTAL DATA 
STATIC STRENGTH REDUCED UP TO 5D% 
LOCAL DELAMINATION AT NOTCH 
FATIGUE LOADING REDUCES STRESS CONCENTRATION 
RESIDUAL STRENGTH HIGHER THAN STATIC STRENGTH 
DATA AVAILABLE FOR VARIOUS STACKING SEQUENCES 
ANALY S I S 
ECCENTRIC BEAM MODEL PREDICTS STRENGTH REDUCTION 
STRENGTH REDUCTION IS SMALL FOR SIZES EXPECTED 
IN SERVICE 
DEFECT CRITICALITY 
NOT CRITICAL FOR DUS < 0.7 
309 
BOLTED ASSEMBLY DEFECTS 
OVERTORQUED FASTENERS IMPROPER FASTENER SEATING 
MISSING FASTENERS FASTENER INSTALLATION DAMAGE 
OVERSIZED AND UNDERSIZED FASTENER 
BONDING DEFECTS 
ADHESIVE POROSITY 
MISCURE 
ADHESIVE-STARVED AREAS 
IMPROPER SURFACE PREPARATION 
310 
REFERENCES 
1. Ryder, J. T.; and Walker, E. K.: The Effect of Compressive Loading on the 
Fatigue Lifetime of Graphite/Epoxy Laminates. AFML-TR-79-4128, U. S. Air Force, 
January 1979. 
2. Hunsziker, R.; Konishi, D.; Burroughs, B.,A.; Altman, J. M.; and Costanza, L.: 
Advanced Composites Serviceability Program. AFWAL-TR-80-4092, U. S. Air Force, 
July 1980. 
3. Ryder, J. T.: Effect of Load History on Fatigue Life. AFWAL-TR-80-4044, U. S. 
Air Force, June 1980. 
311 


Effects of defects in composite structures

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server